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 Stormchaser2007:
Western quadrants convection waning. Still a pretty disorganized hurricane. 



Minor dry air intrusion, the system is filtering the dry air out. Fairly disorganized, but I suspect it'll change pretty soon.
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Ragged eye. The southern semicircle/eyewall is also open and void of any deep convective activity.

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Quoting SLU:
Reports from St. Lucia:

- roofs being blown off
- lots of fallen trees
- power outages
- heavy rains
- tropical storm conditions



Good to hear from you! Been asking about you...be safe!
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edit
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wow....this late in the season?


amazing...

are the models sending this thing into both h. boxes?
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Quoting spathy:

To me that looked like outer cloud collapse/outflow as Tomas tightened its core.
Any thoughts?

Excellent observation!!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Imagine if Tomas formed in August, probably would be dealing with a Category 3-4 instead of a 1.
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Quoting katadman:
Does anyone here know when the HH are going back into Tomas? TIA


260

NOUS42 KNHC 301230

WEATHER RECONNAISSANCE FLIGHTS

CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.

0830 AM EDT SAT 30 OCTOBER 2010

SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)

VALID 31/1100Z OCTOBER TO 01/1100Z NOVEMBER 2010

TCPOD NUMBER.....10-151



I. ATLANTIC REQUIREMENTS

1. TROPICAL STORM TOMAS

FLIGHT ONE -- TEAL 70

A. 31/1800Z

B. AFXXX 0421A TOMAS

C. 31/1630Z

D. 14.5N 66.0W

E. 31/1730Z TO 31/2130Z

F. SFC TO 15,000 FT



FLIGHT TWO -- TEAL 71

A. 01/0600Z

B. AFXXX 0521A TOMAS

C. 01/0430Z

D. 15.0N 68.0W

E. 01/0530Z TO 01/0930Z

F. SFC TO 15,000 FT



2. SUCCEEDING DAY OUTLOOK: BEGIN 6-HRLY FIXES

AT 01/1200Z.



II. PACIFIC REQUIREMENTS

1. NEGATIVE RECONNAISSANCE REQUIREMENTS.

2. OUTLOOK FOR SUCCEEDING DAY....NEGATIVE.

JWP


Member Since: July 15, 2006 Posts: 178 Comments: 56141
Thanks for the info, weatherwatcher.

I noticed that the ensemble models are not posted for Tomas on WU. Have they not come out yet?
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Tomas looks alot like Fay (2008) before making landfall in my town her ein Florida.

TOMAS


FAY 2008
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Quoting SLU:


The worst is yet to come. Wind gusts to over 100 - 115mph are possible later this afternoon especially in the elevated areas.

WOW!!! AMAZING!!!!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Good thing he is just a Cat1... I can't imagine Tomas as a Cat 3 or 4 roaring through the Islands. Hopefully everyone is ok!

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FLIGHT TWO -- TEAL 71
A. 31/0600Z
B. AFXXX 0321A CYCLONE
C. 31/0430Z
D. 13.2N 64.0W
E. 31/0530Z TO 31/0930Z
F. SFC TO 15,000 FT
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting juniort:
I have not experienced anything like that so far in my life, I went through Ivan but this is worse, the wind was horrendous Thank God to be okay, my garage shed is gone have to be repaired...From Barbados


Thanks for the report, good luck going forward. Are there power outages?
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Animated radar loops reveal that Tomas has turned towards a due westward heading. That would correspond to water vapor imagery showing that mid-level trough over the central Atlantic causing a weakness in the subtropical ridge lifting out. Additionally, the subtropical ridge has bridged with the ridge over the southeastern United States. This will likely be the start of westward motion until the next trough over the western United States digs southward and erodes away at the subtropical ridge and Tomas begins a poleward turn.
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Does anyone here know when the HH are going back into Tomas? TIA
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Quoting reedzone:


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

Actually I may have misread. They are going out at around midnight. Someone confirm for me.
Member Since: May 16, 2009 Posts: 1 Comments: 1231
I believe Earl took on an appearance like Tomas's before undergoing rapid intensification shortly afterwards.
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68. SLU
Quoting Bordonaro:


The worst is yet to come. Wind gusts to over 100 - 115mph are possible later this afternoon especially in the elevated areas.
Member Since: July 13, 2006 Posts: 13 Comments: 5367
Quoting cat5hurricane:

I do notice a hint of that on the very last loop.


Convection warming on top of the northern eyewall. New cell firing on the southeastern side.
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Quoting weatherwatcher12:

Tommorow at 12:30 according to TWC. The current one is out there till 4 pm.


TWC didn't even recognize Tomas 24 hours ago, said everything was quite in the tropics, why believe them now?
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St. Lucia reporting a wind gust of 69mph.

Hewanorra, LC (Airport)
Updated: 23 min 6 sec ago
Heavy Rain
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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Tomas will not be weakening, but may hold steady around 75-80 mph. until it reaches west of the Islands. I doubt it will be downgraded as some have said might happen due to the downdrafts.
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Quoting SLU:
Wind gusts to 69mph just clocked in St. Lucia.They are getting hammered!!!!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting Thundercloud01221991:
what time does the next plane take off

Tommorow at 12:30 according to TWC. The current one is out there till 4 pm.
Member Since: May 16, 2009 Posts: 1 Comments: 1231
61. SLU
Wind gusts to 69mph just clocked in St. Lucia.
Member Since: July 13, 2006 Posts: 13 Comments: 5367
Quoting Orcasystems:




Part if the HH data transmitters are obviously bent.. but at least we still have the vortex plots.

Hmm ... Tomas to the south of the model plots.
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting TerraNova:


Wow really? I heard the host say something about "FM...well, we used to be" but I didn't know what he was talking about.

They are broadcasting via the web, until the storm is past..
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting Bordonaro:

They are only broadcasting via the web. Tomas knocked out their FM transmitter!!!!


Wow really? I heard the host say something about "FM...well, we used to be" but I didn't know what he was talking about.
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St. Vincent and the Grenadines beginning to come into the eye.

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Quoting MiamiHurricanes09:
Yep, I was just commenting on that. You can already start to see the beginning of the convective cloud tops warming on infrared (especially along the western semicicle of the eyewall).Tomas is wrapping new convection in from his SE. Weakening is not happening!!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
hope everyone is ok in the Antilles...be back later
Member Since: September 8, 2010 Posts: 0 Comments: 2232




Part if the HH data transmitters are obviously bent.. but at least we still have the vortex plots.
Member Since: October 1, 2007 Posts: 81 Comments: 26516
Quoting TerraNova:
Significant damage in St. Lucia according to 105.3 FM Caribbean Hot Radio>

Other stations streaming online here from all over the Caribbean, including St. Lucia, St. Vincent and Barbados.

They are only broadcasting via the web. Tomas knocked out their FM transmitter!!!!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting Stormchaser2007:
Pretty pronounced downdrafts.


Yep, I was just commenting on that. You can already start to see the beginning of the convective cloud tops warming on infrared (especially along the western semicicle of the eyewall).
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what time does the next plane take off
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Significant damage in St. Lucia according to 105.3 FM Caribbean Hot Radio>

Other stations streaming online here from all over the Caribbean, including St. Lucia, St. Vincent and Barbados.
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Pretty pronounced downdrafts.


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Quoting Stormchaser2007:
Large downdrafts exiting from the Western quadrant.

Convection should collapse soon.




Tell that to Tomas!
Link
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Thank you Dr. Masters.
These reports from the "eye of the NHC" have been fascinating.
I love the fact that they still use the old fashioned paper plotting, using a protractor.
Viva low-tech!!!
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Quoting SLU:
Reports from St. Lucia:

- roofs being blown off
- lots of fallen trees
- power outages
- heavy rains
- tropical storm conditions
Wow...
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I have not experienced anything like that so far in my life, I went through Ivan but this is worse, the wind was horrendous Thank God to be okay, my garage shed is gone have to be repaired...From Barbados
Member Since: Posts: Comments:

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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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