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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35th!
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I don't even understand how you could think that's an eye....
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Quoting 14. TylerStanfield:

No. Frustrated, but not angry, they're the experts and they can make the call if they want. If they're is enough evidence to back it up, that is.
Yeah I understand your point.
Quoting 18. MAweatherboy1:

There's nothing to justify more than 65. They will just leave it at 65 until the next recon plane goes in. I think it's scheduled for this evening.
I agree I doubt they would increase it to 70mph unless the Air force that is going to enter the center at 8pm finds the winds to do it.
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Quoting 24. Envoirment:
Re-posting this to confirm there is no eye formation in Chantal. Taken at 19:45 UTC



Compare that to Soulik



;)
At least we have 2 storms going on at the same time to compare. Thankfully Soulik is not the one in the Eastern Caribbean or we would be talking BIG problems.
Member Since: June 30, 2013 Posts: 12 Comments: 8774
Quoting 9. Tazmanian:
rule 7 Do not "1st!", "1st post!", or any of the numerical/linguistic derivatives. This is a worthless use of blog space.



just saying


And your post criticizing those "1st posts" isn't a waste of blog space? Who cares... there are hundreds of comments an hour. Ignore the ones you don't like
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my 7 day forecast for Chantal
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47 minutes.
Member Since: June 11, 2013 Posts: 20 Comments: 3383
Jumping "back" on the bandwagon...maybe Chantal WILL do something after all!
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Quoting 18. MAweatherboy1:

There's nothing to justify more than 65. They will just leave it at 65 until the next recon plane goes in. I think it's scheduled for this evening.

8PM ET and supposed to stay in Chantal until 2AM ET.
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Re-posting this to confirm there is no eye formation in Chantal. Taken at 19:45 UTC



Compare that to Soulik



;)
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Quoting 10. HurricaneAndre:
I think 70 at the next advisory,what do you think.
um... no? I'm thinking 60 or 65.
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.
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Quoting 15. Camille33:

Do you see an eye or is my eye decieving me?



no eye
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So the Easterly Jet is the same thing as Speed Shear?

"Chantal's fast west-northwest forward speed of 29 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."

This was my earlier thinking, but what if the islands rip apart Chantal, wouldn't it take on a more westward path and not be able to feel the presence of this trough?
Member Since: June 30, 2013 Posts: 12 Comments: 8774
Thanks Doc lol that was fast though new blog and now new blog
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Quoting 10. HurricaneAndre:
I think 70 at the next advisory,what do you think.

There's nothing to justify more than 65. They will just leave it at 65 until the next recon plane goes in. I think it's scheduled for this evening.
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2013JUL09 194500
CI 3.7
3.7 (Initial) 3.9 (Adjusted) 3.9 (Raw)
UNIFRM
15.1N 63.4W

MAweatherboy, they corrected themselves. =P

no more eye feature
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Quoting 938. HurricaneAndre:
Maybe an eye in the making.

No. It has no eyewall, and the convection is very disorganized. the downdraft boundary has created a hole in the convection which Satellite estimates confused with an eye feature.
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Quoting 9. Tazmanian:
rule 7 Do not "1st!", "1st post!", or any of the numerical/linguistic derivatives. This is a worthless use of blog space.



just saying

Do you see an eye or is my eye decieving me?
Member Since: July 2, 2013 Posts: 0 Comments: 1523
Quoting 944. allancalderini:
Would you be angry if they do it?

No. Frustrated, but not angry, they're the experts and they can make the call if they want. If they're is enough evidence to back it up, that is.
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13. auburn (Mod)
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Tips
Member Since: August 27, 2006 Posts: 547 Comments: 50858
49 minutes, guys! 49 minutes!
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Thanks again Dr. M!
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I think 70 at the next advisory,what do you think.
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rule 7 Do not "1st!", "1st post!", or any of the numerical/linguistic derivatives. This is a worthless use of blog space.



just saying
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Quoting 949. WunderAlertBot:
JeffMasters has created a new entry.

Golly Dr. Masters! Take a break ;) 3 blogs in one day!
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Dr. Master sure has a lot to say today.
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Thanks again Dr. Masters.
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3 blogs is a record.
Member Since: June 14, 2013 Posts: 2 Comments: 2002
Thank you Dr. Masters... Looks like another interesting storm to predict, Seems to be happening more and more
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Thanks.
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Thanks doc! Am I first?!
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Thanks Dr. Masters!

Edit: First!!!!!
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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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