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

27 March 2016

Bob Blog 27 March

WEATHERGRAM

YOTREPS

Issued 28 March 2016

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 El Nino index is relaxing over the past week, as seen at the www.farmonlineweather.com.au Climate site

And the seas are losing that storage of heat now.

So the weather pattern in the Pacific is slowly returning to normal.

At present the water surface is sliding downhill from east to west so there is a good west-going current.

Another factor to consider is the extra convergence zone which has been hovering along 3 to 5S between the Galapagos and Marquesas over the past few weeks. To see how this zone is likely to preform over the next week or so,

go to www.windyty.com and click on the Rain accumulation and set this to the next 10 days.

This extra convergence zone marks the north end of the SE trade winds, and there are only light winds between its north-end and the Intertropical convergence zone—-

these may be from the west, so are worth avoiding (wind versus current=choppy).

 

TROPICS :

AT present there is a tropical depression over the sea between South Africa and Madagascar this system is

expected to fade in a few days.

A rather weak tropical low is now lingering around the New Caledonia area and by next weekend, 2/3 April, this – or another feature that follows it—may start deepening over Fiji. 

SO avoid this part of the South pacific for the next week or two if you can.

The rain maps for the past week or two show an increase in activity around Madagascar and around New Caledonia as well as the ITCZ and the extra convergence zone in the South Pacific Ocean just south of the equator.

Rain for the past fortnight is at trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

Panama to Galapagos:

Light winds at present, however, an avenue of useful Northeast winds for this departure seems likely to appear

around Mon 4 April. Convection is mainly around 4 to 6N and mostly west of 85W so not much of a problem.

No real advantage this week in going via Isla Del Malpelo, so may as well follow the current to 4N 83W then go direct. This waypoint may vary, so email me if you’d like a tailored waypoint.

 

Travelling to Marquesas:

Light winds around Galapagos. There is a tail current just to north of the equator, but this is becoming random in strength and position—and there may be some near-equatorial westerly winds, so that would place head wind versus current = choppy and uncomfortable.

Better to dive to 6 south, south of the extra convergence zone, then go direct.

If a small low does form on this extra convergence zone then it may induce some strong SE winds as far south as 6 South, so be on the watch to avoid that.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

SPCZ is expected to spend this week regenerating across the Coral Sea/Fiji area.

A smaller branch should bring squally showers between Samoa and Southern Cooks.

That “extra” CZ near 5S between Galapagos and Marquesas is expected to linger for another week.

 

STR= Sub-tropical Ridge

New HIGH is expected to travel east across Tasmania on Monday and southern Tasman Sea on Tuesday and central NZ on Wednesday and then build as it travels off to the east along 40S.

There is expected to be a squash zone of enhanced easterly / NE winds on the north side /northwest side of this feature, especially next weekend as it travels off to the east of NZ.

 

For NZ and Tasman Sea

A weak trough is forecast to travel across the South Island on Tuesday, and then a HIGH should come from the west and go off to the east.

On the back end of that HIGH, a trough in the Tasman Sea is likely to bring some wind and rain to the north end of the country on Fri/Sat/Sun 1/2/3 April.

>>>>>>

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.

==============================================

22 March 2016

World Met Day

Today is WORLD MET DAY

 

See http://www.wmo.int/worldmetday/

 

The theme this year is

”Hotter. Drier. Wetter. Face the Future.”

 

The home page seems to be loading slowly today,

possibility due to loading,  so maybe try and check it tomorrow.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

21 March 2016

BobBlog 21 March 2016

WEATHERGRAM

YOTREPS

Issued 21 March 2016

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.

 

Welcome to the equinox as at 20 0430 UTC,

Followed by a Full moon = the Passover at  23 1202 UTC

and then an  apogee at 25 1417 UTC,

so EASTER (redemption anniversary) is 270000UTC

(well, maybe 270200UTC corrected to Jerusalem time.)

Enjoy.

 

I don’t have much time this week to say much,

 (been at www.WOMAD.co.nz then a drive back to Auckland and a few forecasts---- have all stolen my time)

 

so here it is, my comments this week are in audio on sailing the South Pacific over the next few months and have been recorded in an itunes audio file at

https://itunes.apple.com/us/podcast/slow-boat-sailing/id1084423845

(open episode 6-- may not be available in your region )

(of course you may listen to the other episodes too, thanks to LINUS WILSON).

 

 

The rain maps for the past week or two show an increase in activity in Indian Ocean and South Pacific. See

http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

>>>>>> 

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.

==============================================

You are on my weathergram list

Our mailing address is:

/\/\etBob

u5, 53 Hamilton Road

Herne Bay

Auckland, AK 1011

New Zealand

 

13 March 2016

Bob Blog 13 March 2016

WEATHERGRAM

YOTREPS

Issued 13 March 2016

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.

Next edition is likely to be postponed to Monday 21 March  I’m off to WOMAD  next weekend: http://metbob.us12.list-manage2.com/track/click?u=297f1d13c59cf6261733851cb&id=25ad564e0e&e=78b77fda36

 

How is El Nino doing?

The Southern Oscillation index is still well in the “pink”= El Nino range.

SOI may be seen at http://metbob.us12.list-manage.com/track/click?u=297f1d13c59cf6261733851cb&id=8ef5bedf6d&e=78b77fda36

 

The amount of heat stored in the target area is slowing easing now.  This event is lasting longer and got slightly stronger than the 1997/8 event (as measured looking at the NINO3.4 index) at

http://metbob.us12.list-manage.com/track/click?u=297f1d13c59cf6261733851cb&id=9ae65c7b2a&e=78b77fda36

Those of you travelling to Marquesas may have heard rumours of weaker than normal trade winds ---well over the past month, the data shows that along the equator the trade winds have actually been slightly STRONGER than normal. That’s good for you.  However the data also shows there have been a few “puddles of calm” near the Central American coast.  These can be a problem.

Wind averages and anomaly for past month may be seen at

http://metbob.us12.list-manage1.com/track/click?u=297f1d13c59cf6261733851cb&id=5df4120ac8&e=78b77fda36

This map also shows that there are really only three features that show up in the monthly average—(even WINSTON didn’t make much of a monthly mark) there’s an anomalous HIGH to NE of NZ, another in the North Atlantic, and a large anomalous LOW over the Aleutians.  These features may last long enough to impact on weather for the next fortnight.

The TOA data for yesterday does show a slight westerly anomaly along the equator—but only from 180 to 140W and not enough to cancel out the trade winds.

See http://metbob.us12.list-manage.com/track/click?u=297f1d13c59cf6261733851cb&id=e9ffbada6e&e=78b77fda36

 

The Tropics:

No tropical cyclone anywhere for now.  However there may be something brewing near North Australia in the Gulf of Carpentaria, and this feature may be able to jump into the Coral Sea by next weekend, and grow.

 

Last week I mentioned how the directly overhead sun tends to trigger an “extra convergence zone” that mirrors the ITCZ in the Pacific around the March Equinox.  This zone stands out clearly in the rain map for the past week.  It should weaken towards the end of the month (Overhead sun is to reach the equator on Sun 20 March UTC, a little earlier this year as a consequence of that leap day. BTW, next full moon, the Passover moon is on 23 March UTC, so Easter Sunday follows on 27March).

 

Rain for the past week can be seen at  http://metbob.us12.list-manage.com/track/click?u=297f1d13c59cf6261733851cb&id=d9af935609&e=78b77fda36

 

Panama to Galapagos:

There is an OK N/NE flow as far as 6N (weak at night) then a zone of light variable winds between 6 and 3N then light tail winds to Galapagos with a reasonable tail current. Convection is mainly at 5N and mostly west of 85W so not much of a problem.  No real advantage this week in going via Isla Del Malpelo, so may as well follow the current to 5deg 30min N 81W then go direct. This waypoint may vary, so email me if you’d like a tailored waypoint.

 

Travelling to Marquesas:

Light tail winds around Galapagos. Very strong tail current along the equator, but the obstacle this week is that extra equinoctial convergence zone.  To avoid it go to 6 or 7S and then go direct.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

SPCZ is expected to spend this week regenerating in the Coral Sea.  We should watch this area for if a low forms there early next week then then it may be on track to affect NZ Easter weather.

That “extra” CZ near 5S is expected to linger this week.  A week trough is crossing New Caledonia early this week and its rain is likely to be south of Fiji by mid-week and over Minerva by next of the week ,  moving east  thanks to upper westerly winds.

 

STR= Sub-tropical Ridge

High east of NZ at beginning of week is fading away.

New HIGH is expected to travel east across southern Tasman Sea on Monday and Tuesday around southern NZ on Wednesday and then to east of NZ along 45S for the remainder of the week.  There is expected to be a squash zone of enhanced easterly winds on the north side of this feature.

 

For NZ and Tasman Sea

Weak front on Monday/Tuesday/Wednesday between the outgoing high and the incoming High.  This front is expected to linger on as drizzly cloud stuck in the eastern Tasman Sea.   Next front is expected to make its way from South Tasman Sea on to Southern NZ this weekend 19/20 March, but may be kept off northern NZ until early next week by the back ridge of the High then east of NZ.  This scenario is likely to bring strong E/NE winds to northern NZ on 19/20 March.

>>>>>> 

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.

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.

==============================================

You are on my weathergram list

 

06 March 2016

BOB BLOG 6 March 2016

WEATHERGRAM

YOTREPS

Issued 6 March 2016

 

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.

 

February Weather maps

During February the averaged isobars show the Siberian high and the Aleutian low and the Bermuda High in their normal positions. The Highs in the Southern Hemisphere have been migratory, with average position of the subtropical ridge along 40S across the Australian Bight to east of central NZ, but closer to 30S in the South Indian ocean.

These may be seen at http://www.esrl.noaa.gov/psd/map/images/fnl/slp_30.fnl.anim.html

Looking at the variations from normal, we can see that the subtropical ridge in the southern hemisphere is stronger and further north than normal, especially around Western Australia. Since TC WINSTON has been bothering the South Pacific for most of February, it has left its mark on the anomaly map too. This anomalous low combines with an anomalous high east of NZ to produce an anomalous NE flow onto northern NZ -- this can be seen at

http://www.esrl.noaa.gov/psd/map/images/fnl/slp_30a.fnl.anim.html

 

Early March

During early March the sun is directly overhead 7S to 4S (a table of the daily changes in sun declination angle may be seen at http://www.wsanford.com/~wsanford/exo/sundials/DEC_Sun.html)

This tends to trigger an extra convergence zone in those latitudes between Galapagos and Marquesas. Some call it a mirror of the ITCZ that forms around the March equinox. This can be seen forming now (see http://wwlln.net/WWLLN_movies/Movie_of_Lightning_in_Americas_BIG.gif) and offers an obstacle to vessels travelling between Galapagos and Marquesas over next few weeks.

 

The Tropics:

No tropical cyclone anywhere at present.

The remains of WINSTON made landfall on the Queensland coast in Australian on Friday 4 March (local). It started as TD09F from Feb 8th, was named as TC Winston on Feb 11th, crossed Fiji as a Cat 5 on Feb 20th, was downgraded Feb 25th, and so has been an entity for 25 days. TC REWA holds the record for longest cyclone duration in South Pacific Dec 1993-Jan 1994 26 days. See https://www.facebook.com/metbobnz/ for track maps.

During March the likelihood of formation of a tropical cyclone in the South Pacific remains high, however over the next few weeks it is expected to ease. It will take a few weeks for the South pacific Convergence zone to replenish itself after WINSTON. Meteo France (New Caledonia) indicate this with a drop of the probability of a cyclone to low levels by mid-March. This can be seen at http://www.meteo.nc/nouvelle-caledonie/cyclone/phenomenes-en-cours

 

Rainfall in the tropics over the past week shows that the South Pacific Convergence zone has been strong near French Polynesia in the past week (thanks to the brief appearance of TC Yalo). It also shows the formation of the "extra" convergence zone between Marquesas and Galapagos.

As seen at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

Panama to Galapagos:

Light winds around Panama for the start this week. May be better to wait for more useful NE winds next week.

 

WEATHER ZONES

 

SPCZ=South Pacific Convergence zone.

SPCZ is expected to spend this week regenerating in the Coral Sea. There is still a part of it lying around Tuvalu and Samoa, and a developing extra zone north of 5S between 160W and 100W.

 

 

STR= Sub-tropical Ridge

HIGH to east of NZ is expected to travel east along 35/40S and form a zone of enhanced trade winds on its northern side between 20 and 30S.

HIGH travelling east across Tasman Sea is expected to linger and fade in northern Tasman Sea on Thursday.

Next HIGH is expected to travel east along 50S into south Tasman Sea on Thursday, shovelling colder southerly winds onto the South island. This HIGH is then expected to cross southern Z on Friday and build east of the South Island on Sat/Sun 12/13 March.

 

For NZ and Tasman Sea:

Weak front on Monday/Tuesday followed by SW wind change.

Stronger front over South Island on Wednesday and North Island on Thursday followed by colder southerlies, turning SE/E across northern NZ by Saturday.

Rain with these wind changes.

>>>>>> 

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.

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.

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