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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Wonder if Chantal will have a substantial enough COC to pump the ridge?
Member Since: Posts: Comments:
1182. pcola57
Quoting 1178. Dakster:


What if Chantal pumps the ridge?


**Edited due to mod comment
Member Since: Posts: Comments:
Quoting 1143. MAweatherboy1:

None of what they are reporting now can be trusted due to the rapid change in altitude.

They're cruising at 1,300 Ft. Now. Reporting Northeasterly winds as the inter from the NW side...
NW Quadrant is closed, NE, SE, and SW quadrants to go.
Member Since: June 2, 2013 Posts: 8 Comments: 1109
1180. Patrap
At 20:57:30Z (last observation), the observation was 284 miles (457 km) to the E (98°) from Bridgetown, Barbados.

Product: Air Force High Density (HDOB) Message (URNT15 KNHC)
Transmitted: 8th day of the month at 20:56Z
Date: July 8, 2013
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 302)
Storm Number: 03
Storm Name: Chantal (flight in the North Atlantic basin)
Mission Number: 1
Observation Number: 16

20:57:30Z 12.550N 55.433W 966.4 mb
(~ 28.54 inHg) 406 meters
(~ 1,332 feet) 1012.2 mb
(~ 29.89 inHg) - From 44° at 25 knots
(From the NE at ~ 28.7 mph) 23.1°C
(~ 73.6°F) 21.2°C
(~ 70.2°F) 26 knots
(~ 29.9 mph) 25 knots
(~ 28.7 mph) 2 mm/hr
(~ 0.08 in/hr) 24.0 knots (~ 27.6 mph)
96.2%
Time Coordinates Aircraft
Static Air Pressure Aircraft
Geopotential Height Extrapolated
Surface Pressure D-value Flight Level Wind (30 sec. Avg.) Air Temp. Dew Point Peak (10 sec. Avg.)
Flight Level Wind SFMR
Peak (10s Avg.) Sfc. Wind SFMR
Rain Rate Estimated Surface Wind (30 sec. Avg.)
Using Estimated Reduction Factor Peak Wind at Flight Level to
Est. Surface Reduction Factor
HDOB Observations
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Recon is now at proper altitude and reported one reading of 42mph, uncontaminated, shortly after leveling out.
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1178. Dakster
Quoting 1168. StormTrackerScott:


Ain't nothing busting thru this ridge come Sunday on.



What if Chantal pumps the ridge?
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Now at cruising altitude.

205730 1233N 05526W 9664 00406 0122 +231 +212 044025 026 025 002 00
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Quoting 1140. Grothar:
Just awoke from my nap. Any new arguments I missed???




I believe you're looking for the Argument Blog.
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Quoting 1169. Dakster:


Darn. I was so looking forward to see it.

Now if two planes went in at the same time - that would be very interesting.


Really, you said that, water coming out of nose.
Nice one.
Back to watching the HH report.
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1174. nigel20
Quoting Grothar:
I seen Chantal is looking a little better than earlier and the models have shifted more to the east. I do expect them to shift back a little later.



Most of the models do want Chantal to strike Florida in the latter models.


It seems as if Hispaniola and Florida is the Target.
Member Since: Posts: Comments:
Quoting 1154. StormTrackerScott:
This is one scary pattern for the SE US & Gulf Coast.



Yes, it sure is! I really don't want a repeat of 2004.
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Guess what ?
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Quoting 1167. will40:


they dont even have the SFMR on yet
....No winds as HH approaching T.S. Chantal..
Member Since: October 15, 2012 Posts: 0 Comments: 372
Closer to home we have lots of rain that will come into FL tomorrow.

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1169. Dakster
Quoting 1157. WhereIsTheStorm:

Sorry there are no pictures/video of the HH penetration while they are searching for the big one eye in the middle.
Intensity expected to rise.


Darn. I was so looking forward to see it.

Now if two planes went in at the same time - that would be very interesting.
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Quoting 1163. Grothar:
I seen Chantal is looking a little better than earlier and the models have shifted more to the east. I do expect them to shift back a little later.



Most of the models do want Chantal to strike Florida in the latter models.



Ain't nothing busting thru this ridge come Sunday on.

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1167. will40
Quoting 1151. interstatelover7166:
..Winds increasing as HH enters T.S. CHANTAL..


they dont even have the SFMR on yet
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1166. 7544
they may call chantel 50 mph imo after the trip

be intresting to see what the models will after they get the data
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Quoting 1159. Dakster:


Sometimes I talk to myself too, I could use the expert advice at times.
Smooth or Crunchy
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Quoting 569. tornadodude:
Oh absolutely. I work for a tour company, definitely have to be safer than normal anyway just for that reason. I seem to be struggling with posting youtube videos on here. Oh well :p



When you click the "share" tab on your video, click the embed function then select "old embed code."
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1163. Grothar
I seen Chantal is looking a little better than earlier and the models have shifted more to the east. I do expect them to shift back a little later.



Most of the models do want Chantal to strike Florida in the latter models.

Member Since: July 17, 2009 Posts: 69 Comments: 25381
In PR, we should be watching a possible adjusted trayectory closer to the island.... and the last frames have shifted it to the NW.... Looks like its going after the low near Florida...



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Quoting 1155. MAweatherboy1:

That probably won't be the end of it. I've noticed they often fly around 5,000ft in stronger storms and much lower, more like 1,000ft, in weak ones.

Oh really? Didn't realize Cruising altitude was different. My bad.
Member Since: June 2, 2013 Posts: 8 Comments: 1109
Based on the forecasted positions of the ridge and a weakness near the Bahamas Chantal should impact Haiti/DomRepub/Puerto Rico and into the Bahamas.
Where it goes from there is anyone's guess.
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1159. Dakster
Quoting 1147. PalmBeachWeather:
Past experience, I think to myself


Sometimes I talk to myself too, I could use the expert advice at times.
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1158. pcola57
Quoting 1146. StormTrackerScott:


That is the day the Bermuda High builds west and forces Chantal across FL and into the Gulf.





She's already at the Leewards and Sunday is 6 days away..
wasn't trying to test you..
I was just wondering what brought that to your thinking as I see Chantal as a gonner by Friday latest..
JMO my friend.. :)
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Quoting 1128. Dakster:


I've never seen it, can someone show it to me?

Sorry there are no pictures/video of the HH penetration while they are searching for the big one eye in the middle.
Intensity expected to rise.
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1156. Patrap
Ridgelake to Bonnabel is my ol stomping grounds one could say.

Lakeview a good memory, esp Maggie & Smittys.

; )
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Quoting 1150. TylerStanfield:

They just finished their descent. Closing in on 8,000 ft.

That probably won't be the end of it. I've noticed they often fly around 5,000ft in stronger storms and much lower, more like 1,000ft, in weak ones.
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This is one scary pattern for the SE US & Gulf Coast.

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1153. Dakster
Quoting 1140. Grothar:
Just awoke from my nap. Any new arguments I missed???




No, same old arguments.

What do you think about the models trending towards the west?
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I am glad to see you still around posting Pat, thank you from Lakeview!
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..Winds increasing as HH enters T.S. CHANTAL..
Member Since: October 15, 2012 Posts: 0 Comments: 372
Quoting 1143. MAweatherboy1:

None of what they are reporting now can be trusted due to the rapid change in altitude.

They just finished their descent. Closing in on 8,000 ft.
Member Since: June 2, 2013 Posts: 8 Comments: 1109
1149. JRRP
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1148. pcola57
Quoting 1133. all4hurricanes:

I remember the train of systems in 2010 and all of them seemed to struggle with dry air even when a system passed ahead of them I think the wave behind Chnatal will still have to deal with dry air but with the ULL leaving it might have a better chance for development


Good point all4hurricanes..
Could this compare to those waves in 2010?
Won't be long before we shall know..
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Quoting 1137. Grothar:


Yes, it was. Yes, it was.
Past experience, I think to myself
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Quoting 1126. pcola57:


Hey Scott..
How's your day going?
What makes you believe Chantal will turn exactly on Sunday?


That is the day the Bermuda High builds west and forces Chantal across FL and into the Gulf.



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Quoting 565. PensacolaDoug:




Sup Oz?


Yo Doug!

It is going to be interesting to see if any of the people we know are going to live broadcast the landfall of Chantal, no?
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1144. JRRP
THE OFFICIAL FORECAST
TRACK HAS BEEN SHIFTED SLIGHTLY TO THE RIGHT OF THE PREVIOUS
ADVISORY TRACK...BUT NOT NEARLY AS FAR RIGHT AS THE MODEL CONSENSUS
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Quoting 1138. TylerStanfield:
Recon is reporting that Flight level winds have jumped up to Tropical Storm Force as they've entered Chantal's Outer bands.

None of what they are reporting now can be trusted due to the rapid change in altitude.
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Quoting 1129. JRRP:
CHANGES WITH THIS ADVISORY...

A TROPICAL STORM WARNING HAS BEEN ISSUED FOR PUERTO RICO.

A TROPICAL STORM WATCH HAS BEEN ISSUED FOR THE U.S. VIRGIN ISLANDS.

THE GOVERNMENT OF THE DOMINICAN REPUBLIC HAS ISSUED A TROPICAL STORM
WATCH FOR THE SOUTHERN COAST OF THE DOMINICAN REPUBLIC FROM CABO
ENGANO WESTWARD TO THE DOMINICAN REPUBLIC-HAITI BORDER.


ONAMET.
Link
Member Since: Posts: Comments:
1141. Patrap
At 20:47:30Z (last observation), the observation was 253 miles (407 km) to the E (94°) from Bridgetown, Barbados.


Product: Air Force High Density (HDOB) Message (URNT15 KNHC)
Transmitted: 8th day of the month at 20:46Z
Date: July 8, 2013
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 302)
Storm Number: 03
Storm Name: Chantal (flight in the North Atlantic basin)
Mission Number: 1
Observation Number: 15

20:47:30Z 12.867N 55.867W 742.3 mb
(~ 21.92 inHg) 2,678 meters
(~ 8,786 feet) 1012.8 mb
(~ 29.91 inHg) - From 78° at 33 knots
(From the ENE at ~ 37.9 mph) 11.4°C
(~ 52.5°F) 7.2°C
(~ 45.0°F) 34 knots
(~ 39.1 mph) - - - -
Time Coordinates Aircraft
Static Air Pressure Aircraft
Geopotential Height Extrapolated
Surface Pressure D-value Flight Level Wind (30 sec. Avg.) Air Temp. Dew Point Peak (10 sec. Avg.)
Flight Level Wind SFMR
Peak (10s Avg.) Sfc. Wind SFMR
Rain Rate Estimated Surface Wind (30 sec. Avg.)
Using Estimated Reduction Factor Peak Wind at Flight Level to
Est. Surface Reduction Factor
HDOB Observations
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1140. Grothar
Just awoke from my nap. Any new arguments I missed???


Member Since: July 17, 2009 Posts: 69 Comments: 25381
Quoting 1117. StormTrackerScott:


They will as the left turn doesn't happen until Sunday


It's going to run into 1016mb of high pressure before then, and it'll turn then, imo. Can't see how it'll make it that far north and east with the looming high and with little change coming to it the way it seems to me. Again, I may be totally missing the bigger picture here. :)
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Recon is reporting that Flight level winds have jumped up to Tropical Storm Force as they've entered Chantal's Outer bands.
Member Since: June 2, 2013 Posts: 8 Comments: 1109
1137. Grothar
Quoting 1100. CybrTeddy:
redundant post


Yes, it was. Yes, it was.
Member Since: July 17, 2009 Posts: 69 Comments: 25381
1136. JRRP
Quoting MAweatherboy1:
Updated track:


a bit more north
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I suspect these 60 mph winds are in one the eastside of the center.

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Quoting 1128. Dakster:


I've never seen it, can someone show it to me?
Only comes out after dark...It's a nocturnal thing
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Quoting 1122. pcola57:


I agree with you Washi..
Chantal is turning heads and getting ooo's and aaahh's but the wave behind her is looking better than she did at that position..
I'm in agreement with Dr. Masters as well as this may be a looong CV season..
Chantal has issues to overcome..
The next wave will have that enviroment all moistened up..
I believe the real show is about to begin sooner than climo suggests..
Remember I'm just a learned observer..
Nothing more..
Just sharing my opinion here FWIW..

I remember the train of systems in 2010 and all of them seemed to struggle with dry air even when a system passed ahead of them I think the wave behind Chnatal will still have to deal with dry air but with the ULL leaving it might have a better chance for development
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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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