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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2783. Dakster
Quoting 2776. KoritheMan:
Darn it... This is one time I wish I didn't have to work tomorrow. I'd really rather look at Chantal than go to work when I wake up.

Waiting is always so suspenseful.


Tonight is my 'Friday' so I get to watch the remainder of the week until Friday, which is my Monday.

Anyways, I will watch Chantal for you. And then we can switch on Friday!

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2782. Skyepony (Mod)
Quoting 2768. ProgressivePulse:


Sure you can. Chantal likely did for some time this evening moving at that rate with lack of deep convection. I think it will be short lived however, personally. Convection is going to cover the center again shortly and in good fashion, just in time for recon, lol.



Looking at it it does appear short lived & Chantal is pulling back together.

Looking a Dvorak it had the pressure come up & the T# fall there a bit but it's strengthening again.


Chantal isn't close enough to land in that pass for me to throw out the OSCAT pass.
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2781. Dakster
Quoting 2772. EricSFL:

Probably it will not change much, except for a slight westward bend at the end of the forecast period.


That is what I am expecting too. If the trend keeps up it may slowly creep further south again.

Time, of course, will tell the tale. For all we know Chantal may be in the history books by the time she gets to the Bahamas.
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2780. j2008
Quoting 2777. JLPR2:
Higher resolution OSCAT says no Closed LLC, but some 50knots barbs. NHC will probably keep it as a TS until they have HH info to confirm it might have opened up into a wave.

Well darn, I might have to rethink my words. She is one of those storms that will keep us guessing I guess.
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Chantal's center is ill-defined, which is what recon found out earlier but they were able to close it off.
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Quoting 2764. Tribucanes:
So if Chantal's retrograded into an open wave just how would that change things forecast wise. Just saying Kori, models showing TS getting forced West over Florida and into the Gulf isn't a good thing. Conditions are far different and panic never did anyone any good.


The fact that Chantal "is" at 23-26mph should be cause for warning. If this thing finds a sweet spot, look out.
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2777. JLPR2
Higher resolution OSCAT says no Closed LLC, but some 50knots barbs. NHC will probably keep it as a TS until they have HH info to confirm it might have opened up into a wave.

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Darn it... This is one time I wish I didn't have to work tomorrow. I'd really rather look at Chantal than go to work when I wake up.

Waiting is always so suspenseful.
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2775. HadesGodWyvern (Mod)
TY 07W

2013JUL09 053200
CI: T4.0
3.8 (Initial) 4.3 (Adjusted) 6.1 (Raw)
EYE
20.0N 139.4E
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Let's see what navy says.
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Skyepony or whitewabit, what's the story on Keeper? Is he coming back?
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2772. EricSFL
Quoting 2744. Dakster:
Does anyone think there will be a cone shift from the NHC at the 5am. I am basing this on the SFWMD model plots posted above. It appears that Chantal, should she make it that far, will be pushed westward across Florida.

Probably it will not change much, except for a slight westward bend at the end of the forecast period.
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Quoting 2766. whitewabit:
Same thing different night looks open on the southwest side. It must really have a tight, shallow center, especially since the hurricane hunters were having trouble earlier today finding one.
Member Since: June 30, 2013 Posts: 12 Comments: 8273
2770. Skyepony (Mod)
Quoting 2762. Camille33:

It doesn't have goodd resolution check ascat it better.


This is the ASCAT..it was only a partial & it's hours older than the OSCAT. Nothing is screaming closed here.

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The center of Chantal, which looks closed on radar by the way, is poised to track very close to Barbados. May be able to get an accurate reading on the pressure.

Barbados radar
Member Since: July 6, 2010 Posts: 113 Comments: 32046
Quoting 2746. Skyepony:
Fresh OSCAT do I dare say open wave?



Sure you can. Chantal likely did for some time this evening moving at that rate with lack of deep convection. I think it will be short lived however, personally. Convection is going to cover the center again shortly and in good fashion, just in time for recon, lol.

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2767. j2008
Quoting 2746. Skyepony:
Fresh OSCAT do I dare say open wave?

No, I dont trust OSCAT at all so I wont believe it until the HH say so or other groups say so, haha maybe I'm just stubborn..
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2766. whitewabit (Mod)
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This answers our questions.
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So if Chantal's retrograded into an open wave just how would that change things forecast wise. Just saying Kori, models showing TS getting forced West over Florida and into the Gulf isn't a good thing. Conditions are far different and panic never did anyone any good.
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OSCAT and WindSAT are like the Stevie Wonder of scatterometers. I rather save my judgement for ASCAT and especially Recon.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting 2746. Skyepony:
Fresh OSCAT do I dare say open wave?


It doesn't have goodd resolution check ascat it better.
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Quoting 2755. KoritheMan:


If true, that's no real surprise. The possibility of degeneration into a tropical wave has been at the forefront of mind since the time of genesis.




all so if that is ture then will still need too keep a eye on it if it can find better FAVORABLE CONDITIONS down the rd
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2760. nigel20
Quoting Skyepony:
Soulik

Hey Skye! It seems as if Soulik will bring high surfs and squally weather to Taiwan.
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Wow, this blog is super busy for that time of the day (and year). Thought it was much quieter when i posted the video below on the record Toronto flooding.
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Quoting 2746. Skyepony:
Fresh OSCAT do I dare say open wave?


Too many flagged barbs on the south side of the circulation. Recon said it was closed, and that's all we have to go on.
Member Since: July 6, 2010 Posts: 113 Comments: 32046
Quoting 2752. Tribucanes:
If Chantal gets into the Bahamas, slows down, intensifies, and then gets pushed West across Florida into the Gulf, "that" comparison is sure to come up.


I hate comparisons to past storms, Katrina or otherwise. Each storm will be different, and panicking about what happened in the past doesn't change anything.
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Quoting 2754. Tazmanian:
well all am going back too bed
Have a goodnight Taz
Member Since: June 30, 2013 Posts: 12 Comments: 8273
Quoting 2746. Skyepony:
Fresh OSCAT do I dare say open wave?



If true, that's no real surprise. The possibility of degeneration into a tropical wave has been at the forefront of mind since the time of genesis.
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well all am going back too bed
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2753. whitewabit (Mod)
Quoting 2746. Skyepony:
Fresh OSCAT do I dare say open wave?



kinda looks that way from the OSCAT ..
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If Chantal gets into the Bahamas, slows down, intensifies, and then gets pushed West across Florida into the Gulf, "that" comparison is sure to come up.
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2751. nigel20
Quoting sar2401:
This is all pretty amazing. The last time I've seen such interest in a tropical storm at 12.4N was in 2004 for Ivan...and he was a cat 3, on the way to a cat 4 at the time. He was supposed to turn poleward, run up the Windwards and end up somewhere in Florida too. He did, just not in the way that any model predicted. If it hadn't been for the fact my wife died in 2004, we would have been living aboard our sailboat and would have been in Grenada on September 7, 2004. I would have run for the ABC's, since no hurricane ever travels west that far south. My boat speed was 11 knots and Ivan was traveling at 13 knots. We would have been overtaken in open seas and I wouldn't be here today. There are 8 yachts and 23 people who's remains have never been discovered, and they were running the same direction I would have run. Life (and models) sometimes turn out way different than you expect.

I'm sorry to hear about your wife as well...It must have been pretty hard on you. I lost my mother to in 2007 to Leukemia and I'm still in shock when I think about it.
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Quoting 2736. Tribucanes:
Really hope Chantal doesn't cross Florida and make the Gulf as a strong TS and have a couple days to grow. Looking like a real possibility. Models show Georgia's under the gun too, but Georgia minus well be Indian, Georgia almost never gets hit.


I see an extremely favorable for upper wind pattern in the GFS, with a ballooning upper ridge. If she survives Hispaniola, she will strengthen. No two ways about it.
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2749. Dakster
Quoting 2746. Skyepony:
Fresh OSCAT do I dare say open wave?



Interesting, It sure looks like it by that graphic.
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Quoting 2746. Skyepony:
Fresh OSCAT do I dare say open wave?

no.
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Quoting 2740. whitewabit:
During name storms .. keep comments on about the storm our the topic of Dr Msters Blog .. adhere to the rules of the road ..

Other off topic comments will not be tolerated ..

It would be a shame for a blogger to be unable to post during a storm ..




am saveing this commet
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2746. Skyepony (Mod)
Fresh OSCAT do I dare say open wave?

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OMG! Sar your are going to kill me for this, I seriously thought you were a female. And I am so sorry to hear about what happened to your husband.
Member Since: June 30, 2013 Posts: 12 Comments: 8273
2744. Dakster
Does anyone think there will be a cone shift from the NHC at the 5am. I am basing this on the SFWMD model plots posted above. It appears that Chantal, should she make it that far, will be pushed westward across Florida.
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One local met is saying Chantal "needs to be watched" and "could over-perform". If it keeps going at this rate though it might not make it through Hispaniola.
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ADT has it even higher.



2013JUL09 054500 3.4 995.2/ 0.0 / 53.0 3.4 3.5 3.5 NO LIMIT OFF OFF -41.56 -48.71 CRVBND N/A 12.81 57.10 FCST

Quoting 2720. MiamiHurricanes09:
Gotta say I'm surprised SAB thinks Chantal looks like a T3.0...especially since it isn't the prettiest tropical storm I've ever seen lol.

To give you an idea...on the Dvorak scale, a T3.0 has winds of 45kts and a pressure of 1000mb.

http://www.ssd.noaa.gov/PS/TROP/CI-chart.html
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2741. EricSFL
Quoting 2728. TropicalAnalystwx13:
Everybody repeat after me.

Tropical Storm Chantal.

Chantal.

Chantal.

ChantAl.

Lol.

Shawn-tall ?
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2740. whitewabit (Mod)
During name storms .. keep comments on about the storm our the topic of Dr Msters Blog .. adhere to the rules of the road ..

Other off topic comments will not be tolerated ..

It would be a shame for a blogger to be unable to post during a storm ..
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2739. Skyepony (Mod)
Soulik
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Quoting 2725. JRRP:


less and less dry air
Blobbing up again, it's 3 am over there right now, right? so D-MAX is about 3 hours away right in time for her to show off in front of the hurricane hunters.
Member Since: June 30, 2013 Posts: 12 Comments: 8273
2737. Dakster
Quoting 2705. sar2401:
This is all pretty amazing. The last time I've seen such interest in a tropical storm at 12.4N was in 2004 for Ivan...and he was a cat 3, on the way to a cat 4 at the time. He was supposed to turn poleward, run up the Windwards and end up somewhere in Florida too. He did, just not in the way that any model predicted. If it hadn't been for the fact my wife died in 2004, we would have been living aboard our sailboat and would have been in Grenada on September 7, 2004. I would have run for the ABC's, since no hurricane ever travels west that far south. My boat speed was 11 knots and Ivan was traveling at 13 knots. We would have been overtaken in open seas and I wouldn't be here today. There are 8 yachts and 23 people who's remains have never been discovered, and they were running the same direction I would have run. Life (and models) sometimes turn out way different than you expect.


Sorry to hear about your wife.

Glad you made it out ok.
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Really hope Chantal doesn't cross Florida and make the Gulf as a strong TS and have a couple days to grow. Looking like a real possibility. Models show Georgia's under the gun too, but Georgia minus well be Indian, Georgia almost never gets hit.
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Quoting 2729. Stormchaser121:


Coming back south tonight. Models don't do well with slow moving storms. I think they had it right earlier today with a landfall somewhere between West Palm and Cape Canaveral.
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Quoting 2724. 7544:
looks chantel and the ull may have a good dmax tonight look for more blobs tomorow imo

that ULL is dying
I hope Chantal make use of that D-max
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Am I just hearing voices above, or are recent developments in the Atlantic basin now pointing to a potentially, "very active hurricane season?"

I hope I'm wrong, but it's also nice to be right, if that makes any sense.

As I said here yesterday in my season update(Post 2553,) "enjoy the show, but don't be happy about it."

Here's my May 29th Forecast - Post 543 ...
Quoting 543. OracleDeAtlantis:
I was going to roll this out on June 1, but it looks like the Atlantic season is starting a bit sooner than I expected. I typically will publish one or two of these a year. You can judge for yourselves how accurate I've been in the past, but considering that last year's highlighted a giant "S" for a backdrop, I hope I can safely assume that I have some bragging rights. It was, after all, an undeniable Superstorm.

The title of this forecast, which was initially published May 25, 2013 is: "Goes with the territory ..." It's based upon a dream that I had several weeks ago.

Note: There's a unique graphic and a short video that accompanies this forecast, also. See below ...



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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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