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 2916. Civicane49:
Circulation is definitely outrunning the main area of convection.




It's been doing that from the get go at different times during the last 24 hours?
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I think we can all agree that the 5:00 AM advisory will be very interesting indeed.
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Quoting 2928. KoritheMan:


Can computers accept apologies? o_O


Oh :P
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DMAX is coming up shortly... we'll see how she'll be handling it.
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High westerlies and high speed have destroyed this system internally.

At Dmax now and convection is waning and dying out and the circulation is well displaced.

I will be looking for a downgrade in strength by morning and possibly degradation to a TD if the present trend is not reversed. Not at all surprised, and actually very pleased if this is the way things turn out.

Means I don't have to worry about a major storm finding its way into the gulf. And neither does anyone else.


Heres to hoping.
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Quoting 2926. AtHomeInTX:


If that happens I may owe the EURO an apology. :)


Can computers accept apologies? o_O
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2927. SLU
Quoting 2918. Stormchaser121:

I'm still thinking this is headed to Freeport or somewhere in the area of. That is...after FL


Time will tell but the most important thing about Chantal is that is gives us a synopsis of what sort of tracks we are likely to see this year and also indicates that a very active if not dangerous season lies ahead given the pattern of strong ridging and early Cape Verde development.
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Quoting 2921. KoritheMan:


That's assuming it survives, dude. If Hispaniola rips it up, particularly if it's open wave, there may not be much left to reap the benefits of the upper ridge over the Bahamas.


If that happens I may owe the EURO an apology. :)
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2925. sar2401
Well, ladies and gents, it's 0315 CDT, and the blog has gone in the last eight hours from Chantal as a hurricane that will flatten every place from Miami to Texas to it's going to be an open wave in eight hours and dissipate. The funny thing is that none of really know any more now than we did eight hours ago. I'll see you all all later this morning, when we can wash, rinse, and repeat. :-)
Member Since: October 2, 2004 Posts: 0 Comments: 12734
Quoting 2820. GTstormChaserCaleb:
Should intensify some more for the next 36 hours before leveling off and undergoing a weakening trend for 48 hours and then intensify again.





And that weakening trend is likely as it crosses Hispanola.
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I don't see any evidence of the northwesterly shear backing to northerly. This may really be the end of the line.
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Quoting 2918. Stormchaser121:

I'm still thinking this is headed to Freeport or somewhere in the area of. That is...after FL


That's assuming it survives, dude. If Hispaniola rips it up, particularly if it's open wave, there may not be much left to reap the benefits of the upper ridge over the Bahamas.
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Quoting 2905. galvestonhurricane:


Yeah, well you aren't evil. I actually agree with you. However, you gain a little bit of fear after you witness an intense hurricane.

Anyway, I've been saying all day that there is no way Chantal can get her act together moving at such a fast forward speed.


A little bit of fear goes a long way. It's called being human. Knowing our limits.
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Quoting 2906. bigwes6844:
Thought I was going crazy i couldn't reload at one point


I usually check this when something like that happens:

Link

It was down. :P
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Quoting 2917. SLU:


Yes is should. It's still a vigorous system. Just that it needs to slow down a bit to avoid the LLC from running away from its convective mass. The NW shear isn't helping either.

I'm still thinking this is headed to Freeport or somewhere in the area of. That is...after FL
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2917. SLU
Quoting 2911. Stormchaser121:

do you think it will survive?


Yes is should. It's still a vigorous system. Just that it needs to slow down a bit to avoid the LLC from running away from its convective mass. The NW shear isn't helping either.
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Circulation is definitely outrunning the main area of convection.

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Quoting 2912. whitewabit:
Seems the site had a glitch for a few minutes ..

Seem to me Chantal is done you see that too? It's becomming like a bow echo on rainbow loop.
Member Since: July 2, 2013 Posts: 0 Comments: 1306
Chantal LLCOC is around 13.0N/13.1N 58.5W/58.6W moving W-WNW

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2912. whitewabit (Mod)
Seems the site had a glitch for a few minutes ..
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Quoting 2910. SLU:


Very disorganised tropical storm indeed.

do you think it will survive?
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2910. SLU
Quoting 2902. KoritheMan:
Horrible. Circulation is outrunning the convection.



Very disorganised tropical storm indeed.
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2909. hulakai
href="http://www.barbadosweather.org/RadarPro/BMS_ RadarDisplayer.php" target="_blank">Link

Barbados radar shows the closed circulation, but overall not much more than a passing thunderstorm.
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Quoting 2902. KoritheMan:
Horrible. Circulation is outrunning the convection.


Rip.
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Quoting 2906. bigwes6844:
Thought I was going crazy i couldn't reload at one point

Same thing happened to me!
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Quoting 2904. KoritheMan:
What was with that random blog hiccup? Site must be generating a lot of traffic...
Thought I was going crazy i couldn't reload at one point
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Quoting 2903. KoritheMan:


Well yeah, I'm not refuting that at all. Ike was enormous.

Anyway, we should get back on topic. Save the reminiscent and the rebuking of someone as evil as me for later. ;)


Yeah, well you aren't evil. I actually agree with you. However, you gain a little bit of fear after you witness an intense hurricane.

Anyway, I've been saying all day that there is no way Chantal can get her act together moving at such a fast forward speed.
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What was with that random blog hiccup? Site must be generating a lot of traffic...
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Quoting 2901. galvestonhurricane:


Good morning all! Kori, I know where you are coming from on this one. Before Ike, I had never seem a hurricane. I was secretly thrilled when it came this way. About a week after the hurricane, I took the ferry down to the Bolivar Peninsula. I was left in awe and also a little shocked. It changed my outlook completely.


Well yeah, I'm not refuting that at all. Ike was enormous.

Anyway, we should get back on topic. Save the reminiscing and the rebuking of someone as evil as me for later. ;)
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Horrible. Circulation is outrunning the convection.

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Quoting 2894. KoritheMan:


And I would have defended myself accordingly. :)

That being said, you'll never see me say things like that with a storm that's actually strong and in the process of killing people. I have desire, but I also have decency.

I'M NOT JFV!


Good morning all! Kori, I know where you are coming from on this one. Before Ike, I had never seen a hurricane. I was secretly thrilled when it came this way. About a week after the hurricane, I took the ferry down to the Bolivar Peninsula. I was left in awe and also a little shocked. It changed my outlook completely.
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If Chantal does dissipate, I would still be cognizant for longer range development west of 75W.
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Chantal - rip it was nice knowing you. Latest satelite loop is quickly degenerating,this may form or is already an open wave soon.
Member Since: July 2, 2013 Posts: 0 Comments: 1306
2898. nigel20
I'm out...good night fellow bloggers!
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Quoting 2895. dfwstormwatch:
this is a bit depressing, convecting is starting to be sheared from east to west as well


S-s-s-s-s-s SPEED SHEAR!
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Should get a mention of the tropical wave that just emerged off Africa at 8 AM, or at least 2 PM.
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this is a bit depressing, convecting is starting to be sheared from east to west as well
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Quoting 2892. Bluestorm5:


If this was at 3 pm and not am, lot of bloggers would've jumped at you with their own survival stories... and why I'm still up? Night, y'all.


And I would have defended myself accordingly. :)

That being said, you'll never see me say things like that with a storm that's actually strong and in the process of killing people. I have desire, but I also have decency.

I'M NOT JFV!
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Quoting 2890. KoritheMan:


It's been exposed since about 0z.
It's 3.38a.m...I'm not paying too much attention. :P
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Quoting 2889. KoritheMan:


noooo nooooo lol

I never said that.

I want a storm. I really do.

But I don't want death and destruction.

Probably doesn't make sense to you, but it does to me. I don't wanna explain it, lol.

It's just... it kinda gets tiring seeing recurve after recurve, you know? I think extratropical cyclones are nice and sexy, but after seeing about 40 of them in the last four years, I'm getting a little bored of things. At least with landfall you can watch the bands come ashore via doppler radar. That's just as mesmerizing in its own right.

But death and destruction? No bruh, I don't.


If this was at 3 pm and not am, lot of bloggers would've jumped at you with their own survival stories... and why I'm still up? Night, y'all.
Member Since: August 1, 2011 Posts: 28 Comments: 7880
Quoting 2889. KoritheMan:


noooo nooooo lol

I never said that.

I want a storm. I really do.

But I don't want death and destruction.

Probably doesn't make sense to you, but it does to me. I don't wanna explain it, lol.

It's just... it kinda gets tiring seeing recurve after recurve, you know? I think extratropical cyclones are nice and sexy, but after seeing about 40 of them in the last four years, I'm getting a little bored of things. At least with landfall you can watch the bands come ashore via doppler radar. That's just as mesmerizing in its own right.

But death and destruction? No bruh, I don't.

I'm right with you on that one Kori!
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Quoting 2888. MiamiHurricanes09:
The circulation is evidently exposed.


It's been exposed since about 0z.
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Quoting 2886. Dakster:


Korithe--- You want death and destruction then, huh?

And I have a feeling that hu2007 is right.


noooo nooooo lol

I never said that.

I want a storm. I really do.

But I don't want death and destruction.

Probably doesn't make sense to you, but it does to me. I don't wanna explain it, lol.

It's just... it kinda gets tiring seeing recurve after recurve, you know? I think extratropical cyclones are nice and sexy, but after seeing about 40 of them in the last four years, I'm getting a little bored of things. At least with landfall you can watch the bands come ashore via doppler radar. That's just as mesmerizing in its own right.

But death and destruction? No bruh, I don't.
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The circulation is evidently exposed.
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Quoting 2885. GTstormChaserCaleb:
Yes the pattern is pretty persistent. I still expect a northward turn and then a bend back west, that high is not going anywhere and will get stronger.

Thats why i'm still saying Freeport.
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2886. Dakster
Quoting 2884. hu2007:
i will be like hell on the heart of hurricane 2013


Korithe--- You want death and destruction then, huh?

And I have a feeling that hu2007 is right.
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Quoting 2882. Stormchaser121:

Do you think this will make it to the Gulf?
Yes the pattern is pretty persistent. I still expect a northward turn and then a bend back west, that high is not going anywhere and will get stronger.
Member Since: June 30, 2013 Posts: 11 Comments: 7358
2884. hu2007
Quoting 2866. Dakster:


I agree.... And then there will always be another one after that. This is just July - August and September should be quite interesting.
i will be like hell on the heart of hurricane 2013
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2883. nigel20
Quoting Dakster:


Interesting statistics. Thanks for sharing.

Here's to a remaining season of Fish storms. (if only that would work)

Yeah, no problem!
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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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