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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This appears to forecast Chantal even a bit more to the West when it passes me...


AMZ101-100945-
SYNOPSIS FOR THE SW N ATLANTIC INCLUDING THE BAHAMAS
535 PM EDT TUE JUL 9 2013

.SYNOPSIS...RIDGE ALONG 32N WILL SHIFT S THROUGH THU THEN RETREAT
EASTWARD. TROPICAL STORM CHANTAL WILL RACE WNW ACROSS THE NE
CARIBBEAN WATERS TONIGHT AND WED...THEN WEAKEN AS IT CROSSES
HISPANIOLA WED NIGHT. THE CENTER OF TROPICAL STORM CHANTAL WILL BE
LOCATED NEAR THE WINDWARD PASSAGE EARLY THU... NEAR 22.0N 75.4W
THU AFTERNOON.
..MOVE ACROSS THE BAHAMAS TO NEAR 26.0N 77.5W FRI
AFTERNOON...THEN NORTHWARD EAST OF FLORIDA TO NEAR 28.0N 78.9W SAT
AFTERNOON AND TO 31.0N 80.0W SUN AFTERNOON.
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105 hrs.

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This has been the hardest storm to forecast
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Quoting 419. stormpetrol:
I don't understand why some are talking about how disorganized Chantal looks, this is best she ever looked to me and some saying that it looks like an open wave, well I guess we're all entitled our opinion and thank goodness we all don't think alike or what a mess the world would be in!
I guess they are looking at convection.
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Chantal reminds me of a Older Kid telling a younger kid to "Go Long", and pumps the ball, waves to the kid again deep, a lil Deeper and never throws da ball.

: )

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428. whitewabit (Mod)
Quoting 416. SFLWeatherman:
84hr


Don't know if I have ever seen that many lows on a model run ..
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Looks like they have a "No Fly" zone over the spill.


Issue Date : July 09, 2013 at 1642 UTC
Location : 75 SW LEV, Louisiana near LEEVILLE VORTAC (LEV)
Beginning Date and Time : Effective Immediately
Ending Date and Time : Until further notice
Reason for NOTAM : Temporary flight restrictions
Type : Hazards
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99 hrs. looks stuck there, might see steering currents collapse.

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Circulation is definetly seen here to be disorganized or in the process of large scale changes.
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Quoting 405. jeffreeysweetypie:
ooops kinda looks like the no left turn into east central coast florida 2 days ago will not happen like i said



Best bets atm are a FL event, that being said there remains a huge amount of questions yet to be answered. I beleive the HH are gunna in fora surprise.
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honestly looking at windsat you wouldn't think there is much of a closed circulation.

Yet its there.

Movement is basically due west right now, and the LLC is definitely reforming. This is going to cause a substantial series of changes in guidance.

I wouldn't be surprised to see a 180 in guidance over the 48 hours all the way back to a WNW track over cuba into the gulf.


Question is what exactly will we be tracking, the system is changing very quickly and very dynamically, yet again.



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Well she is in the graveyard.
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Downdrafts have really stabilized the air within Chantal today, which is evident in the lack of deep organized convection. That massive outflow boundary is also very telling.



Perhaps the coming nightfall will bring better times for the quirky storm?
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I don't understand why some are talking about how disorganized Chantal looks, this is best she ever looked to me and some saying that it looks like an open wave, well I guess we're all entitled our opinion and thank goodness we all don't think alike or what a mess the world would be in!
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Almost here, babe.....
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84hr
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Quoting 412. DataNerd:
Latest windsat imagery:

Circulation appears to be undergoing reformation again.








am hoping when recon gos back in they can short things out
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Miami
NEXRAD Radar

Base Reflectivity 0.50° Elevation
Range 248 NMI



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Latest windsat imagery:

Circulation appears to be undergoing reformation again.





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Member Since: July 17, 2009 Posts: 71 Comments: 26118
Head west Chantal and bring joy to some other wishcaster's heart.
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Quoting 388. wunderkidcayman:
recon leaves the tarmac in about 3 hours
one thing we can say now because of where Chantal is now it will be short flight for recon to get there and when recon fly we will get a much better idea on where the LLCOC because IMO its not where NHC has it now I think


I have the center at 14.9N/64.1W, where do you have it?
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Quoting 401. Patrap:
THE GUIDANCE ENVELOPE SHIFTED WESTWARD IN THE LAST
RUN AND CONSEQUENTLY...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.
Quoting 401. Patrap:
THE GUIDANCE ENVELOPE SHIFTED WESTWARD IN THE LAST
RUN AND CONSEQUENTLY...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.
Quoting 401. Patrap:
THE GUIDANCE ENVELOPE SHIFTED WESTWARD IN THE LAST
RUN AND CONSEQUENTLY...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 supposed this is because the models are now taking into consideration the disorganized nature of Chantal
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Starting to redevelop in 87 hrs. Link
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Quoting 401. Patrap:
THE GUIDANCE ENVELOPE SHIFTED WESTWARD IN THE LAST
RUN AND CONSEQUENTLY...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 mentioned that just a while ago
Member Since: June 13, 2009 Posts: 2 Comments: 11975
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Quoting 395. Hurricane12:
When is DMAX (in EST)?

peaks at sunrise but starts up at about 12 midnight
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Quoting 394. NCHurricane2009:

That would be crazy if they find its a tropical wave still with 65 mph max winds...

not at this hour.
but if you saw the system early this morning it was disorganized and then pulled itself together as it rode over the islands. now it's shattered again.
stranger in a strange land
grok!
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THE GUIDANCE ENVELOPE SHIFTED WESTWARD IN THE LAST
RUN AND CONSEQUENTLY...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.
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The GFS is nowhere near as enthusiastic about a Cape Verde storm as it was yesterday and the day prior. Strange.
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Quoting 390. cchsweatherman:
Just gauging by satellite appearances this evening, I believe the Hurricane Hunters are in for a challenging mission as far as finding an organized tropical system tonight. Tropical Storm Chantal has more of an appearance of a robust tropical wave this evening rather than an organized tropical cyclone, in my opinion.


That could be possible but They may find some near hurricane force winds. It was looking poorly this morning and they stil manages to find strong winds. This is not an ordinary storm
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RECON TEAL 71 goes Wheels up at 8pm EST
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Quoting 393. wunderkidcayman:

when 11pm comes that track will shift W


If it keeps shifting west then that means its pretty much doomed because it will be over more land than water
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Quoting 390. cchsweatherman:
Just gauging by satellite appearances this evening, I believe the Hurricane Hunters are in for a challenging mission as far as finding an organized tropical system tonight. Tropical Storm Chantal has more of an appearance of a robust tropical wave this evening rather than an organized tropical cyclone, in my opinion.


Agreed. From a large-scale forecasting perspective, especially considering that there are mountains to cross, we are essentially talking about a glorified tropical wave that will have a chance at developing north of the Caribbean, but is currently not truly developed.
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When is DMAX (in EST)?
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Quoting 390. cchsweatherman:
Just gauging by satellite appearances this evening, I believe the Hurricane Hunters are in for a challenging mission as far as finding an organized tropical system tonight. Tropical Storm Chantal has more of an appearance of a robust tropical wave this evening rather than an organized tropical cyclone, in my opinion.

That would be crazy if they find its a tropical wave still with 65 mph max winds...
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Quoting 383. Patrap:



when 11pm comes that track will shift W
Member Since: June 13, 2009 Posts: 2 Comments: 11975
Just wondering if a weaker Chantal would change any future model run. I think the models are being a little bit aggressive on it given what the Dr. discussed above.

Any suggestions?
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so close and yet so far
really unusual storm.
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Just gauging by satellite appearances this evening, I believe the Hurricane Hunters are in for a challenging mission as far as finding an organized tropical system tonight. Tropical Storm Chantal has more of an appearance of a robust tropical wave this evening rather than an organized tropical cyclone, in my opinion.
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Quoting 377. VirginIslandsVisitor:


Actually, no. USVI over here, St. Thomas. It's always the "unless something changes" that makes us pull the boats. No one in their right mind wants to have to do that in the dead of night. Better safe than sorry is what we say.

-L


Concur, it is always better to prepare early than later. Stay safe and have a 'pain-killer' for me.
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recon leaves the tarmac in about 3 hours
one thing we can say now because of where Chantal is now it will be short flight for recon to get there and when recon fly we will get a much better idea on where the LLCOC because IMO its not where NHC has it now I think
Member Since: June 13, 2009 Posts: 2 Comments: 11975
Quoting 367. oceanspringsMS:


It must have a heavier hydrocarbon in it than just methane or ethane(natural gas) if it is leaving a sheen. Otherwise it would just dissipate into the atmosphere


Article whitewabit posted says "natural gas and crude oil" There's your answer, crude floats on the water and subsequently sheens out.
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Quoting 383. Patrap:




The SW turn at the end of several of those runs is interesting.
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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.