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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1633. Dakster
Quoting 1601. Sfloridacat5:
Chance of a system making landfall on the N.E. Fl. coast is rather low.
It can and does happen, but the probability is quite low.
Much better chance of the system making landfall up the coast in the Carolinas or further South in Fl.


I don't know why - but that seems to be the case.
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Quoting 1614. Saltydogbwi1:
Time: 22:40:30Z
Coordinates: 12.1333N 54.1167W
Acft. Static Air Press: 964.6 mb (~ 28.48 inHg)
Acft. Geopotential Hgt: 414 meters (~ 1,358 feet)
Extrap. Sfc. Press: 1011.8 mb (~ 29.88 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 159° at 54 knots (From the SSE at ~ 62.1 mph)
Air Temp: 19.6°C (~ 67.3°F)
Dew Pt: 19.6°C (~ 67.3°F)
Peak (10s) Flt. Lvl. Wind: 55 knots (~ 63.2 mph)
SFMR Peak (10s) Sfc. Wind: 60 knots (~ 69.0 mph)
SFMR Rain Rate: 28 mm/hr (~ 1.10 in/hr)
(*) Denotes suspect data


This reading is uncontaminated 69 MPH
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1631. nigel20
Quoting MiamiHurricanes09:
LMAO.

56kt flight level winds.

From 149° at 56 knots
(From the SSE at ~ 64.4 mph)


SFMR winds in the 45-50kt range.

Chantal's a damn good troll.

Hey MH09! I guess that people will now say that Chantal will become an hurricane...not open wave anymore. :)
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Quoting 1624. Thundercloud01221991:
60 knts on SMRF
Rain rate's a little high.

Definitely looks to be in the 45-50kt range though.
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1629. Patrap
At 22:47:30Z (last observation), the observation was 394 miles (634 km) to the E (97°) from Bridgetown, Barbados.

Product: Air Force High Density (HDOB) Message (URNT15 KNHC)
Transmitted: 8th day of the month at 22:46Z
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: 27

22:47:30Z 12.367N 53.817W 967.0 mb
(~ 28.56 inHg) 409 meters
(~ 1,342 feet) 1013.4 mb
(~ 29.93 inHg) - From 147° at 47 knots
(From the SSE at ~ 54.0 mph) 21.2°C
(~ 70.2°F) 19.5°C
(~ 67.1°F) 50 knots
(~ 57.5 mph) 36 knots
(~ 41.4 mph) 1 mm/hr
(~ 0.04 in/hr) 33.8 knots (~ 38.9 mph)
72.0%
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: 423 Comments: 127809
Someone flag Chantal... he's trolling!
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Wow, wasn't expecting that based on recon data up until now.

Time: 22:40:30Z
Coordinates: 12.1333N 54.1167W
Acft. Static Air Press: 964.6 mb (~ 28.48 inHg)
Acft. Geopotential Hgt: 414 meters (~ 1,358 feet)
Extrap. Sfc. Press: 1011.8 mb (~ 29.88 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 159° at 54 knots (From the SSE at ~ 62.1 mph)
Air Temp: 19.6°C (~ 67.3°F)
Dew Pt: 19.6°C (~ 67.3°F)
Peak (10s) Flt. Lvl. Wind: 55 knots (~ 63.2 mph)
SFMR Peak (10s) Sfc. Wind: 60 knots (~ 69.0 mph)
SFMR Rain Rate: 28 mm/hr (~ 1.10 in/hr)
(*) Denotes suspect data
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Quoting 1620. will40:
58.9 knots (~ 67.7 mph)
Tropical Storm

upper level TS winds found

High rain rate though. I think the strongest from that data set with a rain rate under the generally accepted 0.75 inches per hour was 54mph.
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69mph
Member Since: July 19, 2011 Posts: 12 Comments: 2316
60 knts on SMRF
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1623. sar2401
Quoting stormchaser19:
Now we are starting to talk
Time: 22:37:30Z
Coordinates: 12.0167N 54.2167W
Acft. Static Air Press: 966.8 mb (~ 28.55 inHg)
Acft. Geopotential Hgt: 385 meters (~ 1,263 feet)
Extrap. Sfc. Press: 1010.9 mb (~ 29.85 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 165° at 37 knots (From the SSE at ~ 42.5 mph)
Air Temp: 20.9°C (~ 69.6°F)
Dew Pt: 20.9°C (~ 69.6°F)
Peak (10s) Flt. Lvl. Wind: 39 knots (~ 44.8 mph)
SFMR Peak (10s) Sfc. Wind: 45 knots* (~ 51.7 mph*)
SFMR Rain Rate: 15 mm/hr* (~ 0.59 in/hr*)
(*) Denotes suspect data

Did you notice the asterisk? Likely rain contaminated data.
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Everyone have a good evening and see Yall tomorrow....As usual, the Hunter information will be fed into the models overnight and our the runs tomorrow will give us a better picture of what to expect in the short-term.
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1620. will40
58.9 knots (~ 67.7 mph)
Tropical Storm

upper level TS winds found
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Quoting 1602. TylerStanfield:
I think that circulation recon found may have been a vortex after all, Wind shift suggest the circulation is still to the north.
Recon find TS force winds now.
It seems to be barely closed but it is howling over TS force winds in the NE quadrant. 
Member Since: May 25, 2012 Posts: 0 Comments: 2043
So they will issue HURRICANE WATCHES!!

Member Since: October 6, 2007 Posts: 0 Comments: 6164
Quoting 1604. stormpetrol:


That's kinda old I think.


Ya was just using as an example, more recent one is no better:

Member Since: September 23, 2005 Posts: 14 Comments: 11072
Quoting 1609. AllStar17:
WIDE area of 50 kt flight level winds found.

Yep. Some have high rain rates so are useless but many 45-50mph with less rain.
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Time: 22:40:30Z
Coordinates: 12.1333N 54.1167W
Acft. Static Air Press: 964.6 mb (~ 28.48 inHg)
Acft. Geopotential Hgt: 414 meters (~ 1,358 feet)
Extrap. Sfc. Press: 1011.8 mb (~ 29.88 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 159° at 54 knots (From the SSE at ~ 62.1 mph)
Air Temp: 19.6°C (~ 67.3°F)
Dew Pt: 19.6°C (~ 67.3°F)
Peak (10s) Flt. Lvl. Wind: 55 knots (~ 63.2 mph)
SFMR Peak (10s) Sfc. Wind: 60 knots (~ 69.0 mph)
SFMR Rain Rate: 28 mm/hr (~ 1.10 in/hr)
(*) Denotes suspect data
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Chantal may be a 50 mph tropical storm...unflagged SFMR measurements support that.
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Quoting 1602. TylerStanfield:
I think that circulation recon found may have been a vortex after all, Wind shift suggest the circulation is still to the north.
Recon find TS force winds now.


I've watched many of these missions, I'm far from an expert , but for now Chantal is alive and well , just a small system.
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LMAO.

Plenty of 50kt flight-level winds.

Highest were 56kt flight-level winds.

From 149 at 56 knots
(From the SSE at ~ 64.4 mph)


SFMR winds in the 45-50kt range.

Chantal's a damn good troll.
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Quoting 1599. Patrap:
Still holding on. The windward islands about to get some squalls within the next 4-6 hours.
Member Since: May 25, 2012 Posts: 0 Comments: 2043
WIDE area of 50 kt flight level winds found.
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1608. Patrap
ShortWave IR Loop

Member Since: July 3, 2005 Posts: 423 Comments: 127809
1606. nash36
Quoting 1591. CybrTeddy:
Ouch, 18z prevents "Dorian" from going OTS, the ridge shoves it hard right into Georgia/Florida.


Many days out.....and as those of us who have been following these systems for a long time know, the GFS likes to bounce around by about 1,200 miles in the early stages.

Having said that, I certainly hope that does NOT verify in the end! Yowsa.
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Quoting 1597. ncstorm:


but the ensembles show the east coast..I am waiting on the 18z ensembles as that would be a good indicator on where a storm could possibly go..if both the operational and the ensembles disagree on a run, then to me I keep waiting till I see some agreement
We don't need no major running up the east coast.Sandy..I'm still paying for the damages.
Member Since: August 14, 2010 Posts: 10 Comments: 16828
Quoting 1589. nrtiwlnvragn:
Finding basically what the Scatt passes have shown, a weak poorly defined system in the SW, SE quads.




That's kinda old I think.
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1603. sar2401
Quoting Charliesgirl:
Hi All! lurking and learning again this year from Pearl River, La. Thanks for all the insight. I am dreading hurricane season, I am the caretaker of a NOLA oxygen dependent elder and it adds another layer of prep. I guess I need a generator.

You'd be much better off getting about 10 D or E size cylinders. The cost for rental will be much less than a generator, and they can be refilled from a portable, truck mounted unit. If your person is on a nasal cannula getting 30% oxygen, an E cylinder with the correct valve will last almost 36 hours. You don't have to worry about finding gas and keeping a generator running if you're only going to use the generator for an electic oxygen generator. Talk to his doctor and your oxygen supplier now, before you have the need. I'm a former respiratory therapist and paramedic, just for reference.
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I think that circulation recon found may have been a vortex after all, Wind shift suggest the circulation is still to the north.
Recon find TS force winds now.
Member Since: Posts: Comments:
Chance of a system making landfall on the N.E. Fl. coast is rather low.
It can and does happen, but the probability is quite low.
Much better chance of the system making landfall up the coast in the Carolinas or further South in Fl.
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something familiar about this ??? GFS up to it's old ways
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1599. Patrap
Member Since: July 3, 2005 Posts: 423 Comments: 127809
1597. ncstorm
Quoting 1582. washingtonian115:
Last time it showed south texas this run the east coast.


but the ensembles show the east coast..I am waiting on the 18z ensembles as that would be a good indicator on where a storm could possibly go..if both the operational and the ensembles disagree on a run, then to me I keep waiting till I see some agreement
Member Since: August 19, 2006 Posts: 13 Comments: 15137

Quoting 1588. Hurricane12:
Oh --- the HH are finding higher winds in Chantal?

Well, now everyone on the blog is going to speculate that Chantal is on its way of becoming a hurricane!
If thats the case it is going to be a long season. Lmao
Member Since: May 25, 2012 Posts: 0 Comments: 2043
Quoting 1583. MiamiHurricanes09:
Just for the hell of it, the GFS has Dorian making landfall in the exact same place as Chantal in many, many days.

It has it hitting some of most vulnerable cities in hurricane alley.This will change though.Seems Dorian will be our first major hurricane of the season in July..impressive.
Member Since: August 14, 2010 Posts: 10 Comments: 16828
Quoting 1581. SouthernIllinois:
Even if recon only does find TD winds after completed all the passes, I highly doubt the NHC will downgrade her for the 10 PM EDT advisory. If they find the same overnight, then I could see a TD tomorrow morning.


they already found TS force winds
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Quoting 1553. stormpetrol:


This tells me the center has moved due west or just a tad south of due west during this mission so far.

which add to my point
Member Since: June 13, 2009 Posts: 2 Comments: 11774
Ouch, 18z prevents "Dorian" from going OTS, the ridge shoves it hard right into Georgia/Florida.
Member Since: July 8, 2005 Posts: 259 Comments: 23891
Finding basically what the Scatt passes have shown, a weak poorly defined system in the SW, SE quads.


Member Since: September 23, 2005 Posts: 14 Comments: 11072
Oh --- the HH are finding higher winds in Chantal?

Well, now everyone on the blog is going to speculate that Chantal is on its way of becoming a hurricane!
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1587. hydrus
Quoting 1583. MiamiHurricanes09:
Just for the hell of it, the GFS has Dorian making landfall in the exact same place as Chantal in many, many days.

They want a piece of Georgia pie.
Member Since: September 27, 2007 Posts: 1 Comments: 20977
1585. Dakster
Quoting 1558. PalmBeachWeather:
Ever do that while eating a carrot? Now that is gross


Celery was worse...

Is Chantal dead or alive?
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Quoting 1576. jeffreeysweetypie:
i thought they said it was gonna stay a ts for the next 5 days?
Calm down and wait for more info.
Member Since: May 25, 2012 Posts: 0 Comments: 2043
Just for the hell of it, the GFS has Dorian making landfall in the exact same place as Chantal in many, many days.

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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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