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 1863. wunderkidcayman:

I think when Recon fly back to the center they will find it lower



nah no relocation they just being cautious


You don't know.
Member Since: October 6, 2007 Posts: 0 Comments: 6168
Quoting 1877. Neapolitan:
waves


and awayyy we go!
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Patrap, I know it will not come to pass, but the ull pausing in the Bahamas and drifting towards S. Fl. brings back strange memories.
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Quoting 1876. wxchaser97:

Yes, they are going in for another center pass.


Ok, cool...
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Quoting 1861. Tropicsweatherpr:


Why strange?


It's a little dive to the SW... I wasn't expecting this based on Visible sat this afternoon. Though the convective mass has continued its WNW movement.

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1878. whitewabit (Mod)
Quoting 1876. wxchaser97:

Yes, they are going in for another center pass.


I think there will be 2 more passes this one they are on now and when they head back to base ..
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waves
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Quoting 1868. Jwd41190:
Is the recon still out there?

Yes, they are going in for another center pass.
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1875. 7544
Quoting 1872. Hurricane1956:
I was ready to post when I read your comments about the ULL East of Florida,it seems that something is going on,on the last frames,the center of circulation is starting to fill with clouds,maybe is trying to work down to the surface,even thought Levi mention that it will run out of time for anything tropical to form,any system in this very warm waters can give us a surprise!!!,I had seen many systems intensify as the make landfall specially with this ocean temperatures,will see what happens in the next few hours.


thanks im still watchin it too lol
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Barbados Radar
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1873. Patrap
At 23:57:30Z (last observation), the observation was 260 miles (419 km) to the E (99°) from Bridgetown, Barbados.

Product: Air Force High Density (HDOB) Message (URNT15 KNHC)
Transmitted: 8th day of the month at 23:56Z
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: 34

23:57:30Z 12.483N 55.800W 966.8 mb
(~ 28.55 inHg) 406 meters
(~ 1,332 feet) 1012.6 mb
(~ 29.90 inHg) - From 38° at 28 knots
(From the NE at ~ 32.2 mph) 23.0°C
(~ 73.4°F) 21.3°C
(~ 70.3°F) 30 knots
(~ 34.5 mph) 28 knots
(~ 32.2 mph) 1 mm/hr
(~ 0.04 in/hr) 26.1 knots (~ 30.1 mph)
93.3%
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: 424 Comments: 128273
Quoting 1829. 7544:
I was ready to post when I read your comments about the ULL East of Florida,it seems that something is going on,on the last frames,the center of circulation is starting to fill with clouds,maybe is trying to work down to the surface,even thought Levi mention that it will run out of time for anything tropical to form,any system in this very warm waters can give us a surprise!!!,I had seen many systems intensify as the make landfall specially with this ocean temperatures,will see what happens in the next few hours.
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Well...it might not be wrong to say that Chantal looks better than ever.
Member Since: July 19, 2011 Posts: 12 Comments: 2401
1870. eddye
ppl come 2 tropics chat
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Quoting 1853. KoritheMan:


Did anyone think the central pressure wouldn't be high? Chantal is moving upwards of >25 mph, which means the large-scale environment consists of rather high surface pressures.


That explains it, the environmental MSLP is 1014mb.
Member Since: July 8, 2005 Posts: 259 Comments: 24018
Is the recon still out there?
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Quoting 1853. KoritheMan:


Did anyone think the central pressure wouldn't be high? Chantal is moving upwards of >25 mph, which means the large-scale environment consists of rather high surface pressures.
Right on Kori that makes sense.
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1865. ncstorm
156 hours on 18z GFS Ensemble Spread


162 hours


174 hours
Member Since: August 19, 2006 Posts: 13 Comments: 15288
Quoting 1849. wunderkidcayman:
New advisory looks like NHC most likely need to drop their cone S and W at 11



It moved due west over the past 3 hours, so it's back on track to be a bit more southerly than expected, as I thought it might.

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Quoting 1853. KoritheMan:


Did anyone think the central pressure wouldn't be high? Chantal is moving upwards of >25 mph, which means the large-scale environment consists of rather high surface pressures.

I think when Recon fly back to the center they will find it lower

Quoting 1855. CaribBoy:
ADDITIONAL WATCHES AND WARNINGS COULD BE REQUIRED FOR A PORTION OF
THE NORTHERN LEEWARD ISLANDS LATER TONIGHT. INTERESTS IN THIS AREA
SHOULD MONITOR THE PROGRESS OF CHANTAL.


They must be joking... or maybe they feel the center will relocate further North...

I honestly find the 11.8N 55W coordinates strange.


nah no relocation they just being cautious
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1862. SLU
8pm position much further west than expected. A direct hit in Barbados and St. Lucia a great possibility. So far the SHIPS and LGEM have performed almost perfectly with Chantal.

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Quoting 1855. CaribBoy:
ADDITIONAL WATCHES AND WARNINGS COULD BE REQUIRED FOR A PORTION OF
THE NORTHERN LEEWARD ISLANDS LATER TONIGHT. INTERESTS IN THIS AREA
SHOULD MONITOR THE PROGRESS OF CHANTAL.


They must be joking... or maybe they feel the center will relocate further North...

I honestly find the 11.8N 55W coordinates strange.


Why strange?
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1848.
I know that...look at 1849 for what i was trying to say.
Member Since: July 19, 2011 Posts: 12 Comments: 2401
Quoting 1853. KoritheMan:


Did anyone think the central pressure wouldn't be high? Chantal is moving upwards of >25 mph, which means the large-scale environment consists of rather high surface pressures.


I guess Bernoulli doesn't apply on the macro scale of environment...?
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1857. Patrap
Based at St. Croix, the WC-130J has a good loiter time but they should be wrapping up soon and heading fer da Barn.


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.
Member Since: July 3, 2005 Posts: 424 Comments: 128273
.
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ADDITIONAL WATCHES AND WARNINGS COULD BE REQUIRED FOR A PORTION OF
THE NORTHERN LEEWARD ISLANDS LATER TONIGHT. INTERESTS IN THIS AREA
SHOULD MONITOR THE PROGRESS OF CHANTAL.


They must be joking... or maybe they feel the center will relocate further North...

I honestly find the 11.8N 55W coordinates strange.
Member Since: October 6, 2007 Posts: 0 Comments: 6168



Member Since: September 23, 2005 Posts: 14 Comments: 11163
Quoting 1846. GTstormChaserCaleb:
I don't think I have ever heard of a 50 mph. Tropical Storm with a 1010 mb. pressure.


Did anyone think the central pressure wouldn't be high? Chantal is moving upwards of >25 mph, which means the large-scale environment consists of rather high surface pressures.
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Quoting 1830. ScottGridley:
Very odd weather here in MA/RI at the moment.

Look at this (real) feature retrograding from the cape westward towards RI - it's sprinkling at my house ( ) at the northwest tip.

At the current time points, look at the storms popping near Providence 90 degrees offset from the onshore flow.

Amazing.





It's quite simple to explain actually. The line moving west is actually the Atlantic Coast Sea Breeze pushing inland. Happens all the time in Florida and is highly evident on radar most afternoons. The other feature is being caused by a outflow boundary from earlier storms moving south eastward. That outflow boundary is causing storms to fire along it and it just happens to be perpendicular to the Atlantic Coast Seabreeze.
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8PM cone is out, while the track is unchanged I would like to note how far south Chantal is from the 12 hour forecast point. Therefore I wouldn't be suprised of a shift to the left due to intial position, which moved .0 N and 1.1 W from 5PM Advisory.

Every degree counts as far as my impact in SWFL.
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New advisory looks like NHC most likely need to drop their cone S and W at 11

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Quoting 1843. JrWeathermanFL:
Spot on cone looks a little too left..
Cone doesn't change during intermediate advisory.
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1847. Patrap
Western Atlantic - False Color RGB Loop

Click image for Loop

click moving image to ZOOM in the ULL

Member Since: July 3, 2005 Posts: 424 Comments: 128273
I don't think I have ever heard of a 50 mph. Tropical Storm with a 1010 mb. pressure.
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Quoting 1840. Patrap:
At 23:47:30Z (last observation), the observation was 236 miles (380 km) to the E (94°) from Bridgetown, Barbados.

Product: Air Force High Density (HDOB) Message (URNT15 KNHC)
Transmitted: 8th day of the month at 23:46Z
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: 33

23:47:30Z 12.833N 56.117W 967.1 mb
(~ 28.56 inHg) 411 meters
(~ 1,348 feet) 1013.5 mb
(~ 29.93 inHg) - From 49° at 28 knots
(From the NE at ~ 32.2 mph) 23.0°C
(~ 73.4°F) 21.4°C
(~ 70.5°F) 29 knots
(~ 33.3 mph) 25 knots*
(~ 28.7 mph*) 1 mm/hr*
(~ 0.04 in/hr*) 24.1 knots* (~ 27.8 mph*)
86.2%*
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



How long have they been out there? Do they have enough fuel for another pass at the center?
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1844. hydrus
Quoting 1833. Patrap:
,,"there's something a happening here, what it is, aint zactly clear"..

Its Mutha Nature...And she not only deals the cards, she wins most of the hands.
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Spot on cone looks a little too left..
Member Since: July 19, 2011 Posts: 12 Comments: 2401
Higher winds and pressure?
that is kinda weird
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1841. Patrap
Tropical Storm 03L

UW-CIMSS Automated Satellite-Based
Advanced Dvorak Technique (ADT)
Version 8.1.4
Tropical Cyclone Intensity Estimation Algorithm

Current Intensity Analysis



UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.4
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 08 JUL 2013 Time : 224500 UTC
Lat : 12:02:00 N Lon : 54:33:18 W


CI# /Pressure/ Vmax
3.5 / 999.2mb/ 55.0kt


Final T# Adj T# Raw T#
3.1 3.2 3.2

Center Temp : -19.6C Cloud Region Temp : -44.4C

Scene Type : CURVED BAND with 0.62 ARC in LT GRAY

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : ON
Rapid Dissipation Flag : FLAG

C/K/Z MSLP Estimate Inputs :
- Average 34 knot radii : 46km
- Environmental MSLP : 1014mb

Satellite Name : GOES13
Satellite Viewing Angle : 27.6 degrees



Member Since: July 3, 2005 Posts: 424 Comments: 128273
1840. Patrap
At 23:47:30Z (last observation), the observation was 236 miles (380 km) to the E (94°) from Bridgetown, Barbados.

Product: Air Force High Density (HDOB) Message (URNT15 KNHC)
Transmitted: 8th day of the month at 23:46Z
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: 33

23:47:30Z 12.833N 56.117W 967.1 mb
(~ 28.56 inHg) 411 meters
(~ 1,348 feet) 1013.5 mb
(~ 29.93 inHg) - From 49° at 28 knots
(From the NE at ~ 32.2 mph) 23.0°C
(~ 73.4°F) 21.4°C
(~ 70.5°F) 29 knots
(~ 33.3 mph) 25 knots*
(~ 28.7 mph*) 1 mm/hr*
(~ 0.04 in/hr*) 24.1 knots* (~ 27.8 mph*)
86.2%*
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: 424 Comments: 128273
50mph
Member Since: July 19, 2011 Posts: 12 Comments: 2401
1838. Patrap
Miami
NEXRAD Radar

Velocity Azimuth Display Wind Profile ° Elevation
Range 124 NMI

Member Since: July 3, 2005 Posts: 424 Comments: 128273
Up to 50mph.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
BULLETIN
TROPICAL STORM CHANTAL INTERMEDIATE ADVISORY NUMBER 4A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL032013
800 PM AST MON JUL 08 2013

...RECONNAISSANCE AIRCRAFT FINDS CHANTAL A LITTLE STRONGER...


SUMMARY OF 800 PM AST...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...11.8N 55.0W
ABOUT 320 MI...515 KM ESE OF BARBADOS
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 26 MPH...43 KM/H
MINIMUM CENTRAL PRESSURE...1010 MB...29.82 INCHES
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1834. AztecCe


Look at that thing. That's gonna suck for the Chinese
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1833. Patrap
,,"there's something a happening here, what it is, aint zactly clear"..

Member Since: July 3, 2005 Posts: 424 Comments: 128273

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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.