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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2633. Levi32
Quoting 2626. TropicalAnalystwx13:
The northward shunt after entering the Gulf by Chantal is unrealistic. The 0z GFS sends the storm north into potent ridging, which doesn't make sense.

Choo choo...



It forms a second cut-off mid-level low to the north over the Carolinas that brings Chantal north, but it is a random turbulent eddy that was not present on previous runs.

Member Since: November 24, 2005 Posts: 635 Comments: 26698
2632. nigel20
Quoting ncstorm:
00z GFS Ensemble run should be interesting where the ensembles think these systems will go at and with that, Im really going to bed now..sleep tight and dont dream of hurricanes!! :)

Good night nc!
Member Since: November 6, 2010 Posts: 12 Comments: 8418
Extremely dangerous patttern if it comes to pass
Member Since: May 14, 2006 Posts: 8 Comments: 13841
Chantal's LLC is exposed at 13N 56.7W... or maybe I need to change my glasses.
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2629. ncstorm
also, it looks like all the those systems after Chantal traverse through haiti as well..
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Dorian is going to be a very bad bad boy that seems he wants to follow in Dean's path to retirement...
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Quoting 2622. MiamiHurricanes09:
Blog always wakes up when major hurricanes are making landfall in south Florida and Louisiana.
agreed.
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The northward shunt after entering the Gulf by Chantal is unrealistic. The 0z GFS sends the storm north into potent ridging, which doesn't make sense.

Choo choo...

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2625. will40
Quoting 2617. ncstorm:
00z GFS Ensemble run should be interesting where the ensembles think these systems will go at and with that, Im really going to bed now..sleep tight and dont dream of hurricanes!! :)


night again :-)
Member Since: September 19, 2005 Posts: 2 Comments: 4266
Member Since: July 31, 2006 Posts: 56 Comments: 8112
2623. 7544
now lets see what the eruo will show us that one could be further south than the gfs stay tuned dont go to bed yet
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Quoting 2616. CybrTeddy:
Bet this will set the blog aflame.
Blog always wakes up when major hurricanes are making landfall in south Florida and Louisiana lol.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting 2616. CybrTeddy:
Bet this will set the blog aflame.
yep.
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Quoting 2611. AtHomeInTX:

Hallelujah.
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Quoting 2605. MiamiHurricanes09:
Very crazy stuff...especially in the middle of frickin' July. Hopefully it's not the pattern that sets up as we head in into the meat of the season...but then again, when was the last time Florida received an intense cyclone? Almost 8 years.


You are right there my friend. It's not a matter of if here, just when and it's been a long time.
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2618. nigel20
Quoting caribbeantracker01:


Barbados begins to feel her effects

Yeah, you can also Chantal's circulation on the Barbados radar loop.
Member Since: November 6, 2010 Posts: 12 Comments: 8418
2617. ncstorm
00z GFS Ensemble run should be interesting where the ensembles think these systems will go at and with that, Im really going to bed now..sleep tight and dont dream of hurricanes!! :)
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Bet this will set the blog aflame.
Member Since: July 8, 2005 Posts: 259 Comments: 24550
Quoting 2605. MiamiHurricanes09:
Very crazy stuff...especially in the middle of frickin' July. Hopefully it's not the pattern that sets up as we head in into the meat of the season...but then again, when was the last time Florida received an intense cyclone? Almost 8 years.
yep,hurricane Wilma.
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2 storms into the east coast of FL in July is crazy should it come to pass.
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That is the pattern me levi have been harping on for weeks. Will it stick around lets hope not.
Member Since: May 14, 2006 Posts: 8 Comments: 13841
2612. ncstorm
Seriously, I know its long range but if you arent prepared and up to date with your hurricane plans, you need to be..
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Member Since: July 21, 2011 Posts: 83 Comments: 7167
2609. 7544
did anyone else get up to check thier calender !!
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Just speechless at the GFS run, especially since my parents are in Florida (but luckily they are on the west coast near Tampa Bay, where-- if Chantal crosses it should be much weaker)...and then Dorian wants to cross too...
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2607. ncstorm
its going to be a lonnnnnngggggg season..last frame..two more waves coming off Africa

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Could Chantel skip off the south coast of hispanola and come closer to south florida?
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Quoting 2596. ProgressivePulse:


It's going to be a long year me thinks... It is July right?
Very crazy stuff...especially in the middle of frickin' July. Hopefully it's not the pattern that sets up as we head in into the meat of the season...but then again, when was the last time Florida received an intense cyclone? Almost 8 years.
Member Since: September 2, 2009 Posts: 130 Comments: 21194


Barbados begins to feel her effects
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Not good. Two Florida landfalls before August this is not 2004.
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2602. nigel20
Quoting Levi32:
This would be crazy for mid-July. Three systems at once and all from Africa.


Yes indeed!
Member Since: November 6, 2010 Posts: 12 Comments: 8418
Quoting 2595. Drakoen:


Even crazier that they are forming in the tropical atlantic region. Doesn't bode well for the rest of the season.


The pattern looks like late August/Early September.
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Yea GFS doesnt like florida... first it takes chantal in central florida then future "dorian" into south florida. of ocurse it is the very long range and changes will occur
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Ahh Florida..always getting hit as usual...
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2598. ncstorm


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2597. sar2401
Quoting MississippiWx:
Chantal is struggling right now. Can really tell by looking at convection that the southern part of her circulation is weak. Winds are spinning quickly around the east, north, and west sides, but as they slow down, they pile up on the southern end and that's what is causing the convection to blow up there so much.




And I still see that Grenada has no tropical storm watches out, let alone a warning. It appears to me that Chantal is traveling too fast and too far west to gain enough latitude to avoid at least a close brush with Grenada. St. Vincent, whose furthest south point is less than 50 miles from Grenada, at least has a TS watch. I hope the folks in Grenada are at least watching where Chantal is going on satelite and paying attention to TV out of Barbados. Grenada's Met Service is a joke, and it has cost Grenadian's their lives in the past.
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Quoting 2592. MiamiHurricanes09:
And our friend Dorian ends up making landfall right over my house in south Florida. :P




It's going to be a long year me thinks... It is July right?
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2595. Drakoen
Quoting 2591. Levi32:
This would be crazy for mid-July. Three systems at once.



Even crazier that they are forming in the tropical atlantic region. Doesn't bode well for the rest of the season.
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This isn't something you like to see- that is apparently Dorian.
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2593. ncstorm
Quoting 2590. will40:


you wish you had now dont ya lol?


and missed the action??..nah..LOL
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And our friend Dorian ends up making landfall right over my house in south Florida. :P


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2591. Levi32
This would be crazy for mid-July. Three systems at once and all from Africa.

Member Since: November 24, 2005 Posts: 635 Comments: 26698
2590. will40
Quoting 2583. ncstorm:
I thought I was going to bed..the GFS is well showing 5 potential situations unfolding..
\



you wish you had now dont ya lol?
Member Since: September 19, 2005 Posts: 2 Comments: 4266
2589. 7544
hmm did anyone notice the ssw dip it takes over fla just like the k did interesting run to say the least the nhc must be scratching thier heads just about now lol
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2588. ncstorm
276 hours
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Quoting 2564. MississippiWx:
Chantal is struggling right now. Can really tell by looking at convection that the southern part of her circulation is weak. Winds are spinning quickly around the east, north, and west sides, but as they slow down, they pile up on the southern end and that's what is causing the convection to blow up there so much.





It doesn't help that there is all this dry air ahead of it.
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Quoting 2584. GrandCaymanMed:
First Florida got hit by Adrian, now Chantal could impact Florida. That would be 2 storms...


And it's early July, lol. Fla's "Peak" time is August, September, October.
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2585. whitewabit (Mod)
Quoting 2583. ncstorm:
I thought I was going to bed..the GFS is well showing 5 situations unfolding..
\



That looks like 2005 ..
Member Since: August 17, 2005 Posts: 366 Comments: 32124
First Florida got hit by Andrea, now Chantal could impact Florida. That would be 2 storms...
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2583. ncstorm
I thought I was going to bed..the GFS is well showing 5 potential situations unfolding..
\

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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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