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 2424. ProgressivePulse:


Odd for this time of year, lol.

So tough to forecast when you "potentially" have a cut off low backing off to the SW and high pressure moving in. Timing, Timing, Timing. My gut tells me that the high has been dominant this year. Still to far out to be the least bit certain. Truthfully, it will most likely be after it crosses Hispaniola before there is decent confidence.


It really is, and that's what is quite unnerving, will it take a track like the CMC and skirt the East Coast or take a track like the GFS and cross into the Gulf.

Here's to hoping its decoupled and an Ernesto like system when it leaves Hispaniola.
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GFS 0Z 15 hour

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Quoting 2422. caribbeantracker01:


and what do you believe is the movement?

in all honesty W-WNW looking more on the W side though
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2430. 7544
ull is finaly dieing out ?
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//
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2428. Levi32
12.3°N 56.2°W

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2427. will40
Quoting 2422. caribbeantracker01:


and what do you believe is the movement?


I say West/ Northwest
Member Since: September 19, 2005 Posts: 2 Comments: 4266
Quoting 2419. Levi32:
Low-level center is outrunning the CDO again and on a more westward wobble at the moment.


looking at the Barbados radar it looks like it could be more than a wobble
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2425. nigel20
Quoting KoritheMan:
I forgot how active this place can get during active storms threatening land. I can hardly keep up with the posts... -_-

Same here! :)
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Quoting 2405. FIUStormChaser:


Hey PP

How do you feel about track for Chantal?


Odd for this time of year, lol.

So tough to forecast when you "potentially" have a cut off low backing off to the SW and high pressure moving in. Timing, Timing, Timing. My gut tells me that the high has been dominant this year. Still to far out to be the least bit certain. Truthfully, it will most likely be after it crosses Hispaniola before there is decent confidence.
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Quoting 2412. wunderkidcayman:

hey nigel Chantal is now on Barbados radar


and what do you believe is the movement?
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2421. nigel20
Quoting wunderkidcayman:

hey nigel Chantal is now on Barbados radar

Yeah, Its center will be in range of the Bajan radar in a couple hours time.
Quoting CosmicEvents:
Hello Nigel.

Hey Cosmic! How have you been?
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Quick blog update. Haven't done one in a while.

Tropical Storm Chantal Analysis | 11:30p.m EDT
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2419. Levi32
Low-level center is outrunning the CDO again and on a more westward wobble at the moment.

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Quoting 2407. sar2401:


THE UPPER-LEVEL WINDS ARE FORECAST TO BECOME CONDUCIVE FOR RESTRENGTHENING IF THE CYCLONE SURVIVES. THE OFFICIAL FORECAST ASSUMES THAT CHANTAL WILL REMAIN A TROPICAL CYCLONE AND
RE-INTENSIFY UNDER FAVORABLE CONDITIONS AROUND DAY 5.


Don't start not tooting your horn too soon. The only thing that happened is the NHC changed their forecast. If Chantal is still a TS on Day 5, then you can toot your horn.

I say we let him toot his horn. For right now, why not?
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Pressure remains pretty high.its pressure that matters.
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2416. will40
Goodnight NC
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Quoting 2407. sar2401:


THE UPPER-LEVEL WINDS ARE FORECAST TO BECOME CONDUCIVE FOR RESTRENGTHENING IF THE CYCLONE SURVIVES. THE OFFICIAL FORECAST ASSUMES THAT CHANTAL WILL REMAIN A TROPICAL CYCLONE AND
RE-INTENSIFY UNDER FAVORABLE CONDITIONS AROUND DAY 5.


Don't start not tooting your horn too soon. The only thing that happened is the NHC changed their forecast. If Chantal is still a TS on Day 5, then you can toot your horn.


I have got to buy me one of those so I can :o)

Taco :o)
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I forgot how active this place can get during active storms threatening land. I can hardly keep up with the posts... -_-
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Quoting 2408. nigel20:
Good evening fellow bloggers!

hey nigel Chantal is now on Barbados radar
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2411. ncstorm
Good Night All..I cant do the GFS 00z run..work calls tomorrow..

we'll do this again tomorrow..Island friends..you're up first at bat..stay safe..
Member Since: August 19, 2006 Posts: 13 Comments: 16042
Hello Nigel.
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Quoting 2406. Levi32:
Looks like the 11pm NHC forecast picked up on the increasingly favorable pattern off the SE US after Chantal gets into the Bahamas or farther north.

"NEAR THE END OF THE FORECAST PERIOD...THE UPPER-LEVEL WINDS ARE FORECAST TO BECOME CONDUCIVE FOR RESTRENGTHENING IF THE CYCLONE SURVIVES."


Yep.
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2408. nigel20
Good evening fellow bloggers!
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2407. sar2401
Quoting weatherlover94:
now the NHC track and intensity is reasonable....Not to toot my own horn but I was the one that kept saying it will not be as weak as the NHC thought


THE UPPER-LEVEL WINDS ARE FORECAST TO BECOME CONDUCIVE FOR RESTRENGTHENING IF THE CYCLONE SURVIVES. THE OFFICIAL FORECAST ASSUMES THAT CHANTAL WILL REMAIN A TROPICAL CYCLONE AND
RE-INTENSIFY UNDER FAVORABLE CONDITIONS AROUND DAY 5.


Don't start not tooting your horn too soon. The only thing that happened is the NHC changed their forecast. If Chantal is still a TS on Day 5, then you can toot your horn.

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2406. Levi32
Looks like the 11pm NHC forecast picked up on the increasingly favorable pattern off the SE US after Chantal gets into the Bahamas or farther north.

"NEAR THE END OF THE FORECAST PERIOD...THE UPPER-LEVEL WINDS ARE FORECAST TO BECOME CONDUCIVE FOR RESTRENGTHENING IF THE CYCLONE SURVIVES."
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Quoting 2394. ProgressivePulse:


I think they would have had the models not diverged from the pretty good consensus they had earlier today. I wouldn't either personally. They don't even show the slightest bend to the west at the end, lol. It's all covered in the error cone though.


Hey PP

How do you feel about track for Chantal?
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2404. will40
Quoting 2397. Gearsts:
Getting close:Link



thanks for the link
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Quoting 2381. Hurricane12:


Must be heading to Grand Cayman, eh?

nope well don't know yet too early

Quoting 2383. Relix:


If wunderkidcayman had his way every system would pass over the Caymans. Heck, a hurricane at 30N would drop sharply south just to hit him. Kid's funny. Haha.

hell no sorry you gone too far FLAGGED
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Anyone seen Keeper around lately? Has he been caught up in all the flooding in Toronto these past few days?
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Quoting 2391. Gearsts:
Hurac�n Hortense creo que era a 200 en un punto lol


Closest approach to Mayaguez.

Results for Mayaguez, Puerto Rico (18.27N, 67.15W):
The approximate Closest Point of Approach (CPA) is located near 17.0N, 67.8W or about 93.8 miles (151.0 km) from your location. The estimated time of when the center of the storm will be at that location is in about 1 day, 11 hours and 24 minutes from now (Wednesday, July 10 at 10:36AM AST).
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So we roughly have decent guidance right now until about 10 Pm tomorrow.

Wonderful. Not much you can do though, that's the dynamics of the situation.

Hopefully by tomorrow we get a better understanding of where this is going.

I am out for the day on that note, goodnight folks.
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Results for Provo, TCI (21.78N, 72.27W):

The approximate Closest Point of Approach (CPA) is located near 20.9N, 73.2W or about 88.0 miles (141.7 km) from your location. The estimated time of when the center of the storm will be at that location is in about 2 days, 12 hours and 49 minutes from now (Thursday, July 11 at 11:54AM AST).
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2397. Gearsts
Getting close:Link
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Oh well.

Given the new update, this is one of the crappiest 50mph storms I've ever seen.
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Quoting 2377. Clearwater1:
The NHC did not even suggest what will happen after day five, track wise. That seems unusual . . . in many cases they will at least speculate as to where a storm will most likely go.


I think they would have had the models not diverged from the pretty good consensus they had earlier today. I wouldn't either personally. They don't even show the slightest bend to the west at the end, lol. It's all covered in the error cone though.
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2393. Relix
Quoting 2391. Gearsts:
Hurac�n Hortense creo que era a 200 en un punto lol


Yeah that went well for us haha
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2392. Seastep
Quoting 2367. BrandiQ:
Hope the cone keeps moving right... maybe all of fl will be out of the cone tomorrow. .. wishful thinking I guess


I think the left turn is inevitable. But, shouldn't be any big deal. Rain and wind. Nothing strong.
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2391. Gearsts
Quoting 2388. Relix:


I think the closest point of approach is 70 miles. From 150 last night its a big difference. Reminds me of Irene :P
Huracan Hortense creo que era a 200 en un punto lol
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2390. JRRP
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Quoting 2340. wunderkidcayman:

Indicates it is below 13N

br


Sorry about that. I thought it gave a good look at the storm and have only recently realised the 0116 isn't some sort of serial code, but the time LOL Plus, it's late, so I'll read things many times over before posting them again here when I'm up so late (4:14am here). I do love staying up late to look at all these systems/get all the updates from everyone though. :)
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2388. Relix
Quoting 2384. Gearsts:
how much?


I think the closest point of approach is 70 miles. From 150 last night its a big difference. Reminds me of Irene :P
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2387. HadesGodWyvern (Mod)
BrandiQ
Whens the next flight?



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



---
should be around 6:30 AM

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Historical Crests
(1) 29.19 ft on 03/15/1929
(2) 26.76 ft on 07/11/1994
(3) 22.88 ft on 03/23/1990
(4) 22.61 ft on 03/13/1998
(5) 21.48 ft on 04/15/1975
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Quoting 2376. BrandiQ:
Whens the next flight?


Early Tomorrow Morning 6:30 I think.
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2384. Gearsts
Quoting 2382. Relix:


A little.
how much?
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2383. Relix
Quoting 2381. Hurricane12:


Must be heading to Grand Cayman, eh?


If wunderkidcayman had his way every system would pass over the Caymans. Heck, a hurricane at 30N would drop sharply south just to hit him. Kid's funny. Haha.
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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.