Bob Blog 5 Nov 2017
Posted on November 5, 2017
Compiled Sun 05 November 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 STARTED last WEDNESDAY
Now that season has started, New Caledonia Meteo are producing probability maps of TC Genesis /formation.
To see the latest go to
and click on the diagrams under the words
“Cliquez ci-dessous pour afficher les graphes “
and the maps open as a pop-up (will need a browser that allows pop ups).
OCTOBER IN REVIEW
Sea Surface temperature anomalies may be seen at www.ospo.noaa.gov/data/sst/anomaly/2017/anomg.11.2.2017.gif
There continues to be more yellow than blue, more area covered by warm anomalies than by cool anomalies, but the blue is getting darker where it matters – along the eastern Equatorial Pacific, and things are on track for us to have a brief La Nina around the turn of the year, ). And there is still a warm river appearing along east coast of South America. Out to South Atlantic.
To see how the annual weather cycle and the seasons are working out, here is a quick look at the average isobar maps from www.esrl.noaa.gov/psd/map/images/fnl/slp_30b.fnl.html
In October the isobars drifted southwards across New Zealand, pushing the SW winds and fronts of spring away, so that October was more like a regular November. This is consistent with the impact of a La Nina pattern, allowing the subtropical ridge to drift further south than its normal position. The anomaly map shows this has been happening in the South Pacific but not over South America or South Africa, so it’s a regional seasonal thing.
The anomaly rain map shows that the ITCZ is, in parts, further north than normal—this is a LA NINA trait.
Last 30 days of rainfall, and its anomaly, is seen at trmm.gsfc.nasa.gov/trmm_rain/Events/thirty_day.html
After a busy October, cyclone activity is finally slowing, with just TC DAMREY fading away over Asia.
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 Indonesia and the China Sea, and around Solomon islands and between Niue and South Cooks.
SPCZ=South Pacific Convergence zone.
The SPCZ is expected to stay from Solomon Islands to northern Vanuatu to northern Fiji, and hover around Samoa. The more active portion which has been lingering between Niue and Southern cooks is expected to travel onto French Polynesia late in the week.
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. So take care with this.
Subtropical ridge (STR)
The remains of last week’s bfh (big fat high) are travelling off to the east f NZ along 30S. They are being followed by a trough moving off to east of NZ on Monday. Also, on Monday a high briefly crosses the Tasman sea and northern NZ.
The NEXT High is expected to be a slow-moving one, taking its time from Friday 10 to wed 15 Nov to cross the central Tasman Sea and central NZ area. This HIGH should be useful for anyone planning a voyage crossing the Tasman Sea.
Between Tropics and NZ
A trough is expected to cross New Caledonia on Wednesday and then form a low east of Norfolk Island on Thursday that is expected to deepen as it travels SE across northern NZ on Friday 10/Sat 11 Nov.
Those planning a voyage to NZ should arrange to avoid that Low as it has the potential to deliver gale winds and rough seas. Maybe. SO, delay getting south of 30S until around Mon 13 or Tues 14 Nov, +/-.
Between New Caledonia and Australia
On Monday a Low is expected to deepen off New South wales to SW of Lord Howe. Then on Tuesday and Wednesday this low is expected to travel across the South Island bring wind, rain and cold to southern NZ.
Conditions in the central Tasman Sea should ease from Wednesday, but the low forming near Norfolk Island may delay a good voyage from Noumea until Thursday or Friday.
From Friday 10 Nov onwards there should be some good voyages from Noumea to Australia around that slow-moving High in the Tasman Sea.
Any fool can carry on, but a wise man knows how to shorten sail in time.
– Joseph Conrad
If you would like more detail for your voyage, then check metbob.com to see what I offer.
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