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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Barbados Radar showing the center pretty well..13.8 59.2

Link

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CHANTAL is very pathetic :( Looks like Ernesto of last year!
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July Daily Update - GOES East Infrared Hurricane Section Animation

07/01/2013 - 07/08/2013

Member Since: August 26, 2006 Posts: 10 Comments: 3918
3024. jeffreeysweetypie10:12 AM GMT on July 09, 2013
i think at the 8am and 11am advisory we will see even more east of florida track

3025. MahFL10:13 AM GMT on July 09, 2013
My local mets just said Chantal will turn left and cross FL and head into the Gulf.


okay...anyway I actually have a new job!
Off to be fingerprinted.
Have a great morning folks.


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Quoting 3019. AtHomeInTX:


Had completely missed that tidbit. Thanks Mike. :)


Your welcome! Levi definately knows his stuff.

Off to walk Dexter, back after a while with today's GM pic...
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Coming in low and weak this run. loses it after this with Dorian cranking along.

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3025. MahFL
My local mets just said Chantal will turn left and cross FL and head into the Gulf.
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Link WV Loop Chantal

Chantal looks a bit smashed this morning lol
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3021. barbamz

Short morning hello with the colourful waves; Chantal keeps her turning momentum. Have a good day everybody!
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Quoting 3009. mikatnight:


Had completely missed that tidbit. Thanks Mike. :)
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Morning, Largo...
The CATL wave looks happy with itself this morning.


Link WV Loop
Chantal may be getting ready to tap into moister environment. And is still below 15 approaching 60.
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Quoting 3004. SLU:


Ok. it's still very broad so the center may jump around a bit today.

lol yeah it looks to be many micro vortexes within one broad vortex
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From the Tropical Tidbits page (Levi) -

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Morning Chicklit -

Looking at the ULL next to us yesterday, it seemed to me our rain chances for today should've been higher than the NWS's or WU's 30%. Today I see NWS is up to 50% so, probably won't rain at all.
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SLOW STRENGTHENING IS FORECAST FOR THE NEXT 36 HOURS AS CHANTAL REMAINS OVER WARM WATER AND IN AN ENVIRONMENT OF MODERATE WIND SHEAR.

PRONOUNCED WEAKENING IS THEN EXPECTED WHEN CHANTAL MOVES OVER OR INTERACTS WITH THE RUGGED TERRAIN OF HISPANIOLA.

IF THE CYCLONE SURVIVES ITS TREK ACROSS HISPANIOLA...IT COULD RE-INTENSIFY AS THE ENVIRONMENTAL WIND PATTERN IS ANTICIPATED TO BECOME MORE FAVORABLE BY THE TIME THE SYSTEM REACHES THE BAHAMAS.

ONLY SLIGHT MODIFICATIONS WERE MADE TO THE WIND SPEED FORECAST OF THE PREVIOUS ADVISORY...AND THE LATEST NHC INTENSITY FORECAST IS MORE OR LESS IN LINE WITH THE FLORIDA STATE SUPERENSEMBLE AND THE INTENSITY MODEL CONSENSUS.

FORECAST POSITIONS AND MAX WINDS

INIT 09/0900Z 13.3N 58.4W 45 KT 50 MPH
12H 09/1800Z 14.6N 61.7W 50 KT 60 MPH
24H 10/0600Z 16.3N 65.9W 55 KT 65 MPH
36H 10/1800Z 18.2N 69.4W 60 KT 70 MPH
48H 11/0600Z 20.1N 72.0W 40 KT 45 MPH
72H 12/0600Z 23.5N 74.8W 40 KT 45 MPH
96H 13/0600Z 26.5N 76.0W 45 KT 50 MPH
120H 14/0600Z 28.5N 77.5W 50 KT 60 MPH

$$
FORECASTER CANGIALOSI/PASCH
Should be interesting to watch as Chantal waxes and wanes over the coming days. Not crazy over the 50 KT off my coast in 120 hours. Also still reading about the left turn causes some consternation but will see how it all plays out.
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morning
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3007. Dakster
Quoting 3002. jeffreeysweetypie:
the circle cone 3 days ago had all of florida in it at day 7 then yesterday just 3/4th of florida and now today only the east half of florida is in the cone so i believe this east shift will continue like it always does with these storms and by thursday you wont even see florida in the picture anymore


Possible, but not the NHC path is to the EAST of the majority of the models. So who knows.
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Lots of new thunderstorms blossoming around the supposed new center, as we begin to say good morning to Chantal.

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The bigger picture.


EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
141 AM EDT TUE JUL 09 2013

VALID 12Z FRI JUL 12 2013 - 12Z TUE JUL 16 2013

...OVERVIEW AND MODEL PREFERENCES...

THE MEDIUM RANGE FORECAST CONTINUES TO EVOLVE FROM AN AMPLIFIED
PATTERN THAT TRANSITIONS TO NEARLY CONUS-WIDE RIDGING BY EARLY
NEXT WEEK. TROPICAL STORM CHANTAL IS FORECAST TO PUSH THROUGH THE
BAHAMAS EARLY IN THE PERIOD /PER NHC/ BUT THEN ITS FATE BECOMES
MORE UNCERTAIN... DEPENDENT UPON ITS ORGANIZATION AND THE
SURROUNDING ENVIRONMENT. THE MODELS/ENSEMBLES REMAIN IN GOOD
AGREEMENT IN THE SYNOPTIC SETUP THAT PUSHES AN INITIAL FRONTAL
BOUNDARY INTO THE SOUTHEAST BEFORE WASHING IT OUT AS UPPER LEVEL
ENERGY RETROGRADES WESTWARD INTO TEXAS AHEAD OF CHANTAL TO ITS
SOUTHEAST. THE GFS/ECMWF HAVE WAVERED ON THE TIMING/AMPLITUDE OF
THE ENERGY MOVING THROUGH THE PAC NW AND ACROSS THE NORTHERN
PLAINS BUT A BLEND AMONG THEM AND THE ENSEMBLE MEANS PROVIDED A
GOOD BASE TO THE FORECAST... CONSISTENT WITH THE BETTER CLUSTERING
OF SOLUTIONS AND IN LIGHT OF RECENT ENSEMBLE TRENDS /A BIT WEAKER
WITH THE ENERGY RETROGRADING IN THE EAST/. SHOULD CHANTAL SURVIVE
THROUGH THE WEEKEND... THE ENSEMBLES GENERALLY TURN IT WESTWARD AS
HEIGHTS RISE ALONG THE EAST COAST AND THE EASTERLY FLOW GUIDES IT
TOWARDS/INTO FLORIDA. AS OF NOW... HEAVY RAINFALL MAY BE A THREAT
TO NORTHERN/CENTRAL FLORIDA SUN-TUE/D5-7. PLEASE SEE THE NHC FOR
UPDATED INFORMATION ON CHANTAL.


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3004. SLU
Quoting 3001. wunderkidcayman:

nah its around 13.4°N 59.0°W


Ok. it's still very broad so the center may jump around a bit today.
Member Since: July 13, 2006 Posts: 13 Comments: 5362
3003. SLU
Quoting 2987. jeffreeysweetypie:
so what does that mean a completly new and different track?

Not really. It will remain pretty much along the same track.
Member Since: July 13, 2006 Posts: 13 Comments: 5362
Quoting 2985. SLU:
The center of Chantal seems to have reformed further north near the deep convection.

NHC position: 13.3°N 58.4°W

Reformed center: 13.7°N 58.7°W

nah its around 13.4°N 59.0°W
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You all have a good morning....Its 235am in soo cal and this old guy needs a nap....hope our Lady Chantal is ok when i return in 4-6 hours....thanks for all your inputs and I will see you all soon.

out
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Quoting 2985. SLU:
The center of Chantal seems to have reformed further north near the deep convection.

NHC position: 13.3°N 58.4°W

Reformed center: 13.7°N 58.7°W


The center is exposed 0.1n and 0.4W of NHC position. You can see it on radar.

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2997. ackee
chantal looks like a tropical wave to me just my view
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a 1010 mb Tropical storm with 50-60mph winds moving along at 26 mph and now getting sheared has her center jumping into different batches of convection to protect herself has gotten my respect and will not predict her demise until and if it actually happens....lol
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Quoting 2975. HurricaneHunterJoe:
\\ya think Chantal has her sights on the GOM?


I don't buy the Bahamas track I think its a carib storm and will enter the GOM from the Carib and I do expect it to hit Fl IMO
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2993. Dakster
Quoting 2990. jeffreeysweetypie:
ive seen 100's of 5 to 7 day tracks where they have these storms hitting florida on the 5th and 6th day and they almost never do


Yes, us Floridians like it when a 7 day model shows a direct hit. That is typically the last place the storm will be.
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Quoting 2991. Dakster:


Isaac hit NOLA as a Major Hurricane? A direct Katrina like path?


You didn't add that stipulation. :P

Isaac was clearly a test, though. It wasn't Katrina-ish by any means, but a Category 2 storm surge is nothing to sneeze at.
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2991. Dakster
Quoting 2988. KoritheMan:


I thought Isaac already did?


Isaac hit NOLA as a Major Hurricane? A direct Katrina like path?
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2989. Dakster
Quoting 2986. HurricaneHunterJoe:
She looks to be a weak system if she gets that far after crossing florida...however, if she shoots the Florida straits...that could be a whole other ballgame


A weaker storm will typically not move as far north as a stronger storm. So it makes you wonder what the track will do if Chantal weakens.
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Quoting 2984. Dakster:
I just hope Chantal doesn't test the new levee's in NOLA.


I thought Isaac already did?
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She looks to be a weak system if she gets that far after crossing florida...however, if she shoots the Florida straits...that could be a whole other ballgame
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2985. SLU
The center of Chantal seems to have reformed further north near the deep convection.

NHC position: 13.3°N 58.4°W

Reformed center: 13.7°N 58.7°W
Member Since: July 13, 2006 Posts: 13 Comments: 5362
2984. Dakster
I just hope Chantal doesn't test the new levee's in NOLA.
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if the next run of models has the left turn to florida, the NHCwill start bending Chantals track that way IMO.
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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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