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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Thank you whitewabit.
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Quoting 2322. Orcasystems:


ROFL.. gee thanks... I think
Missed you to :)

Hey Orca! :)

-HurricaneDean07
Member Since: June 2, 2013 Posts: 9 Comments: 1414
11pm- no longer expected to weaken to a depression.
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2330. Matt74
Quoting 2118. Stormchaser121:

More and more models moved west. Freeport is still my prediction.
You're going to predict a Freeport prediction this far out? Do you happen to have the winning powerball numbers or Texas lotto numbers?
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Quoting 2324. zoomiami:


rats -- all that green stuff.



Its called mold..from all the rain you guys have been getting.
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TROPICAL STORM CHANTAL FORECAST/ADVISORY NUMBER 5
NWS NATIONAL HURRICANE CENTER MIAMI FL AL032013
0300 UTC TUE JUL 09 2013

CHANGES IN WATCHES AND WARNINGS WITH THIS ADVISORY...

THE GOVERNMENT OF THE DOMINICAN REPUBLIC HAS REPLACED THE TROPICAL
STORM WATCH WITH A TROPICAL STORM WARNING FROM CABO ENGANO TO THE
BORDER WITH HAITI. A TROPICAL STORM WATCH HAS BEEN ISSUED FOR THE
NORTHERN COAST OF HAITI FROM NORTH OF CABO ENGANO TO CABO FRANCES
VIEJO.

A TROPICAL STORM WATCH HAS BEEN ISSUED FOR HAITI.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* BARBADOS
* DOMINICA
* ST. LUCIA
* MARTINIQUE
* GUADELOUPE
* PUERTO RICO
* SOUTHERN COAST OF THE DOMINICAN REPUBLIC FROM CABO ENGANO TO THE
BORDER WITH HAITI

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* ST. VINCENT
* U.S. VIRGIN ISLANDS
* VIEQUES AND CULEBRA
* NORTHERN COAST OF THE DOMINICAN REPUBLIC FROM NORTH OF CABO ENGANO
TO CABO FRANCES VIEJO

INTERESTS IN THE REMAINDER OF THE NORTHERN LEEWARD ISLANDS...THE
SOUTHEASTERN BAHAMAS AND TURKS AND CAICOS SHOULD MONITOR THE
PROGRESS OF CHANTAL.
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2327. wpb
anyone check stats in satellite era how many ts have formed in chantels position at this time of year?
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2326. whitewabit (Mod)
Temp at 50 m

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North of the Bahamas Chantal wouldn't be embedded in the trades.
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Quoting 2304. Orcasystems:


I think either way, Zoo is going to get soaked by this one.


rats -- all that green stuff.

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2323. skook
Not sure of the source, but was posted on 98rock's facebook page.




Waterspout heading for land near Oldsmar Fl.
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Quoting 2317. zoomiami:


oh my goodness -- its the whale!


ROFL.. gee thanks... I think
Missed you to :)
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Sorta related to Hurricanes.. here in Ontario, Toronto as of 10 pm EDT, has had unofficially 123 mm of rain (125 mm = 5 inches). That breaks the single day amount of rainfall in one day of 121 mm - that the "remnants" of Hurricane Hazel dumped on Toronto in 1954

What does 123 mm in Toronto look like?




More pictures an account of the storm(s) as it happenned here
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2320. Relix
I say it goes over Barbados at the current steering
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2319. ncstorm
Quoting 2316. BaltimoreBrian:
ncstorm, that's what 300 miles in 2 days? 6 mph is reasonable slow-moving storm pace.


BB she is booking right now..why would she slow down?
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Quoting 2298. Orcasystems:


TY Levi


oh my goodness -- its the whale!
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ncstorm, that's what 300 miles in 2 days? 6 mph is reasonable slow-moving storm pace.
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I created a New blog. Check it out if you're Interested!
Tropical Storm Chantal ; A Busy July ahead
Member Since: June 2, 2013 Posts: 9 Comments: 1414
Quoting 2307. stormpetrol:
I think Chantal has slowed just a bit.


That could be good for it,but not good for the ones in her path as she could start to strengthen more as the night goes on and through the day tomorrow
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Quoting 2307. stormpetrol:
I think Chantal has slowed just a bit.

maybe
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Quoting 2309. Grothar:


Yes. Depends on the timing though.


How deep is the warm water in the Gulf of Mexico outside the loop?
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2311. ncstorm
Okay..got this from NWS, Wilmington, NC..the ridge is supposed to build back in on Monday..that is what is supposed to turn Chantal back to the SE coast..Monday would put her turning then..my question..the GFS has her at only Florida/GA line on Monday while the NHC has Chantal right at the northern island chain of the Bahamas on Saturday..so you telling me that Chantal will only move northward from the bahamas to Florida/GA in almost two days?


ALL EYES WILL BE WATCHING NEWLY FORMED TS CHANTAL IN THE
CARIBBEAN. ALTHOUGH SHE IS NOT PROGGED TO STRENGTHEN
CONSIDERABLY...WEAKNESS IN MID-LEVEL PATTERN SHOULD STEER HER IN
THIS GENERAL DIRECTION NEXT WKND. IT IS FAR TOO EARLY TO DISCUSS ANY
POSSIBLE IMPACTS...BUT AT THE VERY LEAST IT APPEARS INCREASED
TROPICAL MOISTURE WILL FLOOD INTO THE REGION...CREATING A GOOD
CHANCE FOR SHOWERS AND TSTMS FRI-SUN. BY MONDAY...BROAD 5H RIDGING
BEGINS TO REDEVELOP ACROSS THE SOUTHERN TIER BRINGING SOME DRIER AIR
AND NICER OVERALL SENSIBLE WEATHER TO THE AREA.


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2310. Relix
F5? F5
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2309. Grothar
Quoting 2300. Dakster:


Isn't that why the models have Chantal cutting across Florida?

That could be bad because of the bath water in the GOM.


Yes. Depends on the timing though.
Member Since: July 17, 2009 Posts: 71 Comments: 27211
Grothar thanks for the intensity graphic you posted in 2259. Very interesting!
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I think Chantal has slowed just a bit.
Member Since: April 29, 2007 Posts: 0 Comments: 8134
Anxiously awaiting the 11:00 update
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Too bad new frames have nearly a 30 minute lag time on being published.

Well, it beats last year with the hour long lag times that happened on occasion.
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Quoting 2300. Dakster:


Isn't that why the models have Chantal cutting across Florida?

That could be bad because of the bath water in the GOM.


I think either way, Zoo is going to get soaked by this one.
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2303. Grothar
Quoting 2288. zoomiami:


The models are interesting, and reflect a pattern that I noticed last week. On the radar, the rain was moving from the south almost in a straight line north. This occurred for about 3 days. This is highly unusual for South florida, the movement is almost always west-east or east-west.


Yes, you are right. And living right on the coast we all noticed how strange that was.
Member Since: July 17, 2009 Posts: 71 Comments: 27211
2302. wpb
anyone check stats in satellite era how many ts have formed in chantels position at this time of year?
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Levi thinks this could become a serious player eventually
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2300. Dakster
Quoting 2296. Grothar:


It did change. I am looking into the other ones as we speak. What I am worried about is the High is supposed to be moving back to the west just as Chantal is moving along the Florida coast.


Isn't that why the models have Chantal cutting across Florida?

That could be bad because of the bath water in the GOM.
Member Since: March 10, 2006 Posts: 0 Comments: 10818
Quoting 2289. Levi32:
Good evening.

Blog update:

Tropical Tidbit for Late Monday Evening, July 8th, with Video


TY Levi
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2297. Pallis
Quoting 2265. zoomiami:
No matter how many years you watch the blog, and who comes and goes, it stays the same:

good outflow

no outflow

anticyclone over entire area

no --anticyclone is imaginary

convection shows deepening storm

convection shows little development

If anyone wanted to watch a ping pong match, this place is it.

Watch and learn cricket.
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2296. Grothar
Quoting 2294. ProgressivePulse:


That's quite a flip in the intensity guidance. Less land interaction in today's models, more cloudy in the long term than was portrayed earlier today.


It did change. I am looking into the other ones as we speak. What I am worried about is the High is supposed to be moving back to the west just as Chantal is moving along the Florida coast.
Member Since: July 17, 2009 Posts: 71 Comments: 27211
2295. HadesGodWyvern (Mod)


(98S) "Tropical Disturbance" marked on the Reunion analysis map.
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Quoting 2259. Grothar:


That's quite a flip in the intensity guidance. Less land interaction in today's models, more cloudy in the long term than was portrayed earlier today.
Member Since: August 19, 2005 Posts: 5 Comments: 5458
Quoting 2283. zoomiami:


Hey Taco:

Doing good -- not liking what they are saying about the early development and the way things are lining up. Certainly would not want a repeat of 04/05/06. That wasn't fun.

On a more serious note -- so many new people have come into South Florida in the 7 or 8 years since all the storms that people will not have the same level of preparedness, they don't have the memory of what it was like before.

No I don't like it either.... Just not ready for any kind of repeat of 04 and or 05.... Same goes for this location. We have so many more folks along the beaches that have "Never" been through anything like what we have, that it bothers me.... I have talked to some and they just "Don't Get It"..... But I'm afraid they will soon enough....
It always good to chat with some of the regulars on here....

Play it safe and just be ready I always say....

Taco :o)
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Quoting 2277. Thrawst:
I just realized, Levi didn't post a video today! Ahhh that's unfortunate I was ready to learn!! :)
Link
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2291. JLPR2
Hmm... My idea of Chantal's center is right at the edge of the decaying central convection north of the small stronger cell. To me that seems like a weak feeder band wrapping to the south side of the system.

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2290. Thrawst
And as soon as I say it.. New video from Levi! :)
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2289. Levi32
Good evening.

Blog update:

Tropical Tidbit for Late Monday Evening, July 8th, with Video
Member Since: November 24, 2005 Posts: 635 Comments: 26701
Quoting 2247. Grothar:


The models are interesting, and reflect a pattern that I noticed last week. On the radar, the rain was moving from the south almost in a straight line north. This occurred for about 3 days. This is highly unusual for South florida, the movement is almost always west-east or east-west.
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2287. Grothar
Thanks JP, I forgot I had that one.




This shows my blob much better.

Member Since: July 17, 2009 Posts: 71 Comments: 27211
This maybe explains why 1010 mb storm!!
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Quoting 2274. EyeWonder:
Quoting 2253. stormpetrol:
Barbados will have a very squally early morning as I suspect the center will pass just south of there.



We in Barbados are being informed that the eye is forecast to pass about 50 miles to the north of us.

it may it may pass S and it may pass over you should take precaution and take it like it was coming over you in case of unexpected change
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2284. Patrap
Tropical Atlantic - Rainbow Loop
Member Since: July 3, 2005 Posts: 428 Comments: 129910
Quoting 2270. taco2me61:

Hi a Zoo long time no see :o) how are you doing...
And you are right it will never change :o) just saying

Taco :o)


Hey Taco:

Doing good -- not liking what they are saying about the early development and the way things are lining up. Certainly would not want a repeat of 04/05/06. That wasn't fun.

On a more serious note -- so many new people have come into South Florida in the 7 or 8 years since all the storms that people will not have the same level of preparedness, they don't have the memory of what it was like before.
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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