Bob Blog 5 July 2020

 

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 Sun 5 July 2020

REVIEW OF THE LAST MONTH (June 2020)

Sea Surface temperature anomalies as at start of May can be seen at https://www.weatherzone.com.au/climate/indicator_sst.jsp?lt=global&lc=global&c=ssta

Early July (below)

Looking at the SST during the past few months we now see a weakening warm pool in the Indian Ocean/Tasman Sea/Fiji. This means there may be a NEGATIVE Indian Ocean Dipole is possible later this year over Australia with above-average winter/spring rainfall over parts of Southern Australia, perhaps—3 out of six models say a sort of yes.

According to BoM (Australia) that cooling sea in eastern equatorial Pacific is significant. ENSO (El Nino/southern Oscillation) is likely (around 50%) to bring a La Nina late winter or early spring.

La Nina tends to bring the subtropical ridge southwards.

SAM (Southern Annular Mode) is currently positive for a few weeks., keeping southerly outbreaks away.

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

Last month , there was a belt of low pressure near 40-50S from south of South Africa to the east of N and has gone south to 50-60S allowing the sub-tropical ridge to get as far as 50S, rather strange for winter.

Zooming into the NZ area, and comparing monthly anomalies from last month with now, shows that the subtropical ridge STR has strengthened

The 1020 line has shifted north a little in the Tasman Sea, allowing more fronts to get further north over NZ.

The Tropics

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

Tropical Depression 5 in the Atlantic is expected to move offshore. There are a few moderate patches of potential development especially west of central America, but these are not really expected to come to much. But stay wary.

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is active around Solomon Island, over northern Vanuatu, and Tuvalu/Tokelau/Samoa.

 A tropical trough should cross Fiji/Tonga on local Wednesday and Southern Cooks onlocal Thursday. and then go southeast.

 

Subtropical ridge (STR)

HIGH 1024-1026 to east of NZ moving off along 40-45S,

Next HIGH 1028 expects to cross Tasmania on Tuesday/Wednesday and then northeast across Tasma Sea onto on northern NZ on Friday/Sat/Sun.

Active front crossing North Island tonight/Monday. Another front/Low visits South Island on Tuesday followed by strong SW winds on Wednesday. Big swells in eastern Tasman Sea on Tuesday and Wednesday.

From Panama: Squally due to ITCZ, but some rare NW winds are likely around Panama this Monday/Tuesday followed by light winds for starters. Will need to go south at first and maybe then NW to handle SW winds SW winds as far as 90W. Some tropical features likely to form off west of central America, but not a bother on voyage to Marquesas.

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

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

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 txt 6427 7762212