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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Looks like she is passing between St. Lucia and Martinique right now!
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Hi All,

Hey pottery, Baha etc...

Rain here in Barbados, authorities were very prepared last night, after the lesson from Tomas.

But looks like Chantal is having a bit of a time. Possibly a rain event for folks down the road, could cause some flooding.

The one behind, about four days off Barbados, is what I would worry about more, although one should never discount a storm, so Chantal could still spring a surprise.

Awaiting all clear to get to work.

Have a good day.
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wnw up to the butterfly island? i doubt now it will get up that far north l
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She is passing between St. Lucia and Martinique now! She seems to be getting better organized. Link
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Quoting 3267. WxLogic:
1003MB... not bad given its visual presentation.



1003 is good considering the atmospheric pressure surrounding it.
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Yikes!

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3277. Grothar
120 hours



276 hours

Member Since: July 17, 2009 Posts: 71 Comments: 27114
Quoting 3238. allancalderini:
People please is Chantal not Chantel .Its a totally different name.
Huh! Go figure...LOL
Member Since: May 16, 2010 Posts: 0 Comments: 1472


Surface circulation on the Bahamas system

Gro I see a blobcon being raised in the near future
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Got some stuff to do this morning guys. I will try to talk to you guys some on my I Pod some. It will be interesting to see what happens today with both intensity and new computer model runs....first off i'm getting my morning coffee :P
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I think Dr Masters is waiting on the Data from the HH this morning :o)

Taco :o)
Member Since: July 7, 2005 Posts: 6 Comments: 3261
Quoting 3268. presslord:
since weathermanwannabe has already broken the rules about realism here...I'll offer up my two cents worth: This ain't exactly gonna be the Storm of the Century...or the Decade...or even the Year...
This is going to become a cat 7 and cause unthinkable destruction in NYC and New England as a whole?.What'chu taking about?.lol.
Member Since: August 14, 2010 Posts: 10 Comments: 17654
3271. bwi
Barbados radar use 400km:
http://www.barbadosweather.org/RadarPro/BMS_Radar Displayer.php

14.0 60.6? Further north than I expected.
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3270. pottery
Quoting presslord:
since weathermanwannabe has already broken the rules about realism here...I'll offer up my two cents worth: This ain't exactly gonna be the Storm of the Century...or the Decade...or even the Year...

How utterly disappointing.
Where is your Spirit of Make-Believe??
Sheesh.
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3269. hu2007
chantal looks organize on radars but the cloud tops and structure look desorganize, i think that chantal have peaked intensity of 50mph no more than 60 mph. and tracking wnw and i expect a slight weakening starting tommorrow during the day.on too puerto rico, looks like we are going to get the weak north side of chantal in terms of prolonged rain but is going to get gusty and squally tonight in too wednesday morning,after that it should slow down and take a nw path in to the bahamas as a td or 40mph storm,and either should dissipate or should intensified and go to the carolinas or georgia and florida. stay tune for more updates
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since weathermanwannabe has already broken the rules about realism here...I'll offer up my two cents worth: This ain't exactly gonna be the Storm of the Century...or the Decade...or even the Year...
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3267. WxLogic
1003MB... not bad given its visual presentation.
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Quoting 3192. Grothar:


I don't want to be picky, but do you have any decaf?
Sorry Gro, I drank it... here, let me put on another pot for you...
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Quoting 3248. Hurricanes305:

Something is wrong why does it look like August 9th rather than July 9th I have never seen this much MDR action till mid-late August this is start to send shivers fown my spine. Chantal is a huge test run now.
Maybe it is a sign we will be in for it! Time to blow away 2005 numbers and stats!
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3264. hydrus
I dont mind saying that the upper low over the Bahamas looks a bit more interesting today.
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Quoting 3256. weathermanwannabe:


Thanks.........Just corrected.....Still working on the first cup of coffee..........
No problem.
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3262. pottery
Quoting GetReal:



Amazingly Chantal satellite presentation is not as impressive as it was yesterday at this time, but RECON is finding lower pressure and stronger winds.

Curiouser and curiouser it is.
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Quoting 3219. MAweatherboy1:
Wow, recon found flight level winds near hurricane force, 65mph or so at the surface. Chantal fools us again.
Chantal is one of the biggest trolls that I have ever tracked in the Atlantic if it is really a 65 mph storm right now.
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If it really gets it's act together we could be dealing with a storm stronger than 45 mph after Hispaniola more like 50 mph on the other side....if it moves on the northern edge of the island we could have a much stronger system if it misses the main mountains of Hispaniola....if the models shift just a little farther north that will bring it away from the main mountain chain
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Chantal has been trolling hard these last few days.Just when people think it's the end for her she comes back and laughs in our faces playing pick-a-boo.Shows that we still have a lot to learn in terms of developing cyclones.
Member Since: August 14, 2010 Posts: 10 Comments: 17654
Quoting 3247. Grothar:


She looks pretty good here.

lol sure does have a good ball of convection. If this was not moving so fast it could of have easily been a hurricane by now.
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Quoting 3232. Grothar:


Teddy, think we will busy the next couple of weeks.



Blobs eh gro?

Gfs develops a pair of waves that roll off the African coast. This would be unprecedented for the atlantic over its entire history. (Which I'm sure you remember all of)
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Quoting 3238. allancalderini:
People please is Chantal not Chantel .Its a totally different name.


Thanks.........Just corrected.....Still working on the first cup of coffee..........
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3255. Relix
Chantal is just telling us what matters is the inside, not the outside. :P!
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3254. pottery
Quoting Hurricanes305:

Something is wrong why does it look like August 9th rather than July 9th I have never seen this much MDR action till mid-late August this is start to send shivers fown my spine. Chantal is a huge test run now.

and everything is so low. Troubling !
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Excerpt

D. Estimated (by SFMR or visually) Maximum Surface Wind: 52kts (~ 59.8mph)
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Quoting 3240. weatherlover94:
Good morning ...looks like we have a strengthening Chantal
FINALLY!
Member Since: May 16, 2010 Posts: 0 Comments: 1472
Link
Link for radar showing Chantal
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3249. GetReal



Amazingly Chantal satellite presentation is not as impressive as it was yesterday at this time, but RECON is finding lower pressure and stronger winds.
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Quoting 3232. Grothar:


Teddy, think we will busy the next couple of weeks.

Something is wrong why does it look like August 9th rather than July 9th I have never seen this much MDR action till mid-late August this is start to send shivers fown my spine. Chantal is a huge test run now.
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3247. Grothar
Quoting 3219. MAweatherboy1:
Wow, recon found flight level winds near hurricane force, 65mph or so at the surface. Chantal fools us again.


She looks pretty good here.

Member Since: July 17, 2009 Posts: 71 Comments: 27114
Here is the am NCEP Caribbean Desk Discussion...Good points on the current steering mechanism for Chantal:

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
807 AM EDT TUE JUL 09 2013

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI. GREATEST CONCERN CONTINUES TO BE TROPICAL STORM CHANTAL. AT MID/UPPER LEVELS...RIDGE CENTERS TO THE NORTH OF 20N FROM THE CENTRAL ATLANTIC INTO JUST NORTHEAST OF THE DOMINICAN REPUBLIC. THIS IS HELPING TO STIR CHANTAL TO THE WEST-NORTHWEST. MODELS CONTINUE SHOWING RIDGE BUILDING INTO THE SOUTHWEST WHICH SHOULD KEEP THE SYSTEM JUST TO THE SOUTH OF THE ISLANDS WHILE MOVING STRAIGHT INTO HISPANIOLA...TO THEN TURN TO THE NORTH-NORTHWEST.


Member Since: August 8, 2006 Posts: 0 Comments: 9377
Quoting 3225. Hurricanes305:
Regardless of convective orgnization this storm continues to produce a lot of strong winds could be 60mph at 11pm. If it can slow down today we may see a good day for strengthen. Storm continues to defy odds wonder if this is indicative for the rest of the season. Stronger less organized storms.
You mean 11am...however it just may have those winds now.
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Quoting 3219. MAweatherboy1:
Wow, recon found flight level winds near hurricane force, 65mph or so at the surface. Chantal fools us again.


That surprises me. Doesn't look that good on sat pics. Bit of a raggy doll, is Chantal.
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3243. hydrus
96 Hour Forecast – Favorable Environmental Conditions For Tropical Development
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Quoting 3158. LargoFl:
I gotta admit, I have a lot more faith in that turn to the west than I did the original forecast of a track through the Bahamas. This is because every time in recent years that multiple models have seen this kind of abrupt anomalous turn in a track, we've seen the forecast verify. To wit: Jeanne, with the loop-back; Ike with the southern bend of Cuba that seemed so unbelievable at the time.

So pple in Central FL should be on the lookout... not boarding up or anything, but definitely watching.

WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

THE GOVERNMENT OF THE BAHAMAS HAS ISSUED A TROPICAL STORM WATCH FOR
THE TURKS AND CAICOS ISLANDS AND THE SOUTHEASTERN BAHAMAS.
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3241. pottery
Quoting Hurricanes305:
Regardless of convective orgnization this storm continues to produce a lot of strong winds could be 60mph at 11pm. If it can slow down today we may see a good day for strengthen. Storm continues to defy odds wonder if this is indicative for the rest of the season. Stronger less organized storms.

and yet, no winds reported from B'Dos.
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Good morning ...looks like we have a strengthening Chantal
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Quoting 3218. hydrus:
And this.
Yup!
Member Since: May 16, 2010 Posts: 0 Comments: 1472
Quoting 3206. weathermanwannabe:
As noted by MLC, here is the latest CIMMs chart; the ULL over the Bahamas is working its way down to the surface.......Probably not enough time to develop but we have been watching for this possibility over the past several days.

Link

This will be one of the main influences, as it moves out of the way and breaks downs the ridge, on the trajectory of Chantel, or her remnants, after crossing the Greater Antilles. If the ridge builds back in quickly, Chantel could be forced back towards Florida. If not, Chantel could move a bit further North.

It boils down to how well Chantel survives the land interaction with Hispanola/Cuba and the timing of the ridging. We will not know the answer to this until the end of the week.
Quoting 3206. weathermanwannabe:
As noted by MLC, here is the latest CIMMs chart; the ULL over the Bahamas is working its way down to the surface.......Probably not enough time to develop but we have been watching for this possibility over the past several days.

Link

This will be one of the main influences, as it moves out of the way and breaks downs the ridge, on the trajectory of Chantel, or her remnants, after crossing the Greater Antilles. If the ridge builds back in quickly, Chantel could be forced back towards Florida. If not, Chantel could move a bit further North.

It boils down to how well Chantel survives the land interaction with Hispanola/Cuba and the timing of the ridging. We will not know the answer to this until the end of the week.
People please is Chantal not Chantel .Its a totally different name.
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Quoting 3221. WeatherNerdPR:


Just like I thought, very compact and tight CoC. Better organized than yesterday. Still looks disorganized on satellite though.
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Quoting 3228. MAweatherboy1:

I still can't see it becoming a hurricane with its current structure, but assuming those winds are correct and the 11AM intensity is 60 or 65mph, a hurricane watch may be required for some areas.
At this rate any good blow of convection could result into a Cat. 1
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AL, 03, 2013070912, , BEST, 0, 139N, 603W, 45, 1003, TS, 34, NEQ, 80, 0, 0, 80, 1012, 140, 25, 0, 0,
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3234. Levi32
1003mb is much better than yesterday. She is still struggling with the fast flow though. Her NW quad is empty as a result.

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3233. pottery
Quoting pcola57:
Here's Water Vapor pot..
My SAL isn't updating.. :(


Thanks.
Chanty still can't make an appreciable dent in that dry stuff....
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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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