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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No mention yet of African wave.

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT TUE JUL 9 2013

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON TROPICAL
STORM CHANTAL...THAT IS CURRENTLY MOVING ACROSS THE EASTERN
CARIBBEAN SEA.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BROWN
Member Since: April 29, 2009 Posts: 75 Comments: 14076
Typhoon Soulik looks marvelous


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the 8:00 advisory may be brought down to 60 or 50 mph
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Quoting 655. Joanie38:



Yes I do
Quoting 669. will40:



welcome anytime Joanie



On Firefox....it works YAY!!!
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I know this an internet blog, but for the life of me, I dont understandwhy people write it off or say what they dont know or understand 4-5 days out. Regardless of what happens some where along the SE coast people will be effected by this whether its a rain storm or a CAT12 (sarcasm). OK rant over.
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Quoting 672. RTSplayer:
"Open waves" don't have 360 degrees worth of 50kts winds.



Let's see what recon finds. In-situ measurements are better anyway.
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Quoting 670. heliluv2trac:
chantel will go straight to the carribean and into the gulf the storm is weak weak storms go west strong storms go north it will not feel the weakness


you might should e_mail the NHC and tell them that
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674. FOREX
Quoting 670. heliluv2trac:
chantel will go straight to the carribean and into the gulf the storm is weak weak storms go west strong storms go north it will not feel the weakness
yuuuuuuup
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Quoting 672. RTSplayer:
"Open waves" don't have 360 degrees worth of 50kts winds.



these products are rather unreliable
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"Open waves" don't have 360 degrees worth of 50kts winds.

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You can see the outflow boundaries and the thunderstorms caused by them affecting PR on radar.

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chantel will go straight to the carribean and into the gulf the storm is weak weak storms go west strong storms go north it will not feel the weakness
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Quoting 666. Joanie38:


Ok, thank you Will for your help!!! :)



welcome anytime Joanie
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It is not out of the question that Chantal may need to go on life support a while if convection doesn't start to refire soon. It's waning right now
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Time: 23:17:30Z
Coordinates: 16.7667N 63.6167W
Acft. Static Air Press: 842.9 mb (~ 24.89 inHg)
Acft. Geopotential Hgt: 1,629 meters (~ 5,344 feet)
Extrap. Sfc. Press: 1017.5 mb (~ 30.05 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 132 at 40 knots (From the SE at ~ 46.0 mph)
Air Temp: 15.5C (~ 59.9F)
Dew Pt: 12.6C (~ 54.7F)
Peak (10s) Flt. Lvl. Wind: 42 knots (~ 48.3 mph)
SFMR Peak (10s) Sfc. Wind: 31 knots (~ 35.6 mph)
SFMR Rain Rate: 0 mm/hr (~ 0 in/hr)
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Quoting 658. will40:


try it and see if same thing happens ok?


Ok, thank you Will for your help!!! :)
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Quoting 657. moonlightcowboy:


You got Georgia on you mind, man? ;)


She ain't going to Georgia.


Not likely, no. Prob a FL event if there is an event to be had. LOL!
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Not liking that "bouncing off and backing into" the Florida panhandle. Rained here for 6 days straight, thought I might need to build an ark.

So much rain for the MS/AL/FL coastline this last week that we need to dry out before a tropical event happens.
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Interesting final Viz frames..
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AL032013 - Tropical Storm CHANTAL

Storm Relative 1km Geostationary Visible Imagery

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..weaker go west,.stronger goes Poleward
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Quoting 636. TomTaylor:
See the faster winds out ahead of Chantal, in the Central Caribbean, in the image below?




That is the Caribbean Low-Level Jet (CLLJ). This low-level jet exists semi-permanently as a result of the pressure difference between the subtropical Atlantic ridge and the monsoon/heat low over central America and NW South America (sometimes called the Columbian heat low). Accelerating trade winds ahead of the storm are incredibly detrimental to the low-level organization of a storm. Accelerating trade winds rob the storm of convergence and naturally make it harder for the storm to close off it's circulation. This can cause the storm to degenerate into an open wave, like Ernesto did last year. Additionally, the structure of the low-level flow around the COC gets distorted with accelerating trade winds. The amplitude decreases and wavelength increases creating a duller, less pronounced perturbation in the wind field. This means less convergence, less organization and an expansion of the wind field.

Chantal may very well have degenerated into an open wave by now. Will be interesting to see what recon shows...


Do you have the model image 48 or 96 hours ahead?
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Quoting 655. Joanie38:



Yes I do


try it and see if same thing happens ok?
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Quoting 652. nash36:


Hey MLC!!!

Right now, I am doubting it's survival. IF it manages to not become decoupled, then anywhere from ECFL to GA coastline.


You got Georgia on your mind, man? ;)


She ain't going to Georgia.
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Quoting 636. TomTaylor:
See the faster winds out ahead of Chantal, in the Central Caribbean, in the image below?




That is the Caribbean Low-Level Jet (CLLJ). This low-level jet exists semi-permanently as a result of the pressure difference between the subtropical Atlantic ridge and the monsoon/heat low over central America and NW South America (sometimes called the Columbian heat low). Accelerating trade winds ahead of the storm are incredibly detrimental to the low-level organization of a storm. Accelerating trade winds rob the storm of convergence and naturally make it harder for the storm to close off it's circulation. This can cause the storm to degenerate into an open wave, like Ernesto did last year. Additionally, the structure of the low-level flow around the COC gets distorted with accelerating trade winds. The amplitude decreases and wavelength increases creating a duller, less pronounced perturbation in the wind field. This means less convergence, less organization and an expansion of the wind field.

Well said. This is the cause of the often-mentioned eastern Caribbean "Dead Zone."
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Quoting 644. will40:


ok do you have firefox?



Yes I do
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At 23:17:30Z (last observation), the observation was 197 miles (317 km) to the SE (125°) from San Juan, Puerto Rico (USA).

Product: Air Force High Density (HDOB) Message (URNT15 KNHC)
Transmitted: 9th day of the month at 23:16Z
Date: July 9, 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: 04

23:17:30Z 16.767N 63.617W 842.9 mb
(~ 24.89 inHg) 1,629 meters
(~ 5,344 feet) 1017.5 mb
(~ 30.05 inHg) - From 132° at 40 knots
(From the SE at ~ 46.0 mph) 15.5°C
(~ 59.9°F) 12.6°C
(~ 54.7°F) 42 knots
(~ 48.3 mph) 31 knots
(~ 35.6 mph) 0 mm/hr
(~ 0 in/hr) 29.5 knots (~ 34.0 mph)
73.8%
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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Chantal looks to be heading a little more west now.

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Quoting 638. moonlightcowboy:


Nash! Ol' friend. How the heck are you? What's your take - going east or west of Florida?


Hey MLC!!!

Right now, I am doubting it's survival. IF it manages to not become decoupled, then anywhere from ECFL to GA coastline.
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AMSU Microwave 89GHz Imagery (4 km Mercator)

1329 UTC

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650. Relix
Yeah before the open wave comments fly in let's see what the HH finds.
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Quoting 601. nash36:


Regardless of what Chantal decides to do, we in SC are unfortunately in for another heavy rain event it appears. Stalled front. Lovely.



And flooded Toronto is going to receive some more supplies of fresh water ...
Member Since: October 25, 2008 Posts: 52 Comments: 5738
Granted the convection is limited at the moment and expected at this time of day but, I think Chantal is structurally improved quite well today. Vorticity is increasing, convergence/divergence is the best it's been, the COC is actually surrounded with cloud cover. I think she is primed to take full advantage of the night and "look" like a 65mph TS in the AM. Just my 2 cents.
Member Since: August 19, 2005 Posts: 5 Comments: 5060
With a forward speed of almost 30 m/h, I'm not really surprised to see 60 m/h winds. Chantal herself only has to generate 30 mph winds to make it 60.Or is that too simple?
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Chantal looks like it's degenerating into an open wave. Fast forward motion, high shear and dry air appears to have finally taken its toll. Maybe there's a circulation center somewhere in that disorganized mess, but I don't see it on satellite or radar.. Not that it can't come back, but this is more of a typical short lived tropical storm than anything IMO.
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TS Chantal

FunkTop Loop

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Quoting 629. Joanie38:
I am using google chrome....


ok do you have firefox?
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I do not believe it is an open wave....they may find it slightly WEAKER but by no means is it an open wave
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Quoting 635. MAweatherboy1:
Open waves can be very strong. There's no reason Chantal can't be a 60mph open wave. That may very well be what recon finds.


Erin in 1995 was like that. There were sustained winds of 47 knots outside of thunderstorms before there was a closed circulation.
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Quoting 635. MAweatherboy1:
Open waves can be very strong. There's no reason Chantal can't be a 60mph open wave. That may very well be what recon finds.



yep
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Off topic slightly, but my first college meteorology textbook came in today. Might have to read the hurricane chapter so I can maybe understand some more, lol.

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Quoting 628. nash36:


Very low.


Nash! Ol' friend. How the heck are you? What's your take - going east or west of Florida?
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Quoting 607. 1900hurricane:
Chantal certainly has that classic look of a tropical cyclone right now!



#SaidNobodyEver


Yeah since 2009 that pretty much goes as a cyclone now days
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See the faster winds out ahead of Chantal, in the Central Caribbean, in the image below?




That is the Caribbean Low-Level Jet (CLLJ). This low-level jet exists semi-permanently as a result of the pressure difference between the subtropical Atlantic ridge and the monsoon/heat low over central America and NW South America (sometimes called the Columbian heat low). Accelerating trade winds ahead of the storm are incredibly detrimental to the low-level organization of a storm. Accelerating trade winds rob the storm of convergence and naturally make it harder for the storm to close off it's circulation. This can cause the storm to degenerate into an open wave, like Ernesto did last year. Additionally, the structure of the low-level flow around the COC gets distorted with accelerating trade winds. The amplitude decreases and wavelength increases creating a duller, less pronounced perturbation in the wind field. This means less convergence, less organization and an expansion of the wind field.

Chantal may very well have degenerated into an open wave by now. Will be interesting to see what recon shows...
Member Since: Posts: Comments:

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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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