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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Just for the hell of it, the GFS has Dorian making landfall in the exact same place as Chantal in many, many days.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting 1569. lottotexas:
Dorian @ 288 hrs
Last time it showed south texas this run the east coast.
Member Since: August 14, 2010 Posts: 10 Comments: 17808
Now we are starting to talk
Time: 22:37:30Z
Coordinates: 12.0167N 54.2167W
Acft. Static Air Press: 966.8 mb (~ 28.55 inHg)
Acft. Geopotential Hgt: 385 meters (~ 1,263 feet)
Extrap. Sfc. Press: 1010.9 mb (~ 29.85 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 165° at 37 knots (From the SSE at ~ 42.5 mph)
Air Temp: 20.9°C (~ 69.6°F)
Dew Pt: 20.9°C (~ 69.6°F)
Peak (10s) Flt. Lvl. Wind: 39 knots (~ 44.8 mph)
SFMR Peak (10s) Sfc. Wind: 45 knots* (~ 51.7 mph*)
SFMR Rain Rate: 15 mm/hr* (~ 0.59 in/hr*)
(*) Denotes suspect data
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The 18z GFS has a pretty weird track on potential Dorian, it looks like it's going to run up the East Coast or just out to sea but then turns west into the Southeast US.
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Chantal has a weird shape here, but continues to show good convection even during Dmin
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1575. Patrap
At 22:37:30Z (last observation), the observation was 372 miles (598 km) to the ESE (102°) from Bridgetown, Barbados.

Product: Air Force High Density (HDOB) Message (URNT15 KNHC)
Transmitted: 8th day of the month at 22:36Z
Date: July 8, 2013
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 302)
Storm Number: 03
Storm Name: Chantal (flight in the North Atlantic basin)
Mission Number: 1
Observation Number: 26

22:37:30Z 12.017N 54.217W 966.8 mb
(~ 28.55 inHg) 385 meters
(~ 1,263 feet) 1010.9 mb
(~ 29.85 inHg) - From 165° at 37 knots
(From the SSE at ~ 42.5 mph) 20.9°C
(~ 69.6°F) 20.9°C
(~ 69.6°F) 39 knots
(~ 44.8 mph) 45 knots*
(~ 51.7 mph*) 15 mm/hr*
(~ 0.59 in/hr*) 42.7 knots* (~ 49.1 mph*)
Tropical Storm* 115.4%*
Time Coordinates Aircraft
Static Air Pressure Aircraft
Geopotential Height Extrapolated
Surface Pressure D-value Flight Level Wind (30 sec. Avg.) Air Temp. Dew Point Peak (10 sec. Avg.)
Flight Level Wind SFMR
Peak (10s Avg.) Sfc. Wind SFMR
Rain Rate Estimated Surface Wind (30 sec. Avg.)
Using Estimated Reduction Factor Peak Wind at Flight Level to
Est. Surface Reduction Factor
HDOB Observations
Member Since: July 3, 2005 Posts: 428 Comments: 129834
Let's see if the 18Z GFS is right regarding DORIAN. Cat 1 hurricanes are fun :)
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Cloud Slideshow. Cool little lesson on different clouds...
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I dont she why anyone is celebrating this hurricane season is just beginning Chantal may not amount to too much but Its looking like one wave developing after the other.
Member Since: May 25, 2012 Posts: 0 Comments: 2043
1571. hydrus
120 hours..

144 hours.
Member Since: September 27, 2007 Posts: 1 Comments: 22609
Quoting 1565. AllStar17:
Tropical storm flt. level winds found as recon now heads northeastward.
About time. 40kt flight-level winds are a little better.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Dorian @ 288 hrs
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Quoting 1550. TropicalAnalystwx13:


Thanks for the credit ;)
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So far I think recon has found enough to determine that Chantal is still at least a TD, but I'm not sure how much more it is than that, too early to tell.
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Tropical storm flt. level winds found as recon now heads northeastward.
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Quoting 1536. CybrTeddy:


Oh, that explains this.
37 knots
(~ 42.5 mph)
Flight-level winds haven't exceeded 30kts though.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
1563. sar2401
Quoting TylerStanfield:
Another center pass... 1011 MB... Ummm, Im speechless?

Tyler, the presentation has been looking more sickly for the past four to five hours, the low still hasn't closed off, and it has very little little deep convection. Just looking at it on satellite, it hasn't looked very impressive for a while. That's why HH's are so valuable - they find out "ground" truth compared to satellite estimates.
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Quoting 1543. barbamz:


Wash, as far as I remember, Hanna was bad, really bad. We've even collected money in my german town for the poor victims of Hanna an co. in Haiti back then. Wiki: At least 537 deaths were reported (the final death toll will likely never be known), mostly due to flooding in the northern part of Haiti, making it the deadliest tropical cyclone in the Atlantic basin since Hurricane Stan in 2005. Hanna also caused $160 million in damages to the U.S, but the exact damage in Haiti is unknown.
I'm not saying Hanna wasn't bad because it affected a lot of people and killed 500.In which I think it should have still been retired.But Hanna while we were focused on that the worst storm to come of 2008 was just behind.Ike.
Member Since: August 14, 2010 Posts: 10 Comments: 17808
Quoting 1548. Patrap:




that looks like a open wave i see no turning what so evere
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Hi All! lurking and learning again this year from Pearl River, La. Thanks for all the insight. I am dreading hurricane season, I am the caretaker of a NOLA oxygen dependent elder and it adds another layer of prep. I guess I need a generator.
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Quoting 1530. Dakster:


I should know better than to take a drink when reading your posts Cosmic...

I shot soda through my nose and all over my keyboardddddddddddddddddddddddddddd......

Now my keeeeeeeeyyyyyyyyyysssssssssss aaaare stickiiiiinnnnggg.
Ever do that while eating a carrot? Now that is gross
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1557. hydrus
Latest GFS..Actually has Chantel coming in as a small, but potent storm..

Member Since: September 27, 2007 Posts: 1 Comments: 22609
Quoting 1492. hurricaneSOFLA:
first hurricane of the season? Dorian... it does have a certain ring to it.
Quoting 1492. hurricaneSOFLA:
first hurricane of the season? Dorian... it does have a certain ring to it.
Would be like 2007 that the first hurricane of the season was Dean.The irony that Dorian is its replacement.
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Its still heading WNW. Why are folks saying its going west. Calm down and wait till Recon is over and the new data is inputted into the models.
Member Since: May 25, 2012 Posts: 0 Comments: 2043


This tells me the center has moved due west or just a tad south of due west during this mission so far.
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Quoting 1535. kingcane:
Is there a way to permanently ignore users? Really unintelligent posts coming from a newbie that should observe more than post.


Yes. Go to community page, then scroll down on your right to "View your blog". Click, and on the right again you'll see "Edit ignored list"
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Quoting 1542. MiamiHurricanes09:
And finally 8 days out we have Hurricane Dorian approaching the northern Lesser Antilles.



Next week will be interesting.
Might want to catch up on some sleep then because all nighters are coming.
Member Since: June 30, 2013 Posts: 12 Comments: 8774
Member Since: July 6, 2010 Posts: 113 Comments: 32813
1548. Patrap
Member Since: July 3, 2005 Posts: 428 Comments: 129834
Dorian..."Just keep strengthing, just keep strengthing..."
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Quoting 1514. CosmicEvents:
You should look into a career at air traffic control at Owen Roberts Airport.

its a Gov job which they can't hire because they have no money to hire anyone

Quoting 1521. stormpetrol:


I've seen these HH missions before and Chantal is still a TS, we have to wait until the mission is over, but imo Chantal will probably still pass South of Jamaica, but that's just my take.

yep I think Chantal will pass S of Jamaica as well
Member Since: June 13, 2009 Posts: 2 Comments: 12716
Going to tropics talk if anyone wants to join me.
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1543. barbamz
Quoting 1501. washingtonian115:
Chantal=Hanna,"Dorian"=Bad.


Wash, as far as I remember, Hanna was bad, really bad. We've even collected money in my german town for the poor victims of Hanna an co. in Haiti back then (2008). Wiki: At least 537 deaths were reported (the final death toll will likely never be known), mostly due to flooding in the northern part of Haiti, making it the deadliest tropical cyclone in the Atlantic basin since Hurricane Stan in 2005. Hanna also caused $160 million in damages to the U.S, but the exact damage in Haiti is unknown.
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And finally 8 days out we have Hurricane Dorian approaching the northern Lesser Antilles.





Next week will be interesting.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Everyone needs to quit the speculation, just sit tight and wait for the next advisory
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i have a feeling the nhc will do the last update on Chantal at or 11pm un less the recon starts find some in cool in Chantal
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1539. Kumo
Quoting 1397. jeffreeysweetypie:
50mph hitting east coast florida???? stop already


Stop trying to be so darn divisive, instead focus on offering constructive contributions. There may only be a few dozen people here posting important information, but there are thousands of lurkers who come here for that information. We are not interested in seeing whatever kind of drama that you are trying to stir up.

Thank you for your consideration.
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1538. Dakster
Quoting 1524. TylerStanfield:
Another center pass... 1011 MB... Ummm, Im speechless?


I'm sorry I missed that. What did you say?
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this happens all the time, the jumping to conclusions is so funny

Going to get some popcorn and a fresca
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Quoting 1527. Hurricanes305:
It seems the NHC blew the 45 mph and the pressure with this one. Lol Taz you said it would be funny if this was an open wave when recon when out. You were close.


Oh, that explains this.
37 knots
(~ 42.5 mph)
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Is there a way to permanently ignore users? Really unintelligent posts coming from a newbie that should observe more than post.
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Too many variables at play to put much faith in the five day tracks at the moment for Chantal in spite of the model consensus bringing it between the Bahamas and Florida then turning it back towards Florida.

Gonna have to wait until she clears Haiti/Cuba to see how the large scale patterns and trof timing pans out. Potential nail biter if the storm or the remnants do linger in the vicinity of the Gulf Stream just off the Coast of Florida for any period of time.
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Quoting 1524. TylerStanfield:
Another center pass... 1011 MB... Ummm, Im speechless?


Didn't appear to be the center, it was close but not quite. Note the windshift remained southerly even though there was a westerly component. Wait a few more passes.
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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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