Unusual Chantal Disorganized, but has 65 mph Winds

By: Dr. Jeff Masters , 8:06 PM GMT on July 09, 2013

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Unusual Tropical Storm Chantal has strengthened a bit more as it speeds west-northwestwards at 26 mph away from the the Lesser Antilles Islands. Sustained winds of 38 mph, gusting to 52 mph, were observed at Martinique at 10 am AST as the storm passed. However, an automated weather station at the airport measured sustained winds of 60 mph, gusting to 78 mph, according to an official with Meteo-France. The Associated Press reported that Chantal ripped the roofs off of several homes on neighboring Dominica. An Air Force hurricane hunter aircraft measured top winds at their 1,000' flight level of 89 mph at 12:55 pm AST. Top winds seen by the aircraft's SFMR instrument were about 65 mph, in a small area east of Chantal's center. The Hurricane Hunters have departed Chantal, and the next plane is due in the storm at 8 pm EDT. Chantal's winds are unusually high considering the storm's high central pressure of 1006 mb and disorganized appearance on satellite imagery. Chantal is fighting dry air associated with the Saharan Air Layer (SAL), as seen on water vapor satellite loops. This dry air is creating strong thunderstorm downdrafts that are robbing Chantal of moisture and energy. Visible satellite loops show the outflow boundaries of these thunderstorm downdrafts at the surface, spreading to the northwest of Chantal. Martinique Radar shows a large area of heavy rain that is not well-organized, lying mostly to the west of the Lesser Antilles Islands.


Figure 1. MODIS image of Chantal taken at approximately 1 pm EDT Tuesday, July 9, 2013. At the time, Chantal had top winds of 65 mph, but looked very disorganized, due to high wind shear and dry air. Dry air is creating strong thunderstorm downdrafts that are robbing Chantal of moisture and energy. Outflow boundaries from these downdrafts are spreading out to the northwest of Chantal, as seen on this satellite image. Image credit: NASA.

An small-scale easterly jet creating high shear in Chantal
Chantal is not very impressive on satellite images, with a modest amount of heavy thunderstorms that are not well-organized. Only a small amount of upper-level outflow is visible. The reason for Chantal's rather disorganized appearance can be found by looking at this morning's balloon sounding from Guadaloupe. This island was just northwest of the center of Chantal when the balloon was launched at 8 am EDT. The sounding showed typical easterly trade winds at the surface of 12 knots (14 mph.) However, the winds rose quickly aloft, with a jet of easterly winds of 35 - 53 knots between 800 - 600 mb (about 7,000 - 15,000'.) But, by the time the ballon hit 500 mb (18,000'), the winds had died down to 15 knots. A change of wind speed from 12 knots to 53 knots and back down to 15 knots from the surface to 500 mb is a tremendous amount of wind shear, which will make it very difficult for a tropical storm to keep the surface center aligned with the upper level center. The traditional measure of wind shear, the difference in wind between 200 mb and 850 mb, was 44 knots in this morning's Guadaloupe sounding, but was a much higher 56 knots from 200 mb to 700 mb. The powerful easterly wind jet was not apparent at any of the other balloon soundings this morning at adjacent islands (Barbados, Puerto Rico, Saint Martin), and demonstrates that there is a lot going on the atmosphere at small scales we cannot see which makes intensity forecasting of tropical cyclones very challenging. Thanks go to Jason Dunion of NOAA's Hurricane Research Division for pointing out this morning's interesting Guadaloupe sounding.

Forecast for Chantal
Chantal will have difficulty intensifying much more before hitting Hispaniola on Wednesday afternoon. In their 11 am EDT wind probability forecast, NHC gave Chantal a 29% chance of becoming a hurricane before hitting Hispaniola. Working against intensification will be the high wind shear from the strong mid-level easterly jet discussed above, plus the fast forward speed of the storm--tropical storms moving faster than 20 mph in the deep tropics usually have trouble intensifying. In addition, the Eastern Caribbean is an area where the trade winds accelerate, helping drive sinking air that discourages tropical storm intensification. Dry air will also slow down the intensification process. Interaction with the high mountains of Hispaniola and high wind shear may be able to destroy Chantal by Thursday. The 2 pm EDT Tuesday wind shear forecast from the SHIPS model calls for shear to rise to the high range, 20 - 35 knots, Tuesday night through Friday. On Saturday, when Chantal is expected to be in the Bahamas, moderate wind shear of 10 - 20 knots is predicted. If Chantal survives until Saturday, it will then have the opportunity to re-strengthen. The latest 12Z run of the European model (ECMWF) dissipates Chantal as it crosses Hispaniola. The 12Z run of the American GFS model has Chantal barely surviving.

Chantal's fast west-northwest forward speed of 26 mph will slow to 20 mph by Wednesday morning and then 10 mph by Thursday night, as the storm "feels" the presence of a trough of low pressure over the U.S. East Coast. This trough will steer Chantal to the northwest and then north-northwest across Hispaniola and into the Bahamas. The trough of low pressure pulling Chantal northwards is expected to lift out the the northeast over the weekend, leaving Chantal behind off the coast of Florida. High pressure will likely build in, potentially forcing Chantal westwards into the Florida or Southeast U.S. coast, with a possible Sunday landfall.

Jeff Masters

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Quoting 265. nrtiwlnvragn:


Link


Thanks, really nice. Quote from that interview (especially for WU, lol):

We've had an infusion of new blood in the hurricane specialist unit during the past few years. Do you see in them a little bit of what you went through?

Avila: Oh yes. Some of them are really excited just like me. They think they know how to forecast and come in very "pompous". But everyone will learn, or have already learned, that it's not that simple. When I finished fresh from school, I thought I was going to solve all of the problems, be able to predict intensity, be able to do everything. But as soon as you put your name on that forecast, you become very humble. And that's good. I am glad people are coming with a lot of enthusiasm, and they bring new ideas and new techniques.
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Quoting 278. georgia325:
I'm in Jamaica until Saturday and am really hoping Chantal just skates on by. We have thunderstorms right now.


Chantal may come to Georgia on Sunday/Monday. You'll be just in time!
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Quoting 276. Dakster:


They have a cream for that.

I was a little concerned. I don't like all CAPS either, but all caps is required because some programs/technologies in use still can't handle lower case.
208 was NHC quote as well? I wasn't sure.
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283. FOREX
I'm just happy that the Florida panhandle near Panama City Beach is out of the woods. We have had enough rain.
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Quoting 249. washingtonian115:
What does Alivia look like?
Here Washi, Dr. Lixion Avila image
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Quoting 262. MAweatherboy1:

I think DMIN is actually affecting Chantal now, convection has warmed:



Agreed, its at DMIN now. It's looking very ragged right now. Going to be interesting to see what it looks like in the AM and if it can recover itself.
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Hopefully that oil spill in the gulf is just a little minor thing, sounds like that's all it is and they can get it stopped quickly hopefully. At least at this point Chantal isn't forecast to go into the gulf. There are so many areas that don't need the rain that Chantal will bring with it. I have seen the flooding photos from North Carolina so I know they really don't need it. In a perfect world it would curve out to sea and not bother anyone. Just be a storm that the fine folks on the blog could track and discuss
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Quoting 243. cruzinstephie:

I think it will track west into Florida. I think a more northerly solution is unrealistic.


Maybe your post is before he NHC official 5 pm track, but they already forecast it to be off the GA shore on Sunday.
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I'm in Jamaica until Saturday and am really hoping Chantal just skates on by. We have thunderstorms right now.
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Notice what just a few hours of 29C water has done compared to 28C. Chantal has grown considerably in size and symmetry on visible and RGB.
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Quoting 267. Bluestorm5:
Might be reaction to 208, Dakster.


They have a cream for that.

I was a little concerned. I don't like all CAPS either, but all caps is required because some programs/technologies in use still can't handle lower case.
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275. whitewabit (Mod)
Quoting 250. Dakster:


A respectful question - When you quote the NHC that is how they type. Is cutting and pasting portions of their text inappropriate?


quoting text from the NHC that is capitalized is extempt but don't over do the quotes ..
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However, Chantal is so small and has such a high central pressure that I think it is more likely than not that Hispaniola kills her.
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I met Avila the day after Quikscat failed, he was in NOLA for the Cuban/US Hurricane Conference.
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Looking more and more like a Inital landfall somewhere on the East coast of Florida and a second landfall in the gulf.
Member Since: May 1, 2013 Posts: 0 Comments: 776
Results for Provo, TCI (21.78N, 72.27W):

The approximate Closest Point of Approach (CPA) is located near 20.9N, 73.2W or about 84.3 miles (135.6 km) from your location. The estimated time of when the center of the storm will be at that location is in about 1 day, 15 hours and 40 minutes from now (Thursday, July 11 at 8:42AM AST).

the little shift west in the forecast pleases me
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He's not young. Here is his bio. Received a degree in 1973. A very decorated forecaster too.

http://www.nhc.noaa.gov/staff/avila_2012.pdf

Link
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Quoting 258. Levi32:


In my mind there are only two likely possibilities:

1. Hispaniola/Cuba shreds Chantal and leaves an open wave in a sheared environment incapable of regenerating enough convection to recover.

2. Chantal is able to redevelop a circulation north of the greater Antilles and generate significant convection. The resulting heating aloft would allow Chantal to take advantage of the developing col in the upper-level flow and begin restrengthening about 24 hours after entering the SW Atlantic, continuing through landfall.


Assuming option 2, about how strong do you think Chantal would get?
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Quoting 250. Dakster:


A respectful question - When you quote the NHC that is how they type. Is cutting and pasting portions of their text inappropriate?
Might be reaction to 208, Dakster.
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Seeing more of a surface reflection now from the ULL


click image for Loop

click loop to ZOOM




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Quoting 249. washingtonian115:
What does Alivia look like?


Link
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I think Chantal's LLCOC is near 15.0N 63.9W moving W-WNW
Member Since: June 13, 2009 Posts: 2 Comments: 12697
Quoting 254. Chucktown:


DMAX won't occur until tomorrow morning. It's got awhile until then.

I think DMIN is actually affecting Chantal now, convection has warmed:

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Quoting 246. Dakster:


Yes. This could be disasterous for us both Patrap.


Relax guys. First of all, it has to survive Hispanola and not get decoupled, which is still a possibility. Then, assuming there is a hard left hook over FL, it has to survive that into the Gulf. I'm not saying this is impossible....just unlikely at this point.
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Quoting 238. Patrap:


I always cringe when they start shifting WEST.



"Grumbles, walks away mumbling, Water, Jenny, Pets,"



Right there with ya!

Water: check
Genny: check
Shutters: check
Food: check
Ice: check
Beer: check, check, check, X, X check...
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Quoting 249. washingtonian115:
What does Alivia look like?


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Quoting 234. BaltimoreBrian:


Do you forecast strengthening? I'm not seeing anything that would weaken Chantal off the Florida coast.


In my mind there are only two likely possibilities:

1. Hispaniola/Cuba shreds Chantal and leaves an open wave in a sheared environment incapable of regenerating enough convection to recover.

2. Chantal is able to redevelop a circulation north of the greater Antilles and generate significant convection. The resulting heating aloft would allow Chantal to take advantage of the developing col in the upper-level flow and begin restrengthening about 24 hours after entering the SW Atlantic, continuing through landfall.

It seems to me the environment in the col after 96 hr will allow Chantal to do what she wants. If she's already dead she would be unlikely to come back, but if she has life she would restrengthen, not both or something in between.
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Quoting 252. BaltimoreBrian:


The big question is why do the models keep Chantal weak? What do they 'see'?

dry air, shear, land
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I believe the NHC nailed this one for the first time they show strengthening in the Caribbean and it happen.Many of us actully thought she will not even be a ts when reaching the Caribbean that is why they are the experts.
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Quoting 249. washingtonian115:
What does Alivia look like?


He can't be young. He wrote some of the discussions for Andrew.
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Quoting 231. Hurricanes305:


Starting to take shape structure is definitely improving. As we head for DMAX. The Recon may find stronger winds by then. But she has put on some weight


DMAX won't occur until tomorrow morning. It's got awhile until then.
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Quoting 184. taco2me61:
Do I see 65MPH Chantal and I was told they do not use the 5MPH winds it's either 60 or 70..... Can you help me out Taz

Tanks Taco :o)


They do use winds with 5 as the one's digit. It is only 55 mph that is not used since it doesn't correspond well with a knot value. 45 knots~51.8 mph. 50 knots~57.5 mph. They list 45 knots as 50 mph and 50 knots as 60 mph.

NHC updates are written in the unit of knots, not mph. They translate the speed in knots into miles per hour, but in reality, when we talk about storm strength, it is correct to speak about wind speed in knots.

I believe that the same is true for 95 mph (80 knots=92 mph, so it would be 90, 85 knots=97.8 mph, so it would be 100).
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Quoting 239. TropicalAnalystwx13:

He's probably not comfortable given lack of model support for a stronger storm.



The big question is why do the models keep Chantal weak? What do they 'see'?
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Quoting 237. Envoirment:
JTWC have offically updated Soulik's strength (115kts) and forecast. Expected to be a Super Typhoon (130kts) tomorrow morning



Great looking storm, lousy path. I'm assuming the people in this area are ready for what's coming.
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Quoting 240. whitewabit:
2nd and last warning ..

commenting in upper case is considered shouting and is RUDE ..

this needs to stop !


A respectful question - When you quote the NHC that is how they type. Is cutting and pasting portions of their text inappropriate?
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What does Alivia look like?
Member Since: August 14, 2010 Posts: 10 Comments: 17492
248. txjac
Quoting 232. Patrap:


I dislike all the purple in Texas ...
I heard thunder about an hour ago but no rain.

I see some little storms that might produce something this evening.

Would love to see either the blob around Florida come this way
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I mean, Chantal would cross the Gulf Stream for part of its track. The shelf waters have a thin layer of warm water but enough to sustain a Cat 1 or 2 I would think. Not that it would get to upper-end Cat 1 or 2, I don't think there is enough time, especially if the storm moves more west than forecast. But a strong TS or Cat 1 is reasonable.
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Quoting 238. Patrap:


I always cringe when they start shifting WEST.



"Grumbles, walks away mumbling, Water, Jenny, Pets,"



Yes. This could be disasterous for us both Patrap.
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Quoting 229. Levi32:
Avila still doesn't explain why he forecasts weakening between Days 4 and 5, despite showing restrengthening for a time before that.


Hey Levi, what do you think about the latest northerly track up to the SE coast?
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Quoting 229. Levi32:
Avila still doesn't explain why he shows weakening between Days 4 and 5, despite showing restrengthening for a time before that.



Levi her sat picture looks, well, ugly to say the least. That leading edge squall line is due to dry and and sheer.
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Quoting 235. GTstormChaserCaleb:
Looks like the NHC is expecting another westward shift in the models.
I think it will track west into Florida. I think a more northerly solution is unrealistic.
Member Since: August 31, 2008 Posts: 0 Comments: 5
I wondered how this storm was going to make it through all that shear, and I just got my answer:
It's probably not.


I know the shear is forecast to weaken, but if Chantal is reduced to smithereens in the meantime then there won't be much left to her by the time Hispaniola gets through her. We can hope, anyway.
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Quoting 230. Dakster:
.THE OFFICIAL FORECAST WAS ADJUSTED IN THAT
DIRECTION...BUT NOT AS FAR AS THE MODEL CONSENSUS. IF THIS WESTWARD
MODEL TREND CONTINUES IN THE NEXT CYCLE...I WILL NOT BE SURPRISED
IF ANOTHER WESTWARD SHIFT WILL BE REQUIRED.


Congrats to the few, the proud , the WU bloggers who saw this...
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240. whitewabit (Mod)
2nd and last warning ..

commenting in upper case is considered shouting and is RUDE ..

this needs to stop !
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Quoting 229. Levi32:
Avila still doesn't explain why he forecasts weakening between Days 4 and 5, despite showing restrengthening for a time before that. I think that whatever the trend is in the Bahamas, weakening or strengthening, would continue beyond that point.

He's probably not comfortable given lack of model support for a stronger storm.

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Quoting 230. Dakster:
.THE OFFICIAL FORECAST WAS ADJUSTED IN THAT
DIRECTION...BUT NOT AS FAR AS THE MODEL CONSENSUS. IF THIS WESTWARD
MODEL TREND CONTINUES IN THE NEXT CYCLE...I WILL NOT BE SURPRISED
IF ANOTHER WESTWARD SHIFT WILL BE REQUIRED.


I always cringe when they start shifting WEST.



"Grumbles, walks away mumbling, Water, Jenny, Pets,"

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JTWC have offically updated Soulik's strength (115kts) and forecast. Expected to be a Super Typhoon (130kts) tomorrow morning




Click image for larger size.
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Quoting 209. Dakster:


Yes, we are in agreement...

I can't answer your question. I give up. What interests does it serve us taxpayers?


It doesn't! It serves private industry, against the tax payers. Thus my initial outrage at the implementation of such a tool.

The US is Trillions in Debt. The Blue angels Can't fly. But we can provide this new tool for the energy market? (shakes head)



(Yes Mods, this is weather related. The first post that started this regards a new tool to predict tropical weather impact on energy prices.)
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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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