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

27 December 2015

Bob Blog 27 Dec 2015

WEATHERGRAM

YOTREPS

Issued 27 December 2015

 

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.

 

Tropical Cyclones

There is a MJO (Madden Julian Oscillation) episode travelling into the Pacific Ocean – this increases the activity in the South Pacific Convergence Zone SPCZ and thus the chance of tropical cyclone formation during the next week or so.

 

See http://www.bom.gov.au/climate/mjo/#tabs=MJO-phase and read at this web site  more about the MJO—the main oscillation worth watching during the cyclone season, and note how strong and steady the parameter is at present in its march around its phase diagram.

 

Also, there are some equatorial westerly winds over Kiribati, not good for the local fishing fleet as these winds blow into the harbours that have been built for shelter from the normal SE wind. When these westerly winds blow steadily they increase the amount of spin available on the SPCZ.

 

Interestingly, there is a burst of stronger than normal NE trade winds in the northern Pacific: so this means there is not much of a gap between winds from opposing directions near the equator. In fact the computer models are analysing this as a cyclone near the equator at 177E --- I can't remember seeing such a weather ever before,  and because of the division by sine(latitude) in the wind equation there is not expected to be any curvature in the flow at the equator.

 

Check the MSL analysis as shown on windyty.com showing near-equatorial westerly winds over Kiribati and strong NE trade winds in the northern hemisphere, meeting in and twirling around a cyclone near the equator.

 

There are NO tropical cyclones around at present, however this chance of cyclogenesis is HIGH around the Pacific this week and there are two areas of interest at present---

 

One is 91P near 12.6°S 176.8°W and it has 7 analogues that went all over the place (go to http://www.tropicaltidbits.com/storminfo/  for the images).

 

Another, 92P, is closer to the Coral Sea and only has 4 analogues, and one of those went round the Coral Sea in a wide circle.

 

A third is further west near the active monsoonal trough over Australia near 16.0°S 134.6°E—this system is near Gulf of Carpentaria and had an opportunity to turn into a cyclone during the last week, but is still smouldering away. It has 5 analogues.

 

And there is another possible spot further west to the NW of Australia at 12.8°S 92.2°E

 

AT present there is no watch being kept on that pseudo-low near EQ 177E, however the GFS model indicates that this system may deepen into gales near Majuro by 31 Dec—take care.

 

SO this coming week may get busy in the tropics. A good period to stay put "on holiday" and see in the New Year.

 

Here for your singing enjoyment in Thursday night this week are the words of one of the lesser known verses of "Olde Lang Syne"

 

As written by Robbie Burns:

 

We twa hae paidl'd in the burn,

frae morning sun till dine;

But seas between us braid hae roar'd

sin' auld lang syne.

 

Translation:

 

We two have paddled in the stream,

from morning sun till dine†;

But seas between us broad have roared

since auld lang syne.

 

With this goes my greetings to you for the transition from 2015 to 2016.

 

Weekly rain maps for the tropics over the past two weeks,  as seen at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif,

show intense rain last week over northern Australia (from 99P) and eastern USA.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to increase in activity from Solomons to Samoa/Tonga.

There is an increasing chance of cyclogenesis this and next week. Take care.

 

STR= Sub-tropical Ridge

The "Sydney-Hobart-2015-race-trough" roared thru as expected last night, and although not really a sustained gale it managed to cause enough damage to take out several of the yachts including WILD OATS. It is being followed quickly by a HIGH that is expected to  travel slowly across central Tasman Sea this week and glide across central NZ from Thursday 31 Dec to Sat 2 Jan, with a zone of enhanced easterly winds on its northern side affecting northern NZ.

 

For NZ and Tasman Sea

A deep low with pressure below 990hPa near 40S 170W on Monday has come from the tropics and is moving slowly south. It is blocking a HIGH over NZ for Monday and part of Tuesday, and is expected to delay and weaken the eastwards progression of the "Sydney-Hobart 2015 race trough" (which is now in the central Tasman Sea forming a secondary low). The remains of this trough are now expected to cross southern and central NZ late Tuesday and during Wednesday.

 

>>>>>> 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts– Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

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,  send a reply email saying LEAVE.

 

 

20 December 2015

BOB Blog 20 Dec 2015

WEATHERGRAM

YOTREPS

Issued 20 December 2015

 

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.

 

Summer Solstice is 17:48 NZDT on Tuesday 22 Dec.

It gets later in the year as we get closer to a leap year.

 

El Nino

This El Nino episode seems to be relaxing now.

 

Tropical Cyclones

Tropical cyclones are likely to form around the Australian coast during the next week or so, as picked by the Meteo France model

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

The weather models are not latching into anything specific at this stage,

and the most likely area is around the Gulf of Carpentaria and Queensland coast, so watch that area.

 

The Weekly rain maps show a continued easing of rain in the South Pacific.

They also show a concentration of rain around Indonesia and especially about the Philippines where a STATE OF CALAMITY has been declared. Half a metre of rain in a week.

See the Weekly rain signatures at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is rather weak and spread out mainly between 5 and 10S, with a finger stretching to Fiji.

There is expected to be a build-up of convection in the Coral Sea this week.

 

STR= Sub-tropical Ridge

High that is to NW of NZ on Monday should fade where it is as a front crosses the North Island on Tuesday.

Another HIGH is expected to cross Tasmania on Tuesday and then move towards central NZ for Friday/Saturday

(Christmas/Boxing days). The upper ridge is expected over NZ on 26/27, great for holiday weather, not so good for pasture.

 

For Sydney-Hobart 2015:

Strong hot northerly flow for a spinnaker start, nasty front on Sun 27th,

then there may be a SW wind change on back side of a developing low.

>>>>>>

 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website http://www.metbob.com for information on tailor-made

voyage forecasts– Feedback to bob@metbob.com. Tell anyone you like that

to subscribe they should email me.

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,  send a reply email saying LEAVE.

 

 

 

13 December 2015

Bob Blog 12 Dec 2015

WEATHERGRAM

YOTREPS

Issued 13 December 2015

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.

 

A wonderful occasion for Planet Earth (and there is no Planet B) —190 nations agree to the COP21 in Paris in 13 Dec 2015.  It’s good to be alive during such an historic occasion.

This day may indeed go down in history as being a turning point.  Good way to start the festive season. See http://tinyurl.com/zrnkfty for a FAQ about this.

To mark this occasion there is a very large storm affecting Aleutian Islands (you can see it at  windyty.com).

 

El Nino

There are signs in the data that this El Nino may have peaked, or at least plateaued The NINO 3.4 index which measures the warmth of the sea sin the target area dropped last week, and the SOI index (based on barometers in Darwin and Tahiti) seems to be relaxing.

Latest data can be seen at http://www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekly .

 

Tropical Cyclones

The 28th numbered storm of the northwest Pacific’s tropical cyclone season developed this week rapidly east of the Philippines.

MELOR should be just south of Manila by Wednesday. It marks the first time in recorded history that a named storm has dotted the Philippines region every month of a calendar year, from Mekkhala in January to Melor now.

There is also BOHALE in the south Indian Ocean

 

The Weekly rain maps show an easing of rain in the South Pacific.

They also show an interesting stream of continuous moisture stream from China across the Pacific Ocean to Washington state in USA.

These rain maps may be seen at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is rather weak and spread out between 5 and 15S from 180 to French Polynesia.

Another branch of the SPCZ seems to be redeveloping in the northern Coral Sea.

SO it looks like a relatively quiet week in the tropics this week.

 

STR= Sub-tropical Ridge

High that is SE of Tonga tonight should continue travelling east along 30 to 35S.

High that is in the north Tasman Sea tonight is expected to fade away where it is by Wednesday.

Another HIGH is expected to cross Tasmania on Monday and then travel NE across the Tasman Sea during the week and northern NZ on weekend of 19/20 Dec.

 

Over NZ/Tasman:

Disturbed west to southwest flow.

>>>>>> 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts–

Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

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,  send a reply email saying LEAVE.

 

 

06 December 2015

BOB Blog 6 Dec 2015

WEATHERGRAM

YOTREPS

Issued 06 December 2015

 

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.

 

The Chennai (India) floods death toll is over269, and the Cumbria (UK) flooding/wind death toll attributed to “Winter Storm Desmond” is 1, so far.

See  http://indianexpress.com/article/india/india-news-india/chennai-floods-rains-jayalalithaa-imd-reasons-rescue-news-updates/

 

The averaged isobar anomalies for November, as seen at  http://www.esrl.noaa.gov/psd/map/images/fnl/slp_30a.fnl.anim.html

show that the lowest lows have been in the Arctic, Southern Ocean near NZ,  the south Indian Ocean and off the Mexican west coast.

During the next month we can expect the low anomalies that are now near Mexico to drift south toward Tahiti.

 

Tropical Cyclones

There are currently no tropical cyclones around. However another tropical depression is being picked by GFS model to form near 5N 145W by mid-week.

There is expected to be an eastwards progression of active convection from the Indian Ocean into the Coral Sea region later this month,

and the likelihood of formation of a tropical cyclone in the week finishing 25 Dec may be seen from Meteo France at

http://www.meteo.nc/nouvelle- caledonie/cyclone/coin-des-experts (click on the three overlaid diagrams for the latest).

 

The Weekly rain maps, as seen at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif,

show rain concentrations in TUNI during the past two weeks, and a build up of rain in the Indian Ocean (and around Chennai).

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The main part of the SPCZ remains strong in activity and extends across Tuvalu/ Tokelau and Northern Cooks.

Another weaker convergence zone is lying along 15 to 17S from Vanuatu to Fiji.

 

STR= Sub-tropical Ridge

High is bending around south side of Tasmania tonight and expected to travel NE across the Tasman Sea this week and linger to north of NZ from Friday to Sunday.

 

Over NZ/Tasman:

Weakening front travelling off to north of NZ tonight followed by SW flow on Mon/Tues then a W to NW flow over the North Island for remainder of week. Next front is expected to travel onto North Island late Sunday 13 Dec, associated with a deepening low skirting southern NZ.

 

Travelling Tahiti to Marquesas.

The trough associated with the low that once was TC TUNI is expected to travel north across the Tuamotu region during next few days and weaken- This should bring SE/E winds between Tahiti and Marquesas until mid-week allowing a rare opportunity to sail this route.

 

Between Tropics and NZ:

The subtropical ridge is laying down a curtain of light winds along 25 to 30S.

Fronts over Northland are weak and seem to be arriving on late Sundays at present.

>>>>>> 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts– Feedback to bob@metbob.com.

Tell anyone you like that to subscribe they should email me.

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 send a reply email saying LEAVE.

 

 

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