Bob Blog 29 Oct 2017

WEATHERGRAM

YOTREPS

Compiled Sun 29 October 2017

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.

SOUTH PACIFIC TROPICAL CYCLONE SEASON STARTS on WEDNESDAY

A good website for watching out for Tropical disturbances is

www.tropicaltidbits.com/storminfo/

This site combines information from a number of websites dedicated to watching tropical disturbances. When using it, remember that your insurance companies will mainly be interested in if you heed information that comes from the OFFICAL warning agencies, and in our part of the world that’s Fiji Met Service or NZ MetService (websites given in last weathergram) and, around Australia , the Bureau of Meteorology.

See www.bom.gov.au/qld/forecasts/cyclone.shtml for the Coral Sea region.

TROPICS

TC PHILIPPE formed over Cuba in the past day or so and is now heading northeast where it is likely to follow the Gulf Stream. This system may re-intensity into a mid-latitude system in a few days, thus have a stronger spin of wind around it and get deflected to the northwest and inland near New York. If so it has the potential to deepen to 970hPa and bring a northwest gale to Lake Ontario. Reminds me of Gordon Lightfoot’s ‘Wreck of the Edmund Fitzgerald “(in Lake Superior, 10 Nov 1975)) with lyrics: “When the gales of November come early”. http://www.youtube.com/watch?v=9vST6hVRj2A

clip_image002

In the NW Pacific TC SAOLA is forming over Micronesia near Guam and is expected to travel NW then N towards Japan.

clip_image004

From http://www.tropicaltidbits.com/storminfo/

Looking at the weekly rain maps from last week and the week before, we can see a burst of heavy rain in the past week around central America and Guam., and another near the central Pacific to the north of Hawaii. Intensity seems to be easing around India,  in the ITCZ across the North Pacific,  and in the SPCZ across the South Pacific.

clip_image006

clip_image008

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

WEATHER ZONES

clip_image010

Weather Zones (see text) as expected mid-week on Wednesday (GFS model) showing wind, isobars, current, lightning, Sig wave height purple lines, SPCZ and STR.

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stay where it is, from Solomon Islands  to northern Vanuatu to northern Fiji to between Samoa and northern Tonga to between Niue and Southern Cooks. Any voyage from Tahiti to Tonga will need to sail/motor thru the SPCZ and it is likely to breed several squally showers this week. Avoid.

Subtropical ridge (STR)

There is a Big Fat High (BFH) HIGH east of NZ from Monday to Thursday. This is being supported by a break in the normal upper level Jet Stream pattern, and is indicated by the mid atmosphere (500hPa level) wind map showing the shape of the Greek Capital Letter Omega, but upside down in the Southern Hemisphere.

clip_image012

Omega pattern on Wednesday from Windyty.com. Note how the left and right hooks are associate with surface lows. These lows are both redirected by the BFH.

So, this BFH is expected to BLOCK the troughs in the Tasman Sea this week and redirect them AROUND New Zealand rather than onto NZ.

For more about the Omega pattern see en.wikipedia.org/wiki/Block_(meteorology)

And for a blocking index in the Southern hemisphere see

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/blocking/real_time_sh/real_time_index_nrm.shtml

This site doesn’t show this block yet as it is still forming.

clip_image014

Tropical accumulated rainfall for next week from windyty.com

From Friday this block is expected to weaken, and the surface high should relax and move off to the northeast, allowing a new HIGH to travel east across Tasmania into the Tasman Sea from Saturday.

Between Tropics and NZ

There is a squash zone of strong east to NE winds between the BFH and the tropics.

Those departing from Fiji or New Caledonia to NZ should arrange their voyage so that they do not get near NZ until after Thursday.

This squash zone is expected to visit the Minerva/ South Tongan area from Tuesday to Thursday, so stay put for that.  Should be able to depart Tonga or Minerva from Friday, but may need to try and time your departure taking into account south to southwest winds near NZ.

The next trough to reach northern NZ is likely around 5 to 6 November.

Between New Caledonia and Australia

Looks ok for departure Noumea any day this week.

The trough crossing Brisbane on Monday is expected to deepen into a low in central Tasman Sea by Tuesday, but the BFH should push that off to the south so it just fades away on the Noumea to Brisbane route.

Next intense thundery trough is expected to reach Brisbane/Bundaberg area around late Mon 6 November or Tuesday 7 November, so avoid that as arrival date.

“I can’t control the wind but I can adjust the sail.”
― Ricky Skaggs

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

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

Feedback to bob@metbob.com or txt 6427 7762212

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com,

Click FOLLOW at bottom right to subscribe.

To unsubscribe from WordPress: click the “unsubscribe” link on the bottom of the email.

Or, if email wasn’t from WordPress then send a reply email saying LEAVE.

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

Advertisements