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 228. MisipiGrl:
Walt: "Can anyone (genuinely) identify this scenario?"

I don't think ANYONE on the Mississippi Gulf Coast will ever forget the good ole TD 10, dissipated then named TD 12 scenario. :)
Does anyone think this is a similar setup to what we are looking at now...down the road?
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Quoting 227. StormTrackerScott:
This is not a good pattern for FL residents. Looks like a 2004 set up as we head into the peak of hurricane season.



I agree!!
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People seem to forget the NHC wrote Jeanne off after the pass of Hispanola but we all know what happened after that.

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Quoting 219. PalmBeachWeather:
A couple of dozen Rock Shrimp at Dixie Crossroads might help.

After growing up on seafood in New England I can't stomach it anymore but I enjoy their steak!
Quoting 218. Grothar:


Uh, see what happens when you drop an apostrophe. To answer you question, only one.

At your age proper English should be like breathing but good on you and the missus! :)
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Link


Link
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Walt: "Can anyone (genuinely) identify this scenario?"

I don't think ANYONE on the Mississippi Gulf Coast will ever forget the good ole TD 10, dissipated then named TD 12 scenario. :)
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This is not a good pattern for FL residents. Looks like a 2004 set up as we head into the peak of hurricane season.

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Quoting 217. Patrap:


K, 2005 Genesis
...and do you think there are any similarities to what is happening now, or what possibly could happen?
Member Since: May 16, 2010 Posts: 0 Comments: 1472
Quoting Levi32:
Brand new ASCAT pass is not very telling on whether Chantal's circulation is still closed. Too many flagged wind barbs near the center.





The wind barbs that are black are 'rain flagged', meaning that rain was heavy enough in that area to potentially cause some error in the speed or direction output. Experience indicates that in all but the most extreme cases, the speeds and direction are reliable even when 'flagged'.
Link
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Quoting 211. Waltanater:
Can anyone (genuinely) identify this scenario?

(LOL)


Tropical Depression Twelve formed over the southeastern Bahamas, partially from the remains of Tropical Depression Ten, which had dissipated due to the effects of a nearby upper tropospheric trough. While the normal standards for numbering tropical depressions in the Atlantic indicate that the old name/number is retained when a depression dissipates and regenerates, satellite data indicated that a second tropical wave combined with Tropical Depression Ten north of Puerto Rico to form a new, much more advanced system, which was then designated as Tropical Depression Twelve. Simultaneously, the trough in the upper troposphere weakened, causing the wind shear in the area to relax, thereby allowing the new tropical depression to develop. In a later re-analysis, it was determined that the low-level circulation of Ten had completely detached and dissipated, with only the remnant mid-level circulation moving on and merging with the aforementioned second tropical wave. As a result, the criteria for keeping the same name and identity were not met.
Katrina
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Quoting 190. pcola57:


Thank you Aussie..
I missed it or ??
Anyway sure could use a African continent link for future reference..
(hint-hint) :)

here ya go.
Member Since: October 15, 2012 Posts: 0 Comments: 434
Chantal (and I) dont care about the past and hearing about statistics. She is making her own history.
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Quoting 143. pcola57:
Gro your blob has plenty of moisture and is starting a movement into the Bahamas now..
Curious as to why Dr. Masters gave it no mention..
Even if just to discount it..



Do we even know if Gro's blob is warm or cold-core? Looks great. Hope it hightails it due W to TX, now that ex-94L has opened the door.
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Quoting 198. missionRN14:
Can anyone comment on that Cold core low pressure system just over the Bahamas that DR Jeff Masters mentioned in passing the other day about possible development....
Well last night it looked like just a dry spin and this am looks like a cloud gatherer with a potential development? Any comment. NHC is a no mention...
Please.. I'm in the need to know zone work Emergency Services...
Tks guys


No tropical development is expected.......Just a rainmaker. You nailed already in your question...An upper-mid level feature with a little more meat on it.
Member Since: August 8, 2006 Posts: 0 Comments: 10455
Quoting 183. tropicalnewbee:

Islander I am in Titusville and have been watching this. NHC adjusted the cone slightly to the east but I think as time moves on it will shift back west due to the trough lifting out and the high pressure pushing it back west. As the Doc said this is probably Bad JuJu for us in the East Coast of FL. of things to come...
A couple of dozen Rock Shrimp at Dixie Crossroads might help.
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Quoting 202. tropicalnewbee:


Since the first crossing to the New World how many wives have you had Gro? :)


Uh, see what happens when you drop an apostrophe. To answer you question, only one.
Member Since: July 17, 2009 Posts: 71 Comments: 27895
Quoting 211. Waltanater:
Can anyone (genuinely) identify this scenario?

(LOL)


Tropical Depression Twelve formed over the southeastern Bahamas, partially from the remains of Tropical Depression Ten, which had dissipated due to the effects of a nearby upper tropospheric trough. While the normal standards for numbering tropical depressions in the Atlantic indicate that the old name/number is retained when a depression dissipates and regenerates, satellite data indicated that a second tropical wave combined with Tropical Depression Ten north of Puerto Rico to form a new, much more advanced system, which was then designated as Tropical Depression Twelve. Simultaneously, the trough in the upper troposphere weakened, causing the wind shear in the area to relax, thereby allowing the new tropical depression to develop. In a later re-analysis, it was determined that the low-level circulation of Ten had completely detached and dissipated, with only the remnant mid-level circulation moving on and merging with the aforementioned second tropical wave. As a result, the criteria for keeping the same name and identity were not met.


K, 2005 Genesis
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Quoting 147. washingtonian115:
In his earlier post he was talking about 2006.So that's why I mentioned the El nino.

ok.
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Quoting 201. Grothar:


Again, timing I guess. Thanks, Levi.


That's right. But, if we're talking about the mostly lateral trough over the high plains states, that's a loooonnnnng ways from Chantal. Unless the models are speculating on a trough that isn't visible yet. Look at a sfc map, high pressure above Chantal is quite strong. I just don't see an east coast escape route yet.

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Quoting 186. 7544:
cone didnt budge we have to wait for the hh info anyone know what time est they will go in thanks


5:00 PM
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TS Chantel current forecast closest approach:
Results for Provo, TCI (21.78N, 72.27W):
The approximate Closest Point of Approach (CPA) is located near 20.3N, 74.5W or about 175.6 miles (282.6 km) from your location. The estimated time of when the center of the storm will be at that location is in about 3 days, 3 hours and 16 minutes from now (Thursday, July 11 at 2:24PM AST).


Via
http://stormcarib.com/closest.cgi
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I think the 70 mph forecast is reasonable from the experts, what do you guys think?
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Can anyone (genuinely) identify this scenario?

(LOL)


Tropical Depression Twelve formed over the southeastern Bahamas, partially from the remains of Tropical Depression Ten, which had dissipated due to the effects of a nearby upper tropospheric trough. While the normal standards for numbering tropical depressions in the Atlantic indicate that the old name/number is retained when a depression dissipates and regenerates, satellite data indicated that a second tropical wave combined with Tropical Depression Ten north of Puerto Rico to form a new, much more advanced system, which was then designated as Tropical Depression Twelve. Simultaneously, the trough in the upper troposphere weakened, causing the wind shear in the area to relax, thereby allowing the new tropical depression to develop. In a later re-analysis, it was determined that the low-level circulation of Ten had completely detached and dissipated, with only the remnant mid-level circulation moving on and merging with the aforementioned second tropical wave. As a result, the criteria for keeping the same name and identity were not met.
Member Since: May 16, 2010 Posts: 0 Comments: 1472
TS Chantal

RGB Loop

Click image for Loop



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Quoting 182. ncstorm:


they are the experts..
Oh no someone else might be the experts then if I'm mistaken?.I mean they do have official forecast that come out and a office building in Miami with tools we don't have,If they aren't the experts then who is?.Oh my I've been tricked all these years..
Member Since: August 14, 2010 Posts: 11 Comments: 19149
Quoting 196. Patrap:


Actually doing a decent job, and has been, fighting off the dry air.
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Quoting 177. Levi32:


It's Stewart, lol.

I find it interesting that he says this:

"OTHER THAN THE FAST FORWARD SPEED OF CHANTAL...ENVIRONMENTAL CONDITIONS ARE FAIRLY FAVORABLE FOR AT LEAST SOME MODEST STRENGTHENING TO OCCUR..."

I personally think he is brushing off the forward speed too lightly. It means a lot more than that.


I agree. Stewart is one of my favorite forecasters and I usually agree with his forecasts, but 70mph is a bit much. I still don't see Chantal becoming anything more than a 60mph tropical storm.
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TRMM pass shows whats left of the heavy updrafts in Chantal are located to the south of the LLC or MLC

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I find it interesting the NHC does not mention any decoupling of the LLC in the near term that many on here have observed this morning. The NHC must see something else tthat will prevent it from happening.
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Quoting 154. Grothar:


Or some of us are retired, wives in Europe, children all grown with lives of their own, while we sit here waiting for the nurses to give us our hourly pills. What else are we going to do?

We are in the company of intelligent,interesting people who willingly share information and a bit of humor now and then. What more could one ask for?


Since the first crossing to the New World how many wives have you had Gro? :)
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Quoting 168. Levi32:


To use the GFS as an example, at 108 hours the remnants of Chantal are evident at the 500mb level in the SE Bahamas. Note the trough digging into Virginia, which is helping to bring it northward.



However, look at how just 24 hours later, the base of that trough splits away and moves southwestward towards the north gulf coast, with the Bermuda ridge building back westward towards North Carolina. This retrograding trough split pattern can help rotate storms back NW towards the SE US, that is, if there is actually a storm in the area.



Again, timing I guess. Thanks, Levi.
Member Since: July 17, 2009 Posts: 71 Comments: 27895
Quoting pcola57:


Thank you Aussie..
I missed it or ??
Anyway sure could use a African continent link for future reference..
(hint-hint) :)


Hint hint noted
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Not much weather with Chantal at present.
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Can anyone comment on that Cold core low pressure system just over the Bahamas that DR Jeff Masters mentioned in passing the other day about possible development....
Well last night it looked like just a dry spin and this am looks like a cloud gatherer with a potential development? Any comment. NHC is a no mention...
Please.. I'm in the need to know zone work Emergency Services...
Tks guys
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.
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If Chantal moves S or over Barbados it would change the cone if that happen them in PR are gonna be upset
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Quoting 173. islander101010:
watch the surface winds in the bahamas today and overnight. might in for a surprise. very warm water lies downstream.
Quoting 126. NasBahMan:
I am presently on Harbour Island in the NE Bahamas, for the past week the winds have been out of the SE at 15-25 MPH, overnight and this morning the winds have turned to the NE at 10-15 MPH, ULL could be working a little energy down to the surface


As posted earlier, winds have already shifted at the surface.
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I find the new heading at 285 degrees striking.

PRESENT MOVEMENT...WNW OR 285 DEGREES AT 25 MPH

It has slowed down 1 mph and I think the slow downs in forward speed will continue to occur as it continues to turn more towards the WNW.
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Quoting Grothar:


I don't know. I guess he doesn't want to give me credit since I "saw if first". Hey, he is a busy man. I don't know how he even finds the time to post what he does. It takes a lot of work. Has anyone even read my last blog? I worked on it for hours.


You did a blog!!!!!!

Dang.... I better go read the words of the master. :-)
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Already getting ready to pop out.

Once DMIN hits later, this is going to look ugly

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Quoting 167. AussieStorm:


I posted a true colour image of it at #118


Thank you Aussie..
I missed it or ??
Anyway sure could use a African continent link for future reference..
(hint-hint) :)
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Quoting 181. pcola57:


Well written blog Gro..
A thinking man's blog.. :)

Yeah I know Dr. Masters is busy and all..
Just thinking that maybe the blob would be a player in the GOM and change the dynamics some..
Just me thinking again.. :)


Don't do that too much. It can give one a headache.
Member Since: July 17, 2009 Posts: 71 Comments: 27895
Brand new ASCAT pass is not very telling on whether Chantal's circulation is still closed. Too many flagged wind barbs near the center.

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Have to remember, 70mph at 48hrs and 60mph at 72hrs most likely means land interaction between time. But there is no 60hrs forecast before landfall Chantel will have 12hrs to make it to hurricane strength in the current forecast but they will chance every 6hrs.
Point is. Just cause it's not showing this to become a hurricane, it can cause there will be another 6-12hrs before landfall at the 60hr mark.
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186. 7544
cone didnt budge we have to wait for the hh info anyone know what time est they will go in thanks
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Quoting Neapolitan:
I wouldn't say "no one cares"; it's just that Chantal is hogging most of the attention at the moment, and deservedly so.

At any rate, there are three waves stacked up behind Chantal one over water, one coming off the African coast, and one a few days inland still:

waves


From your image, Chantal is still connected to the following T-wave.
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Quoting 115. weatherh98:


Moving as fast as Chantal
...and just as disorganized!
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Quoting 122. islander101010:
i have not wishcasted this system yet alot of the models have her right on top of us e cen fl.

Islander I am in Titusville and have been watching this. NHC adjusted the cone slightly to the east but I think as time moves on it will shift back west due to the trough lifting out and the high pressure pushing it back west. As the Doc said this is probably Bad JuJu for us in the East Coast of FL. of things to come...
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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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