Bobgram

Bob McDavitt's ideas for sailing around the South Pacific. Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world. Compiled 26 July 2026 NIWA's outlook for next few months in the South Pacific. The full article is at https://niwa.co.nz/sites/default/files/2026-07/ICU-ASO-2026.pdf With the Southern Oscillation index at -2.3 and NINO3.4index at +1.82C we are now well into this El Nino. Trends show further strengthening in the coming months. This shifts the South pacific Convergence zone north and eastwards. Groups near the equator get wetter. Groups neat 15 to 25 South have a "dry season" that is real dry. They give the recent rainfall (30days to 24 July expressed as an anomaly) And here the forecast rain for August ( expressed as a decile of normal) Or the deciles for August to December This shows the expected extreme dryness and wetness for the remainder of the year. TROPICS . Tropical Storm Elida passed well to the west of Baja California and was followed by Hurricane Fausto, which is moving westward across the Pacific, and then Genevieve. . Parts of the U.S. Gulf Coast received pounding surf and squalls from passing Tropical Storm Bertha. . Typhoon NOUL is making landfall on China just to northeast of Hong Kong . WEATHER ZONES The South Pacific Convergence zone remains well north of its usual position. We have a good example of zonal flow this week with features south of the Subtropical ridge travelling almost due east Low L1 crossed NZ over the weekend and on its northern side there is a northerly extension of its frontal system acting as a convergence zone and expected to cross Society Island and Tahiti on local Wednesday--- preceded by a day or so of northerly winds and followed by south to southeast winds. High H1 is expected to cross NZ this week allowing some reasonable voyages between NZ and the tropics and from Aus to NZ. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> If you would like more details about your voyage, check metbob.com Or Facebook at /www.facebook.com/metbobnz/ Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom). Weathergram archive (with translator) is at weathergram.blogspot.co.nz. Contact is bob@metbob.com or text 64277762212. >>>>>>>>>>>>>>>>

Bobgram

Bob McDavitt's ideas for sailing around the South Pacific. Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world. Compiled 19 July 2026 Anticyclonic gloom You have probably heard all about the High-Pressure heat domes giving high temperatures over Europe this summer. And you may have puzzled about the low grey clouds found over the ocean in the high-pressure regions of the South Pacific, especially in winter. These High-pressure regions are three-dimensional. In the vertical the top part of the system contains sinking air. Just as rising air cools, so it is that sinking air warms. But the sinking air doesn't go all the way down to the surface. Instead, the bottom layer hugging the ground gets trapped ---it contains moist-laden marine air with flat grey clouds, mist and maybe fog, smog and polluted air. Anticyclonic gloom-a trapped layer of marine-moistened air. There is a distinct layer separating the warmed air aloft from the bottom trapped layer. Between the sinking warmed air and the trapped layer is a thin interface --- a lid called a subsidence inversion. It is formed by subsiding air and it inverts the normal rate of change of temperature with height. Key Characteristics . Stagnant Air: Light winds inside the high-pressure system fail to push the clouds away, meaning the gloom can linger for days . Temperature Inversion: Warm, sinking air sits above cooler, moist marine air, firmly trapping the cloud layer below . Mild & Drizzly: Despite the grey skies, temperatures usually remain mild. The moisture in the marine layer can occasionally condense into dense fog or light drizzle. The Science Behind the Gloom The mechanics rely heavily on atmospheric physics: 1. Subsidence: Descending air within an anticyclone compresses and warms, forming a stable "lid" or inversion layer. 2. Moisture Trapping: The cool ocean waters keep the lowest level of air moist. Under the lid the air is blocked by the warm air above it, so the moisture spreads out into a blanket of stratus or stratocumulus clouds. 3. Lack of Wind: Without significant wind to mix the atmosphere or break up the cloud deck, the overcast, gloomy conditions remain stationary. TROPICS . After devastating the Northern Mariana Islands, a weaker Bavi crossed the western Pacific and inundated parts of China's Zhejiang province. WEATHER ZONES The South Pacific Convergence zone remains well north of its usual position. And now it has curled around itself on its western side and produced a tropical low. I wonder if this is in response to the strong east-going current at the equator.? Here is MetService streamline analysis, showing a rotating feature very close to the equator (physically impossible to happen AT the equator) . Interesting to see a triplet of lows so close together they almost share the same streamline, with two going clockwise and the third counterclockwise. That doesn't happen often. I've named that feature L2 and it is expected to drift south into an area of strong shear and unwind near northern Vanuatu. Low L1 formed recently near New Caledonia and is expected to travel east along 20 to 30S crossing Minerva on Tuesday night, and followed by some high South to southeast swells. Avoid. After a quick front crossed North Island on Monday, High H1 should travel along 40S across Tasman Sea and NZ, very likely with some anticyclonic gloom. It then may fade but extend a nose to the northeast, weakening the trade winds between Tahiti and Tonga. Typical El Nino. From Friday a series of fronts and strong disturbed westerly winds, all on north side of L3, are expected across the Tasman Sea/NZ area. Typical El Nino. So, after several weeks with stalling systems, the weather this week transits into a mobile pattern. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> If you would like more details about your voyage, check metbob.com Or Facebook at /www.facebook.com/metbobnz/ Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom). Weathergram archive (with translator) is at weathergram.blogspot.co.nz. Contact is bob@metbob.com or text 64277762212. >>>>>>>>>>>>>>>>

Bobgram

Bob McDavitt's ideas for sailing around the South Pacific. Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world. Compiled 12 July 2026 Wave height Marine forecasts give wave heights in "significant metres" Significant wave height (often abbreviated as Hs or Hsig is a statistical measure defined as the average height of the highest one-third (33%) of all waves occurring in a given period. The parameter aligns very closely with what a human observer visually estimates when looking at a body of water. It is the standard metric used by meteorologists and marine agencies for ocean and surf forecasts. Why "Significant" Doesn't Mean "Maximum" Because ocean waves are highly irregular and vary widely in size, Hs provides a more practical representation of the overall sea state than a simple average. It is important to remember the following realities: . The tallest waves: Statistically, individual waves can be significantly taller than the significant wave height. A wave roughly twice (x1.8) Hs can be expected to occur. . Calculation: If an observer measures 100 consecutive waves, the 33 tallest waves are selected and mathematically averaged to find the significant wave height. WALTER MUNK (1917-2018) was one of the first scientists to bring statistical methods to the analysis of oceanographic data. World war II interrupted his doctoral studies at Scripps Institution of Oceanography (Scripps) at La Jolla and led to his participation in U.S. military research efforts. Munk developed methods for forecasting wave conditions which were used in support of beach landings such as on D Day. Munk in 2010 In 1932, Munk was performing poorly in school because he was spending too much time skiing, so his family sent him to a boys' preparatory school in upper New York state. In 1939 he took a summer job at Scripps, and this led to taking on a Master of Science degree at Caltech in 1940. In 1940, Munk enlisted in the US Army then in 1941, a week before the attack on Pearl Harbor, he was assigned to US Navy Radio and Sound Lab at Scripps. Soon he and Sverdrup looked for ways to measure, report and predict wave height (https://commons.wikimedia.org/wiki/File:Animation_for_a_deep_water_wave.gif ) . In 1944 Munk wrote Proposed uniform procedure for observing waves and interpreting instrument records. In this he introduced the significant wave height which was intended to mathematically express the height estimated by a "trained observer". The thing is that because an observer's view of the waves is such that the taller waves block out the smaller, it seems that an observer's "average" is the average of the top third Generally, a set of waves follows the Rayleigh distribution and the whole field can thus be determined from just the significant wave height Hs Note that the "maximum wave height" is close to TWICE the significant wave height (one such wave can be expected once a day). . 1 wave in 7 is higher than Hs. And that occurs around once a minute for waves with period around 8 to 9 seconds) Hence the surfer's rule of thumb to "wait for the 7thwave". Another way of looking at wave height is to rate it according to its energy, or "sea state" E This is from http://www.seafriends.org.nz/oceano/waves.htm This graph uses sea state E to look at relative wave heights (h/SQRT(E)) The graph shows that 80% of the waves are higher than a relative wave height of 1. 50% of the waves are higher than a relative wave height of 1.77 The significant height Hs is at relative wave height of 2.83, and 15% of the waves ( 1 in 7) are higher. Here is an interesting website for anyone wishing to experiment with interference and diffraction patterns play: the ripple simulator at www.falstad.com/ripple/ (simulates sound, radio and microwaves but not sea waves). Click and drag the mouse to make waves). TROPICS .Category-5 Typhoon Bavi caused catastrophic damage on Rota, in the Northern Mariana Islands. China evacuated nearly 2 million people as BAVI made landfall. . Typhoon Maysak unleashed deadly flooding across southern China, trapping residents on rooftops. . Minimal Tropical Storm Douglas formed briefly between Hawaii and Mexico. WEATHER ZONES The South Pacific Convergence zone remains well north of its usual position. Akso there is a very strong east going surface drift along the equator possibly liked to BAVI There is still a quasi-stationary low east of New Zealand near 40S 140W this week, with southwest winds which are tonight affecting Tahiti - these should swing back to be from the SSE in a few days. A High H1 has been over NZ this weekend and most of it is pulling off to the south of L1 next few days. A front is expected to cross South Island on Monday and then fade away over North Island on Tuesday. Then the remains of H1 should stay slow-moving just NE of New Zealand. This allows troughs to form in the Tasman Sea. The isobars marking the Easterly flow over New Caledonia are expected to curl up and bunch together as an upper cold pool forms and that should result in a surface low near Norfolk Island early next week. Labelled as L2 in my map. HIGH H2 is expected to travel east steadily along 35S across the south of Australia until mid-week, and then the slow to a crawl late in the week. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> If you would like more details about your voyage, check metbob.com Or Facebook at /www.facebook.com/metbobnz/ Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom). Weathergram archive (with translator) is at weathergram.blogspot.co.nz. Contact is bob@metbob.com or text 64277762212. >>>>>>>>>>>>>>>>

Bobgram

Bob McDavitt's ideas for sailing around the South Pacific. Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world. Compiled 05 July 2026 A review of last month's weather Here is a link to a YouTube clip giving an animated loop of the isobars and streamlines For last month is at youtu.be/9vEKSmPOgQc Most of the month there where anticyclones along 30 to 40S . In New Zealand it was the warmest June on record. On June 25 a deep low crossed northern NZ The resulting southerly winds triggered an evacuation of Wellington's south coast and power cuts affecting 6500 homes around Taranaki/Whanganui and 4000 in Wellington. Sea Surface temperature anomalies from psl.noaa.gov/map/clim/sst.shtml The waters over eastern equatorial Pacific are warming --- El Nino has started. A warm pool is stretching eastwards along the Aleutians towards Alaska. There has been a cooling trend around Fiji. Average isobars for past month (From www.psl.noaa.gov/map/images/fnl/slp_30b.fnl.html) The Monsoon has arrived over southern India around normal. Not much change elsewhere. Pressure anomalies for past two months (from www.psl.noaa.gov/map/images/fnl/slp_30b.fnl.html) The anomaly pressure pattern for last month now shows a low breeding area northeast of New Zealand and another around Easter Island. The low breeding area that was over New Caledonia has now faded. The 1015 isobar has shifted north over northern Australia . TROPICS .One person was killed and three injured in eastern Japan by severe conditions created by Tropical Storm Higos and former Typhoon Mekkhala, which struck in rapid succession. . Tropical Storm Bavi formed near the Marshall Islands and is on track to strike the Northern Mariana Islands or Guam as an intense typhoon. WEATHER ZONES There has been a multi-centred low NE of New Zealand and south to southeast of southern Cooks for past few days. This system is now being pushed to the southwest and fading. An associated convergence zone is expected to travel east across the Society island early this week. Otherwise, the SPCZ is rather weak, with one section near Samoa and another section over the Solomon Islands. High H1 is slow-moving at 43S well east of NZ. A complex and muti-centred low system is forming under a cold pool over New Zealand expected to be slow-moving until mid-week then travel off to southeast followed by cold southerly flow on Thursday. The FRONT associated with this system is expected over Minerva late on local Tuesday. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> If you would like more details about your voyage, check metbob.com Or Facebook at /www.facebook.com/metbobnz/ Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom). Weathergram archive (with translator) is at weathergram.blogspot.co.nz. Contact is bob@metbob.com or text 64277762212. >>>>>>>>>>>>>>>>

Bobgram Heat Domes

Bob McDavitt's ideas for sailing around the South Pacific. Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world. Compiled 28 June2026 Heat Domes A severe "heat dome" gripped the UK and Western Europe, shattering June temperature records. A "heat dome" happens when a large, strong area of high pressure (a big fat High or BFH) coincides with light winds aloft and so gets parked over a region. It acts like a lid on a pot. It traps hot air and pushes it down toward the ground. This sinking air dries out the clouds. Without clouds to block the sun, the ground gets very hot, which causes the air temperatures to spike. So far humans have caused the planet to heat up by 1.36C above levels of the late 1800s, leading scientists reported earlier this month. That might not sound a lot. But even a small increase in the Earth's average temperature can shift heat extremes to much higher levels. All this has gone viral in a post on Facebook: comparing a mock up forecatss done in 2012 showing French temperature in 2050 compared with an actual forecast for France last week. www.facebook.com/JeffBerardelli/posts/when-reality-surpasses-fictiontop-fict ional-forecast-for-august-2050-broadcast-b/1551964656500367/ Go figure.. TROPICS The latest cyclone activity report is at zoom.earth and tropic.ssec.wisc.edu and Tropical Cyclone Potential is from www.ospo.noaa.gov/products/ocean/tropical/tcfp/ . Tropical Storm Arthur soaked parts of eastern Texas and Louisiana. . Japan braced for a rare one-two punch from Typhoon Mekkhala and Tropical Storm Higos, which were expected to unleash widespread flooding within days of each other's arrival. Tonight there are no named storms but we can see a new tropical depression building this week over Micronesia. WEATHER ZONES Weather Zones Mid-week GFS model showing isobars, winds, waves (purple), rain (red), MT (Monsoonal trough), STR (Subtropical Ridge), SPCZ (South Pacific Convergence Zone) CZ (Convergence Zone) SPCZ is expected to have a normal week and still be situated from Solomon Islands to Samoa. Low1 to NE of NZ extending a trough eastward and has a ridge on its northside over Tonga->Cooks. High H1 near 42S 150W and High H2 1033hPa over Tasmania act like shoulders with the Low as the head, all moving east. Low l2 from the west is expected to reach Tasmania by Thursday and then turn into a complex muti-centred low over NZ from Sunday 5 to Thu 9 July. Rain accumulation for next week below. Wind accumulation for next week from windy.com above >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> If you would like more details about your voyage, check metbob.com Or Facebook at /www.facebook.com/metbobnz/ Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom). Weathergram archive (with translator) is at weathergram.blogspot.co.nz. Contact is bob@metbob.com or text 64277762212. >>>>>>>>>>>>>>>>

Bobgram

Bob McDavitt’s ideas for sailing around the South Pacific. Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world. Compiled 21 June2026 Overnight tonight we are having our winter solstice. So daylength tomorrow is 1 second longer than today. The saying goes that when the days get longer the cold gets stronger. And yes, the coldest time of the year in New Zealand is usually in early August around 6 weeks (or half a season) after the solstice. The Guardian has reported that Antarctic temperatures this winter have risen 10C above average in a record heatwave. The new winter peak temperature was logged by the Argentinian Esperanza base on the Trinity peninsula on 6 June amid a protracted heatwave, when the maximum daily temperature exceeded zero degrees for three consecutive weeks. Scientists said the high of 15.4C broke the previous record set at the same station in 1998 by 2C. It is also about 20C above normal for this time of the year. That is a huge anomaly. Unusually strong warm winds from the north blew across much of the Antarctic peninsula. On King George Island, 100 miles (160km) from Esperanza, researchers said the landscape had changed from mostly white to brown, grey and green after temperatures hit 4.6C on 6 June. “Last weekend was very strange. The temperatures here went very high so everything outside melted,” said Luis Muñoz, a Chilean glaciologist. “Usually there is 20cm of snow and a lot of ice on the ground at this time.” It will be interesting what happens when this El Nino reaches its peak in a few months’ time. Another problem that has arisen this month is the eruption of an undersea volcano on the Titan Ridge in the Bismark Sea. Pumices is coating a large area and floating around surrounding islands. This is likely to affect anyone planning to sail that way later this year. TROPICS TC MEKKHALA is heading towards southern Japan WEATHER ZONES Weather Zones Mid-week GFS model showing isobars, winds, waves (purple), rain (red), MT (Monsoonal trough), STR (Subtropical Ridge), SPCZ (South Pacific Convergence Zone) CZ (Convergence Zone) SPCZ is expected to have a normal week and still be situated north of its normal position. There is a trough tonight between Niue and Tahiti part of the SPCZ. A cold pool has formed aloft on its western side, and this is expected to drop to the surface and form a LOW south of Rarotonga. The Low Lq1 should then deepen and move off to the SE and then to the east. Its associate trough is expected to bring NE wind and rain to Tahi around local Tuesday and then a few days of SW swells. HIGH H1 stretches this evening from Brisbane to Raoul, but this part is expected to shrink next few days and another HIGH crossing the South Island on Monday is expected to enlarge over Chathams on Tuesday then travel east on to the south side of L1. LOW L2 is now forming east of Sydney and is expected to deepen but then develop multiple centres as it crosses northern New Zealand on Wednesday and Thursday finally weakening over Chathams at the weekend. It is expected to be followed by a burst of SW swells over 3.3m that may reach as far north as Fiji to Tonga by Saturday. HIGH H2 is expected to travel east across the Aussie Bight reaching Tasmania by end of the week. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> If you would like more details about your voyage, check metbob.com Or Facebook at /www.facebook.com/metbobnz/ Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom). Weathergram archive (with translator) is at weathergram.blogspot.co.nz. Contact is bob@metbob.com or text 64277762212. >>>>>>>>>>>>>>>>

Bobgram 14 June 2026

Bob McDavitt's ideas for sailing around the South Pacific. Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world. Compiled 14 June2026 Comparison of two recent coastal inundation events at Wellington South Coast Tuesday 9 June brought huge swells that inundated Wellington's south coast This had a Isobar reading 1008 Compare that with the 15-16 Feb 2026 coastal inundation weather pattern On that date the isobar reading was around 998. One of the factors we consider during coastal inundations is the "IB" or inverse baric /inverted Barometer effect. Average atmospheric pressure at sea level on this planet is 1013.35hPa, hence 1012hPa is always the straightest isobar on the weather map and divided High pressure weather from Low pressure weather. Every hPa above that depresses sea level by 1cm Every hPa below that raises sea level by 1cm There is a tidal gauge at Queens wharf in Wellington Harbour. It wasn't exposed to the large swell waves on the South Coast but was measuring the IB on 9 June 2026 The SS trace measures storm surge. More information about coastal inundation is available from one of the blogs I wrote for MetService back in 2011 : blog.metservice.com/Storm-Surge-23-Jan-2011 TROPICS There are no named storms this evening. .Mexico's Guerrero state was soaked by short-lived Tropical Storm Boris. . Tropical Storm Christina brought locally heavy rain and strong winds to parts of Nicaragua, Honduras and El Salvador. WEATHER ZONES SPCZ is expected to have a weak week and be situated well north of its normal position. HIGH H1 travelled east across NZ last week and should continue its migration along 30 to 35S this week. The burst of southerly swells on its eastern side is finally fading over Tahiti tomorrow. An upper trough moved across New Caledonia last few days and now its activity is descending between Vanuatu and Fiji, fading away the trade winds. On Monday it is expected to develop a surface low L1. This Low is then expected to deepen as it travels to the southeast, crossing Minerva on Wednesday. Fronts associated L1 and expected to travel east from Tonga to Tahiti this week . It planning to sail west , it may be a good idea to stay-put until this trough clears Tahiti around local sat 20 June. High H2 that is moving into the Tasman Sea next few days is expected to be diverted to the NE by L1. This opens the southern door. So even though the next Low L2 may start this week near 35S over South Australia, it is expected to brew a series of fronts that may cross the South Tasman Sea and South Island. This is activating the roaring 40s , and is in tune with an El Nino pattern that has now been declared www.noaa.gov/news-release/el-nino-forms-expected-to-strengthen-say-noaa-fore casters >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> If you would like more details about your voyage, check metbob.com Or Facebook at /www.facebook.com/metbobnz/ Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom). Weathergram archive (with translator) is at weathergram.blogspot.co.nz. Contact is bob@metbob.com or text 64277762212. >>>>>>>>>>>>>>>>

Bobgram

Bob McDavitt's ideas for sailing around the South Pacific. Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world. Compiled 07 June2026 A review of last month's weather Here is a link to a YouTube clip giving an animated loop of the isobars and streamlines For last month is at youtu.be/1pKfA8c4s2U May was a LOW INDEX month, with blocking Highs traveling slowly east along around 45S and a series of lows crossing Australia and then traveling east across the Pacific at around 25s. For more information about "Low index weather pattern nz" The index being referred to is the Zonal index, usually Z1, and that is simply the barometric pressure difference (Auckland-Christchurch). When this is high, NZ has westerly winds. Well last month is was low and sometimes negative. Another impact of Low index has been the rainfalls . Parts of eastern Australia have had their wettest May of record. And parts of NZ have a record-breaking DRY month. The thing about the Low index pattern is that it usually flips into a high index pattern after a few weeks. I think this low index pattern is acting as a herald for a switch to a high index pattern. And El Nino encourages a high index. The 500hPa heights and anomalies shows that prolonged upper low over Tasman sea late in the month as seen at http://www.cpc.ncep.noaa.gov/products/intraseasonal/z500_sh_anim.shtml Sea Surface temperature anomalies from psl.noaa.gov/map/clim/sst.shtml The waters over eastern equatorial Pacific are warming --- El Nino is kicking in. There is a well-established warm zone between Hawaii and LA. Since most of the North pacific is now on the warm side, the projections towards a super El Nino seem to be on target. The cool zone around NW of Australia has almost gone. Average isobars for past month From www.psl.noaa.gov/map/images/fnl/slp_30b.fnl.html The subtropical ridge in the southern hemisphere has further intensified and expanded both to north and south. The Monsoon has arrive over southern India around normal. Pressure anomalies for past two months The anomaly pressure pattern for last month now shows a low breeding area between Hawaii and Galapagos. . The southern subtropical ridge intensification is well developed over NZ, and there is still a low breeding area over New Caledonia = Low index. The 1015 isobar has stayed north over Australia near Cairns and there is a 1025 over central New Zealand. TROPICS AMANDA has been named in the northeast pacific. Tropical Storm Jangmi swept across much of Japan, bringing torrential rain, flooding and strong winds from Okinawa to the Tokyo region. At least 23 people were injured and dozens of homes were damaged by the storm. WEATHER ZONES SPCZ is of average intensity but somewhat north of its normal position. GFS model has a low forming near Fiji next week and that would create a squash zone near 20S . Other models disagree but, because of the intensity of a High crossing NZ also have a squash zone stretching across New Caledonia /Fiji to between Samoa and Tonga. Main feature this week is the upper cold pool east of NZ. It is expected to form a series of surface lows and these are expected to produce a burst of long-period southerly swell peaking at 10m near 35S 175W and spreading 4m swells as far west as 175E by Wednesday and as far east as southern Tahiti by local Thursday. This is the sort of swell that Tahitian surfers dream about. Then we have the 1036hPa HIGH slowly crossing Tasman Sea and New Zealand this week. Usually a good pattern for sailing north but complicated this week by those large southerly swells mid-week and a possible squash zone near Fiji early next week. Since the models ideas about the Fiji squash zone early next week may change next few days one idea is to head from NZ to NNW at first, avoiding the larger swells. then neat 25S get an update and if Fiji is getting too yucky then turn left and go to Noumea (Plan B) Lows L1 and L2 in the southern ocean are expected to travel east along 50S , to south of H1. Wind accumulation for next week from windy.com above shows the path of wind accompanying the L1 and the building of squash zone between New Caledonia and eats of Fiji >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> If you would like more details about your voyage, check metbob.com Or Facebook at /www.facebook.com/metbobnz/ Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom). Weathergram archive (with translator) is at weathergram.blogspot.co.nz. Contact is bob@metbob.com or text 64277762212. >>>>>>>>>>>>>>>>

Bobgram

Bob McDavitt's ideas for sailing around the South Pacific. Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world. Compiled 31 May 2026 And they're off... The Solo Trans Tasman is now underway, and tonight the fleet are taking on an active front: www.solo-tasman.co.nz/race-live-2026/ And tonight's satpic shows what the challenge looks like The LOW crossing the Tasman Sea is followed by several shower bands. GLOBAL HEAT Extreme heat waves across South Asia and Europe caused deaths, overwhelmed hospitals and shattered temperature records as scientists warn that dangerous heat is becoming increasingly common and more intense in a warming world. In India, dozens of people died from heat-related causes. At the same time, Europe experienced unusually early heat for May, with Britain recording its hottest May temperature ever at 94.6 degrees Fahrenheit/35C. TROPICS Tropical Cyclone Jangmi is aiming for the east coast of Japan. WEATHER ZONES Wind and rain accumulation this week from Windy.com Rain accumulation from windy.com shows a rather weak and unorganised SPCZ. The Rain accumulation shows a rather weak SPCZ north of Samoa, and an intense group of rain bands around a Low L1 centred south of the Australs, and affecting the Southern Cooks. Wind accumulation this week from Windy.com shows strong wind areas associated with L1 and FRONT1. LOWS and HIGHS Low L1 south of the Australs is expected to move off to the southeast HIGH H1 is expected to remain east of NZ and near 160 to 170W/ Rain is associated the FRONT1 which is crossing North Island on Monday. It also brings some intense falls as far as Minerva on Tuesday night. In the Tasman Se it is followed by several lines of thundery showers each with NW winds. This is the challenge facing the solo trans-Tasman racers this week. Low L2 has deepened SW of Perth over the weekend and is expected to remain an intense system reaching Tasmania by mid-week. Its associated FRONT is expected to cross NZ next weekend and then L2 is expected to deepen around Chathams with an upper cold pool and cut off low next week. Following L2 a southerly flow covers NZ and then HIGH H2 which is expected to travel east along 35 to 40S. This is the classic good pattern for sailing from NZ to the tropics. Hopefully this ends the recent "low zonal index" (google this for more info) weather pattern that has been affected the South Pacific in May GFS is toying with the idea of a low forming near Fiji around 10-11 June, but other models don't agree with that idea. Just keep an eye on that if travelling. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> If you would like more details about your voyage, check metbob.com Or Facebook at /www.facebook.com/metbobnz/ Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom). Weathergram archive (with translator) is at weathergram.blogspot.co.nz. Contact is bob@metbob.com or text 64277762212. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Bobgram Tahiti to Tonga

Bob McDavitt's ideas for sailing around the South Pacific. Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world. Compiled 24 May 2026 Tahiti to Tonga Now that many yachts are about to travel west from Tahiti to Tonga, it is time to review the weather, in general terms, for this route. The main players: 1. Getting from the Tahiti area to Tonga/Fiji means crossing the South Pacific Convergence zone, SPCZ. Like a dragon, it dances . This zone may be weak or may contain squally showers. In the models it is portrayed as a zone of light winds. To see a forecast for this zone, use windy.com and rain accumulation for a period over five days. This zone may linger in the north (it does this in an El Nino) or it usually hovers between Samoa and Southern cooks. To avoid it, choose a different latitude or aim for gaps in the zone. The SPCZ goes thru periods of activity and inactivity and is most active when there is the positive phase of an MJO (Madden Julian Oscillation). Occasionally a tropical low/passing trough will travel east/southeast along the zone, making for a burst of wind/rain travelling east from Fiji to Niue then SE across Southern cooks. These occur on occasions even at this time of the year and can be forecast beforehand and avoided. 2. Another thing to avoid is a SQUASH ZONE when a large High travels east along 30S. When the central pressure in the High is 1030hpa or above, it gets dirty (isobars get bunched together along its rim). So in the tropics the isobars marking the trade winds may get squashed together making a "squash zone" of enhanced winds and rough seas. These usually occur around 20 to 25 South and may last for several days. In Fiji this is called BOGIWALU, in Tonga AHO VALO, and in Tahiti the name used is MARA'AMU. They are reasonably easy to forecast and are worth avoiding. If caught in one, change your latitude rather than your longitude. Bogiwalu sweeps through palm leaves and pandanus; Salt spray and rain drive inland from the seas; Young August shields her face and droops her banners. And strips for flight, and with the wind she flees. July would fain forego her glorious gift of sunshine To breast a portion of the eight nights' strain. July's apparel-not for pain but peace time- Is armour poor against the wind and rain. Oh! linger not, July-with heart-warm kiss of sweetness: Go now-your golden sun-robe scarcely tom. Young August, swift and slim for greater fleetness, Plies through the years, and onward we are borne. V. M. P. COSTER. Suva Point, Fiji, 29/7/1939. (taken from PIM online) 3. The third thing to avoid is the PASSING TROUGH or passing low. The systems tend to form on the eastern end of the SPCZ in which case they travel southeast, propelled by upper NW winds as a steering field. OR they may form on the NW (back) corner of a travelling HIGH., in which case they may get shunted south or sometime to the southwest. They often have their own mini-squash zones (on their polar/southern side), and calm zones (on their equatorial/northern side). Isobars give a clue about the intensity of a passing trough: those above 1010hP are usually weak and those below 1007 are worth avoiding. There are three routes between Tahiti and Tonga, the northern, central and southern: 1. Sometimes the northern route via Suwarrow/Samoa is favored, and sometimes not. The northern route goes via Suwarrow to Samoa. Often this is covered by the SPCZ, but when the SPCZ is further south the northern route and its northeast winds may be best. 2. The middle-route offers stopovers such a Palmerston Island and Niue and is a good alternative when the SPCZ is further north. Watch out for passing troughs and squash zones . these come and go. The middle route allows short hops. 3. The southern route tends to get higher swells from the Southern Ocean SO, all in all, the "best voyage" changes every few days . sometimes it's worth waiting for something that suits, sometimes it isn't. Basically, avoid passing troughs and squash zones, and go thru the SPCZ where/when it is weak. This may mean taking short hops rather than getting direct from Tahiti to Tonga in one go. =-=-=-=-=-=-=-=-=-=-=- TROPICS No named storms at present WEATHER ZONES LOWS and HIGHS LowL1 over the Austral's tonight is finally expected to move off to the southeast after a week of travelling due eats. Low L2 has formed on western side of a cold pool aloft and thus been tracking to the NE . It is expected to weaken over Fiji and Tonga next few days but have lots of lightning in its squall clouds (over eastern Fiji and Tonga tonight). It is expected to travel ESE towards the Austral's this week, following L1. High Hi is quasi stationary over New Zealand. After a SW change along the east coast on Wednesday, it should be replaced by High H2 from Australia. Low L3 is forming under a cold pool over central Australia, so its rain clouds may be intense. Its wind and rain are expected to form a deepening low near Lord Howe by Friday which is expected to bring intense wind and rain from Fiji to New Zealand by Sunday (and that's the middle of a long weekend in New Zealand). Avoid. Rain accumulation from windy.com shows a rather weak and unorganised SPCZ. Also well-defined areas of rain associated with L1, L2 and L3. Parts of Australia have had their wettest May on record, and L3 takes another crack at Sydney. Wind accumulation this week from Windy.com shows a squash zone just north of NZ as part of L2 and the winds associated with L1 mainly about the Austral Islands, and winds from L3 spreading across the Tasman Sea with the approach of the Kings Birthday long weekend. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> If you would like more details about your voyage, check metbob.com Or Facebook at /www.facebook.com/metbobnz/ Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom). Weathergram archive (with translator) is at weathergram.blogspot.co.nz. Contact is bob@metbob.com or text 64277762212. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Bobgram

Bob McDavitt's ideas for sailing around the South Pacific. Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world. Compiled 17 May 2026 TEN REASONS TO HATE A HIGH WE have a 1040hPa anticyclone on our weather map this week. Time to review the ten reasons we should beware of Big Fat Highs. They have their undesirable attributes, especially when they stall. 1. Near the centre are "dead" winds and usually an area of low cloud - trapped below a subsidence inversion - causing dull days called "anticyclonic gloom", or dirty air which may turn into fog. T 2 Round the rim, winds are strong. "If the central pressure is over 1030, the rim may get dirty" --look for a gale somewhere on the outside of a high. 3. Highs intensify the trade winds in the tropics. It may take about a week for a high to travel eastwards past New Zealand, and during this time the stronger trade winds tend to give night-time rain to the eastern side of the larger tropical Islands. In Fiji this is sometimes called BOGI WALU. In Tahitian MARA'AMU 4. The bigger the highs are, the slower they move, blocking the fronts and lows that are trying to follow them. When this block is released, the western ("back") end of a high may become a breeding ground for storms. See www.abc.net.au/news/2026-05-16/most-widespread-may-rain-to-reach-all-austral ian-states/106685072 5. Intensifying highs tend to squash together the isobars between themselves and any nearby low pressure centres, creating "squash zones". 6. A deepening low-pressure system and an intense or lingering anticyclone get together like the arms of an eggbeater and create a zone of enhanced wind and rain. 7. As air flows around a high, it spins out across the isobars and speeds up until it is as much as 20% MORE than that indicated by the isobar-spacing. 8. If a range of mountains blocks the air flowing around a high, the air tends to squeeze around the mountains rather than flow over them. This splits the wind flow over New Zealand into rivers of wind and puddles of calm. Sometimes a narrow gap is made just above the mountains through which pent-up air may be suddenly released at a rapid rate. 9. In winter and spring, a high may bring unwelcome frosty fogs 10. In summer and autumn, a high may allow sea breezes to converge and, if it is cold enough aloft, this can form thunderstorms and hail. TROPICS There are no named storms this evening. WEATHER ZONES SPCZ is weak and scattered this week. There is also a convergence zone lingering around French Polynesia. HIGH H1 over NZ was over1040hPa this weekend - a BFG or Big Fat High. It is expected to slowly travel along 40S. Low L1 is expected to form south of Niue and then move south and east. A squash zone of rain and enhanced wind and swell should form on its south side. On the back end of the BFH there has been a build-up of tropical moisture over Australia, as evidenced by the intense recent rain. This week that moisture is expected to enter the Tasman Sea and produce a series of Lows. These lows , being on the back end of a BFH are likely to stall and rotate around each other. Avoid. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> If you would like more details about your voyage, check metbob.com Or Facebook at /www.facebook.com/metbobnz/ Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom). Weathergram archive (with translator) is at weathergram.blogspot.co.nz. Contact is bob@metbob.com or text 64277762212. >>>>>>>>>>>>>>>>

Bobgram

Bob McDavitt’s ideas for sailing around the South Pacific. Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world. Compiled 03 May 2026 Some good news:  Thanks to the persistence and generosity of Max on Y2K The link listing useful weather links for the South Pacific is back www.y2ksail.com/meteo-link.html Try this out and if you like it Buy him a beer (it’s the bottom link) A review of last month’s weather Here is a link to a YouTube clip giving an animated loop of the isobars and streamlines For last month is at youtu.be/GjGUycWtUYo Cyclone Vaianu breezed across NZ quickly on 11 April and a cold pool convergence zone flooded Wellington on 20 April The 500hPa heights and anomalies shows that prolonged upper low  over Tasman sea late in the month From http://www.cpc.ncep.noaa.gov/products/intraseasonal/z500_sh_anim.shtml Sea Surface temperature anomalies from psl.noaa.gov/map/clim/sst.shtml The waters over eastern equatorial Pacific are warming --- El Nino is coming. The cool zone around NW of Australia is relaxing . There is a well established warm zone between Hawaii and LA. The cool (dry) zone around NW Australia is shrinking. Average isobars for past month (below) The subtropical ridge in the southern hemisphere has further  intensified and shifted north. The HIGHS over Siberia, over the Aleutians and in the North Atlantic have all weakened . Pressure anomalies for past two months (below) The anomaly pressure pattern for last month still shows a low breeding area around Hawaii.   The southern subtropical ridge intensification is well developed east of NZ, but there is still a low breeding area between Tonga and NZ, and another over Australian Bight. The 1015 isobar has shifted north over Australia to Cairns and the 1020 spans from Melbourne to Brisbane. TROPICS No named storms around the planet this evening. WEATHER ZONES SPCZ is weak and scattered this week, but there is some severe convection associated with the clouds around L1, a tropical low that is expected to form on Wednesday around the Southern Cooks --- on the NW shoulder of the large High H1 that is travelling east along 40S and to east of NZ.  L1 is expected to deepen as it travels south near 160W this weekend and early next week. There are two lows and troughs crossing the Tasman Sea /NZ area this week. L1 is expected to weaken over central NZ on Thursday. Then L2 should be followed by a strong cold SW flow on Saturday. If L2 then moves off to the east without leaving behind a secondary development, and if the High following L2 travels steadily along 40S with a central pressure between 1025 and 1030 (no more, no less), then this pattern is consistent with what I call a Southerly flush…. The arrival of the cold air in Northland is such that the marinas are flushed empty of those yachts seeking the warmth of the tropics.  I’m not sure yet, and we may have to wait until Wednesday before the differing models start agreeing. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>  If you would like more details about your voyage, check metbob.com Or Facebook at /www.facebook.com/metbobnz/ Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom). Weathergram archive (with translator) is at weathergram.blogspot.co.nz. Contact is bob@metbob.com or text 64277762212. >>>>>>>>>>>>>>>>

Bobgram

Bob McDavitt's ideas for sailing around the South Pacific. Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world. Compiled 26 Apr 2026 In my Ten Tips last week I referred toY2K Weather Links hub www.y2ksail.com/meteo-link.html Sadly this web page is currently offline-the server put charges up beyond reason.. Max is finding a new server for it now Our cyclone season nominally ends on Thursday. For those hoping to set sail from New Zealand to the tropics in early May, the usual idea is to go with a "Southerly flush" When the chilly southwest wind changes reach north of Auckland that can provide a good weather pattern to hop on the back end of that trough and get carried off to the tropics. That trough which crossed Northland late last week had a cold cut-off upper low attached, bringing squalls and downpours. That was the wrong pattern for departure. There was another cold upper-air cutoff early last week over Wellington. Both these patterns were "left overs" brought about the remains of Cyclone VAIANU as it came south the previous week. We now have a HIGH pushing east along 40to 45South. This is NOT conducive to a "Southerly flush". SO, we may have to wait a week or more for that typical "Southerly flush" pattern. Having said that, the easterly winds on the northern side of this HIGH may get tweaked to southeast enough to allow a reasonable voyage to the tropics. A trough is expected southwest of the Cook Islands by end of the week and that may also help twist the pattern in our favour. As for getting from eastern Australia to Noumea.: That HIGH makes for head winds for this route so stay put until a trough forms in the north Tasman Sea.then there MAY then be a OK opportunity. As winter kicks in, the voyages from NZ and Australia to the tropics will be dominated by the position of the STR or Sub tropical ridge. So here is a description of this feature.. Weather is a mix of pattern and chaos, and meteorologists concentrate on the pattern. In tropical meteorology the first idea given is the Hadley cell. Recipe for the ITCZ 1. Because the sun is most directly overhead near the equator, that's where the warmest seas are, and this causes rising air. 2. Once the rising air reaches high enough it spreads outwards and sideways to the north or south, where it sinks at dries out. 3. The sinking air reaches the surface again around 30N or 30S (subtropical ridge) and then recirculates back to the equator as surface winds know as trade winds. 4. The trade winds from each hemisphere converge together in a zone, and this convergence narrows the zone of rising air into a feature called the Intertropical Convergence Zone or ITCZ But in the Southern Hemisphere, the Andes of South America cause a split in the trade winds. They block a HIGH near 30S around 90 to 110W, or south of Easter Island. It is quasi stationary, just like the High between California and Hawaii, and has a gyre that collects a rubbish heap just as badly (see Henderson Island: blogs.fco.gov.uk/lauraclarke/2018/04/10/henderson-island-plastic-pollution-i n-paradise/). Recipe for the SPCZ 1. There are easterly winds on the north side of this "Andes" High: they are dry due to continental outflow from off South America. These easterly winds travel well to west of the dateline along around 10 to 15S. 2. And there are migratory Highs that travel east along the subtropical ridge from Australia to east of NZ, with a zone of south to southeast winds on their northern side. These South/SE winds come and go according to the migratory high and are usually found around 15 to 25S. 3. The convergence zone between these easterly and Southeasterly winds is called the South pacific Convergence Zone, or SPCZ. It is typically located from the Solomon Islands south-eastwards to the Southern Cooks, and is around 1 to 5 degrees latitude wide, but sometimes may have large gaps or be very quiet. It is affected by many things: . the strongest cycle is the ANNUAL cycle as earth orbits the sun, making the seasons. . the Pacific Decadal Oscillation or PDO which takes many years to switch. . the El Nino/La Nina which lasts a year or so. . and the MJO which comes for a week or so every six weeks or so. Read more about it at en.wikipedia.org/wiki/South_Pacific_convergence_zone I have found that the easiest way to determine the position and severity of the SPCZ is to use satellite imagery, and the easiest way to decide what it may do over next few days is to use the 5day rain accumulation parameter on windy.com. The Sub Tropical Ridge STR This is the zone that separates the trades winds from the "Roaring Forties" and is where high-pressure areas (anticyclones) travel generally from west to east. In the north Atlantic these are called the "horse latitudes'. So called because, in the past, sailing ships would become becalmed in this zone and, when short of water, dump their horses when passing islands. When these Highs cross the prairies of North America during the Autumn seas, the settled weather turns the air hazy allowing the local tribes to hunt bison--- thus the phrase "Indian Summer". This week, New Zealand weather can be described as "Indian Summer". In the South Pacific these highs usually end up merging with the semi-permanent high which is found west of the South America Andes. The area east of New Zealand and south of Tahiti is a place where these Highs often becomes "blocking Highs" and slow-moving. The anticyclone track is, in summer (say, Nov. to April), usually across the Southern Australian Bight and New Zealand latitudes. The track migrates northwards in winter, following the sun. Because of the seasonal variation of land-sea temperature differences, the winter track is further north over Australia than New Zealand. Each anticyclone's strength and size change daily, growing to a maximum in about three days then decaying. Often, as one collapses, a new one forms somewhat to the southwest. It is common for an anticyclone to slow down west of New Zealand whilst a new nose of high- pressure forms east of the Southern Alps. This new centre then moves off to the east while the old one dies. WEATHER ZONES The SPCZ is active from New Guinea to Vanuatu. A weaker convergence zone is sitting over Tuvalu and another between the equator and Marquesas. The trough over Austral Island sis weakening away. The trough over New Caledonia and south of Fiji tonight is expected to drift across Tonga early this week and then go southeast and deepen into a low south of Cook Islands by end of the week. High H1 in central Tasman Sea is expected to slowly travel east across central New Zealand this week. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> If you would like more details about your voyage, check metbob.com Or Facebook at /www.facebook.com/metbobnz/ Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom). Weathergram archive (with translator) is at weathergram.blogspot.co.nz. Contact is bob@metbob.com or text 64277762212. >>>>>>>>>>>>>>>>

Bobgram

Bob McDavitt's ideas for sailing around the South Pacific. Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world. Compiled 19 Apr 2026 TEN TIPS FOR CRUISING SAILORS (2026 edition) Starlink is fast becoming the norm for cruising sailors but may well be outside your budget. Now that cruising sailors are on their final preparations for departing New Zealand for the warmth of the tropical Islands, 'tis is a good time to review the ways to obtain weather forecasts and/or provide position reports when at sea. 1. ZLM/Taupo Maritime Radio offer a continuous 24/7 Trip reporting service, see https://www.maritimenz.govt.nz/about-us/what-we-do/safety-and-response/the-m aritime-radio-service-for-new-zealand/ The HIGH SEAS forecast for the areas SUBTROPIC FORTIES and PACIFIC from MetService is read out in English via ZLM at 0903hr, and 2103hr UTC on 6224 and 12356KHz and repeated an hour later on 8297 and 16531 KHz. SOUTHERN is read out at 0303/2103 (www.metservice.com/marine/radio-schedule) NZ MetService ceased their ZKLF Radio fax 1 July 2023 Australia's Bureau of Meteorology still sends weather maps by HF Radio fax. The nearest transmitter to the South Pacific is VMC in Charleville, schedule is at www.bom.gov.au/marine/radio-sat/radio-fax-schedule.shtml 2. Gulf Harbour Radio ZMH286 www.ghradio.co.nz ghradio@xtra.co.nz Patricia and David keep track of boats that listen to their rollcall/weather service. Firstly, contact them via email or radio with your details - boat name, MMSI, boat type and length. Then let them know when you are about to take off and whether you will be on air each night. They operate 1 May-30 Nov Mon-Fri on 8752USB at 0515 UTC (which is 5:15pm NZST and an hour later during daylight saving, 6:15pm). Each broadcast is live streamed so friends and family can hear your check in and follow along. David gives a weather update each night for the passage routes and the islands. And their web site has articles of general interest and specifically on weather. 3. Passage Guardian passageguardian.nz peter@passageguardian.nz Passage Monitoring is operated by Peter Mott and provides a global free-of-charge service (donations welcome) that monitors the progress of recreational vessels conducting ocean passages. Peter uses a range of tools, including satellite trackers, AIS and email, and multiple maritime radio frequencies to keep a constant watch on yachts that have filed a float plan prior to departure. The service has a formal policy for dealing with a missed check in. Whilst available to all yachts, Passage Monitoring is especially suited to shorthanded and solo sailors, in particular circumnavigators. 4. AMATEUR RADIO/Ham net: PACSEANET pacseanet.gmail.com The Pacific Seafarers Net is a ham (amateur radio) network providing a free of charge check in service on amateur frequency 14300KHz USB in the 20-metre band at 0300UTC. To participate, operator needs to hold an Amateur Radio Operators Certificate (General class or above). In the amateur radio service, the callsign is assigned to the licensed operator, so this is a different callsign from using a maritime callsign. Position reports are received and reported in the well-known YOTREPS format (but missed calls may not be followed up). They have 12 listening station dotted between Australia and Alabama. See pacseanet.blogspot.com 5. EMAIL via HF requires a PACTOR modem sailmail.com Connect a Pictor modem to your SSB radio and send email 6. Weather charts accessed via EMAIL if you only have email (be it win link/sail mail/iridium/Inmarsat/Gmail), Saildocs (saildocs.com) relays details of a TEXT BASED webpage. See weather.mailasail.com/Franks-Weather/Home They allow you to download, e.g., the latest Fiji Met Service High Seas by sending an email, no subject necessary, to query@saildocs.com with message: SEND http://www.met.gov.fj/aifs_prods/10140.txt 7. Y2K Weather Links hub www.y2ksail.com/meteo-link.html Alex and Max have been sailing around the South Pacific for several years now on yacht Y2K. They have compiled of list of marine weather resources for cruising sailors that can be summoned via snail mail . Direct links to key official meteorological services for the region (e.g. MetService NZ, Fiji Met Service, Mateo-France New Caledonia) and other relevant forecast providers. . Links for accessing satellite imagery, weather charts, and sea state analysis. . Access points for text forecasts suitable for low-bandwidth connections. Visit this page BEFORE DEPARTURE and note the links you may need on your voyage. 8.. Fiji Fleet code. How to download a map via HF (thru email) This is real old school stuff, but it still works if you need it. To download the latest Nadi Fleet Code, send an email to query@saildocs.com, no subject needed, saying SEND nadi-fleetcode Or SEND https://tgftp.nws.noaa.gov/data/raw/as/asps20.nffn.txt This can be viewed within the Fleet Code plug in OpenCPN. Download this at opencpn.org/OpenCPN/info/downloadopencpn.html Open the email and select and copy the data (right click, Control A then Control C on a PC). Then, in OpenCPN's Fleet code plugin, there are 4 options: Files, Text, Raw and Downloads. Select Raw and then <paste> or CTRL-V and Voila! the map appears. I still have a copy of the old, no longer supported Fleet code viewing program call Phys Plot. If you want to try it, let me know. 9. Smart phone apps: Some satellite phones now provide Wi-Fi that allow nearby smartphones to use apps. www.predictwind.com provides an app that supplies forecast model data, observations and, at the Professional Account level, tools for routing and comparing departure dates. It also has a position tracking tool and can help with iridium Go! and some other GPS devices. A moderate subscription gives access to its universal AIS package with a regional search option. The Windy.com App has a free basic option. It also has a subscription option that can be used to compile route plots. To make one on a PC: - "right click" anywhere on the map, this will open a small context window. - choose "Distance & Planning"; - place your points on the map; chose 'Boat' and enter your average likely speed. Shift the start time to see which gives the best voyage. Click on "more options" bottom left and in the "table of points" you just made, click the button label "share" in the bottom right corner; - remember and use the short URL link provided or the long URL in the top of your browser. You can also make one by building the URL manually if you are familiar with this. Each time you plug this URL in your browser, Windy will show an updated map of your planned route. 10 YiT, Yachts in Transit, at www.yit.nz or mike@yit.nz has a smart phone app, and offers a subscription service to plot your reports and blogs on the web and to request weather information via coded emails. They also provide info on how to use iridium Go!, YB Tracking, or Garmin inReach for communications. This site was closed for a while but returned in 2023. TROPICS . Typhoon Senkaku raked the Northern Mariana Islands as a Category-4 storm, overturning cars, uprooting trees and ripping off metal roofs in Saipan. . Remnants of former Cyclone Vaianu knocked out power, triggered floods and force hundreds to evacuate in northern New Zealand. WEATHER ZONES The SPCZ is active from New Guinea to Vanuatu to Fiji. A Tropical Low is expected to form on the SPCZ in the New Caledonian region on Sat 25 April and travel southeast onto NZ by mid next week. To may interfere with travel in the region next weekend, but the models are differing with location and timing at this stage so be watchful. High H1 which been blocking proceedings well east of NZ is expected to weaken away next few days. Low L1 has been quasi stationary in Tasman Sea last week (after VAIANU) and is expected to cross NZ on Monday/Tuesday then move off to the southeast as H1 finally relaxes. Associated weak trough over Fiji Tonga is expected to move off to the east in tandem with L1. L1 is followed in NZ by cold southerly flow until Thursday. HIGH H2 is expected to dodge to south of NZ and then go NE L2 south of Australia nis expected to go southeast. HIGH H3 is a fast mover and should move from Aussie Bight mid-week to central NZ on Friday and Saturday. . >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> If you would like more details about your voyage, check metbob.com Or Facebook at /www.facebook.com/metbobnz/ Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom). Weathergram archive (with translator) is at weathergram.blogspot.co.nz. Contact is bob@metbob.com or text 64277762212. >>>>>>>>>>>>>>>>

Bob blog

Bob McDavitt's ideas for sailing around the South Pacific. Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world. Compiled 12 Apr 2026 VAIANU My illustrated edition has wind and rain accumulation map from Cyclone VAIANU over New Zealand (thanks to windy.com)from dawn Sunday 12 April to dawn Monday 13 April And, thanks to Neil Gordon, an animation of Vaianu as seen by MetService radar during Sunday SEA TEMPERATURES March 2026 brought the warmest March land temperatures to USA in the past 132 years. The world's oceans reached their warmest measured peak in 2024 and again reached those levels in late March 2026, relaxing in past few weeks This is shown in the "World Sea Surface temperature" seen at climatereanalyzer.org/clim/sst_daily/ TROPICS .Cyclone Maila intensified to Category-4 strength between the Solomon Islands and Papua New Guinea, where such storms have rarely developed in the past, and never of such force. It helped create a twin , Cyclone SINLAKU in the northern hemisphere thanks the a zone of equatorial westerly winds . Cyclone Vaianu skirted Fiji with Category-3 force and today its remains travelled across the North Island brining wind and rain especially to Northland, Coromandel and Bay of Plenty. . Cyclone Indusa passed over the mid-Indian Ocean. WEATHER ZONES Low L1 remains slow moving near 35 to 40S well southeast of Tahiti until mid -week then moves off to the southeast. High H1 stays quasi-stationary near 40S 140W. MAILA is travelling west and unravelling into a low L3 which weakens after Wednesday. VAIANU is expected to disappear to the southeast on Monday. That is likely to mark the end of this cyclone season, which nominally runs out at the end of this month. A trough from the Tasman Sea is expected to follow VAINUA across NZ on Tuesday night developing a Low L2 near Chathams on Wednesday. High H2 from South Australia is then expected to cross the north Tasman Sea on Thursday then north of NZ on early Friday. This is followed by a LOW L4 from the Southern Ocean, deepening as it crosses NZ on 18 to 20 April. Rain accumulation below. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> If you would like more details about your voyage, check metbob.com Or Facebook at /www.facebook.com/metbobnz/ Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom). Weathergram archive (with translator) is at weathergram.blogspot.co.nz. Contact is bob@metbob.com or text 64277762212. >>>>>>>>>>>>>>>>

Bob Blog

Bob McDavitt's ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world.

Compiled 05 Apr 2026

A review of last month's weather

Here is a link to a YouTube clip giving an animated loop of the isobars and
streamlines
For last month is at youtu.be/f7fN5sa53pQ

Lows affected NZ on 13, 19, 26 and 30 March
Tropical cyclone Narelle formed of Saint Patricks day and deepened by 19
March:
The 500hPa heights and anomalies shows that prolonged upper low  over Tasman
sea late in the month

Sea Surface temperature anomalies from psl.noaa.gov/map/clim/sst.shtml
The waters over eastern equatorial Pacific remain near normal.
The warm patch between Tonga and New Zealand continues to relax.
The cool (dry) zone around NW Australia is shrinking.

Average isobars for past month show that
The subtropical ridge in the southern hemisphere has intensified and shifted
north.
The HIGH over Siberia has intensified at a time of the year it  usually
weakens.

Pressure anomalies for past two months show that
The anomaly pressure pattern for last month shows a low breeding area around
Hawaii… they had a particularly stormy March.   The southern subtropical
ridge intensification also stands out.
The 1015 isobar has shifted north over Australia to Brisbane

TROPICS
Our cyclone season nominally finishes at the end of April, and indeed we
still have a few more cyclones and tropical lows to come. Three are around
this evening .31P and INDUSA are caught in upper NW winds.  MAILA is likely
to be steered east then south then southwest across the Coral Sea.

WEATHER ZONES
MAILA may not start moving southwest until after Wednesday.
31P might earn a name on Monday and is expected to affect Fiji on Tuesday
night/Wednesday and maybe eastern North island of NZ from Friday.
There is an active part of the South Pacific convergence zone mostly over
Southern Cooks to Austral Islands until mid-week, then expected to travel
across Tahiti area this weekend. Avoid.
A trough covers the eastern Tasman Sea this evening and is expected to move
onto NZ on Monday/Tuesday, fading as it moves… Northland and Coromandel take
the brunt of this trough, but it is followed by a cold southerly over
eastern South Island.
HIGH H1 remains quasi-stationary east of New Zealand.
HIGH H2 is expected to bud off eastern Australia by Wednesday and then
travel southeast across the South Island on Friday.
Lows L2 and L3 south of Australia are expected to travel east or southeast.

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Bobgram

Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world.
Compiled 29 Mar 2026

Cyclone NARELLE formed on Saint Paddy's Day and continued to PALM Sunday
Reminds us of another waltzing Matilda -type cyclone called STEVE in the
year2000:

The WMO released their latest "State of the Climate" report to mark WORD
METEOROLOGY DAY WMD last Monday (I celebrated WMD with a toast to
meteorologists everywhere-the weather knows no boundaries).
wmo.int/publication-series/state-of-global-climate/state-of-global-climate-2
025

The main statement in this report is that our planet now has an energy
IMBALANCE -it is trapping more energy from the sun than it is emitting, and
this imbalance is increasing.




TROPICS

NARELLE and last week's tropical depression near Vanuatu have reduced that
cyclone formation potential from the South Pacific Convergence zone There
are no named cyclone on the weather map tonight. However, there is an
interesting zone of high cyclone formation potential now near the Southern
Cooks

WEATHER ZONES

The remains of NARELLE are now moving off to the southeast into the Southern
Ocean.
L1 and its associated fronts developed last few days as an east coast low
off Sydney and is crossing New Zealand tonight and Monday then moving off to
the southeast followed by High H1 bringing NZ a good start to easter.
At the same time High H2 brings a settled Easte to Southeast Australia.
Note that H2 is expected to move inland for a while--- previous highs have
been taking the summer path across the Australian Bight. but now that we
have had the Equinox , the nights over the Australian deserts are longer
than the days. leading to cooler denser air which can support the higher
hectoPascals.
After a brief trough over NZ on Saturday and Easter Sunday, High H2 brings
NZ some more settled "Indian Summer" weather just after Easter.
Lurking in the tropics is another Low L2 forming during Easter between
Vanuatu and Fiji/New Caledonia. The models are still differing about its
future scenarios. more about that next week


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Bobgram

Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world.
Compiled 22 Mar 2026
EQUINOCTUAL CYCLONES
The Equinox was yesterday morning (New Zealand time).

Cyclone NARELLE formed west of Vila last week and since then has been
travelling west.

We now have depression 98P forming in the same place, and it is forecast to
go south this week


TROPICS


Cyclone Narelle spun up over the northern Coral Sea and intensified to cat 4
when making landfall over Cape York peninsular and cat 5 in Gulf of
Carpentaria and is expected to build again in warm seas off northwest of
Australia.
98P is expected to deepen to below 985hPa when it enters the central Tesman
sea by Thursday. This is a good recipe for lowering pressure. take warm
moist air (low density) from the tropics and send it into cooler conditions
(denser air). The less dense air gets raised up high and vented off by
strong winds aloft. when the conditions for this are set up, air is removed
from the system so that its surface pressure lowers (more isobars) and that
squeezes the isobars togethers. more wind.

WEATHER ZONES
Cyclone NARELLE is expected to continue around Aussie coast and deepen again
when over the sea. I suggest that you save its track-a lot will be written
about it in the future.
L2 comes out from the north end of a southern trough. Its associated
convergence zone is expected to bring squalls mainly between Samoa and
Tahiti this week.
HIGH H1 has given a period of "Indian summer" weather to New Zealand with
sunny afternoons but overnight dew or mist. It is moving away and fading
next few days.
L1/98P is expected to bring a period of wet/windy weather to the North
Island on Tuesday night to Thursday as it travels south, and to South Island
on Friday--- possibly with a secondary low forming east of Sydney bringing
them a southerly buster.
H2 is expected to slowly travel east across the Aussie Bight reaching
Tasmania this weekend.

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Bobgram

Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world.
Compiled 15 Mar 2026
Outlook for April
The internet is abuzz with several commentators reporting that there may be
a switch to an extreme El Nino later this year. For now, relax.
Indications are that, during April and into May, the Tasman Sea /New Zealand
area weather is likely to be close to normal.

Our friends at tropical tidbits.com mainly watch tropical cyclones. They
also give access to some climate models which show outlooks for the month of
April based on current trends.
These are called anomalies and they indicate how this April may vary from
normal.

The map has isobars which show the averaged weather forecast for April. In
April, on average, the west-southwest winds of winter reach as far north as
Cook strait, and a High centred near the Australian Bight noses a ridge of
relatively light winds onto the Bay of Islands. Daily weather pattern
shuffle around this idea.
The anomalies show expected difference from a normal April. Papua New
Guinea is above normal --- but only by small amounts. And between Solomons
and Tonga are below normal. Since these are over a low-pressure area (the
South Pacific convergence zone) and this is expected to be accentuated in
April.

Indeed, when we look at the forecast rain anomalies for April:
New Guina highlands are pointing to extremely dry condition. And from the
Solomon Islands to Tonga there is an accentuated South Pacific convergence
zone. A dry zone over Tasman Sea and New Zealand indicates this area may
have light winds and sunny skies that linger in autumnal anticyclones (an
Indian summer).





TROPICS

It has been a quiet week with no named storms.
There OLR trend shows that, for the south Pacific, the next few weeks may be
sunnier than normal (yellow) and so the risk of cyclone formation may be
lower than normal.


WEATHER ZONES
For the New Zealand area: On Monday and Tuesday High H1 travels across
central areas. On Tuesday, Low L1 is expected to form on a trough crossing
Tasmania and then travel southeast on Wednesday past southern New Zealand.
From Wednesday to Saturday Low L2 is expected to deepen over the Kermadecs
and then travel off to the SE sideswiping east coast of North Island. After
Saturday the next High from the Australian Bight is expected to travel
across central New Zealand.


In tropical areas, the SPCZ os expected to be active between the Solomon
Islands and to south of Fiji.
A tropical low L3 may form on Thursday in the Coral Sea and then travel
west into the Gulf of Carpentaria.
Another low L4 may form off west Australian coast and fade as it goes
south.


In my illustrated edition is a diagram that shows a week of rain
accumulation around the equator.

Normally the ITCZ sits between 3N and 10N, but during March another
convergence zone forms south of the equator. I call this a mirror ITCZ. I
think it forms because during March these of the latitudes of the direct
overhead Sun. This month the sun will be directly overhead the equator at
Friday 20 March at 14:46 UTC (early Saturday for Fiji and New Zealand).

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>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Bobgram

Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world.

Compiled 08 Mar 2026

The rate of global warming jumped in 2013.
A recent publication in  Geophysical Research letters as at
agupubs.onlinelibrary.wiley.com/doi/10.1029/2025GL118804
by G.Foster and  S.Rahmstorf   have removed from the temperature records the
three main natural variable factors ( El Nino, volcanism and solar
variation) 
to produce smoother trends. This smoothed data shows there has been an
acceleration in warming with a notable jump around 2013.

There is an observable increase in the Earth's energy imbalance,
as detected by the CERES project and published at
berkeleyearth.org/global-temperature-report-for-2023/

TROPICS
Cyclone Urmil passed over the open waters of the Pacific, well to the south
of Fiji and Tonga. • An unnamed tropical storm formed south of Java.

WEATHER ZONES
For the New Zealand area: On Monday, the front attached to L1 is expected to
be followed by cold southerly conditions.  Then Tuesday to Thursday should
have light winds with the passage of H1 .  Then another front on Friday
attached to L3 followed by SW winds.

For Northern Tasman Sea and Queensland to Kermadecs: That tropical Low L2 is
expected to track steadily from 20S to 30S with strong winds and heavy rain.
Avoid.

For other tropical areas: this is expected to be a relatively quiet week.

For South half of Australia:  That monsoonal trough last week combined with
that front attached to L1 and brought heavy rain to Adelaide area.   This
week's front is expected from Tuesday to Thursday attached to L3 and is
expected to be followed by strong SE winds and 3m swells as far north as
Lord Howe by Friday 13/Sat 14 March.  Then High H3 should spread across
Aussie Bight bringing easterly flow to Australia.  

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 
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