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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.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 
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.
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