Tropical Storm Chantal: a Likely Harbinger of an Active Atlantic Hurricane Season

By: Dr. Jeff Masters , 2:02 PM GMT on July 08, 2013

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Tropical Storm Chantal is speeding westwards at 26 mph towards a Tuesday encounter with the Lesser Antilles Islands. Satellite loops show that Chantal has plenty of spin, with several well-developed low-level spiral bands that have gradually increased their heavy thunderstorm activity this morning. However, Chantal is fighting dry air associated with the Saharan Air Layer (SAL). The heavy thunderstorm activity near Chantal's center is rather thin, and there are virtually no heavy thunderstorms on the storm's north side, where upper-level northwesterly winds are creating light to moderate wind shear of 5 - 15 knots, and driving dry air into the storm. This dry air is readily apparent on water vapor satellite loops. Ocean temperatures are fairly warm, though, at 27.5 - 28°C. There have not been any hurricane hunter missions into Chantal yet, but an Air Force hurricane hunter aircraft deployed to St. Croix on Sunday, and is scheduled to investigate Chantal on Monday afternoon.


Figure 1. MODIS image of Chantal taken at approximately 10 am EDT Monday, July 8, 2013. At the time, Chantal had top winds of 45 mph. Image credit: NASA.


Figure 2. U.S. Air Force Master Sgt. Levi Denham, a WC-130J Hercules aircraft weather reconnaissance loadmaster assigned to the 53rd Reconnaissance Squadron (the Hurricane Hunters), performs pre-engine start-up inspections in St. Croix, Virgin Islands, on Sept. 16, 2010. DoD photo by Staff Sgt. Manuel J. Martinez, U.S. Air Force. Thanks go to wunderground member Patrap for pointing out this photo.

Forecast for Chantal
The 8 am EDT Monday forecast from the SHIPS model predicts that Chantal will experience low to moderate shear through Tuesday afternoon as it heads west-northwest at 25 mph towards Hispaniola. With ocean temperatures expected to warm to 28°C during that time, Chantal has the potential to intensify to a 65 mph tropical storm before hitting Hispaniola. Working against intensification will be 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, and I don't see Chantal making it to hurricane strength before interacting with the mountains of Hispaniola and/or Cuba on Tuesday night and Wednesday. This interaction may be able to destroy the storm, since wind shear is also expected to rise to the high range, 20 - 30 knots, Tuesday night through Thursday. Chantal has the potential to cause big problems for Haiti, which is highly vulnerable to flash flooding due to the lack of vegetation on the deforested mountains. However, there is a lot of dry air to the west of Chantal, which may act to keep rainfall totals in Haiti down to a manageable 2 - 4". Over 300,000 people are still homeless and living in makeshift tent camps in Haiti, three years after the great 2010 earthquake.

Once Chantal crosses Hispaniola and enters the Bahamas late this week, the trough of low pressure pulling the storm to the northwest is expected to lift out. It is unclear at this point whether or not this trough will be strong enough to pull Chantal out to sea, or whether the storm might be forced back to the northwest into the U.S. East Coast by high pressure building in.


Figure 3. There have been only thirteen tropical depressions or tropical storms that have formed July 15 or earlier that have passed through the Lesser Antilles since 1851, an average of one such tropical cyclone every thirteen years. Note that two of these storms, Dennis and Emily, occurred during the notorious Hurricane Season of 2005. There were five other pre-July 16 storms that formed east of the Lesser Antilles Islands, but did not pass through the islands (Bertha of 2009, Barry of 1989, and unnamed tropical depressions in 1967, 1978, and 2001.) Image credit: NOAA's Historical Hurricane Tracks website.

Chantal: an uncommon early-season Cape Verde-type tropical storm
Formation of a tropical storm east of the Lesser Antilles Islands in early July from an African tropical wave is an uncommon occurrence. Since Atlantic hurricane records began in 1851, there have been only thirteen tropical depressions or tropical storms that have formed July 15 or earlier that have passed through the Lesser Antilles, an average of one early-season tropical cyclone every thirteen years. Note that two of these storms, Dennis and Emily, occurred during the notorious Hurricane Season of 2005. There were five other pre-July 16 storms that formed east of the Lesser Antilles Islands, but did not pass through the islands (Bertha of 2009, Barry of 1989, and tropical depressions in 1967, 1978, and 2001 that did not become named storms.)

Chantal: a likely harbinger of an active Atlantic hurricane season
Chantal's formation on July 8 is an usually early date for formation of the season's third storm, which usually occurs on August 13. A large number of early-season named storms is not necessarily a harbinger of an active season, unless one or more of these storms form in the deep tropics, south of 23.5°N. According to Phil Klotzbach and Bill Gray, leaders of Colorado State's seasonal hurricane forecasting team,

"Most years do not have named storm formations in June and July in the tropical Atlantic (south of 23.5°N); however, if tropical formations do occur, it indicates that a very active hurricane season is likely. For example, the seven years with the most named storm days in the deep tropics in June and July (since 1949) are 1966, 1969, 1995, 1996, 1998, 2005, and 2008. All seven of these seasons were very active. When storms form in the deep tropics in the early part of the hurricane season, it indicates that conditions are already very favorable for TC development. In general, the start of the hurricane season is restricted by thermodynamics (warm SSTs, unstable lapse rates), and therefore deep tropical activity early in the hurricane season implies that the thermodynamics are already quite favorable for tropical cyclone (TC) development."

Two of this season's three storms have formed in the deep tropics--Tropical Storm Barry, which formed in the Gulf of Mexico's Bay of Campeche at a latitude of 19.6°N, and now Tropical Storm Chantal, which formed at a latitude of 9.8°N. With recent runs of the GFS model predicting formation of yet another tropical storm southwest of the Cape Verde Islands early next week, it appears that the Atlantic is primed for an active hurricane season in 2013.

Jeff Masters

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Quoting 423. ncstorm:
the 12z Navgem is strengthening Chantal now..currently running

When the NOGAPS is showing a strong storm know that something is ah brewing.
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Quoting 426. HCW:
NHC needs to stop naming storms after strippers :)


Hows Roxy?
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Quoting 420. StormTrackerScott:
Damm! This may have TX written all over it!


Plz change your post. No profanity allowed.
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Latest GFS brings Chantel in around Cape Canaveral.
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Seems like Chantal has a cycle it goes through every 24 hours with her CDO. She sheds off her convection, becoming partially exposed, and then refires a new CDO and holds onto that one for a 18-24 hours, then repeats. Has done this 2 times now, with her CDO.
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426. HCW
NHC needs to stop naming storms after strippers :)
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TS Soulik is up to 55kts in less than 12 hours. Which is significantly faster than the forecast from yesterday.

Forecast and Intensity
=======================
24 HRS: 19.4N 140.6E - 45 knots (CAT 1/Tropical Storm) Marianas Islands
48 HRS: 20.3N 136.4E - 50 knots (CAT 2/Severe Tropical Storm) South Of Japan
72 HRS: 21.3N 131.3E - 55 knots (CAT 2/Severe Tropical Storm) South Of Japan

It will become the first Typhoon of the year and has a good chance of becoming one later today.

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Quoting 419. Grothar:


If you post a globe, at least have a little color in it to entertain the folks.


Sorry to bother you with this Gro but again.Which one is the one the GFS develops?.
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the 12z Navgem is strengthening Chantal now..currently running

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12z GFS

Should be a hurricane by the time it reaches the islands

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Quoting 413. TylerStanfield:

But this is only 4-5 days out, not 10-15 days. Hard to have a ghost storm, when its this close in the timeline.
Oh I understand that my comment was in reference to ncstorms comments about the GFS long range and how it has flaws since I pointed out the CMC flaws. Basically no model is perfect they are each specialized in their own way.
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Damm! This may have TX written all over it!

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Quoting 402. TropicalAnalystwx13:
Wave already looks very nice.



If you post a globe, at least have a little color in it to entertain the folks.


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Quoting 415. jabjb2:
CMC

Don't trust the CMC. It is unreliable.
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The GFS has Chantal becoming a weak system/open wave about a week out and missing the trough due to her lack of depth.

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I so agree with this blog. We are looking at an active hurricane season. Am worried for so many Caribbean islands who have not yet recovered fully from sandy. Poor. Haiti and eastern Jamaica. If wind shear don't slow its chances of intensification then its flash flooding. I am also watching the wave behind chantal to see what's its spin
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CMC
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Quoting 405. WeatherNerdPR:

That ridging in the Atlanitc is worrisome. This is shaping up to be a very dangerous pattern.


A very dangerous pattern for the US indeed. A pattern where almost every storm that forms hits the Caribbean Islands and the US.
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Quoting 392. GTstormChaserCaleb:
That is true can't forget all the ghost storms the GFS has shown us through the years in the long range.

But this is only 4-5 days out, not 10-15 days. Hard to have a ghost storm, when its this close in the timeline.
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Quoting 407. washingtonian115:
GFS pulls a Frances and Ivan combo.Something I commented about earlier.

Oh no!
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171 hours
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Same model, different computers..... you decide







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Got another France/Jeanne like track showing up on the GFS:

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Dr Masters a little correction hurricane ABBY struck St Lucia on the 12th July 1960 when 5 persons lost their livess, after their dwelling house collapsed over them.
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GFS pulls a Frances and Ivan combo.Something I commented about earlier.
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I am not expecting Chantal to survive Hispanola.
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Quoting 401. Ameister12:
GFS 150 hours has Chantal in Florida as a weak system.

That ridging in the Atlanitc is worrisome. This is shaping up to be a very dangerous pattern.
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Folks don't count Chantal out as the GFS really tries to spin her back up and cross FL into the Gulf.

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Quoting 393. StormTrackerScott:
Yikes!




156 hours. Hey, Scott. We can't do this all day.

Member Since: July 17, 2009 Posts: 71 Comments: 26477
Wave already looks very nice.

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GFS 150 hours has Chantal in Florida as a weak system.
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Quoting 386. Tropicsweatherpr:
Hi Storm2007.

The wave that GFS and HWRF develop is now emerging West Africa right?

It will be emerging in 48 hours or so.
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BULLETIN
TROPICAL STORM CHANTAL ADVISORY NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL AL032013
1100 AM AST MON JUL 08 2013

...CHANTAL STRENGTHENS SLIGHTLY...
...TROPICAL STORM WATCH ISSUED FOR PUERTO RICO...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...10.9N 51.7W
ABOUT 550 MI...885 KM ESE OF BARBADOS
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 25 MPH...41 KM/H
MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES
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looking at chantal vis and rgb loops it had a Northern component to its movement but now it appears to have ceased now looks to be moving W and slowing down a bit causing the convection to catch up with the almost naked spin LLCOC seems to be located near 11.2N 51.8W just waiting for more sat images to to come in to verify
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Quoting Tropicsweatherpr:
Hi Storm2007.

The wave that GFS and HWRF develop is now emerging West Africa right?


Its going to be a complicated process, but technically, yes.

There is a strong wave axis that should emerge into an area of strong convection immediately off the African continent.

The wave should emerge in about 48-60 hours
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Quoting 358. washingtonian115:
This reminds me of Hanna and Ike.Hanna was steered into the east coast and was a struggling storm all it's life.While Ike was powerful and went into the gulf.

The only reason why Hanna struggled was because of Hurricane Gustav to her immediate WNW in the Gulf. Gustav's outflow sheared Hanna and kept her weak and made it hard for her to recover. If it wasn't for Gustav, Hanna could've been a Major Hurricane Coming right for the Carolinas... So really, You Carolinians can thank Gustav for saving your butt in 2008.
And those of you in South Texas, You can thank Tropical Storm Lowell in the Eastern Pacific for Combining and Amplifying the Trough and picking up Ike earlier and steering him into the Upper Texas coast instead.
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Quoting 355. TropicalAnalystwx13:

I'm not sure if the blog is able to see these images because they're straight from WxBell, and you have to have a subscription to WeatherBell to see them.


he has a 7 day free trial posted now
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Quoting 362. zampaz:

Yes, you almost finished coloring yours in, and StormTrackerScott barely got started.


You think Paint Shop is easy at my age.
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Yikes!

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Quoting 381. ncstorm:


the GFS was showing how many storms to hit florida in long range? The CMC got 1 to a month of runs in May from the GFS..
That is true can't forget all the ghost storms the GFS has shown us through the years in the long range.
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There's going to be a strong tropical wave ahead of the wave that could become our next cyclone.

This will act as a buffer against dry air, shear should be low, and trades won't be as deadly this go around.

I'm impressed already by the potential conditions.

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NHC track looks good to me. With the global models showing a pretty substantial doorway to the north along the east coast in the form of a trough, I'd be surprised if a decently defined Chantal (read as not a remnant low) goes anywhere else but through there.



However, looking at the mean patterns over a week out, any following system that were to develop may not have the same opportunity.

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Quoting 377. centex:
Chantel looking very raged, looking for exposed center soon. If it opens up all the model tracks are fiction. It's a fighter so not giving up on it.

Looks like it's trying to cover up. Again.
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132 hours

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Hi Storm2007.

The wave that GFS and HWRF develop is now emerging West Africa right?
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Quoting 380. TylerStanfield:
Chantal Off the East coast of Florida.
Dorian Strengthening out in the Central Atlantic.
That is some anomalous ridging in the Atlantic.
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GFS really intensifies Chantal before coming into Volusia County (New Smyrna Beach area).

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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.