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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GFS really intensifies Chantal before coming into Volusia County (New Smyrna Beach area).

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Quoting 375. MississippiWx:
In other news, the ULL in the Bahamas looks better than ever. Looks like a last minute effort to transition to a tropical low.



Think it will attain invest status?
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Quoting 374. GTstormChaserCaleb:
Except the 993 mb. Hurricane that was supposed to come over Sar's house.


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..
Member Since: August 19, 2006 Posts: 13 Comments: 14550
Chantal Off the East coast of Florida.
Dorian Strengthening out in the Central Atlantic.
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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.

That's always comforting -_- Thanks Washi.
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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.
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Quoting 350. bappit:
News from Texas:

THE 594 DAM UPPER RIDGE CENTERED OVER NORTHERN TEXAS WILL BE WHAT CONTROLS OUR WEATHER PATTERN IN THE FORESEEABLE FUTURE. HEAT AND THE LACK OF RAIN WILL BE THE TOPICS DU JOUR.


We'll take any precip we can get here in Austin. So far today almost a tenth of an inch and a 5 degree or so drop in temp from earlier this morning although the forecast is supposed to be back in the triple digits by midweek so I'm afraid that what you say is probably spot on.
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In other news, the ULL in the Bahamas looks better than ever. Looks like a last minute effort to transition to a tropical low.

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Quoting 369. StormTrackerScott:


CMC has done quite well so far this year.
Except the 993 mb. Hurricane that was supposed to come over Sar's house.
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Quoting 366. rmbjoe1954:
I wonder what Joe Bastardi's take on Chantal is?

East Coast rider
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Quoting 363. jabjb2:

Ca you see them? The models page is free so I think they can be seen.

Is it? Wasn't aware. Maybe he allowed public access because of Chantal.
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Soulik is going to be an extremely dangerous cyclone

Wouldn't be shocked to see a 115 knot peak

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Quoting 366. rmbjoe1954:
I wonder what Joe Bastardi's take on Chantal is?


he too busy talking about that "other" stuff..

Member Since: August 19, 2006 Posts: 13 Comments: 14550
Quoting 364. ncstorm:
Im sorry but Im going with the CMC on this one..the GFS has been all over the place with Chantal..CMC score card right now is going to be looking quite pretty if it gets Chantal right..


CMC has done quite well so far this year.
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Quoting 357. Stormchaser2007:
2013 Parallel HWRF, GFS, GFDL, and Experimental FIM are all on board for a tropical cyclone to develop within the next six days.

Judging by the conditions ahead of it, this one could be an extremely rare long-track Cape Verde cyclone

HWRF at 96 hours (Already a depression)






12z GFS with a depression at 111 hours



Even the ECMWF has a strong tropical wave in the same area.


Wow! I'm getting really interested to see what late August/September has in store.
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I wonder what Joe Bastardi's take on Chantal is?
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120 hrs.

Here comes potential Dorian like a bowling ball.

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Im sorry but Im going with the CMC on this one..the GFS has been all over the place with Chantal..CMC score card right now is going to be looking quite pretty if it gets Chantal right..
Member Since: August 19, 2006 Posts: 13 Comments: 14550
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.

Ca you see them? The models page is free so I think they can be seen.
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Quoting 344. Grothar:


We posted the same thing at the same time.

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


I can see them just fine.
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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.


I can see them.
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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.
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2013 Parallel HWRF, GFS, GFDL, and Experimental FIM are all on board for a tropical cyclone to develop within the next six days.

Judging by the conditions ahead of it, this one could be an extremely rare July long-track Cape Verde cyclone

HWRF at 96 hours (Already a depression)






12z GFS with a depression at 111 hours



Even the ECMWF has a strong tropical wave in the same area.

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Quoting 346. jabjb2:

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.
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This animation is for the complete month of June 2013.

Member Since: August 26, 2006 Posts: 10 Comments: 3617
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It's like the Bermuda High will try to pass the baton over to the Central Plains Ridge and say here take over the steering from here.
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Quoting 336. StormTrackerScott:
Lots of warm water in the Bahamas.





Waters off the coast of FL into the Bahamas are actually well below average now thanks to persistent troughing from last week and high pressure to the north and east increasing the pressure gradient. Chantal shouldn't have quite as much energy as it normally would in that location this time of the year. It will still be adequate, however.

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News from Texas:

THE 594 DAM UPPER RIDGE CENTERED OVER NORTHERN TEXAS WILL BE WHAT CONTROLS OUR WEATHER PATTERN IN THE FORESEEABLE FUTURE. HEAT AND THE LACK OF RAIN WILL BE THE TOPICS DU JOUR.
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Quoting 343. Grothar:
GFS


This is interesting..Maybe CMC might not be so on crack like I thought.GFS has a strengthening Chantel,a t.D out in the MDR and "Dorian" which looks like he wants to follo in Dean's foot steps.
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Quoting 286. Grothar:
Expect a shift to the west with all the next model runs.


Yes, thank you. :)
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Quoting 341. MississippiWx:
Chantal looks to have a very small closed circulation on satellite, but it's difficult to tell. The rapidly spinning vortex that is her center is peaking out from underneath the clouds like it did yesterday morning. If the circulation is indeed closed, the west winds don't extend very far south of the center from I can see. Thunderstorms seem to be building back towards the center again (just like yesterday).


She has her Cycles and Struggles... Definitely not going to be anything big, but a nice little system to prime the waters for what's to come.
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Interesting looks like the Central Plains Ridge might try to take over the steering.

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Quoting 342. StormTrackerScott:
99 hrs GFS



We posted the same thing at the same time.
Member Since: July 17, 2009 Posts: 69 Comments: 25371
GFS


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99 hrs GFS

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Chantal looks to have a very small closed circulation on satellite, but it's difficult to tell. The rapidly spinning vortex that is her center is peaking out from underneath the clouds like it did yesterday morning. If the circulation is indeed closed, the west winds don't extend very far south of the center from I can see. Thunderstorms seem to be building back towards the center again (just like yesterday).

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Quoting 280. PalmBeachWeather:
Much too big of word for me...
6 vowels and 4 consonants....Not size ,but content..:)
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Quoting 244. Waltanater:

LOL...well explained there. I think people find it more fun to "shoot the messenger!"

Yep. Can't say anything unless it's critical.
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Those of you that don't want a storm...
Feast your eyes, and Understand Why.
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Lots of warm water in the Bahamas.



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Quoting 321. TylerStanfield:

An Allison, with how hard the soil is from Drought, would be Disappointedly almost non-beneficial.
Most of the rain is off to my Southeast and its slowly creeping up my way.... Not going to get much from it though.

Starting to rain now... :)
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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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