Shary forms; potentially dangerous 91L approaching Lesser Antilles

By: Dr. Jeff Masters , 29. lokakuuta 2010 klo 15:23 (GMT)

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Tropical Storm Shary is here, the eighteenth named storm of this remarkably active 2010 Atlantic hurricane season. Shary's formation makes 2010 tied for 5th place with 1969 for most number of named storms in an Atlantic hurricane season. Only 2005 (28 named storms), 1933 (21 named storms), 1995 (19 named storms), and 1887 (19 named storms) had more named storms than 2010 has had. 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. Shary is going to be a weak and very short-lived storm, and Bermuda is the only land area that needs be concerned with the storm. A Tropical Storm Warning is posted for the island, and rain bands from the storm can be seen on Bermuda radar.

Potentially dangerous 91L approaching South America and Lesser Antilles
A very impressive tropical wave (Invest 91L), about 350 miles east-southeast of the southernmost Lesser Antilles Islands, is headed west-northwest towards the islands at 15 - 20 mph. In discussions I had with hurricane experts at NHC and NOAA's Hurricane Research Division yesterday, it was widely agreed that this system was unusually large and well-organized for this time of year--something one would expect to see in early September, but not late October. The historical Atlantic hurricane data base shows no cases where a tropical depression has formed so far south and east so late in the year. "Ominous" and "unprecedented" were a few of the adjectives I heard used to describe 91L, and this system has the potential to be a dangerous storm for the islands of the eastern and central Caribbean.


Figure 1. Morning satellite image of 91L.

91L is centered very far to the south, near 10°N latitude, and this close proximity to the Equator has slowed development. Also slowing development has been the system's very large size--it takes time to spin up such a large circulation. Aiding development has been low wind shear of 5 - 10 knots, warm ocean temperatures of 29°C, and a very moist atmosphere. A pass by the ASCAT satellite last night revealed a nearly closed circulation, and top winds of about 30 mph. Visible satellite loops do not show a clear surface circulation yet, though the storm has plenty of heavy thunderstorm activity that is increasing in organization, with several impressive low-level curved rain bands.

Forecast for 91L
91L will continue moving west-northwest at a decreasing forward speed through Monday, bringing very heavy rain tonight and Saturday to the northern coast of South America and most of the Lesser Antilles. The center of the storm will track very close the coast of South America this weekend, and it is likely that this will slow or halt development over the weekend. By Monday, the center of 91L may pull far enough away from South America that more substantial development can occur. However, steering currents are expected to substantially weaken in the eastern Caribbean beginning on Monday, as a strong trough of low pressure develops over the Eastern U.S., weakening the ridge of high pressure steering 91L. The trough may be strong enough to pull 91L to the north, resulting in a potential threat to Haiti, the Dominican Republic, Puerto Rico, and the Lesser Antilles Islands by Wednesday of next week. We do have several models--the HWRF and GFS--that develop 91L into a hurricane by Wednesday. Shear is predicted to remain low, 5 - 10 knots, for most of the next five days, and water temperatures are at near record highs, 29 - 29.5°C. There is the potential for 91L to reach hurricane status if passage over South America this weekend does not disrupt the storm sufficiently. An Air Force hurricane hunter aircraft is scheduled to investigate 91L at 2pm this afternoon to see if a tropical depression has formed.


Figure 2. Hurricane Specialist Dan Brown coordinates with the Bermuda Weather Service, alerting them to the possibility that 92L might be upgraded to Tropical Storm Shary, necessitating issuance of a Tropical Storm Watch for the island that evening.

A Thursday evening shift at NHC
I spent another shift yesterday evening at the National Hurricane Center, where I've spent the week as a participant in their visiting scientist program. Each week during hurricane season, NHC invites a hurricane researcher or forecaster in academia, government, or private industry to spend a week shadowing the NHC forecasters as they prepare their forecast products. The evening shift is chosen, since it is less of a zoo, and the presence of the visiting scientist will present less of a distraction to the forecasters.

Once again, I spent the first portion of the shift working with Tropical Analysis and Forecasting Branch (TAFB) forecaster Wally Barnes, who made the intensity and position estimates of 90L, 91L, and 92L based on infrared satellite imagery. This task was accomplished using the Dvorak technique, a system of classifying cloud patterns of tropical cyclones based on how cold the cloud tops are, how much spiral banding is present, and other factors. We classified 92L (later to be Shary) as an ST2.5--a subtropical storm with 40 mph winds. The more dangerous tropical wave Invest 91L approaching the coast of South America got a far weaker classification, since the tops of its thunderstorms were not very cold, and the bands of clouds were fairly fragmented.

We presented our data to Senior Hurricane Specialist Dan Brown, who would be responsible for the decision whether or not to upgrade 92L to Shary. He was impressed with the ST2.5 classification we'd come up with for 92L, but wanted more evidence that the storm was as strong as this satellite estimate indicated. At 9:10pm, we had our evidence. The latest wind observations from NOAA buoy 41049 showed 33.4 knots (38 mph) as 92L passed by. This wind speed is just at the boundary of tropical storm force winds--39 mph. However, since the buoy's anemometer is at an elevation of 5 meters, an adjustment upwards to the wind speed is necessary to correct the winds to the standard measurement height of ten meters, due to frictional slowing of the wind near the surface. Thus, the buoy winds were more like 40 mph, above tropical storm force, and this was Tropical Storm Shary--if a closed circulation existed. Dan told us he was going to start writing an advisory package, in case additional data came in indicating 92L had a closed surface circulation. He called the Bermuda Weather Service to alert them that he was considering naming this system Shary, and that a tropical storm watch or warning might be required for the island that evening. Dan also called the head of the hurricane forecasting branch of NHC, James Franklin, to alert him of the impending new storm.


Figure 3. "This is the part where the world finds out about Shary," Hurricane Specialist Dan Brown told me as he filled out this form on his computer. About an hour before the first package of official advisories on a new tropical depression or tropical storm are sent out, NHC renumbers an Invest with the "AL" prefix and a number indicating how many tropical storms or depressions have occurred so far this year. In this case, 92L got renumbered AL20, since there have been 18 named storms and 2 tropical depressions that did not reach tropical storm strength. The newly numbered storm appears on the Navy Research Lab web site about an hour before the first advisory is sent out to the world. It is rare for NHC to change their mind and not issue advisories after renumbering occurs.

At 9:20pm, we had our proof of a closed circulation. A ship heading towards the center of Shary from the south measured west winds of 15 knots just south of the center, strongly suggesting that Shary had a closed circulation and was a legitimate tropical storm. Dan accelerated his work on the 11pm advisory package--there was a lot of work to do between now (9:30) and 10:30, when he wanted to get the advisories out. The other hurricane specialist on duty, Robbie Berg, helped out, and the two of them worked hard over the next hour to plot positions, scan the latest observations and model data, and type up advisories. Sandwiched between these efforts were several phone calls--a coordination call with other branches of NOAA and the Navy, another call to the Bermuda Weather Service, plus a conversation with Trinidad's weather service, which was concerned about the tropical wave (Invest 91L) approaching their island. Finally, at 10:30pm, the advisory package was complete, and Dan hit the "Send out to the Whole World?" button on his screen, making Tropical Storm Shary the eighteenth named storm of the 2010 Atlantic hurricane season.


Figure 4. Hurricane Specialist Robbie Berg updates NHC's big hurricane tracking board with its newest addition, Tropical Storm Shary.

It's worth noting that we would not have known Shary was a tropical storm without data from the buoy the storm passed over. This buoy was one of the new buoys financed by a special supplemental funding bill approved by Congress several years ago, in an effort to improve hurricane forecasts. Money well spent in this case!

Next update
I'll have an update later today or Saturday morning on the latest from the tropics.

Jeff Masters

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1244. aspectre
30. lokakuuta 2010 klo 09:29 (GMT)
posted into the wrong blog.
Member Since: 21.08.2007 Posts: 0 Comments: 4860
1243. bajelayman2
30. lokakuuta 2010 klo 05:30 (GMT)
This may track quite above original forecast , towards Cuba etc....
Member Since: 13.08.2007 Posts: 0 Comments: 478
1242. bajelayman2
30. lokakuuta 2010 klo 05:15 (GMT)
looks on the satellite loop to be going to our east/north side, not south per the forecast
Member Since: 13.08.2007 Posts: 0 Comments: 478
1241. bajelayman2
30. lokakuuta 2010 klo 05:13 (GMT)
Actually street light is working, dont know what went thump....good thing this is not nightmare on elm street..or a 'b' movie...

things just kinda dark outside...
Member Since: 13.08.2007 Posts: 0 Comments: 478
1240. bajelayman2
30. lokakuuta 2010 klo 05:08 (GMT)
Wind really picking up here in Barbados now, and he aint even here yet!

Good gusts and squalls, I am in South-Centre of Island, closer to South.

Street light in front of me gone, hard a loud thump and not giving light, think it may be down (aluminum pole).

Remember, may stop posting at a certain time, as the Light & Power may actually switch off to prevent worse damage, if things get harsh.
Member Since: 13.08.2007 Posts: 0 Comments: 478
1239. Skyepony (Mod)
30. lokakuuta 2010 klo 04:50 (GMT)
Looking over the 1st 24hr of error on Tomas models was a bit shocking. Even on the 1st run models don't usually over all do that poorly. Worse was OFCL came in 2nd to last overall the models.. & FOr reasons I discussed the other morning.. no suprise.. CMC on top..

Average Position Error (nm) for core models
model Error Trend 24hr Error 48hr Error 72hr Error Day 4 Error Day 5 Error
CMC CONSTANT 36.9 -1 -1 -1 -1
HWRF INCREASING 79.8 215.6 102.2 -1 -1
LBAR INCREASING 107.6 178.3 204.1 -1 -1
BAMD INCREASING 144.1 250.4 315.2 -1 -1
MM5B DECREASING 167.2 144.3 114.4 -1 -1
GFDL CONSTANT 281.1 -1 -1 -1 -1
MM5E CONSTANT 285.8 -1 -1 -1 -1
KHRM CONSTANT 321.9 -1 -1 -1 -1
OFCL CONSTANT 329.9 -1 -1 -1 -1

I still think it has a good chance to eventually be swept NNE, if that's over Hispaniola, Jamaica & Cuba or farther west, we'll have to see.
Member Since: 10.08.2005 Posts: 156 Comments: 36173
1238. Bubu77
30. lokakuuta 2010 klo 03:56 (GMT)
Hello je suis en Martinique et assez inquiet par rapport à ce phénomène car les journalistes et Météo France n'on quasiment pas prévenue la population !!

Et pourtant ca se rapporoche inexorablement et elle se renforce bien !!!

Very Very Bad !!!
Member Since: 6.05.2009 Posts: 0 Comments: 14
1237. sunlinepr
30. lokakuuta 2010 klo 03:23 (GMT)
Hurricane in less than 24 hrs....

Member Since: 2.08.2010 Posts: 21 Comments: 9656
1236. sunlinepr
30. lokakuuta 2010 klo 03:18 (GMT)
Here it comes.... For me Thomas is going to come closer than diagnosed....

Member Since: 2.08.2010 Posts: 21 Comments: 9656
1235. sunlinepr
30. lokakuuta 2010 klo 03:15 (GMT)
Quoting TORMENTOSO83:
What's the scenario for PR?


What I've seen so far, is a system that is moving more N than the supposed WNW... Even the forecasted points are SW of where the COC is....
Even local news, like Wapa and Univision are presenting old model diagnostics....
Member Since: 2.08.2010 Posts: 21 Comments: 9656
1234. TORMENTOSO83
30. lokakuuta 2010 klo 01:54 (GMT)
Quoting DDR:

12n heading wnw,expanding feeder bands,i'd say 50% we get some heavy tonight.

What you mean with 12N?
Member Since: 30.07.2010 Posts: 0 Comments: 286
1233. TORMENTOSO83
30. lokakuuta 2010 klo 01:50 (GMT)
What's the scenario for PR?
Member Since: 30.07.2010 Posts: 0 Comments: 286
1232. MiamiHurricanes09
30. lokakuuta 2010 klo 01:43 (GMT)
New Blog
Member Since: 2.09.2009 Posts: 130 Comments: 21032
1230. hydrus
30. lokakuuta 2010 klo 01:39 (GMT)
Quoting cat5hurricane:

LOL. He's got the fuel there. He's just got to use it.
If you can, try the link I posted . I switched it out to a better one..
Member Since: 27.09.2007 Posts: 1 Comments: 19606
1227. SLU
30. lokakuuta 2010 klo 01:37 (GMT)
Quoting nopepper:
SLU - nice Pitons pic.

Wishing the best for my newfound friends in the Windwards - including Debra, our rainforest guide on St. Lucia, who is the long-lost twin (looks just like her) of my step daughter's best friend.


lol thanks. I hope the guys back home are well prepared for this too. It looks really nasty.

Let's move to the new blog now....
Member Since: 13.07.2006 Posts: 12 Comments: 4734
1226. hydrus
30. lokakuuta 2010 klo 01:36 (GMT)
Quoting cat5hurricane:

Nice pic
You dig the NESDIS water vapor pic.?...Here is the link--Link
Member Since: 27.09.2007 Posts: 1 Comments: 19606
1225. hydrus
30. lokakuuta 2010 klo 01:34 (GMT)
Quoting cat5hurricane:
The red areas are great big bowls of hurricane Wheaties for Tomas,s already well stocked craw...
Member Since: 27.09.2007 Posts: 1 Comments: 19606
1224. XL
30. lokakuuta 2010 klo 01:34 (GMT)
Quoting kmanislander:


Just finished a good curry chicken so doing very well indeed LOL

The models have Tomas making a hard right over or near to Jamaica and for now that forecast looks good to me. Still too early for us to worry about.


Well hopefully it is not over Jamaica. Wouldn't wish it on anyone. Glad to hear I am worrying too soon
lol
Member Since: 19.07.2008 Posts: 0 Comments: 92
1223. SLU
30. lokakuuta 2010 klo 01:34 (GMT)
Quoting pottery:

Well, I did not want to be the one to say it. Yet!


lol
Member Since: 13.07.2006 Posts: 12 Comments: 4734
1222. nopepper
30. lokakuuta 2010 klo 01:33 (GMT)
SLU - nice Pitons pic.

Wishing the best for my newfound friends in the Windwards - including Debra, our rainforest guide on St. Lucia, who is the long-lost twin (looks just like her) of my step daughter's best friend.
Member Since: 25.08.2008 Posts: 0 Comments: 26
1220. SLU
30. lokakuuta 2010 klo 01:32 (GMT)
Quoting DDR:

Hi SLU
are you still in Trinidad?



Yes I am. I was very worried for TnT earlier today but it seems we will be ok.
Member Since: 13.07.2006 Posts: 12 Comments: 4734
1219. 7544
30. lokakuuta 2010 klo 01:32 (GMT)
nhc going tracks south no ne turn hmmmm
could the turn happen further west off western cuba maybe
Member Since: 6.05.2007 Posts: 0 Comments: 6618
1218. hydrus
30. lokakuuta 2010 klo 01:31 (GMT)
Quoting Grothar:


I was told they have a new and improved one, that helps with memory. At least I think that is what they said. Some little storm brewing, eh? I hope it doesn't get too strong.
Well...I think it is a safe bet that Tomas will indeed become our 6th major storm of the season. Chances of this thing remaining below major hurricane status are much slimmer than they are of Tomas attaining cat-3 strength...
Member Since: 27.09.2007 Posts: 1 Comments: 19606
1217. DDR
30. lokakuuta 2010 klo 01:30 (GMT)
Quoting pottery:

Not sure we will get that.

12n heading wnw,expanding feeder bands,i'd say 50% we get some heavy tonight.
Member Since: 27.04.2007 Posts: 14 Comments: 1627
1215. pottery
30. lokakuuta 2010 klo 01:29 (GMT)
Quoting SLU:


Looks like we've got more proof that God is a Trinidadian. lol

Well, I did not want to be the one to say it. Yet!
Member Since: 24.10.2005 Posts: 0 Comments: 23105
1214. geepy86
30. lokakuuta 2010 klo 01:28 (GMT)
new blog
Member Since: 19.08.2008 Posts: 0 Comments: 1691
1213. DDR
30. lokakuuta 2010 klo 01:28 (GMT)
Quoting SLU:


Looks like we've got more proof that God is a Trinidadian. lol

Hi SLU
are you still in Trinidad?

Member Since: 27.04.2007 Posts: 14 Comments: 1627
1212. pottery
30. lokakuuta 2010 klo 01:27 (GMT)
Quoting DDR:
Hey pottery
I just had a light shower pass over me,expecting torrential rains after midnight.

Not sure we will get that.
Member Since: 24.10.2005 Posts: 0 Comments: 23105
1211. kmanislander
30. lokakuuta 2010 klo 01:27 (GMT)
Quoting XL:


lol. Hi how are you doing. This thing is not looking good? Timing wise could this be a repeat of Paloma?


Just finished a good curry chicken so doing very well indeed LOL

The models have Tomas making a hard right over or near to Jamaica and for now that forecast looks good to me. Still too early for us to worry about.
Member Since: 19.08.2006 Posts: 0 Comments: 15671
1210. pottery
30. lokakuuta 2010 klo 01:27 (GMT)
Quoting kmanislander:


Looks like you guys are off the hook on this one, as usual LOL.

Jamaica, and Haiti , are the ones in the cross hairs of a major for now it would seem. Barbados is also in for a very nasty event. Flash flooding tonight coupled with winds to hurricane force in squalls a distinct possibility between midnight and noon tomorrow IMO

Certainly looks good for us now.
And bad for B'Dos and beyond.
Only a trace of rain today here, but would not be surprised to get some showers tonight.
We need some rain, actually.
Member Since: 24.10.2005 Posts: 0 Comments: 23105
1208. CybrTeddy
30. lokakuuta 2010 klo 01:26 (GMT)
RAW T# for Tomas have shot up to 4.0
Member Since: 8.07.2005 Posts: 259 Comments: 23016
1207. amd
30. lokakuuta 2010 klo 01:26 (GMT)
I just checked the pace of activity from August 21st of this year to now and compared that to the same period in 2005:

2005:
Tropical Storms = 15
Hurricanes = 10
Major Hurricanes = 5

2010:
Tropical Storms = 16
Hurricanes = 9 (10 very likely tomorrow)
Major Hurricanes = 5 (6 very likely in the next few days)

This year's activity between August 21st and today has been unprecedented. IMHO.
Member Since: 29.08.2005 Posts: 0 Comments: 1024
1206. TriniGirl26
30. lokakuuta 2010 klo 01:25 (GMT)
Just saw a star in the sky and that is my cue to go get some shuteye...Those in Barbados, Grenada and St. Lucia...make sure and lock up tight.Good night all :)
Member Since: 18.08.2009 Posts: 0 Comments: 201
1205. SLU
30. lokakuuta 2010 klo 01:25 (GMT)
Quoting pottery:

Stay prepared there.
Tomas is full of surprises so far, and more to come for sure...
Quoting DDR:
Hey pottery
I just had a light shower pass over me,expecting torrential rains after midnight.


Looks like we've got more proof that God is a Trinidadian. lol
Member Since: 13.07.2006 Posts: 12 Comments: 4734
1204. AllyBama
30. lokakuuta 2010 klo 01:25 (GMT)
Quoting Grothar:


Funny, my mother-in-law said the same thing when she first met me.


ROFL...that is lots better than what my MIL did at the time..she walked around her house crying and carrying a kleenex!..of course that was 35 years ago..she loves me now - lol
Member Since: 3.08.2006 Posts: 132 Comments: 20614
1203. pottery
30. lokakuuta 2010 klo 01:24 (GMT)
Quoting Mixed:
No Rain Here Yet Just A Wind Gust Here And There Every So Often, Here In St Lucia Just Waiting Patiently, This Thing Has Really Intensified Much Today.

Stay prepared there.
Tomas is full of surprises so far, and more to come for sure...
Member Since: 24.10.2005 Posts: 0 Comments: 23105
1201. XL
30. lokakuuta 2010 klo 01:23 (GMT)
Quoting kmanislander:


You rang ??


lol. Hi how are you doing. This thing is not looking good? Timing wise could this be a repeat of Paloma?
Member Since: 19.07.2008 Posts: 0 Comments: 92
1200. kmanislander
30. lokakuuta 2010 klo 01:23 (GMT)
Quoting pottery:

hehehehhh
Nice one.


Looks like you guys are off the hook on this one, as usual LOL.

Jamaica, and Haiti , are the ones in the cross hairs of a major for now it would seem. Barbados is also in for a very nasty event. Flash flooding tonight coupled with winds to hurricane force in squalls a distinct possibility between midnight and noon tomorrow IMO
Member Since: 19.08.2006 Posts: 0 Comments: 15671
1199. DDR
30. lokakuuta 2010 klo 01:22 (GMT)
Hey pottery
I just had a light shower pass over me,expecting torrential rains after midnight.
Member Since: 27.04.2007 Posts: 14 Comments: 1627
1198. pottery
30. lokakuuta 2010 klo 01:22 (GMT)
Quoting Grothar:


Was that a shot? LOL

From me??
Nahhhh.
Member Since: 24.10.2005 Posts: 0 Comments: 23105
1197. ackee
30. lokakuuta 2010 klo 01:22 (GMT)
looking at Tomas current track does seem like barbados is going to get a pounding. Here in jamaica we will continue keep really good EYE on Tomas
Member Since: 15.07.2008 Posts: 0 Comments: 1341
1196. Mixed
30. lokakuuta 2010 klo 01:21 (GMT)
No Rain Here Yet Just A Wind Gust Here And There Every So Often, Here In St Lucia Just Waiting Patiently, This Thing Has Really Intensified Much Today.
Member Since: 9.08.2010 Posts: 0 Comments: 18
1195. SLU
30. lokakuuta 2010 klo 01:20 (GMT)
Quoting kwads:
It is unfortunate we in St Lucia may not be 100% prepared for a Storm. As you indicated, the information from the NHC was late. The other reason was that we are preparing for our annual Creole Day weekend, which started today. Looking at the system, I am worried that it may be a hurricane before it reaches St. Lucia, which would make things worse. I hope we get some time tomorrow to do some preparation.


Hey kwads. Welcome to the blog. I heard the local news tonight but Tomas didnt even make headlines. Just a comment about the possibility of rains and flooding tonight. Safe to say that the country isn't ready. I hope the doesn't end up being another Tropical Storm Debby scenario.

Member Since: 13.07.2006 Posts: 12 Comments: 4734
1194. weatherwatcher12
30. lokakuuta 2010 klo 01:19 (GMT)
2km Storm Relative IR Imagery with BD Enhancement Curve


From Site:
The same infrared imagery shown in the earth relative framework is displayed in a storm relative framework, with a 2km resolution and enhanced with the "BD Curve" which is useful for directly inferring intensity via the Dvorak Enhanced IR (EIR) technique. Scaling is provided by two lightly hatched circles around the center. The two circles have radii of 1 and 2 degrees latitude, respectively.
Member Since: 16.05.2009 Posts: 1 Comments: 1231

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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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