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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3483. GetReal
5:50 PM GMT on August 02, 2013
It appears that there may be a possible new COC forming under the convection near 26.3N and 79.3W.

The spin to the north not as strong as earlier.
Member Since: July 4, 2005 Posts: 204 Comments: 8873
3482. wunderkidcayman
3:45 PM GMT on July 09, 2013
Looks like next flight is late tonight
Member Since: June 13, 2009 Posts: 2 Comments: 11987
3481. hydrus
2:39 PM GMT on July 09, 2013
Quoting 3466. Grothar:
Doc will be coming on soon and knocking all our stuff off.

GFS models now have Chantal moving into South Florida.



We talked quite a bit about how this pattern would materialize..This may be a rough year for Florida and a lot of other folks.
Member Since: September 27, 2007 Posts: 1 Comments: 21189
3480. stoormfury
1:58 PM GMT on July 09, 2013
wind seems to be stronger in the NE quandrant of shantal. recon constantly finding winds above 60 mph. looks like it will be just short of a minimal hurricane in the next advisory
Member Since: August 22, 2006 Posts: 0 Comments: 2678
3479. gordydunnot
1:55 PM GMT on July 09, 2013
Quoting 3478. gordydunnot:
Well the ascat pass can show what it wants, but the wind right now in NE Dade is light and out of the N to NW what you would expect if a low was to the east. Probably just a local effect but interesting. Some cool air is being mixed down because the breeze is a little cool for this time of year. Surface winds have changed significantly last 12 hrs.
Member Since: August 18, 2008 Posts: 0 Comments: 3113
3478. gordydunnot
1:52 PM GMT on July 09, 2013
Well the ascat pass can show what it wants, but the wind right now in NE Dade is light and out of the N to NW what you would expect if a low was to the east. Probably just a local effect but interesting. Some cool air is being mixed down because the breeze is a little cool for this time of year. Surface winds have changed significantly last 12 hrs.
Member Since: August 18, 2008 Posts: 0 Comments: 3113
3477. Tropicsweatherpr
1:45 PM GMT on July 09, 2013
Quoting 3474. MAweatherboy1:

This is the storm of the year so far:



Agree, worldwide so far.
Member Since: April 29, 2009 Posts: 75 Comments: 14253
3476. Kyon5
1:42 PM GMT on July 09, 2013
Quoting 3471. Tazmanian:



recon found 1008mb


14.167N 60.850W 842.7 mb
(~ 24.88 inHg) 1,572 meters
(~ 5,157 feet) 1008.7 mb
(~ 29.79 inHg
Yeah, it looks like they're heading for the actual center. According to the Barbados radar, it is just south of Martinique.
Member Since: July 7, 2013 Posts: 0 Comments: 191
3475. WPBHurricane05
1:42 PM GMT on July 09, 2013
Quoting 3466. Grothar:
Doc will be coming on soon and knocking all our stuff off.

GFS models now have Chantal moving into South Florida.





You're a psychic.

Or you're actually Dr. Masters.......
Member Since: July 31, 2006 Posts: 56 Comments: 8112
3474. MAweatherboy1
1:41 PM GMT on July 09, 2013
Quoting 3467. HadesGodWyvern:
2013JUL09 130100
CI: 6.0
6.0 (Initial) 6.1 (Adjusted) 6.9 (Raw)
EYE
20.4N 137.8E

---

115 knots

This is the storm of the year so far:

Member Since: February 11, 2012 Posts: 83 Comments: 7779
3473. WunderAlertBot (Admin)
1:41 PM GMT on July 09, 2013
JeffMasters has created a new entry.
3472. FIUStormChaser
1:41 PM GMT on July 09, 2013
Quoting 3461. boltdwright:


Uh, that would be a negative dude.
not even a hint of a north wind on ASCAT near supposed COC.


Vorticity has grown stronger in the past 12 hours, and some aspects of a circulation are being noted and present on satelite, previously it occurred in the upper to mid levels but with shear decreasing, it does appear to be heading in the direction of working its way down to the surface. While it may not be present, it could occur as we have seen time and time before.
Member Since: May 1, 2013 Posts: 0 Comments: 761
3471. Tazmanian
1:41 PM GMT on July 09, 2013
Quoting 3460. WPBHurricane05:
I don't think the 1010 mb reading was the center. Looks to be north of Saint Lucia based on radar.



recon found 1008mb


14.167N 60.850W 842.7 mb
(~ 24.88 inHg) 1,572 meters
(~ 5,157 feet) 1008.7 mb
(~ 29.79 inHg
Member Since: May 21, 2006 Posts: 5091 Comments: 115081
3470. islander101010
1:40 PM GMT on July 09, 2013
neo going to have a field day after this rash of tropical activity is done.
Member Since: September 11, 2010 Posts: 1 Comments: 4582
3469. bajanmet
1:40 PM GMT on July 09, 2013
I give thanks that Barbados has been spared again, some people in this island needs to do the same. If a lot of people prepare for hurricane season at the beginning of the year instead of waiting until a system is on our doorstep,you would have less complaints. There are more systems in the Atlantic that look promising.The way life goes some people may be crying before the end of this week,be grateful.
Member Since: August 8, 2012 Posts: 0 Comments: 8
3468. MAweatherboy1
1:40 PM GMT on July 09, 2013
Recon has changed elevation to 5,000ft. I'm still wondering how the pressure could be 7mb higher on the second pass than the first. 1010mb seems more realistic to me, but everything looked good on the 1003mb reading so I don't know...
Member Since: February 11, 2012 Posts: 83 Comments: 7779
3467. HadesGodWyvern (Mod)
1:40 PM GMT on July 09, 2013
2013JUL09 130100
CI: 6.0
6.0 (Initial) 6.1 (Adjusted) 6.9 (Raw)
EYE
20.4N 137.8E

---

115 knots
Member Since: May 24, 2006 Posts: 50 Comments: 45301
3466. Grothar
1:40 PM GMT on July 09, 2013
Doc will be coming on soon and knocking all our stuff off.

GFS models now have Chantal moving into South Florida.



Member Since: July 17, 2009 Posts: 71 Comments: 26124
3465. BahaHurican
1:40 PM GMT on July 09, 2013
Gotta get on the road... Expect I will see a new blog by the time I get back on... later all! And stay safe down in the Antilles, my friends...
Member Since: October 25, 2005 Posts: 19 Comments: 22087
3464. HurricaneAndre
1:40 PM GMT on July 09, 2013
Quoting 3458. Hurricanes305:
Recon should be going in for a second pass.
no their done for this morning.
Member Since: June 11, 2013 Posts: 20 Comments: 2918
3463. weathermanwannabe
1:39 PM GMT on July 09, 2013
Looking at the floater wv loop (below) it is pretty obvious that she ingested a nice gulp of dry air. It will take a little bit of time to recover from that and rebuild the moisture near the coc.

Link
Member Since: August 8, 2006 Posts: 0 Comments: 9132
3462. FIUStormChaser
1:38 PM GMT on July 09, 2013
Quoting 3448. Matt74:
Wouldn't that throw everybody for a loop...


It would as anything that develops from the ULL will cross over into the gulf, this we will have one system in the gulf, and Chantal making landfall on Florida, plus a possible Dorian in the MDR.... In July.

Member Since: May 1, 2013 Posts: 0 Comments: 761
3461. boltdwright
1:38 PM GMT on July 09, 2013
Quoting 3442. FIUStormChaser:


A believe a surface circulation is forming with the ULL in the Bahamas.




Uh, that would be a negative dude.
not even a hint of a north wind on ASCAT near supposed COC.
Member Since: March 1, 2009 Posts: 5 Comments: 197
3460. WPBHurricane05
1:38 PM GMT on July 09, 2013
I don't think the 1010 mb reading was the center. Looks to be north of Saint Lucia based on radar.
Member Since: July 31, 2006 Posts: 56 Comments: 8112
3459. HadesGodWyvern (Mod)
1:38 PM GMT on July 09, 2013
Sea South Of Japan

At 21:00 PM JST, Typhoon Soulik (950 hPa) located at 20.3N 138.1E has 10 minute sustained winds of 80 knots with gusts of 115 knots. The cyclone is reported as moving west at 11 knots.

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

Gale Force Winds
===============
240 NM from the center

Dvorak Intensity: T5.0

Forecast and Intensity
=======================
24 HRS: 21.5N 133.3E - 95 knots (CAT 4/Very Strong Typhoon) South Of Japan
48 HRS: 22.8N 128.4E - 95 knots (CAT 4/Very Strong Typhoon) South Of Okinawa
72 HRS: 24.5N 123.5E - 95 knots (CAT 4/Very Strong Typhoon) near Yaeyama Island
Member Since: May 24, 2006 Posts: 50 Comments: 45301
3458. Hurricanes305
1:38 PM GMT on July 09, 2013
Recon should be going in for a second pass.
Member Since: May 25, 2012 Posts: 0 Comments: 2043
3457. washingtonian115
1:37 PM GMT on July 09, 2013
Quoting 3453. unknowncomic:
This is not a graphic we want to see heading toward land. Soulik now projected to max out as a CAT 4.

It is in my belief that,that is not a 95mph storm..
Member Since: August 14, 2010 Posts: 10 Comments: 16971
3456. 7544
1:36 PM GMT on July 09, 2013
Quoting 3442. FIUStormChaser:


A believe a surface circulation is forming with the ULL in the Bahamas.



yeap is it did good at dmax is it still moving west seems stuck there tia some people said it was dying last night surpise !
Member Since: May 6, 2007 Posts: 0 Comments: 6812
3455. Hurricanes305
1:36 PM GMT on July 09, 2013
Quoting 3449. boltdwright:


Ahh, I was referring to the dynamic models. I guess statistical models and simple dynamic models like the BAM go out at 8:00am because they don't take long to calculate.


Exactly with more info into the model they have shifted south as a result.
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3454. SLU
1:36 PM GMT on July 09, 2013
Martinique:

ENE @ 35mph with gusts to 47mph

Member Since: July 13, 2006 Posts: 12 Comments: 5126
3453. unknowncomic
1:35 PM GMT on July 09, 2013
This is not a graphic we want to see heading toward land. Soulik now projected to max out as a CAT 4.

Member Since: August 2, 2011 Posts: 0 Comments: 1919
3452. BahaHurican
1:35 PM GMT on July 09, 2013
Quoting 3437. ExumaMET:
Torrential rains and pretty serious thunder from the edge of the ULL here in Little Exuma. Wind has been out of the ENE for the last few days now its due north.
We saw a shift to the NE last night [those car flags are good for something, yes... lol]

Hope we don't get too soggy with this... not with Chantal on the way...
Member Since: October 25, 2005 Posts: 19 Comments: 22087
3451. washingaway
1:35 PM GMT on July 09, 2013
Member Since: July 14, 2006 Posts: 0 Comments: 1162
3450. Tazmanian
1:35 PM GMT on July 09, 2013
Quoting 3446. help4u:
If the pressure is 1010,it will soon be an open wave.




no it wont
Member Since: May 21, 2006 Posts: 5091 Comments: 115081
3449. boltdwright
1:34 PM GMT on July 09, 2013
Quoting 3427. FIUStormChaser:




Ahh, I was referring to the dynamic models. I guess statistical models and simple dynamic models like the BAM go out at 8:00am because they don't take long to calculate.
Member Since: March 1, 2009 Posts: 5 Comments: 197
3448. Matt74
1:34 PM GMT on July 09, 2013
Quoting 3442. FIUStormChaser:


A believe a surface circulation is forming with the ULL in the Bahamas.
Wouldn't that throw everybody for a loop...
Member Since: June 21, 2011 Posts: 0 Comments: 329
3447. 62901IL
1:34 PM GMT on July 09, 2013
Quoting 3445. RTLSNK:


"Violent gusts in Martinique Chantal is there!"

Thanks for translating!
Member Since: June 14, 2013 Posts: 2 Comments: 1605
3446. help4u
1:34 PM GMT on July 09, 2013
If the pressure is 1010,it will soon be an open wave.
Member Since: September 18, 2006 Posts: 0 Comments: 1276
3445. RTLSNK
1:33 PM GMT on July 09, 2013
Quoting 3429. Bubu77:
Rafales violentes en Martinique Chantal est bien là !!


"Violent gusts in Martinique Chantal is there!"
Member Since: September 3, 2008 Posts: 0 Comments: 20940
3444. 62901IL
1:33 PM GMT on July 09, 2013
Quoting 3443. weathermanwannabe:
Next stop for Chantal after clearing the Antilles this morning is Hispanola in around 24 hours. Have to see how she does over this period and whether she is able to reach high-grade TS status.

OK. Let's see...
Member Since: June 14, 2013 Posts: 2 Comments: 1605
3443. weathermanwannabe
1:32 PM GMT on July 09, 2013
Next stop for Chantal after clearing the Antilles this morning is Hispanola in around 24 hours. Have to see how she does over this period and whether she is able to reach high-grade TS status.
Member Since: August 8, 2006 Posts: 0 Comments: 9132
3442. FIUStormChaser
1:32 PM GMT on July 09, 2013
Quoting 3437. ExumaMET:
Torrential rains and pretty serious thunder from the edge of the ULL here in Little Exuma. Wind has been out of the ENE for the last few days now its due north.


A believe a surface circulation is forming with the ULL in the Bahamas.

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3441. Tazmanian
1:32 PM GMT on July 09, 2013
is that a eye on the rader that am seeing on the weather CH?
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3440. Levi32
1:31 PM GMT on July 09, 2013
I have no reasonable explanation for why the pressure was 7mb lower on the previous pass. The plane did ascend during the last penetration, which may have distorted the values. We'll see on the next fly-through in a few minutes.

It is worth noting that the lesser Antilles aren't reporting anything below 1012mb.

Member Since: November 24, 2005 Posts: 635 Comments: 26647
3439. CybrTeddy
1:31 PM GMT on July 09, 2013
Quoting 3432. WPBHurricane05:
Second recon pass has a 1010 mb pressure. What the??


Didn't get the same fix as they did last pass, pressures are around 1003mb, winds up to 60-66mph.
Member Since: July 8, 2005 Posts: 259 Comments: 24017
3438. BahaHurican
1:30 PM GMT on July 09, 2013
Quoting 3419. biff4ugo:
I am falling victim to the "Bad Monkey" syndrome, where Tropical Systems with wimpy names get ignored and then go on to shred the Bahamas.(and miss Miami)
Chantal? Really?

the blob over the Bahamas now has my attention.
Obviously you don't know any Chantals, Shantells or pple of similar names... some of the feistiest, most contrary females you have ever met... in the most lady-like possible way, of course...
Member Since: October 25, 2005 Posts: 19 Comments: 22087
3437. ExumaMET
1:30 PM GMT on July 09, 2013
Torrential rains and pretty serious thunder from the edge of the ULL here in Little Exuma. Wind has been out of the ENE for the last few days now its due north.
Member Since: November 1, 2007 Posts: 0 Comments: 47
3436. HurricaneAndre
1:29 PM GMT on July 09, 2013
Quoting 3432. WPBHurricane05:
Second recon pass has a 1010 mb pressure. What the??
I'dk.
Member Since: June 11, 2013 Posts: 20 Comments: 2918
3435. Tazmanian
1:29 PM GMT on July 09, 2013
Quoting 3431. congaline:

Thanks! Can't wait to see what they find.




you may be a little too late i think there going home



but here what they found this AM

000
URNT12 KNHC 091308
VORTEX DATA MESSAGE AL032013
A. 09/12:57:20Z
B. 13 deg 56 min N
060 deg 42 min W
C. NA
D. 55 kt
E. 062 deg 42 nm
F. 118 deg 70 kt
G. 060 deg 47 nm
H. EXTRAP 1010 mb
I. 20 C / 364 m
J. 23 C / 366 m
K. 23 C / NA
L. NA
M. NA
N. 1345 / 1
O. 0.02 / 2 nm
P. AF302 0203A CHANTAL OB 06
MAX FL WIND 70 KT 060/47 12:41:00Z
SLP EXTRAP FROM BELOW 1500 FT
Member Since: May 21, 2006 Posts: 5091 Comments: 115081
3434. 7544
1:28 PM GMT on July 09, 2013
Quoting 3421. HurricaneAndre:
I wonder what the NHC will say at their next advisory.


anyone see a cone shift at 11 am ?
Member Since: May 6, 2007 Posts: 0 Comments: 6812
3433. Hurricanes305
1:28 PM GMT on July 09, 2013
Quoting 3427. FIUStormChaser:




There we go the 8am models is just updated on the WU and now the GFS taking it over South Florida along with some others.
Member Since: May 25, 2012 Posts: 0 Comments: 2043

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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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