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 1524. TylerStanfield:
Another center pass... 1011 MB... Ummm, Im speechless?


Didn't appear to be the center, it was close but not quite. Note the windshift remained southerly even though there was a westerly component. Wait a few more passes.
Member Since: July 8, 2005 Posts: 259 Comments: 23618
My question is why isnt the NHC going with the intensity that the new model runs are showing ? Why are they still calling for significant weakening ?
Member Since: September 8, 2010 Posts: 0 Comments: 2121
Quoting 1524. TylerStanfield:
Another center pass... 1011 MB... Ummm, Im speechless?


I dont think that is the center just yet
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1530. Dakster
Quoting 1514. CosmicEvents:
You should look into a career at air traffic control at Owen Roberts Airport.


I should know better than to take a drink when reading your posts Cosmic...

I shot soda through my nose and all over my keyboardddddddddddddddddddddddddddd......

Now my keeeeeeeeyyyyyyyyyysssssssssss aaaare stickiiiiinnnnggg.
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Quoting 1524. TylerStanfield:
Another center pass... 1011 MB... Ummm, Im speechless?


I'd be amused if Chantal turns into an open wave and never recovers.
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It seems the NHC blew the 45 mph and the pressure with this one. Lol Taz you said it would be funny if this was an open wave when recon when out. You were close.
Member Since: May 25, 2012 Posts: 0 Comments: 2043
1525. sar2401
Quoting CybrTeddy:
The blog's down in the dumps about the very first recon pass, yet if the recon finds something even slightly more impressive than expected there will be talks about the NHC being too low with the forecast and that Florida should be prepared for a hurricane.

LOL. Especialy if you "know" it's already a 70 mph TS or cat 1 hurricane. We now have models that do everything from kill it before it gets to Cuba or the Bahamas, go to Georgia, Florida, Alabama, Mississippi, Louisiana, Texas, or myabe even the Caymans! So far, the only place I haven't seen for landfall is Cleveland, but that will probably come next. At least we have more waves coming we can start wishcasting. :-)
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Another center pass... 1011 MB... Ummm, Im speechless?
Member Since: June 2, 2013 Posts: 8 Comments: 1145
El grande picture...

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1522. Patrap
At 22:27:30Z (last observation), the observation was 355 miles (572 km) to the ESE (107°) from Bridgetown, Barbados.

Product: Air Force High Density (HDOB) Message (URNT15 KNHC)
Transmitted: 8th day of the month at 22:26Z
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: 25

22:27:30Z 11.633N 54.567W 966.8 mb
(~ 28.55 inHg) 392 meters
(~ 1,286 feet) 1011.1 mb
(~ 29.86 inHg) - From 103° at 2 knots
(From the ESE at ~ 2.3 mph) 22.4°C
(~ 72.3°F) 20.9°C
(~ 69.6°F) 5 knots
(~ 5.8 mph) 17 knots*
(~ 19.5 mph*) 2 mm/hr*
(~ 0.08 in/hr*) 6.8 knots* (~ 7.8 mph*)
340.0%*
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
Member Since: July 3, 2005 Posts: 421 Comments: 127636
Quoting 1497. wunderkidcayman:

may end up much further W and S




I've seen these HH missions before and Chantal is still a TS, we have to wait until the mission is over, but imo Chantal will probably still pass South of Jamaica, but that's just my take.
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Quoting 1511. Ricki13th:
Hello everyone what is going on with Recon it is showing north winds where it should be west? Could it be a open wave?




recon is not find march of any thing with this so far they found olny 1010mb with a vary weak close low
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What is the latest with Recon it not showing a closed low. NHC may have called it to soon or did it just open up recently? Maybe the LLC is further south?
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DORIAN
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Are you notanotherwrongyear?
I have a nephew named Darian..is that to close named Dorian?
Member Since: August 14, 2010 Posts: 10 Comments: 16437
Typhoon Soulik



Looks rather ominous.
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Quoting 1487. wunderkidcayman:

I do agree on the move further W bit a matter of fact its interesting to see Chantal with this recent WNW-NW movement but by the looks of it it should be leveling off heading W-WNW bound
You should look into a career at air traffic control at Owen Roberts Airport.
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1513. AztecCe
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Hello everyone what is going on with Recon it is showing north winds where it should be west? Could it be a open wave?
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Not good!
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Quoting 1487. wunderkidcayman:

I do agree on the move further W bit a matter of fact its interesting to see Chantal with this recent WNW-NW movement but by the looks of it it should be leveling off heading W-WNW bound


Once in the Gulf it may re-strengthen and be stronger.
Member Since: September 2, 2011 Posts: 0 Comments: 1146
Quoting 1495. luvthetropics:
Does a tropical system have to be a major when entering Heberts Box for the predictor to apply? Thanks
Quoting 1495. luvthetropics:
Does a tropical system have to be a major when entering Heberts Box for the predictor to apply? Thanks


Yes, this applies to a major; however, even that is not set in stone.
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Time: 22:17:30Z
Coordinates: 11.4N 54.0833W
Acft. Static Air Press: 966.4 mb (~ 28.54 inHg)
Acft. Geopotential Hgt: 407 meters (~ 1,335 feet)
Extrap. Sfc. Press: 1012.9 mb (~ 29.91 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 186° at 26 knots (From the S at ~ 29.9 mph)
Air Temp: 19.7°C (~ 67.5°F)
Dew Pt: 19.5°C (~ 67.1°F)
Peak (10s) Flt. Lvl. Wind: 27 knots (~ 31.0 mph)
SFMR Peak (10s) Sfc. Wind: 31 knots (~ 35.6 mph)
SFMR Rain Rate: 7 mm/hr (~ 0.28 in/hr)
(*) Denotes suspect data
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1504. Patrap
Member Since: July 3, 2005 Posts: 421 Comments: 127636
Quoting 1495. luvthetropics:
Does a tropical system have to be a major when entering Heberts Box for the predictor to apply? Thanks


Don't think so; the general Hebert box theory looks at analog "hurricanes" passing through the boxes but does not break it down between categories.

From Wiki:

A Hebert Box (pronounced AY-bear, also known as Hebert's Box) is one of two regions of the tropical Atlantic Ocean that are useful as predictors of hurricanes that will strike South Florida, USA. They are named for former National Weather Service and National Hurricane Center forecaster Paul Hebert, who observed in the late 1970s that most strong hurricanes (characterized as those with winds exceeding 110 miles per hour (177 km/h)) which had struck South Florida since 1900 had also passed through one of these two small 335-mile-by-335-mile (517-km-by-517-km) square geographic regions.[1]

Examples include unnamed hurricanes in 1926, 1928, 1933, and 1935, as well as the major hurricanes Donna and Betsy, all of which came through an Hebert Box

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Chantal=Hanna,"Dorian"=Bad.
Member Since: August 14, 2010 Posts: 10 Comments: 16437
1500. Patrap
At 22:17:30Z (last observation), the observation was 392 miles (630 km) to the ESE (107°) from Bridgetown, Barbados.

Product: Air Force High Density (HDOB) Message (URNT15 KNHC)
Transmitted: 8th day of the month at 22:17Z
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: 24

22:17:30Z 11.400N 54.083W 966.4 mb
(~ 28.54 inHg) 407 meters
(~ 1,335 feet) 1012.9 mb
(~ 29.91 inHg) - From 186° at 26 knots
(From the S at ~ 29.9 mph) 19.7°C
(~ 67.5°F) 19.5°C
(~ 67.1°F) 27 knots
(~ 31.0 mph) 31 knots
(~ 35.6 mph) 7 mm/hr
(~ 0.28 in/hr) 29.9 knots (~ 34.3 mph)
114.8%
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
Member Since: July 3, 2005 Posts: 421 Comments: 127636
Going to be dealing with two storms before the weeks out. Off and running. When will a lull come? Troubling.
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1498. sar2401
Quoting WhereIsTheStorm:

No trolls aren't worse this year than in the past. As for banning an IP this is a little more difficult than it sounds and is usually left as a last resort effort. There have only been a couple of bad trolls this year and it will get worse; but most of the long time members know to ignore and not engage and they go away on their own. If someone in the group that you know and trust states that they suspect that someone is a troll, just put them on your ignore list and move along.

Post #1454 already reported and ignored. If you've been around for a bit, you'll know who it is.
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Quoting 1472. bwi:
Weaker than expected Chantal might end up further west/south of forecast points.

may end up much further W and S


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Quoting 1492. hurricaneSOFLA:
first hurricane of the season? Dorian... it does have a certain ring to it.
It will never get older...
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Does a tropical system have to be a major when entering Heberts Box for the predictor to apply? Thanks
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I very much doubt Chantal will make landfall in Georgia. Everyone knows tropical cyclones don't make landfall in Georgia! :P
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first hurricane of the season? Dorian... it does have a certain ring to it.
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Hurricane 'Dorian'.

Member Since: July 6, 2010 Posts: 113 Comments: 31532
1490. nigel20
Quoting CybrTeddy:
The blog's down in the dumps about the very first recon pass, yet if the recon finds something even slightly more impressive than expected there will be talks about the NHC being too low with the forecast and that Florida should be prepared for a hurricane.

Agreed.
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1489. Levi32
The GFS waiting until hour 144 for Chantal's landfall is exactly the kind of situation that could result in her re-strengthening in earnest near or north of the Bahamas before backing straight into the SE US coast due to the trough-split west of her. She will need time in that area. A landfall in 96 hours means she'll be nothing, but a landfall in 144 hours means we have to worry about her re-developing between two upper lows that will provide a great outflow setup.

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Quoting 1464. SouthernIllinois:

I agree. West she goes into the Gulf. And stays weak. I don't see this amounting to all too much.

I do agree on the move further W bit a matter of fact its interesting to see Chantal with this recent WNW-NW movement but by the looks of it it should be leveling off heading W-WNW bound

Member Since: June 13, 2009 Posts: 2 Comments: 11168
GFS shows near hurricane in the MDR.The wave immediately develops once it comes off the coast.
Member Since: August 14, 2010 Posts: 10 Comments: 16437
Quoting 1437. allancalderini:
You haven`t met Jason if you think that.He was the most persistant troll I had ever met I have like 24 accounts of him on ignore XD,and the tales say he is still here watching us.
LOL, I do remember that now that you mention it. Will just use the ignore button and appreciate all of the useful information the majority have to offer.
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Quoting 1482. stormchaser19:
Opean weave? Ha!!!




yep right now am calling that a open wave with a vary weak close low
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Quoting 1477. Ameister12:

Looks like Georgia.
Beryl part deux?
Member Since: June 30, 2013 Posts: 11 Comments: 7572

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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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