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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193. JRRP
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192. unf97
Tha
Quoting Levi32:


Yeah not very likely when the trough reaches down to Belize lol.



Thanks levi for providing that map analysis. Yeah, as I explained earlier, that trough currently on the U.S. West Coast will move east and really dig southeastward deep down all the way to the NW Carribbean Sea by the end of the week. That definitely will be the wall that will bring Tomas to a screeching halt on its approach southeast of Jamaica sometime mid week. A trough that deep should pull Tomas more NE and that will take him more towards Haiti and the SE Bahamas as he turns out to sea into the Atlantic. A bad situation for hait should this materializes and God knows those folks just can't take any more disaster. My prayers to all in those areas who may see Tomas' fury. Hope everyone is preparing.


Also, that trough looks to bring our first really big significant cool down of the Fall season by week's end in the SE U.S. many areas in Northern and Central AL, North and Central GA and the Carolinas could see frost and even a first light freeze of the season.
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Deep convection building on the S side of the eyewall as of the latest frame.

Member Since: July 8, 2005 Posts: 259 Comments: 23892
Quoting Levi32:


Weather456 lives in St. Kitts, not St. Lucia.

I know, however that St Kitts and St Lucia islands are one nation..
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What's that blob behind Tomas to the south east?
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New blowup south of the center


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I hate only having Vortex plots :(
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting Jedkins01:


That is an irrational statement, you have the right to believe what you want, but the chances of a CONUS hit is extremely unlikely.

In meteorology, and science in general, you can never say never count anything out completely. However, to say Tomas has the highest risk of a CONUS hit then any other hurricane has had this year is just straight out wrong. It definitely has a lower chance than several hurricanes have had this year.


I stand corrected.
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Quoting Bordonaro:

A St Lucian met, possibly Weather 456 is jumping on the NHC for not declaring Tomas a TS earlier :O)!!!!


Weather456 lives in St. Kitts, not St. Lucia.
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Quoting weatherman12345:
no not in the beginning of November. It will recurve one way or
Another.


Hopefully not like Wilma... (I know Wilma wasn't a CV storm..)

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Quoting MiamiHurricanes09:
Something must have caused the downdrafts that resulted in the large lower-level outflow boundaries coming out of the western quadrant.


Yes. It is not hard to imagine that a circulation this large pulled in some less than perfectly moist air parcels.
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21L/H/T/C1
MARK
13.21n/60.53w


WEAKENING FLAG FLAG
Member Since: July 15, 2006 Posts: 170 Comments: 53553
Quoting katadman:


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.


That is an irrational statement, you have the right to believe what you want, but the chances of a CONUS hit is extremely unlikely.

In meteorology, and science in general, you can never say never count anything out completely. However, to say Tomas has the highest risk of a CONUS hit then any other hurricane has had this year is just straight out wrong. It definitely has a lower chance than several hurricanes have had this year.
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lots if houses damaged here in Barbados
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Quoting weatherlover94:


what about Florida? the us?


No threat to Florida.

The only potential impacts on the U.S. are if the storm phases with the trough up the eastern seaboard and merges into a nor'easter.
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Quoting cat5hurricane:

I like your answer better :)

A St Lucian met, possibly Weather 456 is jumping on the NHC for not declaring Tomas a TS earlier :O)!!!!
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Quoting weatherlover94:
poll time

how strong will Tomas be at 2 pm?

A: 80
B: 90
C:100
D: 110
E:no change in intensity...75


E.
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Quoting wunderkidcayman:
I don't buy the Northerly track that the models are showing I think the NHC track is correct and to go further west to Jamaica and the Cayman Islands then to Central Cuba the bahamas then out to sea


what about Florida? the us?
Member Since: September 8, 2010 Posts: 0 Comments: 2187
Quoting Jedkins01:


Just because Tomas isn't exploding into a category 5 doesn't mean anything is inhibiting it, do not be quick to jump to conclusions. This is a category 1 hurricane, what you are seeing is completely normal for an intensifying category 1, for it is only a category 1 hurricane. Plus, it has a 30 to 40 nmi wide eye as well.

There is no dry air whatsoever present anywhere near or within Tomas. Tomas is saturated entirely in high PWAT air.
Something must have caused the downdrafts that resulted in the large lower-level outflow boundaries coming out of the western quadrant. A cyclone's convection isn't just going to die without some other factor impeding upon it. The likely suspect is dry air intruding into the core and causing the lower-level outflow.
Member Since: September 2, 2009 Posts: 130 Comments: 21122
I don't buy the Northerly track that the models are showing I think the NHC track is correct and to go further west to Jamaica and the Cayman Islands then to Central Cuba the bahamas then out to sea
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Quoting weatherlover94:
poll time

how strong will Tomas be at 2 pm?

A: 80
B: 90
C:100
D: 110
E:no change in intensity...75

E. BUT not for long!!!
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Quoting spathy:

My terminology is awful.
The down draft outflow to the West of Tomas is moving west.
The line of outflow seems to all be moving West in a linear pattern.
Not moving outward from a central point.
Not a circular radiation,but a linear movement.
Edit
Would that suggest an origin of outflow much farther from Tomas center?


There are downdraft outflow boundaries in the northwest quadrant too if you look towards St. Kitts and Barbuda, and they are all moving outward.

These simply mean that there is some dry air having to get mixed out on the western side of the storm, and is likely messing with the core a little bit, but that is common with a very large developing system and it will just take a little bit of time for Tomas to get rid of it and organize a solid core.



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poll time

how strong will Tomas be at 2 pm?

A: 80
B: 90
C:100
D: 110
E:no change in intensity...75
Member Since: September 8, 2010 Posts: 0 Comments: 2187

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Quoting MiamiHurricanes09:
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.



Just because Tomas isn't exploding into a category 5 doesn't mean anything is inhibiting it, do not be quick to jump to conclusions. This is a category 1 hurricane, what you are seeing is completely normal for an intensifying category 1, for it is only a category 1 hurricane. Plus, it has a 30 to 40 nmi wide eye as well.

There is no dry air whatsoever present anywhere near or within Tomas. Tomas is saturated entirely in high PWAT air.
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Quoting amd:
latest center fixes from recon suggest that Tomas is already struggling to gain latitude, and the ridging is still building into place.

I wouldn't be shocked if Tomas misses the turn north and misses Haiti/DR in about 5-6 days and continues to head toward Nicaragua .

2nd Latest Vortex Fix:
A. Time of Center Fix: 30th day of the month at 15:09:10Z
B. Center Fix Coordinates: 13�11'N 60�35'W (13.1833N 60.5833W)

Newest Vortex Fix:
A. Time of Center Fix: 30th day of the month at 16:29:50Z
B. Center Fix Coordinates: 13�09'N 60�46'W (13.15N 60.7667W) (View map)


Yeah not very likely when the trough reaches down to Belize lol.

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Deep convection starting to wrap around the southern semicircle.

Member Since: September 2, 2009 Posts: 130 Comments: 21122
Could Tomas pump the ridge and bust the trof, continuing West into Central America?

Where's the "other guy" when you need him?
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Large cumulonimbus building in the southern eyewall


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Quoting katadman:


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.
Once it organizes further on its structure, it'll likely start to intensify quickly. As for track, ridging is already starting to build north of Tomas which will keep it in the Caribbean likely on a west to west-northwest heading over the next few days. The trough over the western United States will be advecting eastward towards the eastern United States and begin to erode away at the ridging north of Tomas. This trough will likely be the deciding factor as to where Tomas goes in the long-term.

As for United States impact, I think there's a low chance of that occurring, but anything is possible, especially since it is so far out.

Member Since: September 2, 2009 Posts: 130 Comments: 21122
149. MZT
Sure does look like a storm about to wrap together.
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Quoting amd:
latest center fixes from recon suggest that Tomas is already struggling to gain latitude, and the ridging is still building into place.

I wouldn't be shocked if Tomas misses the turn north and misses Haiti/DR and continues to head toward Nicaragua in about 5-6 days.

2nd Latest Vortex Fix:
A. Time of Center Fix: 30th day of the month at 15:09:10Z
B. Center Fix Coordinates: 13°11'N 60°35'W (13.1833N 60.5833W)

Newest Vortex Fix:
A. Time of Center Fix: 30th day of the month at 16:29:50Z
B. Center Fix Coordinates: 13°09'N 60°46'W (13.15N 60.7667W) (View map)


trough is too strong I think, it would turn north eventually
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Looks to me like Tomas is trying to wrap some convection on the south side

Also radar is very impressive and shows the eye may be getting slightly smaller
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146. amd
latest center fixes from recon suggest that Tomas is already struggling to gain latitude, and the ridging is still building into place.

I wouldn't be shocked if Tomas misses the turn north and misses Haiti/DR in about 5-6 days and continues to head toward Nicaragua .

2nd Latest Vortex Fix:
A. Time of Center Fix: 30th day of the month at 15:09:10Z
B. Center Fix Coordinates: 1311'N 6035'W (13.1833N 60.5833W)

Newest Vortex Fix:
A. Time of Center Fix: 30th day of the month at 16:29:50Z
B. Center Fix Coordinates: 1309'N 6046'W (13.15N 60.7667W) (View map)
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I am on the Isle of Dominica and a really strange day indeed. First thing this morning it felt like all hell would break loose and I ran around getting things nailed down. The forecast was 50khm plus winds. But now I am sat with a very small breeze from the East ... less than a normal day around here.

There seems to be an 'air' about the day though that stops me being complacent.

We MUST get some battering tonight. It's impossible to imagine that nothing will happen.
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Hewanorra, LC (Airport), St. Lucia
Updated: 1 hr 11 min 29 sec ago

73 F
Heavy Rain
Humidity: 100%
Dew Point: 73 F
Wind: 48 mph from the NE

Wind Gust: 69 mph
Pressure: 29.68 in (Falling)

Visibility: 0.6 miles
UV: 5 out of 16
Clouds:
Few 600 ft
Scattered Clouds 1200 ft
Mostly Cloudy 1400 ft
Overcast 6000 ft
(Above Ground Level)
Elevation: 10 ft
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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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