Translator

Bob McDavitt's ideas for sailing weather around the South pacific

19 November 2017

Bob Blog issued 19 nov 2017

WEATHERGRAM

YOTREPS

Compiled Sun 19 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.

 

For those of you who may be interested:  I’ve been invited to speak for an hour or so at 3pm Friday 24 Nov at the All Point Rally 2017 seminar being held by ICA in Opua.  I wonder what I should talk about-----

 

Some interesting photos of this month’s weather:

On Tuesday 7 November Bundaberg was hit by a passing heat trough with thunderstorms This visit was unusually windy, with wind gusts reaching 68 knots (image at metbob.wordpress.com courtesy of John Hembrow from the Downunder rally).

 

And I received an image from a yacht I’m forecasting for on its way across the equator towards Hawaii (Courtesy of Jono Wishart), taken at 11S 170W of a Brooks and Gatehouse monitor showing sea temperature of 35.3C where weather global model was forecasting sea temperature of 30C.   He says he has seem 35.8 since.

 

 

I’ve compiled a 3min 25sec video using windyty.com to show the development of that Low on Friday 17 November --- the one I referred to last week as “Something to avoid” and if you have access to good Internet you can view this at website  youtu.be/6_U-IRXZCVI

 

TROPICS

It has been busy around Vietnam recently, and Tropical Sytem KIROGI  is currently heading west across the South China Sea onto South East Asia, but should soon fade.

  

Looking at the weekly rain maps from last week trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif, and the week before, we can see some interesting bursts of rain in the Northern Hemisphere particularly in Bengal Sea, in North Pacific west of Hawaii, and from Cuba to central North Atlantic. There is also an increase in rain in the South Pacific Convergence Zone, especially from Coral Sea to Fiji/Tonga.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is hovering from Coral Sea to northern Vanuatu to northern Fiji at present, and is expected this week to drift south onto all of Vanuatu and Fiji and maybe onto parts of Tonga. These areas can expect some random squally downpours.   Another convergence zone, a continuation of the main zone, is expected to be draped from Tuvalu to south of Samoa to parts of Tahiti. 

 

Subtropical ridge (STR)

HIGH H1 in the south Tasman sea on Monday is expected to move towards central NZ by Wednesday and off to the east of NZ on Friday.   It may be a useful HIGH for anyway intending to cross the Tasman Sea

 Weak trough should cross southern NZ on Thursday/Friday and deepen into a Low and it travels off to the south on Sunday. Then another HIGH H2 is expected to travel northeast from the southern Tasman Sea onto central NZ by Tuesday 28 Nov.   These are good conditions from anyone planning to ail west-wards across Northern Tasman Sea.

 

Between Tropics and NZ

The Low to NE of NZ is already moving away, and today’s data shows it is followed by a week or more with High pressures dominating over NZ and thus easterly wind from tropics to NZ, so if anyone is still waiting to come south then this week is looking OK.

Winds may be variable near northern NZ from Fri 24 to Mon 27 Nov due to a passing trough.

Note that there may be a squash zone of strong SE winds on the northern side of the High over NZ from Tuesday to Thursday, near 20S.

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

The Sea is the last free place on earth

- Humphrey Bogart

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

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

I’m on Facebook at /www.facebook.com/metbobnz/

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 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.

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

12 November 2017

Bob Blog 12 Nov 2017

WEATHERGRAM

YOTREPS

Compiled Sun 12 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.

Correction to my Facebook entry last week: Tonga is NOT having Summer time this year .

 

The state of the ENSO = La Nina trend now showing

El Nino and La Nina are opposite ends of an identifiable tropical influence on our seasonal weather. La Nina brings cooler than normal seas along the equatorial eastern pacific, is associated with stronger than normal trade winds and shifts the subtropical ridge (and its jetstream) away from the equator. El Nino with its weaker than normal trade winds and warmer than normal seas draws the subtropical ridge closer to the equator. Their comings and goings can last several months, maybe over a year, and so their status can be used to forecast the weather for the coming season.

 

NOAA have declared this to now be a (weak) LA NINA event with a good chance of lasting next 3 to 6 months. See www.cleveland.com/weather/blog/index.ssf/2017/11/noaa_la_nina_underway_with_a_6.html

Bureau of Met, Australia, is on a LA NINA watch and says the La Nina remains possible, but the effect on Australia’s climate may be less than recent events.

Implications for NZ area in the next 6 weeks is that we should have an early start to summer, with anticyclones crossing the Tasman Sea and New Zealand mainland bringing periods of sunny weather and light winds. After New year, there may be periods of strong easterly winds over Northland. In the South Pacific, convergence zones should be further south than normal, and trade winds may be stronger than normal, especially along the equator.

 

The Atmosphere:

The main parameter we watch from the atmosphere is the Southern Oscillation Index SOI (30 day running mean) as it sums up the whole weather pattern over the South Pacific in one number. It is based on the standardized difference in the barometer readings between Tahiti and Darwin, in other words the placement of isobars on the weather map. When the SOI is more than plus one (standard deviation from its mean) for more than a month we call it a LA NINA event, and when it stays more than minus one we call it an EL NINO event.

Since August the SOI has been more than 0.5, and two weeks ago it was over the +1 threshold. In the past week it has relaxed a little. Weak La Nina is seen at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekly

(Note that in this graph on the vertical axis 10= 1 standard deviation).

 

The Ocean:

NINO3.4 is a region in the eastern equatorial Pacific Ocean that acts as a heat storage area during an El Nino, or becomes cooler than normal during a La Nina. This plays with the heat budget of the atmosphere and thus with the weather patterns.

At the farmonline web site we can see that since August there has been a cool trend for NONO3.4, and a few weeks ago the seas were almost 1-degree cooler than normal.

Weak La Nina is seen at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=nino34&p=monthly

 

The International Research Institute of the Climate Prediction Centre compiles data from several ENSO prediction models. The mid-October edition shows NINO3.4 temperature may keep dropping (a little) until JFM (Jan Feb Marc) 2018.   CPC/IRI predictions are at  iri.columbia.edu/our-expertise/climate/forecasts/enso/current/

 

TROPICS

It has been busy around Vietnam recently, and Tropical Storm HAIKUI is currently heading west across the South china Sea after visiting the Philippines, but should soon fade.

Looking at the weekly rain maps at trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif from last week and the week before, we can see a burst of heavy rain travelling east along the Indian ocean equatorial region towards Indonesia, and a burst of rain about Cuba (passing cyclone).

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stay from Solomon Islands to northern Vanuatu to Fiji. A Low is expected to form on this zone by Thursday between Vanuatu and Fiji by Thursday. This low is expected to deepen to around 1000 hPa near 27S 174E by Friday.

A secondary convergence zone is expected to hover from Samoa to Southern cooks.

Any voyage from Tahiti to Tonga will need to sail/motor thru this secondary zone —it has several weak spots, so this may be worthwhile with a little guidance.

 

Subtropical ridge (STR)

HIGH H1 in the south Tasman sea on Monday is expected to move towards central NZ by Thursday and off to the east of NZ on Friday. It may be a useful HIGH for anyway intending to cross the Tasman Sea

Weak trough should cross southern NZ on Thursday, followed by another HIGH H2 spreading slowly into South Tasman Sea from Friday to Sunday (19 Nov). This may be a useful pattern for anyone intending to cross the Tasman Sea next week.

 

Between Tropics and NZ

Models are picking LOW to form between Fiji and NZ and deepen on Friday with strong, maybe gale, easterly winds near 30 to 33S (a squash zone with H1). Something to avoid.

The Low is expected to move off to the east/southeast on Sat/Sun 18/19 Nov, or maybe early next week--- its future depends on sneaking in-between H1 and H2.

 

Between New Caledonia and Australia

H1 allows a good voyages from New Caledonia to Australia this week and H2 next week.

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

It is the set of the sails, not the direction of the wind, that determine which way we will go

- Jim Robin

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

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

I’m on Facebook at /www.facebook.com/metbobnz/

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 unsubscribe  send a reply email saying LEAVE.

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

 

05 November 2017

Bob Blog 5 Nov 2017

Bob Blog 5 Nov 2017

Posted on November 5, 2017

WEATHERGRAM

YOTREPS

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

www.meteo.nc/nouvelle-caledonie/cyclone/coin-des-experts

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

 

TROPICS

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.

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

 

WEATHER ZONES

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.

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.

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

 

 

Blog Archive