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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1732. Grothar
Quoting 1704. allancalderini:
Still he predict a 600mph storm and he might not be far off.maybe Chantal will surprise us and become a hurricane tomorrow.Never now the tropics are unexpected.


Then we would all be a little off with those winds.


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Playing with the satellite enhancements. This one definitely makes Chantal look the most intense. :P

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting 1718. stormpetrol:
I think Chantal will be upped to a 60mph at 7 pm cst advisory.

Recon CDM says 50 Mph. It needs more 60 mph winds to upgrade it further.
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1729. sar2401
Quoting washingtonian115:
Everyone including me.We need to apologize to ScottTracker2K.He almost hit the nail with a 60mph tropical storm.

I hadn't read anything official from the NHC that Chantal has 60 mph winds, have you? Go back and look at his predictions for 94L before you start apologizing.
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1728. hydrus
Quoting 1709. TropicalAnalystwx13:
Decent-looking tropical storm. Convection seems to be wrapping into the center, meaning it could attempt to pull something off like last night.

Chantel is a tough girl...I am impressed...I said several days ago that the wave she came from looked textbook, especially so early.
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Probably 50mph at 8PM unless recon finds anything more. 55 may be more accurate but they don't use that, and I don't think there's currently enough to upgrade to 60mph.
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1726. nigel20
Quoting TropicalAnalystwx13:
Decent-looking tropical storm. Convection seems to be wrapping into the center, meaning it could attempt to pull something off like last night.


Hey Cody!
Agreed. It could also be the sign of what is to come later in the season.
Member Since: November 6, 2010 Posts: 11 Comments: 8229
Quoting 1709. TropicalAnalystwx13:
Decent-looking tropical storm. Convection seems to be wrapping into the center, meaning it could attempt to pull something off like last night.


I'm just mentally frustrated with this storm, its just curveball after curveball, when you expect it to twist, it turns... I think I'm going to take a break...
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Quoting 1715. stormchaser19:
1010 mb 55mph TS, at this point will be a 100mb cat.1 hurricane!!!




guys they dont do 55mph any more its 50 or 60mph
Member Since: May 21, 2006 Posts: 5091 Comments: 115255
Pressure are high because there is not a whole lot of convection right now as while as the strong High to it north. With that being said it packing a lot of wind and while I think the NHC may put it at 50mph for 11pm. Anymore convective organization with the support of DMAX will get pressures to lower and raise the surface winds to higher much easier. Dont take your eyes off this storm just yet.
Member Since: May 25, 2012 Posts: 0 Comments: 2043
It is just a matter of patience and learning how vaulable HH data is. 5 hours ago I was reading Chantal was decoupling and game over on this blog. The NHC spoke none of that, if the HH Data shows something different from the weather data from Satelite photos and other tools the NHC will state it. Those on the blog for a long time know how valuable HH data is.
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Chantal (already a small storm) does appear to be tightening up a bit.
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Quoting 1704. allancalderini:
Still he predict a 60mph storm and he might not be far off.maybe Chantal will surprise us and become a hurricane tomorrow.Never now the tropics are unexpected.

I highly doubt it with the way trade winds are and based on the overall organization it will struggle. a lot.
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I think Chantal will be upped to a 60mph at 7 pm cst advisory.
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Link

Really moving W or WSW ? No.
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1010 mb 55mph TS, at this point will be a 1000mb cat.1 hurricane!!!
Member Since: June 20, 2012 Posts: 0 Comments: 2159
Uncontaminated 60 knots at the surface?

Impressive...


Probably a downburst, though...
Member Since: September 22, 2005 Posts: 18 Comments: 2343
Quoting 1701. jeffreeysweetypie:
OMG DO WE NEED TO START BOARDING UP YET AND HUNKER DOWN?
Definitely.

Try to get into your backyard and dig a nice 30 foot deep bunker underneath the ground.

Then make sure to set your laptop on fire for safe measures.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Chantal even if the center is open it could be a interesting scenario if she misses most of the mountainous and start to slow down.
Could become a hurricane later down the road?
Member Since: August 14, 2010 Posts: 10 Comments: 17163
Tornado Warning issued for Pinellas County in the Tampa Bar area:





Waterspout over North Bay - near Safety Harbor and Oldsmar ....photo courtesy of @grouper22
Member Since: June 30, 2013 Posts: 12 Comments: 8579
1710. scott39
Chantal will not survive the wind shear in her near future.
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Decent-looking tropical storm. Convection seems to be wrapping into the center, meaning it could attempt to pull something off like last night.

Member Since: July 6, 2010 Posts: 113 Comments: 32354
1708. Kumo
Quoting 1674. sar2401:

Hmmm...1011mb and surface winds higher than flight level winds...looks like more analysis will be required.


I know from severe weather on the CONUS, forward motion of a thunderstorm often serves to amplify wind gusts associated with the storm. Could the forward motion of this tropical storm be a factor in these higher winds in the NE quadrant?
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1707. Patrap
At 23:07:30Z (last observation), the observation was 405 miles (652 km) to the E (92°) from Bridgetown, Barbados.

Product: Air Force High Density (HDOB) Message (URNT15 KNHC)
Transmitted: 8th day of the month at 23:06Z
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: 29

23:07:30Z 12.917N 53.600W 966.5 mb
(~ 28.54 inHg) 424 meters
(~ 1,391 feet) 1014.6 mb
(~ 29.96 inHg) - From 134° at 36 knots
(From the SE at ~ 41.4 mph) 22.0°C
(~ 71.6°F) 19.9°C
(~ 67.8°F) 37 knots
(~ 42.5 mph) 34 knots
(~ 39.1 mph) 1 mm/hr
(~ 0.04 in/hr) 33.1 knots (~ 38.0 mph)
91.9%
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: 426 Comments: 128875
Quoting 1691. thunderstromsmike:
so whats the deal with chantal?

She's trolling us
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Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting 1697. TylerStanfield:

I'd rather not. Chantal is almost equal to an open wave with gale force winds... So. Either way, its a 50 Mph storm that will most certainly not become a hurricane tomorrow like he predicted...
Quoting 1697. TylerStanfield:

I'd rather not. Chantal is almost equal to an open wave with gale force winds... So. Either way, its a 50 Mph storm that will most certainly not become a hurricane tomorrow like he predicted...
Still he predict a 600mph storm and he might not be far off.maybe Chantal will surprise us and become a hurricane tomorrow.Never now the tropics are unexpected.
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That forward speed is messing with Chantal, and the weenies here!
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1702. Patrap

Miami
NEXRAD Radar

Base Reflectivity 0.50° Elevation
Range 248 NMI

Member Since: July 3, 2005 Posts: 426 Comments: 128875
Quoting 1676. washingtonian115:
Everyone including me.We need to apologize to ScottTracker2K.He almost hit the nail with a 60mph tropical storm.


Yep he should get a "Crow-Free" award for his

next guess.....
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1699. Grothar
Quoting 1678. CybrTeddy:


When you put it in that light, I feel arrogant! Nah, I never claim to be right or wrong, I just put a prediction out there and wait to see if it gets shoved in my face. I do know however how this blog works after observing for nearly a decade. The mood changes with the organization of the cyclone.


As PsychicMaria would say, "I knew you were going to say that!"

Good Call Teddy and StormTracker.
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South West casters make me smile sometimes.
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Quoting 1676. washingtonian115:
Everyone including me.We need to apologize to ScottTracker2K.He almost hit the nail with a 60mph tropical storm.

I'd rather not. Chantal is almost equal to an open wave with gale force winds... So. Either way, its a 50 Mph storm that will most certainly not become a hurricane tomorrow like he predicted...
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That is why Hurricane Emily of 2005 was upgraded post season if I remember correctly as a Cat 5 with a pressure of 929mb. because of its small size.
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1695. sar2401
Quoting Saltydogbwi1:


This reading is uncontaminated 69 MPH

Look at the flight level winds. The 69 knot surface wind is very suspect.
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Quoting 1688. ncstorm:


I plussed his comments always..the guy does have a good knowledge of tropical weather and has been right quite a few times when the blog will tear him apart..where is yonzabam anyway..is he waiting in NY for that Cat 6?
I didn't bash him just thought Chantal for her it would be impossible to see a cat 1.Now that's not looking to far off.Espeically if the pressure starts lowering.
Member Since: August 14, 2010 Posts: 10 Comments: 17163
Quoting 1656. Grothar:
Ominous. I would move this to 1%.


Gonna drench Florida if it keeps the thunderstorm activity up.
Member Since: September 2, 2009 Posts: 130 Comments: 21194

I see Grothar's ULL got the yellow crayon today.....
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Tried to post a pic of my prediction but it wont post :/
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1688. ncstorm
Quoting 1676. washingtonian115:
Everyone including me.We need to apologize to ScottTracker2K.He almost hit the nail with a 60mph tropical storm.


I plussed his comments always..the guy does have a good knowledge of tropical weather and has been right quite a few times when the blog will tear him apart..by the way where is yonzabam??..is he waiting in NY for that Cat 6?
Member Since: August 19, 2006 Posts: 13 Comments: 15751
1687. nigel20
Quoting MiamiHurricanes09:
Hey Nigel!

Yeah, I was quite the downer myself though, didn't expect that they'd find these winds by any means.

Chantal definitely has some surprises.

Agreed.

Quoting TylerStanfield:

Too late. StormTrackScott beat you too it. He was betting on crow that it would make it there... All I want to do it laugh.

Lol!
Member Since: November 6, 2010 Posts: 11 Comments: 8229
Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 8th day of the month at 23:01Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 302)
Storm Number & Year: 03L in 2013
Storm Name: Chantal (flight in the North Atlantic basin)
Mission Number: 1
Observation Number: 10
A. Time of Center Fix: 8th day of the month at 22:27:40Z
B. Center Fix Coordinates: 11°38'N 54°34'W (11.6333N 54.5667W)
B. Center Fix Location: 355 miles (572 km) to the ESE (107°) from Bridgetown, Barbados.
C. Minimum Height at Standard Level: Not Available
D. Estimated (by SFMR or visually) Maximum Surface Wind: 27kts (~ 31.1mph)
E. Location of the Estimated Maximum Surface Wind: 25 nautical miles (29 statute miles) to the ESE (115°) of center fix
F. Maximum Flight Level Wind Inbound: From 179° at 29kts (From the S at ~ 33.4mph)
G. Location of Maximum Flight Level Wind Inbound: 28 nautical miles (32 statute miles) to the ESE (116°) of center fix
H. Minimum Sea Level Pressure: 1010mb (29.83 inHg) - Extrapolated
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 20°C (68°F) at a pressure alt. of 395m (1,296ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 22°C (72°F) at a pressure alt. of 392m (1,286ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 22°C (72°F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Not Available
M. Eye Shape: Not Available
N. Fix Determined By: Penetration, Wind and Temperature
N. Fix Level: 1,500 feet
O. Navigational Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 9 nautical miles
Remarks Section - Remarks That Were Decoded...
Sea Level Pressure Extrapolation From: Below 1,500 feet
Maximum Flight Level Temp: 22°C (72°F) which was observed 11 nautical miles (13 statute miles) to the ESE (106°) from the flight level center
Remarks Section - Additional Remarks...
PRELIMINARY, DO NOT RETRANSMIT
MAX OUTBOUND AND MAX FL WIND 58 KT 042/37 22:39:30Z
MIN SLP 1010MB 042/21 22:35:00Z

VDM... Dang.
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1685. Patrap
Member Since: July 3, 2005 Posts: 426 Comments: 128875

Quoting 1659. Patrap:
RainBow Top Loop

Hey pay attention to where the Recon is finding those winds in the NW where there is a good pop up of deep convection. Convective this is not supporting 60mph but it may start to get going as DMAX settles in. Patients is key if you want to track the tropics.
Member Since: May 25, 2012 Posts: 0 Comments: 2043
VDM out.

Doesn't include the intense winds outside of the remarks section.

New HDOB showing more 45kt+ winds.
Member Since: September 2, 2009 Posts: 130 Comments: 21194

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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.