Bob Blog 8 Dec 2019

WEATHERGRAM

YOTREPS

Compiled Sun 08 Dec 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 WEEK

A series of fronts with heavy rain and strong winds battered South and central NZ in the past week. The main cause of this “river of wind” has been the squash zone between and quasi-stationary HIGH east of NZ and a very deep (at times below 960 hPa) Low caught in an upper low so that it looped as shown in the weather map below for Sat 7 Dec. The red arrows track the Low back to 2 Nov.

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The HIGH managed to keep winds mostly light NW for yachts arriving in northern NZ from the tropics in the past week (except for last Tuesday night with a passing front).

The wild weather is expected to cross the North Island overnight tonight, then weaken away.

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The Tropics

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

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Active cyclones at present is AMBALI and BELNA in South Indian Ocean. AMBALI almost broke the Global record for central pressure drop , intensifying from cat 2 to borderline cat 5 in 24 hours. (PATRICIA holds the global record) . At one stage last week there were 5 tropical systems in the West Indian Ocean.

There is potential for cyclone formation showing in the Coral sea and about around Guam.

WATHER ZONES

Weather Zones (see text) as expected Wednesday 00UTC showing isobars, winds, waves(magenta) STR, and SPCZ. Pink area = lightning likely (high CAPE)

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SPCZ=South Pacific Convergence zone.

The SPCZ is expected to be active in the north Coral Sea and from Samoa to southern parts of French Polynesia, mainly stretching from Solomons, across northern Vanuatu to between Fiji and Samoa to Southern Cooks.

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Accumulated rainfall for next week from windyty.com (isobars are for Sunday night).

Subtropical ridge (STR)

HIGH east of NZ over 1025hPa is expected to finally move a little to the east on Monday a n d then hover around 40 to50S 150E until Sun 15 Dec.

Next High is expected to enter the Tasman Sea (from East Aus) on Monday and slowly spread east, reaching Northern NZ on Thu and Fri then further east on Sat and Sunday.

Tasman Sea /NZ/Aus

Trough crossing North island tonight, followed by SW S flow on Tuesday and Wednesday, the light winds from a passing high on Thursday /Friday. Next trough from the Tasman is expected over northern NZ on Sat/Sun/Mon 14/15/16Dec local followed by a SW flow for several days. .

For Noumea to Aus: With mainly High pressure in Tasman Sea this week it OK until Thursday. However, passing trof 1009 over Noumea this weekend/early next week.

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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 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

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