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 1318. Grothar:


I believe a little further south.

I agree with this also

Taco :o)
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Looks to me what we saw was a vorticity rotating around Chantal, or being spit out judging by the location.
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Quoting 1304. BaltimoreBrian:
18Z was at 2 p.m. so the data can't have been put in yet.

The first model run with the complete data from this recon mission will be the 06Z.


Should make the 00Z easily, not that much data goes into the models.
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1330. Gearsts
But you can see the center here a bit north of 12n.
Member Since: August 2, 2010 Posts: 0 Comments: 1036
Quoting 1314. DataNerd:
Will wait for a vdm to confirm this but we could be back to 95L here.

Not at all, with uncontaminated SMFR readings at 35kts they will keep it at 40 mph or more depending what they find in the northern quadrants. The story right now is, storm relative shear.
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Chantel looks like it's going to be another head banger to forecast.
Hey friend :).
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1326. Levi32
The center is closer to 12N, 54W. Plane might find lower pressures there.
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I am thinking that Chantal is too far away, too weak of a system still, to feel the much further away, mostly lateral and over the Great Lakes trough that models seem to be picking up on to pull it more north and east of Florida.

A strong storm can only push hard up against 1016mb of high pressure, and certainly not go through it. A storm has to work around that level of high pressure, especially a weaker one like Chantal.
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Quoting 1317. TropicalAnalystwx13:

Why would we have 95L again? It has a closed circulation.


It may not be closed still. Recon moving south and not really finding any wind yet coming around.

Remains to be seen lets watch.
Member Since: June 24, 2012 Posts: 0 Comments: 1534
Quoting 1314. DataNerd:
So much for 55 mph upgrade! proof that rain loves to mess with windsat.


There is just nothing there:

Time: 21:37:30Z
Coordinates: 11.35N 54.5167W
Acft. Static Air Press: 966.7 mb (~ 28.55 inHg)
Acft. Geopotential Hgt: 395 meters (~ 1,296 feet)
Extrap. Sfc. Press: 1012.0 mb (~ 29.88 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 229 at 6 knots (From the SW at ~ 6.9 mph)
Air Temp: 20.8C (~ 69.4F)
Dew Pt: 20.8C (~ 69.4F)
Peak (10s) Flt. Lvl. Wind: 8 knots (~ 9.2 mph)
SFMR Peak (10s) Sfc. Wind: 38 knots (~ 43.7 mph)
SFMR Rain Rate: 16 mm/hr (~ 0.63 in/hr)


Will wait for a vdm to confirm this but we could be back to 95L here.


No, the circulation's still closed.
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Quoting 1290. jeffreeysweetypie:
looks like the 5pm numbers have chantal disapating in the bahamas


no they dont, still winds of 35mph
Member Since: March 10, 2010 Posts: 1 Comments: 7233
1320. ncstorm
With ground already saturated, Chantal could be significant flooding threat
Submitted by Christina Anthony on Mon, 07/08/2013 - 5:40pm.READ MORE:

News
Weather
Columbus County News
Flooding
Rain
Tropical Storm Chantal

TABOR CITY, NC (WWAY) -- After flooding rains in the Carolinas the last several weeks, we're finally getting a break. But now Tropical Storm Chantal looms in the Atlantic. So can our area handle any more rain?

Chantal formed in the Atlantic Sunday night. The storm's track brings it just east of Florida by the weekend.

Forescasters say Chantal could weaken over the mountains of Haiti, but any leftover tropical moisture is not good for the Carolinas.

"June was an incredibly wet month," National Weather Service meteorologist Josh Weiss said. "Across this area we had roughly 11 to 16 inches of rainfall, so any additional rainfall right now will lead to immediate flooding problems."

Like the flooding on NC 409 near Tabor City. The road is blocked due to high water after all the rain last week, and residents say it will need much longer than a week to dry out.

"It can handle up to three inches of rain, but not up to the 12 inches of rain we have had," one neighbor told us. "It won't handle that."

Forecasters say this scenario could be history repeating.

"Hurricane Floyd occurred just two weeks after Hurricane Dennis, which dropped six inches of rain and saturated the environment already," Weiss said.


It's a similar situation to the 11 inches plus that fell across southeastern North Carolina last week.

"Any more tropical moisture will just enhance flooding, and may cause even worse flooding than we would get with just a tropical system itself," Weiss said.
Member Since: August 19, 2006 Posts: 13 Comments: 13483
Nope that is definitely the center or near to it. Look at the temperature and dewpoint:



This system has degraded.
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1318. Grothar
Quoting 1288. BaltimoreBrian:


Do you think it more likely that Chantal will make landfall in FL north or south of that track?


I believe a little further south.
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Quoting 1314. DataNerd:
So much for 55 mph upgrade! proof that rain loves to mess with windsat.


There is just nothing there:

Time: 21:37:30Z
Coordinates: 11.35N 54.5167W
Acft. Static Air Press: 966.7 mb (~ 28.55 inHg)
Acft. Geopotential Hgt: 395 meters (~ 1,296 feet)
Extrap. Sfc. Press: 1012.0 mb (~ 29.88 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 229° at 6 knots (From the SW at ~ 6.9 mph)
Air Temp: 20.8°C (~ 69.4°F)
Dew Pt: 20.8°C (~ 69.4°F)
Peak (10s) Flt. Lvl. Wind: 8 knots (~ 9.2 mph)
SFMR Peak (10s) Sfc. Wind: 38 knots (~ 43.7 mph)
SFMR Rain Rate: 16 mm/hr (~ 0.63 in/hr)


Will wait for a vdm to confirm this but we could be back to 95L here.

Why would we have 95L again? It has a closed circulation.
Member Since: July 6, 2010 Posts: 109 Comments: 30297
If the MSLP is at 1011mb, Chantel goes down as a pretty good troll.
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Give it a few passes before making any conclusions.
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So much for 55 mph upgrade! proof that rain loves to mess with windsat.


There is just nothing there:

Time: 21:37:30Z
Coordinates: 11.35N 54.5167W
Acft. Static Air Press: 966.7 mb (~ 28.55 inHg)
Acft. Geopotential Hgt: 395 meters (~ 1,296 feet)
Extrap. Sfc. Press: 1012.0 mb (~ 29.88 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 229° at 6 knots (From the SW at ~ 6.9 mph)
Air Temp: 20.8°C (~ 69.4°F)
Dew Pt: 20.8°C (~ 69.4°F)
Peak (10s) Flt. Lvl. Wind: 8 knots (~ 9.2 mph)
SFMR Peak (10s) Sfc. Wind: 38 knots (~ 43.7 mph)
SFMR Rain Rate: 16 mm/hr (~ 0.63 in/hr)


Will wait for a vdm to confirm this but we could be back to 95L here.
Member Since: June 24, 2012 Posts: 0 Comments: 1534
1313. Patrap


Courtesy: NASA/Goddard Space Flight Center Scientific Visualization Studio

'Towers in the Tempest' is a narrated animation that explains recent scientific insights into how hurricanes intensify. This intensification can be caused by a phenomenon called a 'hot tower'. For the first time, research meteorologists have run complex simulations using a very fine temporal resolution of 3 minutes. Combining this simulation data with satellite observations enables detailed study of 'hot towers'. The science of 'hot towers' is described using: observed hurricane data from a satellite, descriptive illustrations, and volumetric visualizations of simulation data. The first section of the animation shows actual data from Hurricane Bonnie observed by NASA's Tropical Rainfall Measuring Mission (TRMM) spacecraft. Three dimensional precipitation radar data reveal a strong 'hot tower' in Hurricane Bonnie's internal structure. The second section uses illustrations to show the dynamics of a hurricane and the formation of 'hot towers'. 'Hot towers' are formed as air spirals inward towards the eye and is forced rapidly upwards, accelerating the movement of energy into high altitude clouds. The third section shows these processes using volumetric cloud, wind, and vorticity data from a supercomputer simulation of Hurricane Bonnie. Vertical wind speed data highlights a 'hot tower'. Arrows representing the wind field move rapidly up into the 'hot tower, boosting the energy and intensifying the hurricane. Combining satellite observations with super-computer simulations provides a powerful tool for studying Earth's complex systems.

Member Since: July 3, 2005 Posts: 415 Comments: 125736
Quoting 1307. Gearsts:
Not the center

There was an obvious windshift, and recon has made a turn to investigate the Southern side to see if it's closed off. Which it is. But the Central Pressure is 1010MB right now.
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There's your closed circulation, winds coming in from the west at the south side of the circulation. Pressures are high, nearly 1011mb.
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1309. bwi
Some decent westerly winds in SFMR, but with very light winds not much higher up at flight level.

21:37:30Z 11.350N 54.517W 966.7 mb
(~ 28.55 inHg) 395 meters
(~ 1,296 feet) 1012.0 mb
(~ 29.88 inHg) - From 229° at 6 knots
(From the SW at ~ 6.9 mph) 20.8°C
(~ 69.4°F) 20.8°C
(~ 69.4°F) 8 knots
(~ 9.2 mph) 38 knots
(~ 43.7 mph) 16 mm/hr
(~ 0.63 in/hr) 28.5 knots (~ 32.8 mph)
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Recon appears to have fixed the center (will wait for a VDM) significantly further west than expected, and out away from the convection suggesting westerly decoupling.

Not find much at all in the way of wind or pressure

(Near center):
Time: 21:35:00Z
Coordinates: 11.4333N 54.4167W
Acft. Static Air Press: 966.7 mb (~ 28.55 inHg)
Acft. Geopotential Hgt: 393 meters (~ 1,289 feet)
Extrap. Sfc. Press: 1011.2 mb (~ 29.86 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 267° at 3 knots (From the W at ~ 3.4 mph)
Air Temp: 22.2°C (~ 72.0°F)
Dew Pt: 20.4°C (~ 68.7°F)
Peak (10s) Flt. Lvl. Wind: 4 knots (~ 4.6 mph)
SFMR Peak (10s) Sfc. Wind: 19 knots (~ 21.8 mph)
SFMR Rain Rate: 0 mm/hr (~ 0 in/hr)
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1307. Gearsts
Quoting 1301. TylerStanfield:
Just entered Chantal's Center 1010 MB pressure... LOL
Not the center
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Interesting the models show this stronger entering the caribbean.
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GFS at 39HR look at PR!
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Quoting 1289. GTstormChaserCaleb:
I thought so, but I just wanted to make sure.
18Z was at 2 p.m. so the data can't have been put in yet.

The first model run with the complete data from this recon mission will be the 06Z.
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1302. Patrap
Last Viz frame today



Member Since: July 3, 2005 Posts: 415 Comments: 125736
Just entered Chantal's Center 1010 MB pressure... LOL
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Looks like this is gulf bound again.It looks like it's coming for gator22 now :).
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1299. Levi32
Plane is near the center but pressures are not below 1010mb yet.

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Going to wait on recon but the latest ambsub imagery says this is >55kt storm with a partial eyewall structure.

If there was more convection I'd be more convinced, I think this is just intense at the low levels right now.

Going to bank on 50-55mph upgrade.
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The ocean around the Bahamas and east of Florida (besides the Gulf Stream) doesn't have very high heat content yet, does it?
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1295. ncstorm
WPC Model Diagnostic Discussion

PREFERENCE: 12Z CMC/GFS/ECMWF
CONFIDENCE: AVERAGE

THE 12Z NAM IS SLOWER WITH THE UPPER LOW INITIALLY...THEN SEEMS TO
LOSE THE COHESIVENESS THAT THE REMAINDER OF THE GUIDANCE MEMBERS
APPEAR TO RETAINED. FOR THIS REASON...AND THE FACT THAT THE NAM
HAS BEEN SLOWING WITH TIME CONCERNING THIS FEATURE...IT CANNOT BE
RECOMMENDED WITH THE UPPER LOW. THE 12Z CMC/GFS/ECMWF CLUSTER WELL
WITH THEIR SOLUTIONS IN TERMS OF TIMING AND PLACEMENT...AND A
BLEND OF THESE MODELS IS PREFERRED.
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Quoting 1290. jeffreeysweetypie:
looks like the 5pm numbers have chantal disapating in the bahamas

Not true,please check nhc page again,a td is not dead storm.
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1293. Gearsts
Look at this:

12z

18z
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1292. Patrap
Member Since: July 3, 2005 Posts: 415 Comments: 125736
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Quoting 1271. BaltimoreBrian:


It did not.
I thought so, but I just wanted to make sure.
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Quoting 1277. Grothar:


Current GFS solution. I am close to this, but off by a few hundred miles. I believe it will enter the middle Windward Islands first and then begin more WNW going to the southern portion of Hispaniola. Then North into the Bahamas and then a sharp turn west into Florida



Do you think it more likely that Chantal will make landfall in FL north or south of that track?
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Quoting 1259. MiamiHurricanes09:
Nothing impressive whatsoever coming from Recon just yet.

Yep that is why the global models doesn't have anything and it has nothing to do with how strong it is.The issue is the circulation is extremely tiny,that is the issue I have come to understand.
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Shear is evident as the storm approaches Florida, but it's not very detrimental...not as much as the NHC says I think, anyways. Probably he reason most statistical models don't weaken the storm too much after Hispaniola.



Going to have to watch it after it crosses the state. Upper-level low backing away from the storm is a favorable shear environment with warm waters.
Member Since: July 6, 2010 Posts: 109 Comments: 30297
there you go there a oh pages of W too WSW and NNW winds
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1283. docrod
One heck of a train coming off Africa ....

Link
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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.