Tropical Storm Chantal: a Likely Harbinger of an Active Atlantic Hurricane Season

By: Dr. Jeff Masters , 2:02 PM GMT on July 08, 2013

Share this Blog
95
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 533 - 483

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70Blog Index

Quoting 517. BaltimoreBrian:



No to Francis and Jeanne. But to this I say YES. 15 days off the East Coast. The blog would EXPLODE.



Cracking me up Colonel..

we don't need anymore water in south Florida.. they are dumping a billion gallons of polluted water a day into the St. Lucie River right now... sooo, should a Ginney happen, I have to hope that the rain stays offshore..
Member Since: Posts: Comments:
Quoting 516. Camille33:

Over night this was likely a 60 mph storm,it weakened and now getting stronger.It had a partial eye wall over night while most were sleeping.

Member Since: Posts: Comments:
Quoting 496. weatherlover94:
I just dont think Chantel will weaken as much as the NHC calling for especially now that the GFS is calling for a stronger system ...they may need to change there long term forecast ...just my opinion though
Chantal!
Member Since: Posts: Comments:
Quoting 453. FIUStormChaser:
It appears the ULL over the Bahamas is working down to the mid levels, nevertheless it will provide a path for Chantel to follow
..Chantal!
Member Since: Posts: Comments:
TS Chantal

Dvorak Loop

Member Since: Posts: Comments:
Quoting 450. hydrus:
If our little trough does not have enough influence and Chantel remains weak, she could feasibly make the gulf...
It's "Chantal" not Chantel.
Member Since: Posts: Comments:
The critical period for Chantal, in terms of a US impact, will certainly depend on the brush with Hispanola-Cuba before she/it emerges into the Florida Straights/Bahamas as noted by several including Levi.

Too far out (5 days) to speculate as to what could happen but a viable circulation, if combined with a real relaxation in sheer and the warm waters in that Region/Gulf Stream area could make things a little more interesting in the long-term.

Again, a good drill for the folks in South Florida to take adequate preparations this season for what may come their way in August-September.
Member Since: Posts: Comments:
Member Since: Posts: Comments:


just when its about to outrun itself....
Member Since: Posts: Comments:
Looking at Satellite pictures of Atlantic I'd swear it was late August, pretty scary.
Member Since: Posts: Comments:
Quoting CycloneOz:


Yes! It is good to be back around.

I was unbanned back in May after some years.

Ecuador is my new home. I live up in the Andes Mountains now.


whoa, that's a little different than New Mexico

Member Since: Posts: Comments:
Quoting 516. Camille33:

Over night this was likely a 60 mph storm,it weakened and now getting stronger.It had a partial eye wall over night while most were sleeping.


I saw the "eye" that Chantal tried to develop. Not sure if that was the real thing or what, it's gone now. Reminds me of Ernesto last year, when for multiple pages, this place was discussing whether or not that was an actual eye forming.
Member Since: Posts: Comments:
HH info should start coming in around 2 PM EDT, according to the good ol' NHC [Twitter feed]
Member Since: Posts: Comments:
Quoting 501. Levi32:
Convection is actually rebuilding back towards Chantal's low-level center, and the surface circulation is looking slightly more vigorous in recent frames. It will be interesting to see what central pressure the recon measures this afternoon. Often tiny systems like this one can have stronger tight little cores than we anticipate.




thanks levi she's still fighting dry air

seems like 25n is were the jog back to west may begin, we'll have to wait and see
Member Since: Posts: Comments:
Quoting 507. Chucktown:


No.


Why not? what propels a storm through the air around it and not with the air around it?
Member Since: Posts: Comments:
Quoting 502. indianrivguy:


he's know as BD in most circles.. "Before Dirt" :0

Just say no to a Francis/Jeanne.... NO! say it!



No to Francis and Jeanne. But to this I say YES. 15 days off the East Coast. The blog would EXPLODE.

Member Since: Posts: Comments:
Quoting 508. Stormchaser2007:
Against all odds, it's actually developing convection over a very tight center.


Over night this was likely a 60 mph storm,it weakened and now getting stronger.It had a partial eye wall over night while most were sleeping.
Member Since: Posts: Comments:
515. Mikla
While Chantel will produce some rain, wind, and hazardous conditions, along with some possible late week surprises... I think the next wave off of Africa is the one to watch.
Member Since: Posts: Comments:
Quoting 469. TylerStanfield:

Can I get your definition of Better Organized? Want to take note of this.
i actually believe she is. convection is rebuilding back if she can can continue she can survive more.
Member Since: Posts: Comments:
513. L1990
looks like its putting soldier storms in front to fight the dry air
Member Since: Posts: Comments:
Quoting 454. CycloneOz:
I can post a "Month of July 2013" GOES East Infrared Hurricane Sector animation UPDATED DAILY.

It might be cool to see Chantal move in unison with all the other weather in the sector.

Are you interested in me creating a new animation everyday for this system?
Yes.
Member Since: Posts: Comments:


Levi, potential video today? Thanks in advance!!
Member Since: Posts: Comments:
Quoting 501. Levi32:
Convection is actually rebuilding back towards Chantal's low-level center, and the surface circulation is looking slightly more vigorous in recent frames. It will be interesting to see what central pressure the recon measures this afternoon. Often tiny systems like this one can have stronger tight little cores than we anticipate.



Not too far from the islands... the uptick in intensity (if recon finds stronger winds) might catch the islands off guard a bit.
Member Since: September 2, 2006 Posts: 110 Comments: 6878
I'm curious to see what the generally more pessimistic ECMWF has to say about the tropical Atlantic this afternoon.
Member Since: Posts: Comments:
Against all odds, it's actually developing convection over a very tight center.

Member Since: Posts: Comments:
Quoting 492. BaltimoreBrian:



How does a storm 'outrun' the dry air around it? wouldn't they all be moving together?


No.
Member Since: Posts: Comments:
I'll be back on when Recon heads for Chantal.
Have a Good Early Afternoon everyone.
Member Since: Posts: Comments:
I came on here to check on Chantal, only to find Chantal, Dorian, and the comedy hour. :)

Chantal does seem to be doing a little better from just a few hours ago, but the dry air and forward speed are still inhibiting the potential for her development. I could see her as a hurricane if she gets her act together though.
Member Since: Posts: Comments:
Quoting 313. stormpetrol:
I still think Chantal will track further south and west , than what most models suggest.
Yep! That's what I've been saying all along!
Member Since: Posts: Comments:
Quoting 490. BaltimoreBrian:


Grothar remembers taking his great-grandson out to plant this.


he's know as BD in most circles.. "Before Dirt" :0

Just say no to a Francis/Jeanne.... NO! say it!
Member Since: Posts: Comments:
Convection is actually rebuilding back towards Chantal's low-level center, and the surface circulation is looking slightly more vigorous in recent frames. It will be interesting to see what central pressure the recon measures this afternoon. Often tiny systems like this one can have stronger tight little cores than we anticipate.

Member Since: Posts: Comments:
got my best ruler out she heading to barbados
Member Since: Posts: Comments:
the GFS kills the storm in the caribbean and gulf in all of its runs. i dont know if we should follow that but it does show dorian developing in a couple of days
Member Since: Posts: Comments:
D4

Member Since: Posts: Comments:
I just dont think Chantel will weaken as much as the NHC calling for especially now that the GFS is calling for a stronger system ...they may need to change there long term forecast ...just my opinion though
Member Since: Posts: Comments:
The 12z GFS shows the Caribbean islands pretty much killing the next potential CV storm, but it starts to redevelop it in the GOM at the end of the run:

Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting 488. Gearsts:
Did you saw the conference here on endi about the TS watch for the island?


No I did not. But I heard in radio the NWS director saying rain will be the main threat for us.
Member Since: Posts: Comments:
Quoting 486. Chucktown:


I don't think so, its ingesting a lot of dry air right now. However, the speed of Chantal may actually help for it to remain a tropical storm as it out runs this pocket of dry air. Eventually, shear will become an issue by late week as it interacts with the approaching trough in the eastern US and land interaction will also become an issue. Chantal will most likely peak in the next 72 hours.



How does a storm 'outrun' the dry air around it? wouldn't they all be moving together?
Member Since: Posts: Comments:
Something to Note: Chantal has actually gone a little north of the next Forecast point.
Member Since: Posts: Comments:
Quoting 476. Grothar:


I remember Mary Alice.


Grothar remembers taking his great-grandson out to plant this.
Member Since: Posts: Comments:
Quoting 484. ncstorm:


no thats not Chantal on the west coast of Florida..Chantal is heading west in that run down by the islands
I edited my comment.
Member Since: Posts: Comments:
Quoting 481. Tropicsweatherpr:


And the WNW movement is clear.
Did you saw the conference here on endi about the TS watch for the island?
Member Since: Posts: Comments:
Quoting 482. Gearsts:
Do you think she will slow down a bit as she gets close to us?


To you in PR, probably not much. The trade wind flow is well-established across your region, and the major bend northward in track will likely occur west of you, which is when she would slow down.
Member Since: Posts: Comments:
Quoting 464. SLU:
Chantal getting better organised.



I don't think so, its ingesting a lot of dry air right now. However, the speed of Chantal may actually help for it to remain a tropical storm as it out runs this pocket of dry air. Eventually, shear will become an issue by late week as it interacts with the approaching trough in the eastern US and land interaction will also become an issue. Chantal will most likely peak in the next 72 hours.
Member Since: Posts: Comments:
Quoting 474. SLU:


You can see that a new burst of convection has began right over the previously partially exposed center and the quality of the convection looks better with more curvature.


Ok. :)
Member Since: Posts: Comments:
Quoting 454. CycloneOz:
I can post a "Month of July 2013" GOES East Infrared Hurricane Sector animation UPDATED DAILY.

It might be cool to see Chantal move in unison with all the other weather in the sector.

Are you interested in me creating a new animation everyday for this system?


Oz.. good to see ya around brother!
Member Since: Posts: Comments:

Viewing: 533 - 483

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Overcast
35 °F
Overcast

JeffMasters's Recent Photos

Lake Effort Snow Shower Over Windsor, Ontario
Sunset on Dunham Lake
Pictured Rocks Sunset
Sunset on Lake Huron