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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Here in Orlando, I could definitely go for some gusty, rain showers (as long as it doesn't mean a full-fledged hurricane for S. Florida). From what I understand, this is unlikely as we go into November though.
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692. JLPR2
Quoting MiamiHurricanes09:
Eye is beginning to clear. That convective cluster around the western quadrant continues to wrap around the eye.


Yes a closer look confirms that.


The eye is clearing.
Member Since: September 4, 2007 Posts: 7 Comments: 8747
Quoting TriniGirl26:


LOL... i don't need a hurricane to experience that...electricity goes ever so often :)
Here too and of course only one power company. Lines are still above ground.
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Quoting cat5hurricane:

Not sure about the 8pm EDT but I think he has a shot for the 11am EDT.


11AM or PM?
Member Since: March 7, 2007 Posts: 597 Comments: 21090
Quoting MiamiHurricanes09:
Eye is beginning to clear. That convective cluster around the western quadrant continues to wrap around the eye.

Yep. And it should continue to do so until it completely closes off that eastern semicircle near the inner-core. Microwave and radar signatures already showing a tightening denser eyewall beginning to compact. After that, a period of RI is very likely.
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Quoting stormwatcherCI:
Tell me about it. My end of the island was without power for 2 1/2 months after Ivan.


What? u serious?
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Lightning Rate Graph - last 24 hours





159? wow should be a record
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Quoting KoritheMan:


The lack of electricity sucks too.


LOL... i don't need a hurricane to experience that...electricity goes ever so often :)
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Quoting KoritheMan:


The lack of electricity sucks too.
Tell me about it. My end of the island was without power for 2 1/2 months after Ivan.
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Quoting KoritheMan:


The lack of electricity sucks too.




Especially when it lasts 6 months!!!!
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Quoting cat5hurricane:
Click For Animation
Eye is beginning to clear. That convective cluster around the western quadrant continues to wrap around the eye.
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Quoting CaribbeanStorm:


Better to be prepared that sorry...however I will wait until Monday or Tuesday.


and where do u live....just wondering if us in sfla needs to go to home depot, publix and the liquor store...
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Quoting MarcoIslandCat5:
Eye is becoming really distinct now i think tomas will be classed cat 2 on next update..
thoughts?

Not sure about the 8pm EDT but I think he has a shot for the 11am EDT.
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The last few hours of sat imagery show two well separated areas of convective buildup and little evidence of closed circulation. OTOH, Martinique radar shows excellent closed circulation with a distinct eye. Anybody explain why they look so different and what the separated areas of convection might indicate?
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Quoting Saltydogbwi1:


Alan 1980 the year I moved to the cayman islands
I don't remember them.. Gilbert and then nothing until Ivan. LOL
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Quoting stormwatcherCI:
What about Felix in 2007 ?



He was just a Tropical Storm, did some damage to a boatyard and we lost power for a while, hmmm yes I did forget him too. I suppose I was thinking hurricanes and Ivan was definitely terrible.

Trinigirl, we were supposed to be hurricane safe too :)
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Click For Animation
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Quoting TriniGirl26:


Very True...I definitely pray never to experience a major hurricane in my lifetime :) Too much unnecessary destruction.


The lack of electricity sucks too.
Member Since: March 7, 2007 Posts: 597 Comments: 21090
thunderstorms in barbados

Lightning/2000 v5.2.2 Summary (Saturday, October 30, 2010 at 7:23:29 PM N)

Since midnight (1163.5 mins.):
Total strokes: 29,093 (avg. 25.0/min.)
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Eye is becoming really distinct now i think tomas will be classed cat 2 on next update..
thoughts?
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Quoting stormwatcherCI:
I have lived in Grand Cayman since 1973 and other than Gilbert I don't remember anything prior to Ivan but remember all that came after. I guess it just takes one big one.


Very True...I definitely pray never to experience a major hurricane in my lifetime :) Too much unnecessary destruction.
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18z SHIPS suggests very low shear and also conducive rich, moisture levels to be present at the mid levels for Tomas for his Journey across much of the Caribbean. He's gonna be a monster.

TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120

SHEAR (KT) 10 15 18 19 14 19 11 12 14 10 9 10 7
700-500 MB RH 63 65 65 65 67 68 69 69 72 69 71 66 69
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Quoting stormwatcherCI:
I have lived in Grand Cayman since 1973 and other than Gilbert I don't remember anything prior to Ivan but remember all that came after. I guess it just takes one big one.


Alan 1980 the year I moved to the cayman islands
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Quoting stormwatcherCI:
Link


Try this.


Thanks,
I found some training resources there which I will spend some time studying.
...here is the link for training:
http://rammb.cira.colostate.edu/visit/visithome.asp
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Quoting TriniGirl26:


i hope you don't take this the wrong way but the last storm i could remember was some 17 years ago and i was either 9 or 10 years old
I have lived in Grand Cayman since 1973 and other than Gilbert I don't remember anything prior to Ivan but remember all that came after. I guess it just takes one big one.
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Quoting cat5hurricane:

No low-level outflow boundaries caused by dry air entrained downdrafts in that pic. That's a strengthening TC.


Precisely.
Member Since: March 7, 2007 Posts: 597 Comments: 21090
Quoting KoritheMan:
Looks like that large convective band to the east will soon wrap into what appears to be the formation of an eye:


No low-level outflow boundaries caused by dry air entrained downdrafts in that pic. That's a strengthening TC.
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Quoting CaribbeanStorm:


Better to be prepared that sorry...however I will wait until Monday or Tuesday.
If I were you I would not wait any longer than Monday or you might not be able to get what you need.
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Quoting Grenada:



2005 yes, nearly forgot Emily.




i hope you don't take this the wrong way but the last storm i could remember was some 17 years ago and i was either 9 or 10 years old
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Quoting Grenada:



2005 yes, nearly forgot Emily.


What about Felix in 2007 ?
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Quoting kimoskee:
Call me paranoid but I bought my plywood today and did the supermarket.


Better to be prepared that sorry...however I will wait until Monday or Tuesday.
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Quoting tropicaltank:
How about the GOM?


Nah.
Member Since: March 7, 2007 Posts: 597 Comments: 21090
Base reflectivity feedback, ir signatures, and Microwave passes all look much improved. It's go-time for Tomas.

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Quoting stormwatcherCI:
Us too. 2004, 2005, 2007 and 2008. LOL I hope 2010 also.



2005 yes, nearly forgot Emily.


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Quoting weatherlover94:


it could go any were now
How about the GOM?
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Quoting Stormchaser2007:
Impressive


Looks just about due west.
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Impressive


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Quoting Grenada:



It was our turn, we had the bad luck in 2004. :)
Us too. 2004, 2005, 2007 and 2008. LOL I hope 2010 also.
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I am on Dominica. Got a brief report from a friend in St. Lucia this afternoon. And now that Tomas has broken through into the Caribbean Sea the swells from the hurricane will now start to lash the vulnerable west coasts of the islands of the mid Lesser Antilles.

We have a Creole Festival in Dominica this weekend and about two dozen yachts came over on Friday from Martinique and Guadeloupe to attend thinking that nothing much was going on weatherwise. Now they are stuck off Dominica without protection. I watched them coming into Prince Rupert Bay, Portsmouth through heavy seas this afternoon, hoping for some better shelter here than in the south, but when the surges start coming in from the south west tonight and tomorrow, dont know what they can do.
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Quoting CaicosRetiredSailor:
I have read many times that the IR JSL enhancement was developed by Jim Lynch for use in tropical cyclone classification.

Does anyone have a link which explains, or can describe how one "deciphers" that image?

TIA
CRS
Link


Try this.
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Quoting Grenada:



A bit of rain lots of cloud and a nice gentle breeze..... lucky or what.

Definitely luck :)
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Looks like that large convective band to the east will soon wrap into what appears to be the formation of an eye:

Member Since: March 7, 2007 Posts: 597 Comments: 21090
RI/21L/H/T/C2
MARK
13.57n/62.19w


Member Since: July 15, 2006 Posts: 175 Comments: 54847
Quoting Tazmanian:
any one think will make it too the W storm


Yup.
Member Since: March 7, 2007 Posts: 597 Comments: 21090
Quoting stormwatcherCI:
I would say blessed more than lucky.



It was our turn, we had the bad luck in 2004. :)
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I have read many times that the IR JSL enhancement was developed by Jim Lynch for use in tropical cyclone classification.

Does anyone have a link which explains, or can describe how one "deciphers" that image?

TIA
CRS
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Quoting Grenada:



A bit of rain lots of cloud and a nice gentle breeze..... lucky or what.
I would say blessed more than lucky.
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Quoting TriniGirl26:
Good Night All. Grenada what were the effects of Tomas up there...Here in Trinidad was hot sun...not a drop of rain.



A bit of rain lots of cloud and a nice gentle breeze..... lucky or what.
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Member Since: July 15, 2006 Posts: 175 Comments: 54847
any one think will make it too the W storm
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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.