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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2583. ncstorm
I thought I was going to bed..the GFS is well showing 5 potential situations unfolding..
\

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Looks to turn poleward and make landfall on the Florida panhandle.

216 hours.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
216 hours:

Member Since: July 21, 2011 Posts: 83 Comments: 7167
Quoting 2575. Drakoen:
NHC will probably bend the track westward at the end of the forecast period if the trends continue.


I would hope so, they are one of the few that don't at this point, lol. They seem to be liking the GFS reading the discussion so with that coming south and west, I agree.
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2579. nigel20
Quoting Ameister12:
Typhoon Soulik. Quickly becoming a monster typhoon.

I'm happy that this isn't anywhere close to me at thee moment. :)
Member Since: November 6, 2010 Posts: 11 Comments: 8136
Just as I thought look at the precip. plot. out 189 hrs.

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Quoting 2574. TropicalAnalystwx13:
Let's see what goes on from here.



It actually looks like it meanders a bit WSW from landfall to the point it re-emerges. Should be interesting to see if all that time over land (albeit, flat, swampy land surrounded by water...) has much affect on intensity before it reaches the GOM.
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Quoting 2574. TropicalAnalystwx13:
Let's see what goes on from here.



This might get interesting....
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2575. Drakoen
NHC will probably bend the track westward at the end of the forecast period if the trends continue.
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Let's see what goes on from here.

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Typhoon Soulik. Quickly becoming a monster typhoon.
Member Since: August 9, 2009 Posts: 10 Comments: 5026
Hi everybody! I'm catching up on blog. Can I ask a question? This may be stupid.

A isobar is 2 points of equal pressure between the 2 points? Can you have just one isobar to form a closed low? Or a Tropical Depression,T Storm,Hurricane or can you even have just 1 isobar in a circular or oblong closed low? Did that make sense? I looked around a bit and really did not get a good understandable answer.

I am under the impression that TS Chantal's circulation is barely closed...How many isobars does it have?
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Quoting 2561. Stormchaser2007:
Chantal gets into the Gulf by 180 hours...
Looks like a 2 day event for the Central FL. could have some serious flooding in that time.
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Quoting 2563. GTstormChaserCaleb:
162 hrs we have landfall but it continues to strengthen. At least the vorticity continues to tighten up.


Westward bound....into Gulf...
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gfs bottoms chantal out at 990 mbs before landfall somwhere near the cape
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2567. sar2401
Quoting KoritheMan:


Another shortwave is forecast to move into the eastern United States by that time. The models show this feature lifting out and leaving Chantal behind, but not fast enough to cause an immediate westward turn.

I'm not buying that one, Kori. Our mets are concerned that this low doesn't even get out of here by Sunday and we have another five day long blob event. The only way I can see this happen is for the Florida blob, the shortwave blob, and Chantal remnant blob all team up and get stuck in a trough again. The trough by itself, or the Florida blob, by itself, should not be enough to cause another blob to hang around this long. I think Chantal ends up in another interminable 94L like situation.
Member Since: October 2, 2004 Posts: 0 Comments: 16025
Current GFS is directly on the TVCN.

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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.



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162 hrs we have landfall but it continues to strengthen. At least the vorticity continues to tighten up.

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Quoting 2557. SavannahStorm:
If Chantal comes to a full stop like that over Florida- it could be a major, major flooding event.


yup and if that verifies it will be right over my house!
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Chantal gets into the Gulf by 180 hours...
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2560. nigel20
Quoting MiamiHurricanes09:
Just stalls over the central Florida coast and weakens.

And there you have Dorian coming into the picture.


The eastern Caribbean could be dealing with a serious threat, If the pans out.
Member Since: November 6, 2010 Posts: 11 Comments: 8136
168 hours:

Member Since: July 21, 2011 Posts: 83 Comments: 7167
Quoting 2532. GTstormChaserCaleb:
144 hrs. down to 992 mb.


I wonder what she will do once in the Gulf...
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If Chantal comes to a full stop like that over Florida- it could be a major, major flooding event.
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Someone is going to need a boat.

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2555. nigel20
Quoting FIUStormChaser:


Lmao.. Out of all the negative things people say about Florida, no one has ever called it a "Nipple"

Lol!
Member Since: November 6, 2010 Posts: 11 Comments: 8136
Quoting 2551. WPBHurricane05:
No rush to make a full landfall.

Could be a long one next week.

Reminds me of Frances the slow movement that is. That was a long few days.
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Just stalls over the central Florida coast and weakens.

And there you have Dorian coming into the picture.

7 days:

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting 2532. GTstormChaserCaleb:
144 hrs. down to 992 mb.



What's the general correlation between mb and storm strength (i.e. category)
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No rush to make a full landfall.

Could be a long one next week.
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Quoting 2540. MiamiHurricanes09:
Nipple is a great way to refer to the Florida coastline LOL.


Well I thought it would be easier for those not familiar with towns or cities in FL. It is Merritt Island but would Nub have been more appropriate? :)
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Quoting 2544. GTstormChaserCaleb:
156 hrs. vorticity 

Looks like it stalls off of the coast for a little bit.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting 2540. MiamiHurricanes09:
Nipple is a great way to refer to the Florida coastline LOL.


Lmao.. Out of all the negative things people say about Florida, no one has ever called it a "Nipple"
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A lot of discrepancy in the long term..

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Quoting 2539. Stormchaser2007:
Definitely not doing too good right now.

LLC is just barely under the cloud canopy


Not again! This system likes to play peek a boo too much.
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Member Since: July 21, 2011 Posts: 83 Comments: 7167
156 hrs. vorticity 

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Wow- GFS shows it lingering just off Cape Canaveral for almost 24 hours, without moving much at all...
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0Z GFS 150 hours

Hurricane landfall

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2541. Drakoen
Chantal definitely needs to be watched. The weakness in the 500mb longwave pattern may lift northward with an upper level low cutting off over the northeast allowing the subtropical ridge to build westward and the U.S. continental high to build eastward. This would allow Chantal to impact the southeast with favorable upper level conditions.
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Quoting 2534. tropicalnewbee:
Looks like I better do a check run on my genny as I am in east central FL. That nipple that sticks out is directly to my east we are about 5 miles inland and seems like Chantal will be a PIA for me.
Nipple is a great way to refer to the Florida coastline LOL.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Definitely not doing too good right now.

LLC is just barely under the cloud canopy

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Looks like Chantal will make it in the gulf this run.
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Quoting 2527. TropicalAnalystwx13:
Chantal makes landfall as, or very close to, a hurricane.

Yep and here comes Dorian.
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2536. nigel20
Quoting GTstormChaserCaleb:
Goodnight everyone!

114 hrs. down to 997 mb. turning back towards the west.


Night Caleb!
Member Since: November 6, 2010 Posts: 11 Comments: 8136
00z GFS basically portrays the type of path that I'm thinking of. A rightward track with a sharp bend towards the west. This time it looks like it's making landfall across central Florida as a minimal hurricane in about 6 days.

Now let's see what it does if it gets into the Gulf.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Looks like I better do a check run on my genny as I am in east central FL. That nipple that sticks out is directly to my east we are about 5 miles inland and seems like Chantal will be a PIA for me.
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Quoting 2525. will40:



yes see the break starting to form the weakness?


The low is to cut off and the high to build west with Chantal. Chantal will head west from that point forward.
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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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