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 1358. cchsweatherman:
Given the lack of hurricane hunter data except for in the northwest quadrant and the advisory coming within the next 20 minutes, I'd expect that the NHC will maintain continuity with the intensity of Chantal until they get better data and then may do a special advisory later if there are any changes.
They've sampled both the northwestern and northeastern octants with extremely unimpressive winds.
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1385. Patrap
Member Since: July 3, 2005 Posts: 428 Comments: 129844
Quoting 1348. unknowncomic:
Nice clip. Do you chase Canes too.


yup yup!! just drives that thing out to the MDR and waits for one to come along! :)
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this thing could be dying on us i guess
Member Since: September 8, 2010 Posts: 0 Comments: 2231
And there you go, lol. Local MET says she is dying. HH having trouble finding center let alone tropical storm force winds. Lil Red ball is gone.

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1381. Relix
Quoting 1365. sunlinepr:


Wind gust 28mph and rain band in Caguas, PR....


Looking at the radar....

FINALLY!
Member Since: August 3, 2006 Posts: 0 Comments: 2741
So now the pressures are falling as they approach 16N... what the heck is going on?
Member Since: September 22, 2005 Posts: 18 Comments: 2343
1379. GetReal







I don't see this system turning more northerly until it is just off the NE tip of Jamaica.
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Quoting 1360. bappit:
They fly the mission to collect data, not satisfy voyeuristic tendencies. Now, what are they doing now? Hmmmmm.


Neither.
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1377. Patrap
Member Since: July 3, 2005 Posts: 428 Comments: 129844
Who flies into Asian pacific storms like Soulik to gather data?
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1375. will40
15.983N 66.200W

they still north
Member Since: September 19, 2005 Posts: 2 Comments: 4266
Quoting 1360. bappit:
They fly the mission to collect data, not satisfy voyeuristic tendencies. Now, what are they doing now? Hmmmmm.


I'm sorry, but they haven't flown a proper route to collect data about the entire circulation.
Member Since: January 25, 2012 Posts: 33 Comments: 1520
PR!
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1372. FOREX
Quoting 1354. scottsvb:
Chantal is pulsating. Her pressure is still around 1009mbs and is really a weak TS. Her winds exceeded 55Kts earlier today as she went through the leeward islands. Combination of her winds, easterly trades and wind blowing through the islands of St Lucia-St Martinque could of helped increase the gradient somewhat (unknown). She should continue to pulse into weds morning. Once she slows down and gets north of Cuba....she can get better organized. I think though she will get further west. Might not even turn NW-NNW until Thurs evening and make it to central Cuba around 21N and 77W. Best guess is Haiti-Central Cuba and be SE of the Keys and south of Andros island Bahamas by Friday.


nope.
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Quoting 1360. bappit:
They fly the mission to collect data, not satisfy voyeuristic tendencies. Now, what are they doing now? Hmmmmm.
Lol.
Member Since: August 14, 2010 Posts: 10 Comments: 17814
1370. Patrap
backo

At 02:17:30Z (last observation), the observation was 168 miles (271 km) to the S (183°) from San Juan, Puerto Rico (USA).



Product: Air Force High Density (HDOB) Message (URNT15 KNHC)
Transmitted: 10th day of the month at 02:40Z
Date: July 10, 2013
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 306)
Storm Number: 03
Storm Name: Chantal (flight in the North Atlantic basin)
Mission Number: 3
Observation Number: 22

02:17:30Z 15.983N 66.200W 714.1 mb
(~ 21.09 inHg) 3,015 meters
(~ 9,892 feet) 1012.3 mb
(~ 29.89 inHg) - From 133° at 31 knots
(From the SE at ~ 35.6 mph) 10.7°C
(~ 51.3°F) 8.0°C
(~ 46.4°F) 36 knots
(~ 41.4 mph) - - - -
Time Coordinates Aircraft
Static Air Pressure Aircraft
Geopotential Height Extrapolated
Surface Pressure D-value Flight Level Wind (30 sec. Avg.) Air Temp. Dew Point Peak (10 sec. Avg.)
Flight Level Wind SFMR
Peak (10s Avg.) Sfc. Wind SFMR
Rain Rate Estimated Surface Wind (30 sec. Avg.)
Using Estimated Reduction Factor Peak Wind at Flight Level to
Est. Surface Reduction Factor
HDOB Observations
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my guess is that they wont send the 11:00 update until about 10:55
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Quoting 1343. Dakster:


Yes - because they know it annoys us.


Lol
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1367. will40
just got a recon ob
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Quoting 1357. Relix:


Send some to metro area please :P


Wind gust 28mph and rain band in Caguas, PR....
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Quoting 1344. RTSplayer:
Ok, this thing agrees with me for center fix, so either we're both wrong, or we're both right.



If you can't see it, there is a yellow dot imbeded in the black shading in the nw side of the convection in the center of the concentric rings.



That jives nicely with PR radar, and the recent wind barbs from recon. (though they still haven't gotten to the South side (or if they did we sure don't have the data yet).
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Quoting 1350. aislinnpaps:
Had to do some Club business, hate when I miss what's going on. What's this about model from SC to LA?


Well, ask Patrap about it, I'm not sure where he gets that product. The LA model was an outlier, HOWEVER it is somewhat consistent with 2 of the top 6 models' present forecast track.
Member Since: January 25, 2012 Posts: 33 Comments: 1520
And thus the suspense continues lol this is one unique storm.
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1360. bappit
They fly the mission to collect data, not satisfy voyeuristic tendencies. Now, what are they doing now? Hmmmmm.
Member Since: May 18, 2006 Posts: 10 Comments: 6157
HH needs to fly in the convective burst. They also need to try and find a center. lol
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Given the lack of hurricane hunter data except for in the northwest quadrant and the advisory coming within the next 20 minutes, I'd expect that the NHC will maintain continuity with the intensity of Chantal until they get better data and then may do a special advisory later if there are any changes.
Member Since: April 14, 2007 Posts: 8 Comments: 5169
1357. Relix
Quoting 1332. raggpr:
I just got a wind gust of 35 mph on the southeast part of Puerto Rico


Send some to metro area please :P
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1356. Dakster
Quoting 1350. aislinnpaps:
Had to do some Club business, hate when I miss what's going on. What's this about model from SC to LA?


Wait for the new NHC update at 11pm.
Member Since: March 10, 2006 Posts: 0 Comments: 10790
AF HDOB (URNT15) (26) (Minutes since ob are noted)


"Turn off the instruments, guys! This is pointless..."
Member Since: September 22, 2005 Posts: 18 Comments: 2343
Chantal is pulsating. Her pressure is still around 1009mbs and is really a weak TS. Her winds exceeded 55Kts earlier today as she went through the leeward islands. Combination of her winds, easterly trades and wind blowing through the islands of St Lucia-St Martinque could of helped increase the gradient somewhat (unknown). She should continue to pulse into weds morning. Once she slows down and gets north of Cuba....she can get better organized. I think though she will get further west. Might not even turn NW-NNW until Thurs evening and make it to central Cuba around 21N and 77W. Best guess is Haiti-Central Cuba and be SE of the Keys and south of Andros island Bahamas by Friday.
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Quoting 1348. unknowncomic:
Nice clip. Do you chase Canes too.


I've intercepted two of them, Hurricane Irene in Atlantic Beach, NC. And Hurricane Isaac in Gulfport, Mississippi.
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1350. aislinnpaps
2:38 AM GMT on July 10, 2013
Had to do some Club business, hate when I miss what's going on. What's this about model from SC to LA?
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1349. weatherlover94
2:38 AM GMT on July 10, 2013
the hurricane hunters may be having equipment trouble
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1348. unknowncomic
2:38 AM GMT on July 10, 2013
Quoting 1336. tornadodude:
Just put together a clip with some of my highlights from this past storm chase season, check it out!

Nice clip. Do you chase Canes too.
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1347. will40
2:38 AM GMT on July 10, 2013
Quoting 1342. MechEngMet:


You noticed that too huh?


yes and usually after i say that they update but no luck yet
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1346. viman
2:38 AM GMT on July 10, 2013
It will be very interesting to read the 11pm discussion. Must be having a meeting of the minds on this one... Well gee one minute it was there and then... poof... where did it go, where did it go???
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1345. sunlinepr
2:37 AM GMT on July 10, 2013
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1344. RTSplayer
2:37 AM GMT on July 10, 2013
Ok, this thing agrees with me for center fix, so either we're both wrong, or we're both right.



If you can't see it, there is a yellow dot imbeded in the black shading in the nw side of the convection in the center of the concentric rings.
Member Since: January 25, 2012 Posts: 33 Comments: 1520
1343. Dakster
2:37 AM GMT on July 10, 2013
Quoting 1339. cchsweatherman:
Any particular reason why there has been an absence of data for nearly a half hour now from the Hurricane Hunters?


Yes - because they know it annoys us.
Member Since: March 10, 2006 Posts: 0 Comments: 10790
1342. MechEngMet
2:37 AM GMT on July 10, 2013
Quoting 1323. will40:
hh hasnt updated on the Atlantic site in quite a while


You noticed that too huh?
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1341. Patrap
2:36 AM GMT on July 10, 2013
I have no downlink in google.

my last recieved.

Product: Air Force High Density (HDOB) Message (URNT15 KNHC)
Transmitted: 10th day of the month at 02:07Z
Date: July 10, 2013
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 306)
Storm Number: 03
Storm Name: Chantal (flight in the North Atlantic basin)
Mission Number: 3
Observation Number: 21
Member Since: July 3, 2005 Posts: 428 Comments: 129844
1340. Camille33
2:36 AM GMT on July 10, 2013
Quoting 1334. hurricanes2018:
20 west!!

What is going on in bahamas?
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1339. cchsweatherman
2:36 AM GMT on July 10, 2013
Any particular reason why there has been an absence of data for nearly a half hour now from the Hurricane Hunters?
Member Since: April 14, 2007 Posts: 8 Comments: 5169
1338. MechEngMet
2:36 AM GMT on July 10, 2013
Quoting 1319. bappit:
Amateurs in the cheap seats know more than the pros? Then they should get out there and fly the plane.


Okay! Turn heading 150, and then keep the wind direction straight down your left wing. When the wind shifts to straight up the right, wing mark the GPS coord. (hint that'd be the center)
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1337. SavannahStorm
2:36 AM GMT on July 10, 2013
Does anyone know if they'll send the G-IV in to gather upper-air data? I haven't seen anything on their Plan of the Day that indicates they intend to.
Member Since: September 22, 2005 Posts: 18 Comments: 2343
1336. tornadodude
2:35 AM GMT on July 10, 2013
Just put together a clip with some of my highlights from this past storm chase season, check it out!

Member Since: June 28, 2006 Posts: 25 Comments: 8360

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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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