Strengthening Tomas headed for the Lesser Antilles

By: Dr. Jeff Masters , 1:27 AM GMT on October 30, 2010

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Tropical Storm Tomas has exploded into existence in spectacular fashion, becoming the nineteenth named storm of this amazingly active 2010 Atlantic hurricane season. I'm reporting to you live from the National Hurricane Center tonight, where forecasters are working hard to stay abreast of Tomas' intensification. Three hurricane specialists are on duty tonight--Dave Roberts, who is handling Tropical Storm Shary, and Robbie Berg and Dan Brown, who are focusing on Tomas. The Hurricane Hunters have just left Tomas, as of 8pm EDT, and they found a significant increase in winds. Winds at their 1500 foot flight level were 70 mph, and surface winds as measured by the SFMR instrument were near 60 mph. This supports an increase in Tomas' winds to 60 mph in tonight's 8pm EDT public advisory. Since this is such a large increase in intensity from what was forecast--Tomas was not supposed to have 60 mph winds for another 24 hours--this necessitates issuance of a special advisory package. A full set of forecast maps, a marine advisory, wind probability forecast, and a discussion just went out to the world. While all this was occurring, several phone calls to Barbados, St. Lucia, and Martinique were made, alerting the islands to the fact that a Hurricane Warning may be required with the 11pm advisory tonight. NHC has both French speaking and Spanish speaking meteorologists on staff that can coordinate with the islands that don't have English as their main language. I listened in on a 5-minute conversation in French between the weather service in Martinique and NHC meteorologist Mike Tichacek, as they discussed when Martinique may want to issue a Hurricane Warning.


Figure 1. Warren VonWerne (right) of CARCAH presents the latest data from the Air Force Hurricane Hunters to hurricane specialist Robbie Berg.

Intensity forecast for Tomas
The forecasters at NHC are puzzling over the latest intensity forecasts for Tomas. The latest intensity forecast from the GFDL, HWRF, and SHIPS models are not that impressive, and they keep Tomas as a strong tropical storm or weak hurricane for the next five days. The wind shear forecast from SHIPS is particularly odd--the latest 18Z forecast predicts high wind shear of 20+ knots beginning Sunday morning, and the previous SHIPS forecast held wind shear below 15 knots for the next five days. The latest runs by the GFS, ECMWF, and UKMET models all show a very favorable environment for intensification over the next five days over the Caribbean, with Tomas positioning itself beneath an upper level high in a light wind shear environment. The best bet is that Tomas will intensify into a major hurricane over the Central Caribbean by early next week.


Figure 2. NHC meteorologist Mike Tichacek discusses the latest intensity forecast for Tomas with the Martinique weather service (in French.) In the background, hurricane specialist Dave Roberts works on advisories for Tropical Storm Shary.

Track forecast for Tomas
After Tomas reaches the central Caribbean 4 - 6 days from now, there are two possible track scenarios depicted by the models--a continued westerly motion towards Nicaragua, or a sharp turn to the north, with a track over Hispaniola or Puerto Rico. Steering currents will be weak, and we'll just have to wait and see how the steering currents evolve.

Tomas' formation location unprecedented this late in the season
Tomas' formation ties 2010 with 1995 and 1887 for 3rd place for most number of named storms in an Atlantic hurricane season. Only 2005 (28 named storms) and 1933 (21 named storms) were busier. Atlantic hurricane records go back to 1851, though there were likely many missed named storms prior to the beginning of satellite coverage in the mid-1960s.

The formation of a tropical storm so far south and east this late in the season is unprecedented in the historical record; no named storm has ever been present east of the Lesser Antilles (60°W) and south of 12°N latitude so late in the year. Hurricane Six of 1896 came close--it was also a tropical storm south of 12°N and east of 60°W on October 29, but nine hours earlier in the day. That storm recurved to the north and missed the Lesser Antilles. Tomas' track through the southern Lesser Antilles so late in the year is unprecedented. There have been only two other tropical storms that formed after October 15 south of 12°N and east of 60°W: Hurricane Jose, which was a tropical storm in that region on October 18, 1999, and Tropical Storm Nicolas, on October 16, 2003. Tomas most reminds me of Hurricane Joan of 1988, which was a tropical storm on October 14 near Tomas' current location, and later strengthened into a Category 4 hurricane that hit Nicaragua.

Another unusual aspect of Tomas' formation is that we now have two simultaneous named storms in the Atlantic Ocean on October 29. There have been only four hurricane seasons since 1851 that have had two simultaneous named storms later in the year. The record was set way back in 1887, when Hurricane Eighteen and Tropical Storm Nineteen were both active on December 8. There were three years that had simultaneous November named storms: 1932, 1961, and 2001.

Next update
I'll have more late Saturday morning.

Jeff Masters

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Some people here need glasses.

http://www.meteo.fr/temps/domtom/antilles/pack-public/animation/animMOSAIC2.html


Radar again......:rolleyes.jpg:
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Vortex Plotted... due west

Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting kmanislander:


The dropsonde in your google image is off the SW corner of Barbados
URNT12 KNHC 301301
VORTEX DATA MESSAGE AL212010
A. 30/12:31:30Z
B. 13 deg 07 min N
060 deg 12 min W
C. 700 mb 3044 m
D. 65 kt
E. 056 deg 18 nm
F. 143 deg 62 kt
G. 052 deg 28 nm
H. EXTRAP 995 mb
I. 9 C / 3047 m
J. 12 C / 3047 m
K. 2 C / NA
L. RAGGED
M. C50
N. 12345 / 7
O. 0.02 / 1 nm
P. AF300 0221A TOMAS OB 10
MAX FL WIND 66 KT E QUAD 11:47:10Z
SLP EXTRAP FROM DROPSONDE
NOT A SOLID EYEWALL FIXED CTR NEAR END OF A SPIRAL IN THE EYE AREA
MAX SFC WINDS WELL WITHIN THE RADAR CENTER
SONDE RELEASED NEAR MAX SFMR WINDS RECORDED 72 KTS AT SFC
;



Hurricane ?
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Quoting CyclonicVoyage:
Models are still flopping around like a wounded whaoo on the deck.



Typical when you have a late season system. Trying to forecast the track more than 24 to 48 hours out becomes a real challenge.
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Quoting thebandman:
I will be leaving for St. Thomas on Thurs. Will Tomas impact my travel?
nah your good to go
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Quoting asdip:
Here in St Lucia, v.strong winds, trees and poles down, not looking good.

Hey, Stay safe please.
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Quoting kmanislander:


The dropsonde in your google image is off the SW corner of Barbados


The dropsonde/Observation reports are not displayed on the track, they are offset. The second Vortex run has not been plotted yet, but its due west.
Member Since: October 1, 2007 Posts: 81 Comments: 26511
I will be leaving for St. Thomas on Thurs. Will Tomas impact my travel?
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Models are still flopping around like a wounded whaoo on the deck.

Member Since: January 30, 2010 Posts: 0 Comments: 3259
Quoting kmanhurricaneman:
sorry didnt realise caps was on , my apologies.
Thanks
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Quoting Orcasystems:


Actually.. due west


The dropsonde in your google image is off the SW corner of Barbados
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sorry didnt realise caps was on , my apologies.
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LAte season buri anes are very hard to predict because the atmosphere is so dynamic. The ridge that is supposed to keep the Thomas south has not formed yet and the track is totally dependent on the depth and intensity of that ridge. Right now there is a trough north of Thomas that if it stalled he would go up into. Luckily for us islanders it's moving and not digging down enough.
But still dependingon that ridge the track may move north or south 150 miles or so. The GFS has had it all the way down over SA and allthe way to 16N on various runs over the last two days. It also appears there are competing upper level centers on IR but Thomas is intensifying anyway.

As a note limiting factor to intensification will bee DRY AIR that will be filling in to the north. But with all that hot water to draw on I can see a cat 3 especially if it takes the soutthern track
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Quoting kmanislander:


There you go. The center is right where I said it was, immediately to the SW of Barbados


Actually.. due west
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting kmanhurricaneman:
Link
CHECK RADAR
please quit shouting. My head is hurting.
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Link
SHORTWAVE IMAGERY
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The high over the GOM continues to press on to the East and the weakness in the steering caused by Shary is closing off quickly. The track of Tomas will respond to this by flattening out during the course of the next 18 hours to a more Westerly heading, say 280 to 290 degrees IMO.

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661. asdip
Here in St Lucia, v.strong winds, trees and poles down, not looking good.
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Link
CHECK RADAR
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Tomas looks to be going W or just N of W
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Quoting AussieStorm:

What does your untrained eye see on this RADAR loop?


Big! Nasty and, yep, a center. Poor Haiti. Almost has to get hit no matter where Tomas goes because of the size and Haiti is a permanent disaster zone even in years when they don't get a direct hit.
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It looks like St Vincent is going to be in the Southern half of the eye
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Quoting Orcasystems:




There you go. The center is right where I said it was, immediately to the SW of Barbados
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TropicalStormTomas's heading turned westward to (3.7degrees west of) WestNorthWest
from its previous heading of (8.9degrees west of) NorthWest
TS.Tomas's average speed moving between its last 2 reported positions decreased to ~14.3mph(~23.1km/h) from its previous travel speed of ~19.3mph(~31.1km/h)
TropicalDepression21
29Oct 12pmGMT - 10.0n55.3w - 30knots(~55.6km/h) - 1003mb - ATCF
TS.Thomas
29Oct 06pmGMT - 10.8n56.8w - 35knots(~64.8km/h) - - 998mb - ATCF
29Oct 09pmGMT - 11.1n57.5w - 40mph(~64.4km/h) - . - 998mb - NHC.Adv.#1
30Oct 12amGMT - 11.6n57.6w - 60mph(~96.6km/h) - . - 999mb - NHC.Adv.#2
30Oct 03amGMT - 12.2n58.4w - 65mph(~104.5km/h) - - 997mb - NHC.Adv.#3
30Oct 06amGMT - 12.4n58.8w - 65mph(~104.5km/h) - - 997mb - NHC.Adv.#3A
30Oct 09amGMT - 12.9n59.5w - 70mph(~112.7km/h) - - 994mb - NHC.Adv.#4
30Oct 12pmGMT - 13.1n60.1w - 70mph(~112.7km/h) - - 993mb - NHC.Adv.#4A

Copy&paste 10.0n55.3w, 10.8n56.8w, 11.1n57.5w, 11.6n57.6w-12.2n58.4w, 12.2n58.4w-12.4n58.8w, 12.4n58.8w-12.9n59.5w, 12.9n59.5w-13.1n60.1w, ccs, gbj, svd, 13.1n60.1w-13.442n61.13w into the GreatCircleMapper for a look at the headings and the distances traveled over the last 12^hours.

Using straightline projection upon the speed&heading averaged
over the 3hours spanning the last two reported positions:
~4hours from now to passing ~4.1miles(~6.7kilometres)north of Fancy,St.Vincent

^ The westernmost line-segment is the straightline projection.
Member Since: August 21, 2007 Posts: 0 Comments: 4860
AL, 21, 2010103012, 131N, 601W, 60, 993, TS
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Quoting CybrTeddy:



Bad link.


Put a www into the link
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Member Since: October 1, 2007 Posts: 81 Comments: 26511
For the directionally challenged

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Quoting kmanhurricaneman:
SOME PEOPLE ON THIS BLOGG HAVE NO IDEA ON COMPASS DIRECTIONS.

Looking at RADAR and also watching the HH'ers, Tomas is going slightly north of due west. hence, WNW.
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649. txjac
Nice analysis P451, very interesting. Thank you for presenting it in "layman's terms"
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SOME PEOPLE ON THIS BLOGG HAVE NO IDEA ON COMPASS DIRECTIONS.
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Good morning everyone

The wind flags in this image pretty much tell us where the center is. To me,I would say it is immediately to the SW of Barbados where they now have winds straight out of the South.

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I'm looking the radar also and is tracking WNW, ok.
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644. Gorty
Quoting AussieStorm:

What does your untrained eye see on this RADAR loop?


Much better but infrared Sat and normal Sat presntation doesnt look as good as the radar mainly at the center I am talking about. But based on reprts from tjose islands and the radar, I can see Tomas being Cat. 1 at 11:00 am. But he will take some time to get up to cat 3.
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Quoting P451:
I think Tomas' broad center is fooling us into thinking maybe he's tracking west. Seems to be a large wobbling center.

Tomas always had trouble caused a tight core presentation on color infared imagery. This appears no different. Radar shows a different story as does the reports out of Barbados.


Going WNW to me. this loop shows it also.
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i am looking at the radar and the coc is tracking west, ok!!!!
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Movement of Tomas, still W-NW, what's happening is that it's building an eye wall, it's strengthening.See this radar loop.

http://www.meteo.fr/temps/domtom/antilles/pack-public/animation/animMOSAIC2.html
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638. ackee
latest 8am model runs have shift again further South last run was further North and East
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Quoting Gorty:
To my untrianed eye, it seems like Tomas is not doing very good. He seems disorganized to me with a hard to find center.

What does your untrained eye see on this RADAR loop?
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keep posting them! mark my word it will shift because Tomas is going to slow down
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635. IKE
6Z GFDL...
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634. JRRP
Quoting kmanhurricaneman:
track chart will shift to the south, TOMAS is tracking west now.

really ?
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things sound bad in barbados, just lost thier PM and now hit by a cat 1 hurricane, hang in there barbados we are all praying for you.
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Quoting kmanhurricaneman:
Link
It does look to be more west for now.
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The way that Shary is hanging in there, increasing in intensity and riding the front reminds me of Vince from 2005 who did much the same thing over coldish water in the Eastern Atlantic. I seem to remember at the time there was commentary on a peculiar kind of tropical system that could do this over colder than average water and still intensify. Never heard any more on this though since.

Tomas is bad news I feel.....
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Link
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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