Bobgram

WEATHERGRAM

YOTREPS

Compiled Sun 3 March  2019

 

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.

 

REVIEW of FEBRUARY

Sea Surface temperature anomalies as at start of this month may be seen at www.weatherzone.com.au/climate/indicator_sst.jsp?lt=global&lc=global&c=ssta

The eastern equatorial Pacific around Galapagos is the focal region for ENSO and the warm area there seems to have expanded in the past month. The other main change during February is that seas between Japan and Philippines and along the China Sea have become warmer than normal. Also, the South Indian Ocean. The Tasman Sea warm area has weakened a little, and extended to the northeast of NZ. And the Southern Ocean is showing a lot of melt water, which is cooler than normal.

 

To see how the annual weather cycle and the seasons are working out, check the average isobar maps from

www.esrl.noaa.gov/psd/map/images/fnl/slp_30b.fnl.html

The subtropical ridge in the southern hemisphere reaches its annual southern-most position in February and early March. It is stronger than normal from Indian Ocean and across Tasman Sea and to east of NZ.

The tropical South Pacific was affected by a strong MJO and a monsoonal trough, and this shows as low-pressure anomalies.

The low-pressure anomalies around the Arctic is related to the Polar vortex. Note that there is a large anomalous HIGH around the Antarctic.

Zooming into the NZ area, and comparing February with January shows that to north of NZ, the 1010hP (between light blue and dark blue) isobar is in much the same place, but further north the isobars in the tropics significantly lowered during February.

To the south of NZ, the 1010 line has shifted form near 45South to near 50South.

 

The rain during February can be seen at trmm.gsfc.nasa.gov/trmm_rain/Events/thirty_day.html

This shows that during the past month, Vanuatu and Kiribati/Tuvalu were the wettest areas and (after the flooding in late Jan over norther Queensland), Northern Australia to the Philippines was much drier than normal.

 

THE TROPICS

Latest cyclone activity as at tropic.ssec.wisc.edu and TCFP tropical Cyclone Formation Potential as seen at

www.ssd.noaa.gov/PS/TROP/TCFP/index.html

TC WUTIP reached Cat 5 over open sea, but is now fading and recurving to the north.

TC HALEH has formed over South Indian Ocean,

This indicates that the MJO wave of increased activity is now in the Indian Ocean, and that the South Pacific can expect a relatively quiet time over the next two to three weeks (afte ra month of activity).

 

The weekly rain maps for the past 2 weeks clearly shows the slow path of TC OMA, WUTIP and POLA.

See trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

OMA and POLA have taken a lot of energy/moisture from the SPCZ and it is now weakening at 15 to 20S between Samoa and French Polynesia, and slowly redeveloping between equator and 7 South. The trade winds are back across the South pacific, so it is a good week to do some island hopping (westwards). As good as it gets in March, so if you have been waiting, then this is the week.

 

Subtropical ridge (STR)

HIGH travelling eastwards across North Island on Monday and then to east of NZ

Next HIGH is likely to travel eastwards across Tasmania around Thursday and around southern NZ on Sat/Sun.

 

Australia/Tasman Sea / New Zealand

Trough is expected to travel eastwards across New South Wales on Wednesday and then across Tasman sea. Its front should cross Northland on Saturday.

 

Panama to Marquesas

Light northerly winds for starters around Panama last week, but the forecast is for more useful northerly winds from local Tuesday to Friday. There is a good west-going north of Galapagos.

Then go SE to 5S 100W, to avoid the building “mirror convergence zone” along around 3 south, This CZ grows due to the sun being directly overhead these latitudes at this time of the year (reaches equator on 21st/Equinox)

 

Port Vallarta to Marquesas

There may light winds for starters over next few days, but a good northerly flow is likely for a start around 11 March, perhaps. Weak ITCZ likely between 5N and 2N, and then a “mirror CZ” near 3 to 4S

 

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

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Weathergram archive (with translator) is at weathergram.blogspot.co.nz.

Contact is bob@metbob.com or txt 6427 7762212

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