Unprecedented Hurricane Tomas pounding the Lesser Antilles

By: Dr. Jeff Masters , 3:38 PM GMT on October 30, 2010

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Hurricane Tomas, an unprecedented Lesser Antilles hurricane for so late in the season, is bearing down on the islands of St. Lucia and St. Vincent with Category 1 winds of 75 mph. Recent radar imagery from the Martinique radar shows that Tomas is still in the organizing stage, with an eyewall that just closed off, and a weak area of echoes on the south side, due to modest wind shear of 10 knots caused by southerly upper-level winds. The Hurricane Hunters reported top surface winds in the northern eyewall near 75 mph. St.Lucia figures to get the worst blow from Tomas, as this island will experience the strong right-front quadrant of the storm--the north eyewall. Winds on the island were sustained at 46 mph, gusting to 67 mph, at 11am EDT. Winds at Barbados peaked at 37 mph, gusting to 56 mph, early this morning, and the pressure bottomed out at 994 mb. Satellite loops of Tomas show a large and well-organized Cape Verdes-type hurricane, with good upper level outflow on all sides except the south, and an impressive amount of heavy thunderstorm activity. This is a very dangerous hurricane that is just beginning to get going. You can follow the progress of Tomas through the islands today with our wundermap zoomed in on St. Lucia.


Figure 1. Morning radar image from the Martinique radar shows the eye of Tomas moving between the islands of St, Lucia to the north and St. Vincent and the Grenadines to the south. The southern portion of the eyewall had just closed off with this image. Image credit: Meteo France.

Intensity forecast for Tomas
Now that the eyewall of Tomas has completely closed off, a period of steady and possibly rapid intensification lasting until Sunday afternoon is likely. The intensification rate may then be slowed by an increasing flow of southwesterly upper-level winds, which are expected to bring dry air and a moderate 15 - 20 knots of wind shear to Tomas Sunday through Tuesday, according to the latest SHIPS model forecast. Shear is then expected to relent, allowing more intensification on Wednesday. Water temperatures are a record warm 29.5°C and the Tropical Cyclone Heat Potential--a measure of the total heat content of the ocean--is a very high 100 kJ/cm^2, which is very favorable for rapid intensification. I expect the Tomas will strengthen to a Category 3 or 4 hurricane by Wednesday.


Figure 2. Hurricane specialists Robbie Berg (background) and Dan Brown (foreground) discuss the latest data on Tomas last night at the National Hurricane Center.

Track forecast for Tomas
The computer models have come into better agreement this morning that after Tomas reaches the central Caribbean 4 - 5 days from now, a turn to the north or northeast is likely, in response to a strong trough of low pressure expected to develop over the Eastern U.S. The exact timing of this turn to the north or northeast is difficult to predict at this time, as steering currents will be weak in the Caribbean after Tomas passes through the Lesser Antilles today and Sunday. At this time, is appears that the Dominican Republic and Haiti are most at risk from a strike by Tomas, though the storm could move as far west as Jamaica, or as far east as the northern Lesser Antilles Islands.


Figure 3. Hurricane specialist Dan Brown computes Tomas' radius of tropical storm force winds using the old-fashioned paper track plot and dividers technique. Hurricane specialists at NHC commonly use a paper track plot to mark all storm center fixes and compute the current motion of the storm. A storm's current heading and speed in NHC advisories is usually a 12-hour average of the motion up until the final fix position.

Tomas, Shary, and the 2010 hurricane season in perspective
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 intensification of Shary and Tomas into hurricanes today brings the total number of hurricanes this season to twelve, tying 2010 with 1969 and 1887 for second place for most hurricanes in a season. The record is held by 2005 with fifteen hurricanes, and I don't think we'll beat that record this year!

The formation of Tomas 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 (61.5°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 61.5°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 61.5°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 a storm I flew into with the Hurricane Hunters--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. According to Chenoweth (2008), Tomas is the first tropical storm to cross through the Lesser Antilles Islands south of 16°N this late in the year since 1724. In that year, a tropical storm on 12 November crossed the islands at 13.7°N 61.5°W, and later became a hurricane that affected Jamaica. There was also a hurricane on 30 October 1671 that crossed 61.5°W at 13.3°N, and did damage on Barbados.

Another unusual aspect of Tomas' formation is that we now have two simultaneous hurricanes in the Atlantic Ocean on October 30. There has been only one hurricane season since 1851 that had had two simultaneous hurricanes later in the year--1932, when Hurricane Ten and Hurricane Eleven both existed November 7 - 10. Today is also the 5th latest date in the season that there have been two simultaneous named storms in the Atlantic. 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.

References
Chenoweth, M. and D. Divine (2008), "A document-based 318-year record of tropical cyclones in the Lesser Antilles, 1690-2007", Geochemistry, Geophysics, Geosystems, 9, doi:10.1029/2008GC002066.

Next update
I'll have more on Sunday by 3pm EDT. I'm headed home to Michigan today, after a very valuable week here at the National Hurricane Center. The experience gave me a new appreciatation for just how good the forecasters are at what they do. NHC's hurricane experts are truly world-class, and we are very fortunate to have such a talented group of hard-working forecasters keeping us informed on the dangers we face from Atlantic hurricanes.

Jeff Masters

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Quoting spathy:


Just a question about outflow.
The North / South orientation of directly moving West outflow would seem to me not to originate from a collapse of a circular system/cloud pattern.


I am not sure what you mean by "north/south orientation of directly moving west outflow."
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Quoting seflagamma:


Hi Dakster, Nope, my shutters are up all the time, I just have to pull them close when necessary. Accordians are ugly but so easy and convenient!

ALL the models have this storm making a very sharp turn north then northeast quickly and long before it gets west enough to affect us.
Why would we even think this will come this far west?
Do you know something I don't know? :o)


I don't have any inside info from mothernature. Just curious if you checking the house or not. For the moment I doubt that Tomas will threaten CONUS, but anything is possible. Hurricanes don't sign contracts on where they go.

Som neighbors were checking their shutters this morning and a co-worker WAS going to take his shutters down (He put his up when he went out of town when Nicole could have come our way) - but has now decided to wait until Tomas is no longer around. Why jinx it this late in the season, because you know if he took them down Tomas would go to Florida.

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Quoting MiamiHurricanes09:
It will be interesting to see if the convective cluster along the western semicircle wraps around the southern semicircle into the other large convective cluster along the eastern semicircle. The likely reason that Tomas is not intensifying quickly is because of the lack of closed eyewall...but if the convection were to wrap around the circulation, the development of a closed eyewall will come along easier and quicker.



Well, MH09, we all know it's coming. It is simply a matter of sooner or later. I was amazed when I looked at the structure and size of this system as it began spinning on Friday afternoon. This will not only reach major status but with it's size will probably be one of the fiercest storms this year with a much higher probability of a CONUS hit than any of the previous majors. I expect that by Wednesday we will have a much clearer projection of path as far as the US is concerned.
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I really hope Tomas keeps its warm tropical air-mass away from the southeast. That would ruin our chance of snow next week here in North Carolina.

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HurricanTomas's heading held*steady at (3.6degrees west of) WestNorthWest
H.Tomas's average speed moving between its last 2 reported positions remained ~14.3mph(~23.1km/h)
* The 0.1degree difference fits well within the rounding error
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
H.Thomas
30Oct 03pmGMT - 13.3n60.7w - 75mph(~120.7km/h) - - 993mb - NHC.Adv.#5

Copy&paste 10.0n55.3w, 10.8n56.8w, 11.1n57.5w, 11.6n57.6w, 12.2n58.4w-12.4n58.8w, 12.4n58.8w-12.9n59.5w, 12.9n59.5w-13.1n60.1w, 13.1n60.1w-13.3n60.7w, ccs, gbj, 13.3n60.7w-13.444n61.13w 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:
H.Tomas should now be passing ~4.2miles(~6.8kilometres)north of Fancy,St.Vincent

^ The westernmost line-segment is the straightline projection.
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Quoting Sfloridacat5:


Not based on the models. The models still indicate that Tomas will eventually be pulled Northward towards Haiti.


good news for the us bad news for hati
Member Since: September 8, 2010 Posts: 0 Comments: 1820
Quoting serialteg:


where can i see that? thanks

I'm not sure which type of imagery would show it, perhaps some 500-700 mb layers would show it. However here is a piece from the NHC supporting it
"UPPER-AIR DATA FROM SAN JUAN REVEALED 30-METER 500 MB HEIGHT
INCREASES DURING THE PAST 24 HOURS...WHICH CLEARLY INDICATES THAT
MID-LEVEL RIDGING TO THE NORTH OF TOMAS HAS STARTED AS THE
DEEP-LAYER TROUGH THAT HAS CAPTURED HURRICANE SHARY LIFTS RAPIDLY
TO THE NORTHEAST AWAY FROM THE CARIBBEAN REGION. LOW- TO MID-LEVEL
RIDGING IS FORECAST BY ALL OF THE GLOBAL MODELS TO CONTINUE
BUILDING WESTWARD ACROSS THE LESSER AND GREATER ANTILLES FOR THE
NEXT 72-96 HOURS."
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting weatherlover94:


then that could mean a bigger threat to Cuba and the us??


Not based on the current models. The models still indicate that Tomas will eventually be pulled Northward towards Haiti.
Member Since: September 16, 2007 Posts: 0 Comments: 4805
Quoting Sfloridacat5:


Looks like it sits and stalls out over the central Caribbean and then moves straight north.


then that could mean a bigger threat to Cuba and the us??
Member Since: September 8, 2010 Posts: 0 Comments: 1820
Good morning all.

Tropical Tidbit for Saturday, October 30th, with Video
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Quoting weatherwatcher12:

Mid level ridge north of the Greater Antilles.


where can i see that? thanks
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124. unf97
Quoting mgreen91:
Is there a chance that Tomas can hit the US?


I am fairly confident that the chances of it affecting the Continental U.S. are "extremely" slim.

A trough currently over the West Coast of the U.S. will deepen and move east and later dig southeast all the way down through the GOM to the NW Carribean by latter part of this upcoming week. That will place a huge wall in front of Tomas and I expect the cyclone to turn poleward or northeastward on its approach SE of Jamaica either on Wednesday or Wednesday evening. Bad news for Haiti should this manifest, and the SE Bahamas. But, I am confidently optimistic that Florida will not be impacted by Tomas.
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Quoting Dakster:


Putting your shutters up?


Hi Dakster, Nope, my shutters are up all the time, I just have to pull them close when necessary. Accordians are ugly but so easy and convenient!

ALL the models have this storm making a very sharp turn north then northeast quickly and long before it gets west enough to affect us.
Why would we even think this will come this far west?
Do you know something I don't know? :o)
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Quoting weatherlover94:


i dont think the 12Z GFS is showing that any more its not completely loaded up yet but from what i can tell right now it may not go north


Looks like it sits and stalls out over the central Caribbean and then moves straight north.
Member Since: September 16, 2007 Posts: 0 Comments: 4805
Quoting serialteg:
the lack of steering westward for a strengthening hurricane confuses me when i see the nhc plot and what steering is supposed to mean... if i climb mb's in the steering layers there is still what we call weakness far and wide to the N... then why forecast it to go so WNW?

Mid level ridge north of the Greater Antilles.
Member Since: May 16, 2009 Posts: 1 Comments: 1231
It will be interesting to see if the convective cluster along the western semicircle wraps around the southern semicircle into the other large convective cluster along the eastern semicircle. The likely reason that Tomas is not intensifying quickly is because of the lack of closed eyewall...but if the convection were to wrap around the circulation, the development of a closed eyewall will come along easier and quicker.

Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting weatherlover94:


i dont think the 12Z GFS is showing that any more its not completely loaded up yet but from what i can tell right now it may not go north


thats what i dont get
but wont be the first time this season that happens tho

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117. SLU
Quoting largeeyes:
A lot of St. Lucia is elevated, so winds in many places will be higher than if it was a much lower Island.


Yes that's right, most of the land is over 1000ft so that's why gusts to 115mph are very real.
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Quoting weatherlover94:


i dont think the 12Z GFS is showing that any more its not completely loaded up yet but from what i can tell right now it may not go north

It all depends on the trough off the western US coast.
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Wouldn't want to be on the Pitons right now...
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if the high pressure sets up over this storm tomas could track into the w. caribbean.


Link
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the lack of steering westward for a strengthening hurricane confuses me when i see the nhc plot and what steering is supposed to mean... if i climb mb's in the steering layers there is still what we call weakness far and wide to the N... then why forecast it to go so WNW?
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Quoting Relix:


They will wait for further verification of this happening.


i dont think the 12Z GFS is showing that any more its not completely loaded up yet but from what i can tell right now it may not go north
Member Since: September 8, 2010 Posts: 0 Comments: 1820
Quoting seflagamma:


Hi Nea, I hate giving you Kudos, (LOL J/K) but if I remember correctly.. you called this one as it came off Africa weeks ago when everyone else said it was too close to equator to develop...
is that correct or am I giving you credit for something someone else said???
I think it was you and if so.. great call!
Gams


Hi everyone,
will try to check in and out today as I can..very busy at work...




Putting your shutters up?
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Quoting cat5hurricane:

Interaction with the rugged terrain of the inland? Some of those peaks supposedly are 1300 meters.
The islands are way too small to cause that large of a downdraft and convective wane. Dry air intrusion into the western and southern semicircles is the most likely cause. I will like to add that once it mixes out the dry air and established a closed eyewall, rapid intensification is likely to commence. Like TerraNove pointed out earlier, Tomas looks rather similar to Earl right before it underwent rapid intensification.

Member Since: September 2, 2009 Posts: 130 Comments: 21032
Is there a chance that Tomas can hit the US?
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107. unf97
Quoting CybrTeddy:


Minor dry air intrusion, the system is filtering the dry air out. Fairly disorganized, but I suspect it'll change pretty soon.


Once Tomas moves away from the Windward Islands later tonight and gets over the open waters of the Eastern Caribbean, I expect the cyclone to begin to tighten its inner core and steadily intensify. Conditions up to the next 36 hours look very favorable for him to intensify.
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106. SLU
Quoting largeeyes:



Good to hear from you! Been asking about you...be safe!


Thanks man. I'm in Trinidad now undertaking some studies so I don't have the time for chat on the blog these days.

Good to hear from you too.
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105. Relix
Quoting weatherlover94:
who thinks this thing will turn north like twc is saying? the nhc is not saying any thing about a turn north over hati


They will wait for further verification of this happening.
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A lot of St. Lucia is elevated, so winds in many places will be higher than if it was a much lower Island.
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Complete Update



AOI
AOI AOI AOI

AOI AOI AOI

TS BUSTED FORECAST ALIBI
Member Since: October 1, 2007 Posts: 81 Comments: 26493
Quoting katadman:
Thanks for the info, weatherwatcher.

I noticed that the ensemble models are not posted for Tomas on WU. Have they not come out yet?

No problem. If you are looking for the latest dynamic models, here they are:
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Infrared satellite imagery reveals that the convection along the western quadrant is beginning to warm.
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spin behind thomas...
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Quoting Neapolitan:
"I expect that Tomas will strengthen to a Category 3 or 4 hurricane by Wednesday."

Incredible...


Hi Nea, I hate giving you Kudos, (LOL J/K) but if I remember correctly.. you called this one as it came off Africa weeks ago when everyone else said it was too close to equator to develop...
is that correct or am I giving you credit for something someone else said???
I think it was you and if so.. great call!
Gams


Hi everyone,
will try to check in and out today as I can..very busy at work...


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who thinks this thing will turn north like twc is saying? the nhc is not saying any thing about a turn north over hati
Member Since: September 8, 2010 Posts: 0 Comments: 1820
Quoting reedzone:


TWC didn't even recognize Tomas 24 hours ago, said everything was quite in the tropics, why believe them now?




never believe the weather channel now.....nbc bought them and they are lying and covering up the truth in the news just like nbc and general electric have always done. their socialist push to destroy free enterprise in america along with obama is underway and just like the soviets did with their media, these idiots at nbc are lying to cause "tranquility" in america. they want tranquility and lies while they try to tear america apart at it's foundation.

take my advice or don't, you will find that media matters and soros are in bed with general electric, and they have been for years.
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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.