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Bob McDavitt's ideas for sailing weather around the South pacific

24 September 2017

Bob Blog 24 Sep 2017

WEATHERGRAM

YOTREPS

Compiled Sun 24 September 2017

 

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.

 

The equinox was Friday 22 Sep at 22:02 UTC and so several nations around the South Pacific are switching from ST/ Standard Time to DT/ Daylight time over the next few weeks as follows:

 

Sep 24 (today)

 

NZST (UTC +12) switches to NZDT (UTC +13)

 

Samoa (UTC+13) switches to Samoa DT (UTC+14)

 

 

 

1 October (next Sunday)

 

AEST = UTC+10 switches to AEDT= UTC+11

 

Lord Howe ST = UTC+11 switches to Lord Howe DT = UTC +12

 

 

 

5 November

 

Fiji ST = UTC+12 switches to Fiji DT = UTC+13

 

Tonga ST = UTC+13 switches to Tonga DT = UTC +14

 

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When calculating your departure from the Islands to Australia /NZ be mindful of the public holidays:

 

 

Tonga: Monday Nov 6 Constitution.

 

 

 

Fiji: Tues Oct 10 = Fiji Day, Thursday Oct 19 = Diwali

 

 

 

New Caledonia:

 

National Day : Sep 24th, All saints Day 1 November, Armistice Day 11 November

 

 

 

New Zealand: Labour Day Monday 23 October.

 

 

 

Australia: On Mon 2 October Queensland observes Queens Birthday  (NSW/ACT/Sa observe Labour day the same day).

======================

 

Topics

 

TC MARIA has done its dash in the Caribbean, and is expected to stay offshore from now on, but may sideswipe Bermuda.

LEE is also still going but further east

PILAR is affecting Mexican west coast

And there are a couple of tropical depressions in the NW Pacific.

 

Rainfall for the past week   as seen at trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif, shows the path of the Atlantic cyclones, with a peak over Puerto Rica.

 

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ starts this week from Solomon Islands to Tuvalu/Tokelau area.

A weak upper trough is fading between Tonga and Niue on Monday UTC.

Another trough is expected to travel east across Tonga and Niue on Thurs/Fri UTC reaching the Rarotonga area on Sun/Mon 1/2 Oct UTC, preceded by NE/N winds, accompanied by variable winds and showers, and followed by SW/S/SE winds.

 

 

Subtropical ridge (STR)

HIGH moving off to east of NE New Zealand on Monday is expected to intensify to over 1032 near 35S 150W by Friday, and this may increase the trade winds between French Polynesia and the Cook Islands to around 20 gusting 30 knots. This is a slow-moving High, so the winds on its western side—over NZ are expected to be intensified on Monday and Tuesday.

Another HIGH is expected to move off eastern Australia on Tuesday and slowly move to between NZ and New Caledonia/Fiji by Thursday and then linger there until early next week..

 

French Polynesia to the west:

The main obstacle this week is that travelling trough over Tonga/Niue on Thursday/Friday UTC, but it may Ok to sail thru this trough. It is looking to be a fading feature after it travels east past Niue.

 

Between NZ and the tropics:

Very strong NW winds over the North island on Monday and Tuesday, and then a passing trough on Wednesday. Thursday, with a passing ridge, is the best day of the week for arrival/departure. Then there is likely to be another trough on Friday followed by another on late Saturday and decreasing SW winds on Sunday.

Best date to depart/arrive is either Wednesday 27 or Monday/Tuesday 2/3 Oct.

With that High lingering between New Zealand and New Caledonia/Fiji from Thursday, the voyage is likely to face a few days of light winds.

 

Between New Caledonia and Australia

This week the wind between New Caledonia and the Brisbane area are likely to be mainly northerly. A southerly change is likely for Sun 1 to Tuesday 3 October.

Further South, in the central Tasman sea, a trough is expected to be travelling east on Monday and Tuesday, followed by light winds with a passing ridge on Wednesday and the another trough with NW winds on Thursday and variable/southwest winds on Friday/Saturday.

 

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

If you would like more detail for your voyage,

then check metbob.com to see what I offer.

Feedback to bob@metbob.com or txt 6427 7762212

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com,

Click FOLLOW at bottom right to subscribe.

To unsubscribe send a reply email saying LEAVE.

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17 September 2017

Bob Blog 17 Sep 2017

WEATHERGRAM

YOTREPS

Compiled Sun 17 September 2017

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.

The state of the ENSO = weak La Nina trend now showing

The Atmosphere:

El Nino and La Nina are opposite ends of an identifiable tropical influence on our seasonal weather:  the La Nina, caused by cooler than normal seas along the equatorial eastern pacific. shifts the subtropical ridge away from the equator, and the El Nino, with warmer than normal seas, draws the subtropical ridge closer to the equator.  Their comings and goings can last several months, maybe over a year, and so their status can be used to forecast the weather for the coming season. 

The main parameter we watch from the atmosphere is the Southern Oscillation Index SOI (30 day running mean) as it sums up the whole weather pattern over the South Pacific in one number. It is based on the standardized difference in the barometer readings between Tahiti and Darwin, in other words the placement of isobars on the weather map.  When the SOI is more than plus one (standard deviation from its mean) for more than a month we call it a LA NINA event, and when it stays more than minus one we call it an EL NINO event.

So far this year there have been an unsteady swings either way, and in Aug/Sep the SOI has settled around plus 0.5 (or 5 units in the graph shown here), in the zone which some call a weak La Nina.  So, this is a hint that the subtropical ridge line may shift southwards faster than normal over the next three months.  The warming of spring/summer should reach Australia and NZ faster than normal.   Maybe this also means the tropical wet season may start earlier than normal.

Weak La Nina may be seen at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekly

(Note that in this graph on the vertical axis 10= 1 standard deviation)

The Ocean:

NINO3.4 is a region in the eastern equatorial Pacific Ocean that acts as a heat storage area during an El Nino, or becomes cooler than normal during a La Nina.  This plays with the heat budget of the atmosphere and thus with the weather patterns.

At the farmonline web site we can see the trend in the sea surface temperature in the NINO3.4 area. The diagram shows the weekly temperature anomalies since Jan 2014, with the El Nino of 2015 looking like a hump on a camel. Since then there has been a cool period late 2016/early2017, and then a warm period until July 2017.  We are now in a cool period again. But only around half a degree below the old "normal"( maybe 1 degree below the new normal).

Weak La Nina is seen at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=nino34&p=monthly

The International Research Institute of the Climate Prediction Centre compiles data from several ENSO prediction models.  The early September probabilistic forecasts show the chance of La Nina is as high as 60% over next few months, dropping below 50% again early next year. CPC/IRI predictions from iri.columbia.edu/our-expertise/climate/forecasts/enso/current/

 

The sea surface temperature anomaly map has been showing MOSTLY WARMER THAN NORMAL on planet earth for months now, so that climate change is beginning to warp out the seasonal influences. The warmer than normal seas in the Atlantic has been breeding stronger than normal cyclones, but it seem that HARVEY has managed to stir the Gulf waters so they are now cooler than normal.  Reminds us that tropical cyclones are one way this planet gets rid of excess energy. Without them, worse would happen.

Latest SST anomaly map shows the wonderful cooler eddies along the equator of a typical La Nina, but the ENSO values involved are only half a degree and so it’s only half-a-La-Nina, and not being called as such yet.  I’m wondering that if we could remove the climate change trend for the data, then maybe it’d exceed the La Nina threshold. 

Sea surface temperatures are at www.ospo.noaa.gov/Products/ocean/sst/anomaly/index.html

 

TROPICS

IRMA has done its damage and JOSE is staying offshore,

LEE is Fading away,

Next in line is MARIA in the Caribbean,

And NORMA off Baja California,

and to west of NORMA is OTIS.

Meanwhile over in Northwest pacific, TC TALIM has turned away from Taiwan  and is now affecting Japan.

See www.livemint.com/Politics/s0eTyRYVnX3ZdpXLua5weJ/Typhoon-Talim-slams-Japan-hundreds-of-flights-grounded.html

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ starts this week from Solomon Islands to Samoa area, and is expected to drift South so as to visit Fiji and maybe northern Tonga this weekend sat/sun/mon 23/24/25 Sep.

A passing, mainly upper, trough, is expected to travel eastwards across Niue on local Monday night and Southern Cooks on local Tuesday/Wednesday, preceded by NE/N winds, accompanied by variable winds and showers, and followed by SW/S/SE winds.

Tropical accumulated rainfall for next week may be seen at windyty.com

 

Subtropical ridge (STR)

HIGH moving off eastern Australia tonight is expected is expected to move northeast across the North Tasman Sea next few days, fading near the date line after Thursday.

Another HIGH is expected to move off eastern Australia on Thursday and travel across Northern NZ on Sunday 24 Sep and remain above 1022 and it travels east along 30S to east of NZ next week.

When these Highs are in the Northern Tasman Sea we can expect a weak squash zone in the Coral sea.

 

French Polynesia to the west:

The main obstacle this week is that travelling trough over Niue on local Monday and Rarotonga on local Wednesday. This trough may bring a day or two of variable winds south of 18S, but not much disturbance to the surface winds further north. Take into account that Tonga may receive some tropical showers early next week ( 25/26 Sep Local) from a visit from South Pacific Convergence zone.

Between NZ and the tropics:

LOW#1 is travelling Northeast across eastern NZ on Monday/Tuesday followed by strong squally SW winds and a burst of SW swell over 4 metres as far north as 28S. Avoid.

Low#2 is expected to travel northeast across central NZ on Thursday and Friday followed by a period of strong SW winds and a burst of SW swell over 4 metres as far north as 30S. Conditions easing Friday night/Saturday morning.

Best dates to depart/arrive is either Wednesday or Sunday 24 Sep.

 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

 

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

See my website http://www.metbob.com for more information

Feedback to bob@metbob.com or txt 6427 7762212

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com,

Click FOLLOW at bottom right to subscribe.

To unsubscribe, send a reply email saying LEAVE.

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

10 September 2017

Bob Blog 10 Sep 2017

WEATHERGRAM

YOTREPS

Compiled Sun 10 September 2017

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.

TROPICS

CAT 4 IRMA is damaging parts of Florida as I write this:

Some good news about Cyclone JOSE is that it is expected to do a loop and then stay offshore as it goes north.

KATIA has gone inland, and may end up off the west coast of central America.

Meanwhile over in Northwest pacific, TC TALIM is heading for Taiwan.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

This week, a thin SPCZ is expected to remain across the Coral Sea.  Part of it may visit Vanuatu/ Southern Fiji and Southern Tonga tonight, and then weaken.  A smaller convergence zone may form near 8 to 10S to north and east of Samoa.

A passing, mainly upper, trough, is expected to travel eastwards across Niue on local Monday night and Southern Cooks on local Wednesday, preceded by NE winds, accompanied by variable winds and showers, and followed by SE winds.

Another passing trough may reach New Caledonia area around Monday 18  Sep local.

 

Subtropical ridge (STR)

HIGH around 1022hPa is expected to move into North Tasman Sea on Monday and then spread east along around 25 to 30S this week reaching south of French Polynesia by end of week.

Another HIGH around 1024hPa is expected to spread from Australia into northern Tasman Sea on Friday.

And then spread along 25 to 30S over next few days.

These High should maintain reasonable trade winds for sailing across the South pacific this week

French Polynesia to the west:

The main obstacle this week is that travelling trough over Niue on local Monday and Rarotonga on local Wednesday.

 Apart from that this should be a god settled week with reasonably steady winds for sailing.

Between  NZ and the tropics:

On Monday and Tuesday, the SW winds and associated large swells over NZ around a LOW to east of the South Island should slowly ease as the Low moves away.

Next front from the Tasman Sea is likely to pass across NZ on Friday,

and then a deep Low may cross southern NZ on Mon/Tue 18/19 Sep.

 

There may be some gaps between these passing fronts with OK departure for arrival/departure.

If you would like more detail for your voyage, then check metbob.com to see what I offer.

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

See my website http://www.metbob.com for more information

Feedback to bob@metbob.com or txt 6427 7762212

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com,

Click FOLLOW at bottom right to subscribe.

To unsubscribe send a reply email saying LEAVE.

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

03 September 2017

Bob Blog 3 Sep 2017

WEATHERGRAM

YOTREPS

Compiled Sun 3 September 2017

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.

 

Last month

Sea Surface temperature anomalies may be seen at www.ospo.noaa.gov/data/sst/anomaly/2017/anomnight.8.31.2017.gif

There continues to be more yellow than blue, more area covered by warm anomalies than by cool anomalies.

And there is still a warm river appearing along east coast of South America.

The eddies of cooler than normal water along the Eastern Equatorial Pacific looks like symptom of LA NINA, but the surrounding warmer than normal seas dilute this.

To see how the annual weather cycle and the seasons are working out, look at the average isobar maps from www.esrl.noaa.gov/psd/map/images/fnl/slp_30b.fnl.html

 

In August, the subtropical ridge in the southern hemisphere lay in its normal seasonal latitudes between Fiji and NZ, with a disturbed westerly flow as far north as Bass strait to North Cape, somewhat further north than normal. Looking at the anomalies, we can see that wave 3 has been dominating proceedings, with HIGHS lingering in 3 places: South Atlantic and South Indian Oceans, and to SE of French Polynesia, and LOWS lingering in 3 places: over Chile, well south of South Africa, and over the Tasman Sea. Cyclonic northerly winds for NZ have been bringing a wet winter.

 

The wetter than normal conditions over northern NZ also show in the monthly rain map—but this map shows that peak anomaly has been to NE of NZ, and, when averaged over the whole month, is surprisingly near neutral over the NZ mainland.

 

Last 30 days of rainfall, and its anomaly, may be seen at trmm.gsfc.nasa.gov/trmm_rain/Events/thirty_day.html

The monthly rain map shows heaviest rainfall along equatorial area from Indian Ocean to Indonesia, with some heavy rain over India, Nepal and Bangladesh, and a spot of heavy rain over Houston, Texas… (Three days of epic rainfall looks minor when averaged over a month).  The anomaly map shows that the ITCZ is further north than normal--- this is a LA NINA trait, but it’s a real LOCAL La Nina.

 

TROPICS

Deluging rain from HARVEY brought damaging flooding to Houston.

The intensity of the rain in HARVEY was so much that NWS had to add a new colour to their rain map…

see www.youtube.com/watch?v=x28AcE5bxIo

And the intense monsoon continued in southeast Asia with a death toll of around 1,200 people, see www.theguardian.com/world/2017/aug/30/mumbai-paralysed-by-floods-as-india-and-region-hit-by-worst-monsoon-rains-in-years

 

This week, TC IRMA is in the Atlantic Ocean and model’s, at this stage, are suggesting that it might make landfall on North Carolina later this week.

And on the US west coast, TC LIDIA is expected to remain over the ocean put travel almost parallel to the coast.

And in the NW Pacific, remains of TC SANVU is fading as it approaches the Korean Peninsula, and a depression (MAWAR) is expected to make land fall to north of Hong Kong.

 

Last week’s rain map from trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif shows enhancements in the rain over SE Asia, along the equatorial Indian Ocean, about the south of Japan (due to SANVU), over Eastern Pacific in the ITCZ, and a hotspot near Houston.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

This week, the SPCZ is expected to remain near Solomon Islands to Tuvalu and occasionally affect Tokelau.

A passing, mainly upper, trough, is expected to travel eastwards across Niue on local Sunday night and Southern Cooks on local Tuesday, preceded by NE winds, accompanied by variable winds and showers, and followed by SE winds.

Another passing trough may reach New Caledonia area around Saturday9 Sep local.

 

Subtropical ridge (STR)

HIGH over 1034hPa is travelling east along 40S for the next few days well south of French Polynesia, and as it moves away the winds over French Polynesia should weaken and turn easterly then Northeasterly.

 

Another HIGH, around 1022hPa, in northern Tasman Sea on Monday is expected to travel east along 25 to 30S this week across the South Pacific. it should help maintain moderate SE trade winds.

 

French Polynesia to the west:

The main obstacle this week is that travelling trough over Niue on local Sunday and Rarotonga on local Tuesday.

 

Departing northern NZ to the north or east for the tropics:

On Monday, a low travelling off to east of NZ should bring SW flow to the northern north Island.

On Tuesday, there should be a passing ridge with lighter winds.

On Wednesday, the forecast is for an increasing NW winds ahead of an approaching trough.

On Thursday and Friday, expect squally west to WSW winds, and rough seas.

By Saturday night, a Low around 1002hpa is expected to travel across northern N., followed on Sunday and Monday by showery SW/S winds.

SO maybe this isn’t the week to come or go, unless you can time departure on Tuesday or arrival on early Saturday.

 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

 

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

See my website http://www.metbob.com for more information

Feedback to bob@metbob.com or txt 6427 7762212

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com,

Click FOLLOW at bottom right to subscribe.

To unsubscribe from WordPress: click the “unsubscribe” link on the bottom of the email.

Or, if email wasn’t from WordPress then send a reply email saying LEAVE.

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