Bob Blog 6 Sep

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 6  Sep 2020

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REVIEW OF THE LAST MONTH (August 2020)

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

A noticeable cooling of SST along eastern Pacific Equatorial zone, A sign that we are likely to have a La Nina. Soon, and this tends to bring the southern hemisphere’s subtropical ridge southwards, especially in the South Pacific.

The North pacific and Atlantic have warmed between 30 and 50N but this may be seasonal.

 

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 monsoon is much like last month. The northern hemisphere sub-tropical ridge has weekend and the southern hemisphere subtropical ridge is in much the same place, has shrunk a little, but for the High near western South America has intensified.

 

Zooming into the NZ area, and comparing monthly anomalies from last month with now, shows that the sub-tropical ridge has shifted north over NZ (as per a normal July), but strangely has intensified over Australia.

The 1015 line over NZ has shifted north, allowing more fronts to spread north over NZ.

The 1025 over Australia has weakened but the High near the Andes has intensified.

The Antarctic high has also intensified.

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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

MAYSAK last week affected Japan and South Korea and sunk a cattle ship .

HAISHEN follows , possibly stronger.

JULIO is moving offshore from west Mexico.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

SPCZ is moderate and in two bits, one from Solomon islands to Vanuatu to south of Fiji, t’other over Tuvalu to Samoa, briefly Tonga.

Passing trough over Fiji/Tonga mid-week, turning into a Low that goes Southeast.

 

Subtropical ridge (STR)

HIGH 1034hPa in Tasma Sea Monday travels onto central NZ 1028hPa on Tue/Wed then goes off to east.

Next HIGH expected to cross Tasmania on Thu 1032hPa , then ENE to Northern NZ 1022hPa by Sunday.

 

Tasman troughs

Trough is crossing NZ North Island tonight.

Next Tasman trough is expected to reach NZ South Island on Wednesday, lingering on Thu and developing into a Low over northern NZ on Friday, moving off to east on Sat.

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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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