Bob Blog 1 Sep 2019

WEATHERGRAM

YOTREPS

 

Compiled Sun 01 September 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 THE LAST MONTH

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

The main pattern changes are the ribbon of cooler than normal sea around the Galapagos. There is also a return to near normal in the Tasman Sea and a cooling off western Australia (an continuation of the Positive Indian Dipole).

 

To see how the annual weather cycle and the seasons are working out, we can check the average isobar maps for past 30 days and their anomaly from www.esrl.noaa.gov/psd/map/images/fnl/slp_30b.fnl.html

The southern subtropical ridge is much the same as last month. The monsoonal trough is a little further east. The trough around NZ has got bigger.

Zooming into the NZ area, and comparing monthly anomalies for end of last month with now, shows that the subtropical ridge STR is in much the same place but slightly weaker than a month ago. The anomalous trough over NZ has stronger SW flow over NZ than a month ago.

 

THE TROPICS

The latest cyclone activity report is at tropic.ssec.wisc.edu and TCFP tropical Cyclone Formation Potential at www.ssd.noaa.gov/PS/TROP/TCFP/index.html

 

TC DORIAN is expected to hit Bahamas and then approach Florida, but may swing north and remain mainly offshore. For the latest see www.tropicaltidbits.com/storminfo/

 

There are several areas for potential development, especially around Bangla Desh, NW Pacific and west of Central America, --- as expected at this time of the year.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to hover over PNG and Solomon Islands, with another branch hovering around Tuvalu and Samoa.

Passing trough now crossing Tahiti is expected to be followed by a good SE flow on local Monday.

Passing trough, associated with Low approaching NZ, is expected to travel from New Caledonia today to Fiji on local Tuesday night to Tonga on local Wednesday night to Niue on local Wednesday night to Palmerston on local Thursday and then fade as it moves SE.

 

Subtropical ridge (STR)

Hight to E of NZ is traveling east along 30 to 35S and should hover to south of FP until end of the week.

There is a gap until the next high. It is expected to travel east into the Tasman Sea around Tuesday next week, but not before.

 

Tasman Sea /NZ/Aus

Low deepening in mid -N Tasman Sea on Monday SW flow is expected to travel SE across North Island on Tues/Wed/Thursday down to 990 hPa and then go south away from NZ deepening to 980hPa at 55S, followed by a SW flow. On Friday another Low may form in mid-N Tasman Sea and then travel east across North Island on Saturday. This may be followed by another Low on Monday.

Looks OK to sail from QLD to New Cal early this week in the winds following Monday’s low but no good from Thursday, from then OK for going from New Cal to QLD.

Sailing to NZ this week means skirting around several fronts.

 

Tahiti to Tonga

Looks Ok to depart from Monday this week, voyage is likely to encounter one passing trough, but should be able to skirt around it over the open sea.

 

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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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Contact is bob@metbob.com or txt 6427 7762212

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