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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1643. KEEPEROFTHEGATE (Mod)
Quoting Orcasystems:


GASP.. you have your wife trained to fetch Timmies.. I am jealous and impressed.
she even got timbits as well to go with my three coffees
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To avoid Haiti i think thomas must continue very very slowly
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Quoting weatherlover94:
i dont see this becoming a major

I see Tomas going through the motions just like most storms/hurricanes, IMO it will reintensify and become at least a solid Cat3, feel sorry for the poor Haitians, even if not a direct hit , the rains alone will probably cause a significant lost of life for them, they have every right to turn their eyes to the skies and wonder if they have been a forsaken people, JMO.
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Quoting Cat5hit:
Wow... Snow? You'all have white Halloweens?


You'all my Butt.. its sunny here and I am going Golfing.
Member Since: October 1, 2007 Posts: 81 Comments: 26493
Quoting KEEPEROFTHEGATE:
the wife just came back from tims and said it was trying to snow i went out to check and yes there are some very fine snow grains floating in the wind so ya its offically trying to snow

don't dance to hard it could back fire


GASP.. you have your wife trained to fetch Timmies.. I am jealous and impressed.
Member Since: October 1, 2007 Posts: 81 Comments: 26493
1636. KEEPEROFTHEGATE (Mod)
Quoting Orcasystems:


Happy Dance Happy Dance :)
the wife just came back from tims and said it was trying to snow i went out to check and yes there are some very fine snow grains floating in the wind so ya its offically trying to snow

don't dance to hard it could back fire
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Quoting Cat5hit:


Can you translate that from Canadian English to American English?


Its starting to SNOW in Toronto :)
Member Since: October 1, 2007 Posts: 81 Comments: 26493
Quoting weatherlover94:
i dont see this becoming a major
Wish I could agree. Unfortunately, once Tomas gets past about 63-65W, potential for major status goes way back up... I'm still not ruling out cat three by Friday, just HOPING it won't happen....
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Not much to add but Tomas doesn't look to good this morning. Which in hindsight is about what you would expect this time of year. I thought sw shear was a little high on the water vapor loop yesterday, but didn't want to jump into the fray.Still a very interesting storm for this time of year. Hope not to much damage was done in the islands.
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Quoting weatherlover94:
i dont see this becoming a major


Ummm, sorry but you did just the other day and hitting FL.
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Quoting AtmosphericWrath:


That is an extremely strong, deep low pressure center which peaked around 938-940mb. One thing to note is this system underwent very strong cyclogenesis deepening more than 50mb over a 24 hour time frame making it a "Meteorological Bomb" The low has occluded and the system itself is beginning to slowly decay.


I hate those... they go right over my house :(
Member Since: October 1, 2007 Posts: 81 Comments: 26493
Hurrican Tomas - the aftermath in St. Lucia
By Arnold Henry Autobiography · View Photos

http://www.facebook.com/album.php?aid=239477&id=123712035193&l=87851c32d6

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Quoting KEEPEROFTHEGATE:
as of 1145 am we are reporting light snow grains its coming big fish


Happy Dance Happy Dance :)
Member Since: October 1, 2007 Posts: 81 Comments: 26493




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Quoting Cat5hit:


It is forecast to stall and then resume in that direction...



Yes, Tropical systems tend to slow down or stall before making abrupt changes in direction.

A faster moving TC would tend to make a more gradual turn (like rounding a corner).

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1625. KEEPEROFTHEGATE (Mod)
as of 1145 am we are reporting light snow grains its coming big fish
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Quoting weatherwatcher12:
Location of the trough. Also, what is that south of Alaska?


That is an extremely strong, deep low pressure center which peaked around 938-940mb. One thing to note is this system underwent very strong cyclogenesis deepening more than 50mb over a 24 hour time frame making it a "Meteorological Bomb" The low has begun to occlude and the system itself is beginning to slowly decay.
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Quoting scott39:
How does a TC turn as fast as the NHC is showing?
The trough that digs into the Gulf of Mexico and southwestern Atlantic will erode away at the subtropical ridge to the north of Tomas. With that taking place, steering currents will basically collapse. That trough will cause a weakness in the subtropical ridge. When a weakness is caused in a high pressure system, a cyclone will get attracted to it and want to gravitate towards it. That's pretty much what will happen. The cyclone turns poleward into the weakness since steering currents are weak. That's how the poleward turn on the NHC cone of uncertainty will verify.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting Cat5hit:
That new track is bad for Haiti, looks like Jacmel would get a hit. Hopefully not a Cat5hit!

Obviously Tomas can end up anywhere inside the 5-day cone--or even somewhat outside it. Having said that, however, I'll state this other obvious fact: almost any right-angle hit from a major hurricane on the south-facing coast of Hispaniola would be devastating. Wind damage would be bad enough, but the greatest destruction would likely come from surge and rain-caused flooding.

The water just offshore southern Hispaniola is very deep, and the shelf is very thin. This has the effect of making a smaller surge than would occur in an area with a shallow shelf, though with larger, more battering waves due to the dynamics of wave energy. Some coastal towns on the south side of the island, such as Jacmel, sit on relatively flat ground directly facing the ocean with no protection whatsoever; in such places, surge damage would be tremendous.

Now, the rain. One saving grace for Port au Prince would be that there is a mountain range running east west on the Tiburon Peninsula that serves to separate the capital from the Caribbean. Some peaks in this range reach well over a mile into the sky; obviously, these peaks would diminish the storm's intensity for areas north of the range. The bad news is that this diminishing would happen at the expense of the coastal towns and villages to the south; orographic uplift would force the storm to unleash super torrents of rain, which would rush unimpeded down the mostly denuded hills, resulting in horrendous flooding.

As I said before, I am seriously hoping the current cone is wrong, as it represents for the moment a nearly worst-case scenario. I don't deal much in apocalyptic predictions, but this would be bad. Very, very bad...
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1621. KEEPEROFTHEGATE (Mod)
1607. Orcasystems 3:32 PM GMT on October 31, 2010
Quoting Fla727:
Looks like a Hati landfall and a fish after that.


Thats right.. whats it going to do.. kill a couple 1000 Haitians.. and since they aren't really like you.. its still basically a fish storm right?

Idiot

Action: Quote | Ignore User
Member Since: October 1, 2007 Posts: 42 Comments: 18316


couple of 1000 iam afraid it will be a couple of 100,000

and that guy is still an idiot

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via Twitter:

terryfinisterre
I understand there is still some rain in the south of St Lucia, Vieux Fort in particular, but winds have died down. #Tomas 3 minutes ago

Previous Tweets
Soufriere is cut off. Choc & Bois d'Orange bridges are out. Bexon is underwater. Barre de l'Isle is impassible. #Tomas hit St Lucia hard. 4 minutes ago

Communication is being restored islandwide. Mobile / landline are up on much of St Lucia, but please keep voice traffic to a minimum! #Tomas 8 minutes ago
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1619. scott39
Quoting Cat5hit:


It is forecast to stall and then resume in that direction...
That makes sense.
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For the next 48 hours, Tomas will likely not intensify due to the factors mentioned in post 1593. But beyond that time-frame, mid-level relative humidity increases beyond 70%, and vertical wind shear sinks to below 10 knots. That will likely allow for the system to repair any circulatory problems and begin to undergo a more rapid phase of intensification.

Additionally, OHC will increase to 100+ kJ cm-2.

TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120
V (KT) NO LAND 85 86 85 83 80 74 71 69 66 67 71 77 82
V (KT) LAND 85 86 85 83 80 74 71 69 66 67 71 77 82
V (KT) LGE mod 85 86 85 83 80 74 69 68 70 75 81 89 96

SHEAR (KT) 19 18 23 25 21 22 17 15 11 10 3 9 12
SHEAR ADJ (KT) 13 8 8 6 8 -1 -5 -5 -4 -3 -1 -3 -2
SHEAR DIR 246 238 241 242 255 237 247 213 238 168 149 104 113
SST (C) 29.4 29.5 29.6 29.6 29.6 29.5 29.5 29.5 29.5 29.5 29.6 29.7 29.7
POT. INT. (KT) 158 160 162 162 162 159 158 157 157 157 159 160 161
ADJ. POT. INT. 154 158 160 160 158 153 150 147 147 146 147 146 147
200 MB T (C) -52.9 -52.2 -52.2 -52.2 -52.3 -51.7 -51.9 -51.5 -52.2 -52.0 -52.6 -51.5 -51.5
TH_E DEV (C) 9 9 9 8 8 9 7 8 7 7 6 6 6
700-500 MB RH 65 63 63 67 68 67 75 75 77 75 75 75 77
GFS VTEX (KT) 14 13 13 12 11 10 10 10 12 14 17 19 20
850 MB ENV VOR 20 20 19 22 22 31 50 65 79 89 82 93 86
200 MB DIV 66 84 85 62 39 32 51 87 103 74 95 134 100
LAND (KM) 366 390 405 369 350 333 281 256 274 321 277 223 155
LAT (DEG N) 14.0 14.2 14.4 14.6 14.8 15.0 14.8 14.8 14.9 15.1 15.5 16.0 16.6
LONG(DEG W) 63.3 64.3 65.3 66.4 67.4 69.2 70.6 71.5 72.3 73.0 73.8 74.0 73.9
STM SPEED (KT) 9 10 10 10 9 8 6 4 4 4 3 3 3
HEAT CONTENT 106 104 84 79 89 87 94 101 121 123 110 110 110
Member Since: September 2, 2009 Posts: 130 Comments: 21032
ADT about 1 hour old.

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 31 OCT 2010 Time : 144500 UTC
Lat : 13:59:39 N Lon : 63:39:54 W


CI# /Pressure/ Vmax
4.3 / 985.3mb/ 72.2kt


Final T# Adj T# Raw T#
4.3 4.3 3.0

Latitude bias adjustment to MSLP : +3.1mb

Center Temp : -56.6C Cloud Region Temp : -48.0C

Scene Type : UNIFORM CDO CLOUD REGION w/ MW EYE

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : MW ON
Weakening Flag : OFF
Rapid Dissipation Flag : OFF

****************************************************
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting justalurker:
anything can happen 5 days out, seen in the past how model runs and projected path change..lets hope for the best for haiti!!!


I am really hoping this thing some how misses the ridge, and shoots the Yucatan/Cuba gap.

Or even better yet, a couple models have it stalling to the South of the track, and getting killed by the sheer later in the week.

Member Since: October 1, 2007 Posts: 81 Comments: 26493
Quoting MiamiHurricanes09:
Tomas is likely nearing tropical storm strength. Satellite imagery along with microwave overpasses reveal that the cyclone is not vertically aligned and is tilted towards the northeast (meaning that the mid-level circulation is not directly above the surface one). The convective organization is also rather poor with the circulation at the western edge of an asymmetric CDO. The banding on the western quadrant is also rather poorly organized. This is likely due to some dry air entrainment and about 20 knots of southwesterly vertical wind shear.

Hope this also means less opportunity for major status in 4-5 days....

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1613. KEEPEROFTHEGATE (Mod)
21L/H/T/C1
MARK
14.23n/63.71w


weakening flag on
rapid disp. flagged
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anything can happen 5 days out, seen in the past how model runs and projected path change..lets hope for the best for haiti!!!
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1611. scott39
Quoting MiamiHurricanes09:
No. The trough will basically have the same effect on him if he's a tropical storm or a category 4 major hurricane. More importantly is the location that the cyclone is at when the trough digs and erodes away at the subtropical ridge. Whatever happens, the trough will dig down, erode the subtropical ridge, induce a weakness, and make the cyclone turn poleward. The specifics are what make the forecasting complicated.
How does a TC turn as fast as the NHC is showing?
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1610. JRRP
Quoting KEEPEROFTHEGATE:
my only advice to that grapic is

save as many as you can

yeah
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Quoting weatherman12345:
No. The trough will basically have the same effect on him if he's a tropical storm or a category 4 major hurricane. More importantly is the location that the cyclone is at when the trough digs and erodes away at the subtropical ridge. Whatever happens, the trough will dig down, erode the subtropical ridge, induce a weakness, and make the cyclone turn poleward. The specifics are what make the forecasting complicated.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
i dont see this becoming a major
Member Since: September 8, 2010 Posts: 0 Comments: 1820
1606. scott39
Quoting MiamiHurricanes09:
Tomas is likely nearing tropical storm strength. Satellite imagery along with microwave overpasses reveal that the cyclone is not vertically aligned and is tilted towards the northeast (meaning that the mid-level circulation is not directly above the surface one). The convective organization is also rather poor with the circulation at the western edge of an asymmetric CDO. The banding on the western quadrant is also rather poorly organized. This is likely due to some dry air entrainment and about 20 knots of southwesterly vertical wind shear.

This is a good sign!
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Weakens and I believe it will be TS by Monday. that should help Haiti.
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Unfortunately, based on the models, the odds of Tomas affecting Haiti in some way are pretty high.
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1602. scott39
Quoting Orcasystems:


I have just spent the last 30 minutes trying to find a location for this, so I can put it on my google maps... no luck.

Any kind of geographical information (supported) would be nice.
i just saw your post. I put this in my search engine(graveyard for tropical cyclones in the Eastern Caribbean). The way I understand it is that whole East Caribbean is more hostile for many weather reasons. One thing interesting to note is that the article said its not as hostile in the latter part of the season. This maybe one of the reasons Tomas has made it.
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Quoting Fla727:
Looks like a Hati landfall and a fish after that.




if a storm makes land fall some where it wont be call a fish even when it gos out too sea when its done it still wont be a fish
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Quoting Sfloridacat5:


Maybe Bermuda after that. But by then it shouldn't be a hurricane.


to early to tell it may not even go near Hati or Bermuda so lets wait a couple of days to see
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1599. SLU
Quoting CaicosRetiredSailor:


following links from

http://search.twitter.com/

search for St. Lucia


Thanks a lot
Member Since: July 13, 2006 Posts: 12 Comments: 4734
Thomas has been moving due west since 5am per the NHC coordinates.
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looking at the last frame of the vis loop looks like the low level center is about to be exposed about 13.8N 64.1 W could be wrong though
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Quoting Fla727:
Looks like a Hati landfall and a fish after that.


Maybe Bermuda after that. But by then it shouldn't be a hurricane.
Member Since: September 16, 2007 Posts: 0 Comments: 4798
Quoting MiamiHurricanes09:
Tomas is likely nearing tropical storm strength. Satellite imagery along with microwave overpasses reveal that the cyclone is not vertically aligned and is tilted towards the northeast (meaning that the mid-level circulation is not directly above the surface one). The convective organization is also rather poor with the circulation at the western edge of an asymmetric CDO. The banding on the western quadrant is also rather poorly organized. This is likely due to some dry air entrainment and about 20 knots of southwesterly vertical wind shear.



tomas is now a cat 2 hurricane

http://tropicalatlantic.com/models/
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1594. Fla727
Looks like a Hati landfall and a fish after that.
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Tomas is likely nearing tropical storm strength. Satellite imagery along with microwave overpasses reveal that the cyclone is not vertically aligned and is tilted towards the northeast (meaning that the mid-level circulation is not directly above the surface one). The convective organization is also rather poor with the circulation at the western edge of an asymmetric CDO. The banding on the western quadrant is also rather poorly organized. This is likely due to some dry air entrainment and about 20 knots of southwesterly vertical wind shear.

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

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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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