Bob Blog 6 May 2018

WEATHERGRAM

YOTREPS

Compiled Sun 06 May 2018

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.

ONE addition to last week’s Blog:

In French Polynesia: the PolyMagNet (Polynesian Magellan net) takes reports from vessels under way and is a good source for information exchange about anchorages, weather, services, events and activities. Twice daily on 8173 kHz at 18:00 and 4:00 UTC. Most of the 7 net controllers have been around French Polynesia for many years and have plenty of info to share with new arrivals.

 

Weather trend over the last month.

Sea Surface temperature anomalies as at end of April may be seen at www.ospo.noaa.gov/data/sst/anomaly/2018/anomnight.4.30.2018.gif

The SST anomaly image is now noticeably different from what it was at end of March.  With sea temperature sin the south Tasman Sea near normal, and the cool anomalies near the equatorial East Pacific much weaker than what they were.  In fact, some warm anomalies are starting to show near the Galapagos

The Gulf Stream off the east coast of North America continues to stand out as being much warmer than normal; this extra heat continues to energize storms over the northeast of North America into their spring.  Warm anomalies continue over much of the North Pacific, and that may be an indicator to a busy cyclone season there later this year.

During April there really was only one cyclone KENI which started near Vanuatu and peaked near Kadavu in southern Fiji. There was intense monsoonal rain over Fiji during the fortnight ahead of KENI, and the cyclone managed to take those clouds away. A full time-map of the season’s cyclones can be seen on wikipedia at en.wikipedia.org/wiki/2017%E2%80%9318_South_Pacific_cyclone_season

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

The averaged-isobar map shows that subtropical ridges are looking good in both hemispheres.  The anomalies show that the HIGHS which were affecting NZ have been replaced by lows. The 1015hP (between blue and white) isobar has retreated during the last month to a smaller area over the NZ region, and can be seen shifting northwards over Australia.

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

This rain map shows the “extra convergence zone” stretching from just south of Galapagos westwards to NW of Marquesas, but weaker than normal.  It also shows very dry conditions for the past month over northern Australia, and dry in Brazil.

 

 

TROPICS

The MJO oscillation is traveling across northern Australia this week, but is weak and not expected to do much.There is a weak tropical depression between Philippines and Micronesia and it is expected to shift off to the north this week.

 

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to remain close to where it was last week, with  its activity focused on a line stretching from Solomon Islands to Rotuma to Samoa to Southern Cooks.

Convection between Galapagos and Marquesas is expected to continue to weaken.   

Accumulated rainfall for next week from windyty.com.

 

Subtropical ridge (STR)

HIGH in the central Tasman Sea on Monday is expected to slowly travel is expected to slowly travel across northern NZ on Wed and Thursday, and then off to the northeast of NZ from Friday.  There is likely to be a squash zone of enhanced trade winds on the north side of this HIGH from Southern Cooks to Tonga early next week.

Around Tasman Sea

Deep Low from the Southern Ocean is expected to whip past southern NZ on Monday /Tuesday /Wednesday with strong westerly winds and large swells.

Another Low is expected to visit Tasmania on Thursday and then travel northeast into the central Tasman sea on Sunday and Monday. Avoid.

This Low should bring a S/SW wind change to the Southport to Noumea route on Sunday/Monday 13/14 May. The SE winds should return to the Noumea area by end of Tuesday 15 May, but it may be a few weeks before this pattern repeats, so this opportunity may be best on offer for a while for sailing from Southport to Noumea.

 

New Zealand to Tropics

Looks Ok for departures until Tuesday. After that, voyages going north  are likely to encounter northerly winds ahead of the next incoming trough by Friday.

New Zealand to French Polynesia

Light winds over northern NZ until Wednesday, and then northerly winds, which may be somewhat wet, but ok for sailing east.

 

Panama to Galapagos /Marquesas

For sailing from Panama, the upcoming week looks to be just light winds as far as 5North and then  SSW to SE winds.  Difficult.

From Galapagos area to Marquesas, departure can be any time this week. Best path for wind and current is to motor/sail to 4 South 95W, then sail to 7S 130W and then go direct

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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

I’m on Facebook at /www.facebook.com/metbobnz/

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

Weathergram with graphics is at metbob.wordpress.com.

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