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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18z GFS; 5 days out.



Very impressive EATL feature.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
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Quoting 1410. DataNerd:



Someone already put a bet on this to be a Hurricane? By tomorrow or now?


I didn't even think I would wake up today to chantal at all.

Yeah. He said it would become a hurricane tomorrow... *Facepalm*
Member Since: June 2, 2013 Posts: 8 Comments: 1383
42HR you can see the next TS!:)
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1428. nash36
Quoting 1416. washingtonian115:
Maybe CMC wasn't so crazy after all?.I really don't want to say that though since the model was showing a cat 1 impacting N.C and riding up the east coast...


Stop it!!!!! I do not want any more heavy rain! It can feel free to croak over the mountains :-)
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Quoting 1417. CybrTeddy:
Fun times ahead per the 18z GFS (full resolution model).
And this time it hasn't dropped the cape verde storm like yesterday's 18z.
Member Since: August 14, 2010 Posts: 10 Comments: 17492
18z GFS is quite a bit stronger with both Chantal and the wave behind it that develops.
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1425. Patrap
At 22:07:30Z (last observation), the observation was 407 miles (655 km) to the ESE (110°) from Bridgetown, Barbados.

Product: Air Force High Density (HDOB) Message (URNT15 KNHC)
Transmitted: 8th day of the month at 22:06Z
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: 23

22:07:30Z 11.083N 53.950W 966.7 mb
(~ 28.55 inHg) 408 meters
(~ 1,339 feet) 1012.9 mb
(~ 29.91 inHg) - From 170° at 21 knots
(From the S at ~ 24.1 mph) 21.7°C
(~ 71.1°F) 19.3°C
(~ 66.7°F) 21 knots
(~ 24.1 mph) 15 knots
(~ 17.2 mph) 3 mm/hr
(~ 0.12 in/hr) 15.0 knots (~ 17.2 mph)
71.4%
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
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Quoting 1363. washingtonian115:
He's trolling.He also forecast 94L to be a cat 4 Audrey part 2 which never happened.
Is it my imagination or are the trolls much worse this year? Seems to be one coming back with a different name every few weeks but gives himself away with the same speech (writing) patterns. Must have lots of devices and locations since I would assume bans use IP and/or MAC addresses to block.
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111 hours out the EATL system is a little more intense than Chantal.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Gonna take a break and be back when we have a VDM or another pass completed

Time: 21:57:00Z
Coordinates: 10.9833N 54.5167W
Acft. Static Air Press: 966.6 mb (~ 28.54 inHg)
Acft. Geopotential Hgt: 403 meters (~ 1,322 feet)
Extrap. Sfc. Press: 1012.2 mb (~ 29.89 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 194° at 15 knots (From the SSW at ~ 17.2 mph)
Air Temp: 23.0°C (~ 73.4°F)
Dew Pt: 18.7°C (~ 65.7°F)
Peak (10s) Flt. Lvl. Wind: 16 knots (~ 18.4 mph)
SFMR Peak (10s) Sfc. Wind: 11 knots (~ 12.6 mph)
SFMR Rain Rate: 1 mm/hr (~ 0.04 in/hr)
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111HR
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Quoting 1391. GrandCaymanMed:
My Forecast for Madame Chantal...
She's already up to 45...going up to 90 IMO with shear not so bad

A storm doesn't just simply strengthen because wind shear is low. There are many factors, and right now, the main thing that has disrupted, and will likely continue to disrupt Chantal is the Fast Trade winds. These winds will keep any strengthening very slow, and there's about a 15% chance or less of this thing becoming a Hurricane in it's lifetime. The maximum intensity this storm is capable of right now is 65 Mph...
Member Since: June 2, 2013 Posts: 8 Comments: 1383
Chantal = DOA? :o)
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Quoting 1401. BaltimoreBrian:


You joined only yesterday and are so expert on everything. Amazing!


A troll by another name is probably the same troll who's gone by a hundred other names through the years. Yawn, ignore, report, and empathize with their obvious difficulties.
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Fun times ahead per the 18z GFS (full resolution model).
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Maybe CMC wasn't so crazy after all?.I really don't want to say that though since the model was showing a cat 1 impacting N.C and riding up the east coast...
Member Since: August 14, 2010 Posts: 10 Comments: 17492
Quoting 1403. washingtonian115:
Opps.I've been calling it Chantel all this time.lol.Local forecasters were messing up terribly with the name all day.
It could be worst and say Shantal, now that would really throw people off. It would definitely have some of the newcomers saying we're already on "S"?
Member Since: June 30, 2013 Posts: 12 Comments: 8706
1413. Relix
With the massive high above Chantal I think 1010mb is fine
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Quoting 1399. RufusBaker:
Local met in Tampa says Chantal is nothing to worry about and is not a threat to FL

Really? I'd switch the channel. Good Grief, it is at least 5 days away.
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Quoting 1397. jeffreeysweetypie:
50mph hitting east coast florida???? stop already


Never mind i had the start intensity wrong...hold up time to do a little tinkering
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Quoting 1400. TylerStanfield:
Looks like StormTrackerScott will be eating crow. :)
I knew what Chantal was going to be like, it was definitely not going to be 60-65 Mph TS when Recon went in, and this storm will, most likely, not become a hurricane tomorrow, or at all.



Someone already put a bet on this to be a Hurricane? By tomorrow or now?


I didn't even think I would wake up today to chantal at all.
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It is too early to make any real accurate predictions for what Chantal will be in the Bahamas. Things change.
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1313 - Pat
Thanks! Added to the 'Facts and Figures' section...
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Quoting 1387. will40:


there were plenty of W winds plus this


41.1 knots (~ 47.3 mph)
Tropical Storm


top wind speed has nothing to do with whether its closed or not.

all the winds thus far except for two barbs were out of the North.

They went through the center found the south may be open turned east and are now finally getting winds out of the south.

So its closed but barely there is a fairly substantial gap there that is just dead.

Could just be a large CDO trying to form but further passes will have to justify that.

Second of all this: oduct: Air Force Tropical RECCO Message (URNT11 KNHC)
Transmitted: 8th day of the month at 21:59Z
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: 07

Mandatory Data...

Observation Time: Monday, 21:27Z
Radar Capability: Yes
Aircraft Altitude: Below 10,000 meters
Coordinates: 11.7N 54.2W
Location: 378 miles (608 km) to the ESE (105°) from Bridgetown, Barbados.
Turbulence: None
Conditions Along Flight Route: In the clear
Pressure Altitude: 400 meters
Flight Level Wind: 5 knots (~ 5.8 mph) (Bearing was unavailable.)
- The above is a spot wind.
- Winds were obtained using doppler radar or inertial systems.
Flight Level Temperature: 20°C
Flight Level Dew Point: 19°C
Weather (within 30 nautical miles): Thunderstorm(s)
Mean Sea Level Pressure (MSLP): 1010 mb (extrapolated)

Optional Data...

Estimated Surface Wind Direction: Bearing was unavailable.
Estimated Surface Wind Speed: 5 knots (~ 5.8 mph)

Remarks Section - Remarks That Were Decoded...

Surface Wind Speed (likely by SFMR): 10 knots (~ 11.5mph)

Remarks Section - Additional Remarks...

TURN POINT AT CENTER AREA


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1405. ncstorm
this blog..sigh
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Well, looks like Chantal wants to throw us some curveballs and keep us guessing :p
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Quoting 1396. TropicalAnalystwx13:

Chantal. :)
Opps.I've been calling it Chantel all this time.lol.Local forecasters were messing up terribly with the name all day.
Member Since: August 14, 2010 Posts: 10 Comments: 17492
18z GFS is stronger with Chantal in the Bahamas, and slightly farther right.

Member Since: July 6, 2010 Posts: 113 Comments: 32558
Quoting 1386. jeffreeysweetypie:
im gonna take a picture of the 5pm models and by tommorow they will be completly different


You joined only yesterday and are so expert on everything. Amazing!
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Looks like StormTrackerScott will be eating crow. :)
I knew what Chantal was going to be like, it was definitely not going to be 60-65 Mph TS when Recon went in, and this storm will, most likely, not become a hurricane tomorrow, or at all.
Member Since: June 2, 2013 Posts: 8 Comments: 1383
Local met in Tampa says Chantal is nothing to worry about and is not a threat to FL
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As soon as the 07/08/2013 23:45 UTC imagery is uploaded, I will have my first daily update for July 2013 featuring TS Chantal.

GOES EAST Infrared Hurricane Sector Season 2013 - 06/01 thru 06/30

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Quoting 1380. washingtonian115:
The GFS spares Chantel the trouble of land interaction with the mountainous areas.

Chantal. :)
Member Since: July 6, 2010 Posts: 113 Comments: 32558
The convection has kind of an odd shape, does it appear ragged to you guys?



sorry did it again guys, this https thing makes me so frustrated, ahhh!
Member Since: June 30, 2013 Posts: 12 Comments: 8706
Quoting 1362. AllStar17:


Always be a struggling tropical storm?

Maybe struggling isn't the right word, but RI will probably not happen, and I doubt Chantal will become a hurricane.
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Quoting 1383. CybrTeddy:


I'm aware of that. Regardless, it is unwise to base a systems organization off of one single pass unless that pass was directly over the CoC. The CoC appears to be farther north based on satellite. We'll see.


Okay then lets see:

Link

Right around:

11.5 N

54.1 west


They flew through

11.45 N
54.2 west

so far.

So I will wait for another pass but I am relatively sure that was the center.
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Quoting 1384. AllStar17:


Interesting.
We'll see.Some models forecast a sharp rise in shear though once it get's in the Bahamas.It's all about watch and wait with this one.
Member Since: August 14, 2010 Posts: 10 Comments: 17492
Sorry folks had the starting intensity wrong at 60 mph
My predicition- Prior to Hispanola- 70 mph
After Hispanola- 40 mph
Strengthen to 45 mph in the Bahamas
but shear knocks it down to 40 mph.
Hit Florida at 40 mph
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For a while Andrew in 1992 had a central pressure of 1015 mb while it was a tropical storm.
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1389. Kyon5
They are on the eastern south side. They haven't even made a pass over the system and the COC. All we need is to wait for them to make a pass over the thunderstorms, where the center might be.
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1388. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Advisory #16
SEVERE TROPICAL STORM SOULIK (T1307)
6:00 AM JST July 9 2013
=============================

SUBJECT: Category Two Typhoon Named Cyclone Near Marianas Islands

At 21:00 PM UTC, Severe Tropical Storm Soulik (975 hPa) located at 19.7N 140.9E has 10 minute sustained winds of 60 knots with gusts of 85 knots. The cyclone is reported as moving west northwest at 11 knots.

Storm Force Winds
==================
40 NM from the center

Gale Force Winds
===============
260 NM from the center in north quadrant
240 NM from the center in south quadrant

Dvorak Intensity: T3.5

Forecast and Intensity
=======================
24 HRS: 20.9N 136.1E - 75 knots (CAT 3/Strong Typhoon) South Of Japan
45 HRS: 21.8N 131.8E - 80 knots (CAT 3/Strong Typhoon) South Of Japan
69 HRS: 23.2N 127.0E - 85 knots (CAT 4/Very Strong Typhoon) South Of Okinawa
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1387. will40
Quoting 1344. DataNerd:


Barely.


there were plenty of W winds plus this


41.1 knots (~ 47.3 mph)
Tropical Storm
Member Since: September 19, 2005 Posts: 2 Comments: 4266
Quoting 1356. Ameister12:

Either you're trolling, or you're completely oblivious to the fact that Chantal will always be a struggling tropical storm.
Quoting 1363. washingtonian115:
He's trolling.He also forecast 94L to be a cat 4 Audrey part 2 which never happened.

- and ! and Ignore User. I did the same yesterday.
Member Since: June 2, 2013 Posts: 8 Comments: 1383
Quoting 1380. washingtonian115:
The GFS spares Chantel the trouble of land interaction with the mountainous areas.


Interesting.
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Quoting 1378. DataNerd:



Ernesto did this and then Recon fixed the correct new center and we suddenly realized we had a decoupled dying system and the previous NHC advisory plus all other assumptions as to were the center was were wrong including my own.

Like I said, I will wait for a VDM on whatever pass that comes on to confirm where the center is but regardless of that, there is no wind thus far on the entire southern periphery of this system. That basically means its half dead.


I'm aware of that. Regardless, it is unwise to base a systems organization off of one single pass unless that pass was directly over the CoC. The CoC appears to be farther north based on satellite. We'll see.
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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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