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 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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Quoting 318. TropicalAnalystwx13:
I don't think I've ever seen a model depict such a powerful cyclone.




Woah! 925!?
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GFS shows Chantel splitting in half.Just like it did Andrea.
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GFS is strengthening Chantal in the Bahamas at 93hrs.

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Quoting 318. TropicalAnalystwx13:
I don't think I've ever seen a model depict such a powerful cyclone.




I have. I remember the ECMWF bombing Igor out run after run to a sub 900 mb storm when it was in the vicinity of Bermuda. Needless to say, that didn't verify.
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84 hrs


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Plan of the Day


000
NOUS42 KNHC 071607
REPRPD
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1200 PM EDT SUN 07 JULY 2013
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 08/1100Z TO 09/1100Z JULY 2013
TCPOD NUMBER.....13-037

I. ATLANTIC REQUIREMENTS
1. SUSPECT AREA (NEAR WINDWARD ISLANDS)
FLIGHT ONE -- TEAL 70 FLIGHT TWO -- TEAL 71
A. 08/2100Z A. 09/1200Z,1800Z
B. AFXXX 01BBA INVEST B. AFXXX 0203A CYCLONE
C. 08/1815Z C. 09/1030Z
D. 12.5N 54.7W D. 14.0N 60.8W
E. 08/2030Z TO 09/0030Z E. 09/1130Z TO 09/1800Z
F. RESOURCES PERMITTING

2. OUTLOOK FOR SUCCEEDING DAY: CONTINUE 6-HRLY FIXES WHILE
SYSTEM REMAINS A THREAT.

II. PACIFIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.

$$
SEF
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Good morning all. It appears that the Atlantic has started waking up. Chantal as small as it is seems to be moving almost as quickly as it's wind speed. Impressive although given the storm's small stature I don't think it could survive hitting any decent size land mass i.e. Hispaniola. Also, Patrap, kudos on the honorable mention in the blog. That is a sharp photo.
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Quoting 320. stormpetrol:
Anyone knows when Recon is taking off.



000
NOUS42 KNHC 071607
REPRPD
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1200 PM EDT SUN 07 JULY 2013
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 08/1100Z TO 09/1100Z JULY 2013
TCPOD NUMBER.....13-037

I. ATLANTIC REQUIREMENTS
1. SUSPECT AREA (NEAR WINDWARD ISLANDS)
FLIGHT ONE -- TEAL 70 FLIGHT TWO -- TEAL 71
A. 08/2100Z A. 09/1200Z,1800Z
B. AFXXX 01BBA INVEST B. AFXXX 0203A CYCLONE
C. 08/1815Z C. 09/1030Z
D. 12.5N 54.7W D. 14.0N 60.8W
E. 08/2030Z TO 09/0030Z E. 09/1130Z TO 09/1800Z
F. RESOURCES PERMITTING

2. OUTLOOK FOR SUCCEEDING DAY: CONTINUE 6-HRLY FIXES WHILE
SYSTEM REMAINS A THREAT.

II. PACIFIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.

$$
SEF
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78 hrs. o_O

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Quoting 303. txjac:
Tyler, are you receiving any rain today? Houston is finally getting some decent rain ...it needs to rain all day today but unfortunately it probably wont.

I'm loving what we are getting at the moment though

And yes, I agree we need at TS ...just not like Allison though

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.
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Anyone knows when Recon is taking off.
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Quoting 316. GTstormChaserCaleb:
Yes madame it is still running :)
Thanks.
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I don't think I've ever seen a model depict such a powerful cyclone.



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I watching to see if the center passes just south of Barbados.
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Quoting 302. washingtonian115:
Got the rest of the run?.
Yes madame it is still running :)
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315. txjac
Quoting 308. tropicalnewbee:


So the third makes you one of a very select few people who can still speak, read, and write Latin?!


My daughter is taking Latin in college. She loves it
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I still think Chantal will track further south and west , than what most models suggest.
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Global models

Member Since: July 17, 2009 Posts: 71 Comments: 26117
Here comes Chantal. I think the conditions in the Bahamas will be more than favorable for strengthening. FL watchout!

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Yay, Pouches are back..... just quite not ready yet (no data).
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Quoting 278. Grothar:


Don't forget. English is not my really my first language. It is my third. I first learned Old English then gradually worked by way up. :)


So the third makes you one of a very select few people who can still speak, read, and write Latin?!
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anyway guys I'll be back later see what progress chantal makes
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306. JRRP
Quoting GTstormChaserCaleb:
48 hrs. and here comes Cape-Verde wave too.


stronger on this run than the previous
Member Since: August 16, 2007 Posts: 0 Comments: 5789
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Quoting 299. AussieStorm:
Before I go... the latest True Colour Image of Chantal. Enjoy :-)


g'night.
Member Since: February 2, 2011 Posts: 3 Comments: 904
303. txjac
Tyler, are you receiving any rain today? Houston is finally getting some decent rain ...it needs to rain all day today but unfortunately it probably wont.

I'm loving what we are getting at the moment though

And yes, I agree we need at TS ...just not like Allison though
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Quoting 289. GTstormChaserCaleb:
48 hrs. and here comes Cape-Verde wave too.

Got the rest of the run?.
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Quoting 299. AussieStorm:
Before I go... the latest True Colour Image of Chantal. Enjoy :-)


That was from Yesterday Afternoon before it was named, yes?
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Quoting 293. redwagon:
Only problem is Dorian would probably hit us as a cat 2-3.

Intensity is not foreseeable at this point... But I know what you mean, I guess.
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Before I go... the latest True Colour Image of Chantal. Enjoy :-)



Goodnight all
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Quoting 285. Patrap:
O-kay'

ob·se·qui·ous
/əbˈsēkwēəs/
Adjective
Obedient or attentive to an excessive or servile degree.
Synonyms
servile - subservient - slavish - menial - fawning


Leave the guy alone. At least he wasn't being obstreperous, but just a little loquacious.
Member Since: July 17, 2009 Posts: 71 Comments: 26117
Quoting 289. GTstormChaserCaleb:
48 hrs. and here comes Cape-Verde wave too.


Starting to become Consistent with this next Cape Verde storm.
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Quoting 289. GTstormChaserCaleb:
48 hrs. and here comes Cape-Verde wave too.

I see it starts developing it almost immediately.
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Quoting 278. Grothar:


Don't forget. English is not my really my first language. It is my third. I first learned Old English then gradually worked by way up. :)
My boyfriend in high school wore Old English... Give me Jade East any day
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Quoting 246. TylerStanfield:
06Z GFS brings "Dorian" into the Western Gulf. *Crosses Fingers* Hopefully it makes it's way for Texas. We need all we can get.
Only problem is Dorian would probably hit us as a cat 2-3.
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Nice ascat of Chantal, potent little storm.
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I know Chantal is the big story but I'm looking at the upper level low to the east of me since its closer to home. I know anything is possible, but is there any chance it could come down to the surface? And how would that happen? I'm still expecting rain and gusty winds, but the hype of a tropical system would be cool lol thanks!
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You bring no good news with that last Gro.

Grumbles, goes check Jenny, Battery stocks, etc, etc,..
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48 hrs. and here comes Cape-Verde wave too.

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Quoting 267. washingtonian115:
I hate to say it.But you guys need a hurricane of Ike proportions to bust you all's drought.Don just vaporized and Jim Cantore seemed so dissapointed.lol.
Correct. Just not the surge iy brought us.
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It's cold again tonight so I am going to bed a little early.

Find more about Weather in Rydalmere, New South Wales, Australia
Aussie's Weather Forecast

As I always say, Be safe, Stay safe, Play safe, Blog safe.

Goodnight :-)

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Expect a shift to the west with all the next model runs.
Member Since: July 17, 2009 Posts: 71 Comments: 26117
O-kay'

ob·se·qui·ous
/əbˈsēkwēəs/
Adjective
Obedient or attentive to an excessive or servile degree.
Synonyms
servile - subservient - slavish - menial - fawning
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Quoting 273. uptxcoast:


We need the rain, but I will pass on the Hurricane. We do not need one of those.

Not After Ike. Category 1 or less would be more than worth it though.
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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.