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 123. Grothar:
Many of the models are turning Chantal back towards the east coast after moving through the Bahamas




That is a fairly likely scenario with a retrograding trough in the SE US ahead of Chantal. The big question is will there even be a Chantal at that time.
Member Since: November 24, 2005 Posts: 635 Comments: 26543
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Quoting 123. Grothar:
Many of the models are turning Chantal back towards the east coast after moving through the Bahamas




My main concern is (as for me being on the east coast) is once it reaches the Bahamas, it will begin feeding off these warm gulf stream waters, allowing it to intensify, assuming that the atmospheric environment is favorable. That has me worried.
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Quoting 103. washingtonian115:
El nino was also to blame.

I think he meant 2010, gaston wasnt in 2008, and it wasnt an El Niño.
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Quoting 121. 7544:


is that the new run looks like they shifted more south and west towards south fl ?



The most recent and yes you are right. More models indicating that the trough will not be strong enough to fully recurve Chantal. If it were to get trapped under high pressure it could have some time to regain a punch as it heads toward the coast. If there is anything left to restrengthen that is.
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Quoting 123. Grothar:
Many of the models are turning Chantal back towards the east coast after moving through the Bahamas




Revenge for hitting me. ;)
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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
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F5 Keys ready to be used thoroughly in the next 10 minutes or so.
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This is why it would be an East Coast landfall, subtropical ridge rebuild, trough lifts out, should it survive the trek through the Caribbean and across the mountainous terrain.



My bad I am always forgetting to take out the s in https.
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Many of the models are turning Chantal back towards the east coast after moving through the Bahamas


Member Since: July 17, 2009 Posts: 68 Comments: 25090
i have not wishcasted this system yet alot of the models have her right on top of us e cen fl.
Member Since: September 11, 2010 Posts: 1 Comments: 4268
121. 7544
Quoting 107. ProgressivePulse:
Not many storms have hit FL from the east in July. Not that there will be much left of Chantal by then, just highlighting the climatology aspect if that were to happen.





is that the new run looks like they shifted more south and west towards south fl ?
Member Since: May 6, 2007 Posts: 0 Comments: 6676
Quoting 115. weatherh98:


Moving as fast as Chantal

Lol
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Quoting 105. flcanes:

Um, read his post. It looks like somewhere between south florida and north carolina, but anything is possible.
Um, which post exactly?
Member Since: May 16, 2010 Posts: 0 Comments: 1455
Fresh True Colour pass of T-Wave behind TS Chantal.



Lager image(49mb)
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Member Since: July 17, 2009 Posts: 68 Comments: 25090
How is Chantal like a Wonderbra? She is beginning to "lift and separate."




I'm gonna throw in this global image so you can see how it tapped into a big pool of moisture off the South American coast. Click to embiggin.


Member Since: September 22, 2005 Posts: 18 Comments: 2307
Quoting 109. interstatelover7166:
The blog is moving so fast I can't tell if Chantal will survive or not.


Moving as fast as Chantal
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Quoting 97. all4hurricanes:

I think it is one of the main limiting factors 2006 was forecasted to have 17 storms but dry air was blamed for the bust. Tropical storm Gaston in the busy 2008 season died at least in part due to dry air and that storm was forecasted to be a hurricane in the Caribbean. Dry air usually lightens up some during peak season though.



2006 was a strong el ninio year difficult to say if was only SAL
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Good Morning everyone, I was wondering I may get this wrong, but someone posted this a year or two ago. It's looks like a compass. What I'm getting at it's hard to explain. you know how there saying it's moving at 280 degrees there's something that looks like a compass that show all the degrees and what that degree means like nwn or wnw. Do you all understand if so can some one post it agian. I lost alot of my stuff I had saved when my computer crashed. I hope this made sense.

Sheri
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112. SLU
Quoting 62. Tropicsweatherpr:
SLU, Dr Masters nalied 100% the discussion about what Chantals presence means for the rest of the season which is not good at all for us who are in hurricane alley.


I agree 100%. I predicted named storm days east of 75W this year in my 2013 forecast.

Excerpts:

CSU identified the 1961, 1996, 2005, 2007 and 2011 hurricane seasons as possible analog years for 2013. So let us analyse these years to determine what sort of trends that obtained in these seasons and may also occur this year.

4. They featured 16.0 named storm days, 6.25 hurricane days and 2.0 major hurricane days south of 23.5 north and east of 75 west before August 1st which is a strong indicator of an active season.

Based on this analysis, I believe that the following factors are possible in 2013:

1. A rapid start to the season with 3 - 5 named storms pre-August 1st.

2. Pre-August 1st named storm days south of 23.5 north and east of 75 west.
Member Since: July 13, 2006 Posts: 12 Comments: 4797
Quoting 82. Grothar:


It does not have to be developed to be dangerous or of concern. Systems moving that slowly have often brought flooding rains and some dangerous winds in thunderstorms. When something that large is off a coast and moving in the direction of land and over the Bahamas, it should be watched very closely. Even if only for maritime interests.

I've been watching it on satellite all night. Sure is pretty :)
I have to wonder about the amount of energy in a feature such as this. Thermal and angular momentum.
I guess spinning fascinates me because I still don't know my highs from my lows :)
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Quoting 68. Grothar:
Still at BlobCon 1.



Always on blob watch:)
Quoting 80. 7544:


may have to upgrade to a 2 gro

maybe get a tag 96l by the nhc only because its getting very close to fl and not moving too much imo


But why if its just a ULL

The only way they would tag it is if there was some surface circulation
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The blog is moving so fast I can't tell if Chantal will survive or not.
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108. 7544
Quoting 91. Levi32:
Just so everyone knows, the GFS (and every other model) expected the ULL in the Bahamas to start producing convection today. However, it doesn't expect it to have enough time to produce anything significant at the surface, and it is probably right.

Simulated IR satellite valid 21z today:



its been there for days now if it does get some deep reds it may make it down to gthe surface right sometimes we seen this in other ull thats been around even spining for there days the become warm core this has been spining for almost 5 days so i would think there is small chance but im no expert lol
Member Since: May 6, 2007 Posts: 0 Comments: 6676
Not many storms have hit FL from the east in July. Not that there will be much left of Chantal by then, just highlighting the climatology aspect if that were to happen.



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LinkTexas rain gauge
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Quoting 102. Waltanater:
Looks like it just might go west and under all the islands. It certainly has enough speed to do so. Could be a Gulf storm!

Um, read his post. It looks like somewhere between south florida and north carolina, but anything is possible.
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AN UPPER LEVEL LOW TO THE SOUTH OVER THE BAHAMAS NEAR
24N74W IS ENHANCING ACTIVITY NORTH OF A TROPICAL WAVE NEAR 75W.
SCATTERED SHOWERS/THUNDERSTORMS ARE FROM 22N-28N BETWEEN 68W-
77W.

TWD 8AM
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Quoting 97. all4hurricanes:

I think it is one of the main limiting factors 2006 was forecasted to have 17 storms but dry air was blamed for the bust. Tropical storm Gaston in the busy 2008 season died at least in part due to dry air and that storm was forecasted to be a hurricane in the Caribbean. Dry air usually lightens up some during peak season though.
El nino was also to blame.
Member Since: August 14, 2010 Posts: 10 Comments: 16327
Quoting 83. GTstormChaserCaleb:
I know flcanes I just felt like teasing you. As of right now I really can't make a call until it gets into the E Carib. Just judging by past storms around the same position and the conditions around them I would say Chantal will have moments where the convection pulsates and the convection wane. It will also be interesting to see what Hispaniola does to the circulation, rip it apart, bounce off and around it, or just tracks through it intact. Then once it emerge on the other side how will the wind shear be like from the approaching trough along the east coast or will that trough lift out and a high settles in above it which is a nice recipe for strengthening. Lots of questions that are yet to be answered. The verdict is still out on this one.
Looks like it just might go west and under all the islands. It certainly has enough speed to do so. Could be a Gulf storm!
Member Since: May 16, 2010 Posts: 0 Comments: 1455
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As I hear the sound of chain saws nearby trimmed heavy trees, our blob offshore wants to be something evidently.

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Quoting 95. washingtonian115:
Does any one know if the CMC is developing the cape verde storm?.

Nope.
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Quoting 88. kingcane:
Is the Bermuda high going stay in that position for a while? What is it's climatological trend with this years conditions?

Mostly florida east coast landfalls.
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Quoting 48. biff4ugo:
So the wide dry SAL isn't strong enough or permanent enough to dampen the season, long term? Is the SAL a relatively minor generation factor compared to SST and Shear, or only come into play when looking at intensification?

I think it is one of the main limiting factors 2006 was forecasted to have 17 storms but dry air was blamed for the bust. Tropical storm Gaston in the busy 2008 season died at least in part due to dry air and that storm was forecasted to be a hurricane in the Caribbean. Dry air usually lightens up some during peak season though.
Member Since: March 29, 2008 Posts: 0 Comments: 2342
Quoting 82. Grothar:


It does not have to be developed to be dangerous or of concern. Systems moving that slowly have often brought flooding rains and some dangerous winds in thunderstorms. When something that large is off a coast and moving in the direction of land and over the Bahamas, it should be watched very closely. Even if only for maritime interests.
Yep..This season has a lot going for it as far as landfalls are concerned. It also has the potential to generate powerful storms as well. Bad combination.
Member Since: September 27, 2007 Posts: 1 Comments: 20340
Does any one know if the CMC is developing the cape verde storm?.
Member Since: August 14, 2010 Posts: 10 Comments: 16327
Quoting 82. Grothar:


It does not have to be developed to be dangerous or of concern. Systems moving that slowly have often brought flooding rains and some dangerous winds in thunderstorms. When something that large is off a coast and moving in the direction of land and over the Bahamas, it should be watched very closely. Even if only for maritime interests.
Grothar, what would be the inhibiting factor on this ULL working it's way down to the surface? Thanks
Member Since: June 21, 2011 Posts: 0 Comments: 329
chantal is looking very small even if it get at around 17 south of puerto rico will not going to get much from storm. some gust and rain but thats it and it will not survive the upper westerly south of hispañola and land interaction
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Not a healthy storm at all:



I'm interested in what recon finds for winds. While it may be an open wave by the time they get there, it could still have winds higher than you would think.
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Just so everyone knows, the GFS (and every other model) expected the ULL in the Bahamas to start producing convection today. However, it doesn't expect it to have enough time to produce anything significant at the surface, and it is probably right.

Simulated IR satellite valid 21z today:

Member Since: November 24, 2005 Posts: 635 Comments: 26543
Quoting 81. hurricanes2018:
we need to watch the next tropical wave back of invest 95L

It is now TS Chantal.
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Quoting 71. flcanes:

When will it upgrade?


No time soon. I want to see deep red in there.
Member Since: July 17, 2009 Posts: 68 Comments: 25090
Is the Bermuda high going stay in that position for a while? What is it's climatological trend with this years conditions?
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Quoting 18. GetReal:


Look for Chantal to hug the extreme left side of the current forecast cone, with the center of the official forecast cone slowly shifting west over time.


I tend to agree with that especially since it looks like Chantal is going to stay on the weak side. Weak storms tend to not feel the weakness as much and like to continue West.
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Quoting 82. Grothar:


It does not have to be developed to be dangerous or of concern. Systems moving that slowly have often brought flooding rains and some dangerous winds in thunderstorms. When something that large is off a coast and moving in the direction of land and over the Bahamas, it should be watched very closely. Even if only for maritime interests.


BlobCon: 1?

Officially not worried about this anymore!
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Still lots of low level moisture in the gulf...you can
see and feel it ...
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Quoting 79. mcdsara1:
didn't someone post yesterday that the CMC sandwiched Florida with 2 storms.


Yes, but the CMC often does that.
Member Since: July 17, 2009 Posts: 68 Comments: 25090
Quoting 63. flcanes:

First of all, i had no mean to doomcast. 2nd I believe you. My scenario was hypothetical. 3rd, do you think this will make landfall in south florida?
I know flcanes I just felt like teasing you. As of right now I really can't make a call until it gets into the E Carib. Just judging by past storms around the same position and the conditions around them I would say Chantal will have moments where the convection pulsates and the convection wane. It will also be interesting to see what Hispaniola does to the circulation, rip it apart, bounce off and around it, or just tracks through it intact. Then once it emerge on the other side how will the wind shear be like from the approaching trough along the east coast or will that trough lift out and a high settles in above it which is a nice recipe for strengthening. Lots of questions that are yet to be answered. The verdict is still out on this one.
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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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