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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3233. pottery
Quoting pcola57:
Here's Water Vapor pot..
My SAL isn't updating.. :(


Thanks.
Chanty still can't make an appreciable dent in that dry stuff....
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3232. Grothar
Quoting 3223. CybrTeddy:
Looks like recon pegged the CoC, pressures are around 1003mb or so.


Teddy, think we will busy the next couple of weeks.

Member Since: July 17, 2009 Posts: 69 Comments: 25362
Quoting 3223. CybrTeddy:
Looks like recon pegged the CoC, pressures are around 1003mb or so.


Chantal has been very difficult to forecast in terms of intensity. I may get here more than what is forecast.
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good morning everyone.i see chantal is shocking all of us. 0z and 6z GFS both develop dorian again. if it can avoid hispanola, dorian will most likely become a hurricane given the favorable environment shown on the GFS
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3229. Relix
Quoting 3222. allancalderini:
If the NHC upgrade the winds to 60 or 65 in the next advisory she might very well reach hurricane intensity before landfall in DR.


I am not sure it will make landfall in DR. It looks to be aiming at that spot in Mona Passage, maybe clip the east tip of DR, unless the high does flatten it and forces it west.
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Quoting 3222. allancalderini:
If the NHC upgrade the winds to 60 or 65 in the next advisory she might very well reach hurricane intensity before landfall in DR.

I still can't see it becoming a hurricane with its current structure, but assuming those winds are correct and the 11AM intensity is 60 or 65mph, a hurricane watch may be required for some areas.
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Quoting 3212. Waltanater:
Maybe he rents and hates his landlord.


Odds are he's not yet old enough to rent or own and doesn't have to pay for things. He/She will learn in time. Weather watching can be fun, living through it isn't always fun.
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ime: 12:04:00Z
Coordinates: 13.8667N 60.3W
Acft. Static Air Press: 969.5 mb (~ 28.63 inHg)
Acft. Geopotential Hgt: 300 meters (~ 984 feet)
Extrap. Sfc. Press: 1003.2 mb (~ 29.62 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 163° at 1 knots (From the SSE at ~ 1.1 mph)
Air Temp: 22.4°C (~ 72.3°F)
Dew Pt: 21.7°C (~ 71.1°F)
Peak (10s) Flt. Lvl. Wind: 5 knots (~ 5.8 mph)
SFMR Peak (10s) Sfc. Wind: 19 knots (~ 21.8 mph)
SFMR Rain Rate: 1 mm/hr (~ 0.04 in/hr)
(*) Denotes suspect data

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Regardless of convective orgnization this storm continues to produce a lot of strong winds could be 60mph at 11pm. If it can slow down today we may see a good day for strengthen. Storm continues to defy odds wonder if this is indicative for the rest of the season. Stronger less organized storms.
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Quoting 3206. weathermanwannabe:
As noted by MLC, here is the latest CIMMs chart; the ULL over the Bahamas is working its way down to the surface.......Probably not enough time to develop but we have been watching for this possibility over the past several days.

Link

This will be one of the main influences, as it moves out of the way and breaks downs the ridge, on the trajectory of Chantel, or her remnants, after crossing the Greater Antilles. If the ridge builds back in quickly, Chantel could be forced back towards Florida. If not, Chantel could move a bit further North.

It boils down to how well Chantel survives the land interaction with Hispanola/Cuba and the timing of the ridging. We will not know the answer to this until the end of the week.


This sort of factual, realistic approach will not be tolerated here!!!!!
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Looks like recon pegged the CoC, pressures are around 1003mb or so.
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Quoting 3219. MAweatherboy1:
Wow, recon found flight level winds near hurricane force, 65mph or so at the surface. Chantal fools us again.
Quoting 3219. MAweatherboy1:
Wow, recon found flight level winds near hurricane force, 65mph or so at the surface. Chantal fools us again.
If the NHC upgrade the winds to 60 or 65 in the next advisory she might very well reach hurricane intensity before landfall in DR.
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3220. pcola57
Here's Water Vapor pot..
My SAL isn't updating.. :(

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Wow, recon found flight level winds near hurricane force, 65mph or so at the surface. Chantal fools us again.
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3218. hydrus
Quoting 3202. Waltanater:
That's because she is going really fast and has not slowed down.
And this.
Member Since: September 27, 2007 Posts: 1 Comments: 20505
Quoting 3192. Grothar:


I don't want to be picky, but do you have any decaf?


But of course, let me put the pot out!
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3216. pottery
Quoting bajanmet:
Good morning from the island of Barbados,what happen to the wind and rain? Hardly had any rain and no wind at all in Speightstown.

Mornin' Bage ! Trini here.

Looking at the radar I thought you got plenty.
Better luck next time :):))
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Quoting 3155. moonlightcowboy:
Good morning, weathergeeks! :)

No coffee yet, but a couple of quick obs.

1. Chantal has slowed, obviously butting up against the 1016mb of high pressure north of the system.
2. Motion likely to have more of a westerly component now that it has hit the strong high.
3. Slowed system has allowed better organization, layers now more symmetrical and vertically stacked. No maturity to the 200mb layers so still a burgeoning system.
4. ULL over the Bahamas has gotten a much better surface reflection at the 850mb layer.
5. Slowed system seems to be firing more convection, but is also experiencing the beginning of some upper level shear blowing tops from the CDO.

Back later when both eyes are open! ;)
Hey MLC you think I has already slow down it looks to be going around 20-25mph. If it get get under 20mph that would be substantial for development
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3214. Relix
Quoting 3205. Kyon5:

Oh, sorry about that, lol.


Don't worry, we are here to learn as we go :)
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Quoting 3184. Neapolitan:
Yes, fun. Power outages; beach erosion; property damage; escalated insurance premiums; inflated food and fuel prices; etc. Yep! A real barrel of laughs!


At least in my neck of the woods, the only storm to ever cause an outage in my life was Charley. We've never had property damages despite 3 storms of TS force to pass over us in 2 years. WE don't buy food, we grow it so we don't worry about the prices and if Chantal was a Cat. 4..no but a TS, sure.
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Quoting 3184. Neapolitan:
Yes, fun. Power outages; beach erosion; property damage; escalated insurance premiums; inflated food and fuel prices; etc. Yep! A real barrel of laughs!
Maybe he rents and hates his landlord.
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3211. hydrus
Looks like August.
Member Since: September 27, 2007 Posts: 1 Comments: 20505
3210. FOREX
Quoting 3198. HurricaneAndre:
What do you think the winds will be at the next advisory.
A 60
B 65
C 70
D same


d
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Good morning from the island of Barbados,what happen to the wind and rain? Hardly had any rain and no wind at all in Speightstown.
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Could it be Chantal is stacked and ready to strengthen? Still, she is moving fast.
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3207. zampaz
Quoting 3201. Grothar:


Specificity. Which Blob? 1,2, or 3?

Well, I was speaking of Bahamas...but any blob friend of yours is a friend of mine!
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As noted by MLC, here is the latest CIMMs chart; the ULL over the Bahamas is working its way down to the surface.......Probably not enough time to develop but we have been watching for this possibility over the past several days.

Link

This will be one of the main influences, as it moves out of the way and breaks downs the ridge, on the trajectory of Chantal, or her remnants, after crossing the Greater Antilles. If the ridge builds back in quickly, Chantal could be forced back towards Florida. If not, Chantal could move a bit further North.

It boils down to how well Chantal survives the land interaction with Hispanola/Cuba and the timing of the ridging. We will not know the answer to this until the end of the week.
Member Since: August 8, 2006 Posts: 0 Comments: 8785
3205. Kyon5
Quoting 3200. Relix:
Those are flight winds, you must look at SFC Winds

Oh, sorry about that, lol.
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Quoting 3198. HurricaneAndre:
What do you think the winds will be at the next advisory.
A 60
B 65
C 70
D same
A surface winds are 60
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3203. pottery
Anyone have a WV loop ?
Mine is not working right now. SAL images down too.
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Quoting 3180. hydrus:
If Chantel remains disorganized, she get as far west as Eastern Cuba..Which would change things considerably.
That's because she is going really fast and has not slowed down.
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3201. Grothar
Quoting 3194. zampaz:

What's today's Blobcon Gro?


Specificity. Which Blob? 1,2, or 3?
Member Since: July 17, 2009 Posts: 69 Comments: 25362
3200. Relix
Quoting 3181. Kyon5:
Recon just measured winds over 70mph.
Time: 11:48:30Z
Coordinates: 14.3833N 60.4167W
Acft. Static Air Press: 864.9 mb (~ 25.54 inHg)
Acft. Geopotential Hgt: 1,358 meters (~ 4,455 feet)
Extrap. Sfc. Press: 1011.6 mb (~ 29.87 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 80° at 64 knots (From the E at ~ 73.6 mph)
Air Temp: 16.6°C (~ 61.9°F)
Dew Pt: 14.4°C (~ 57.9°F)
Peak (10s) Flt. Lvl. Wind: 67 knots (~ 77.0 mph)
SFMR Peak (10s) Sfc. Wind: 47 knots (~ 54.0 mph)
SFMR Rain Rate: 1 mm/hr (~ 0.04 in/hr)
(*) Denotes suspect data
Those are flight winds, you must look at SFC Winds
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Seems Chantal strengthened nicely overnight. Some hurricane force flight-level winds and 55-60mph winds at the surface. Pressure is much more typical to that of a Tropical Storm now.
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What do you think the winds will be at the next advisory.
A 60
B 65
C 70
D same
Member Since: June 11, 2013 Posts: 19 Comments: 2517
3197. Grothar
Quoting 3151. Waltanater:
Yeah, you don't sound too sure about that!



I'm 90 - 10 on it. But I'm not going to tell you which way.
Member Since: July 17, 2009 Posts: 69 Comments: 25362
storms that are already developed flourish over the warm waters of the leeward and windward islands. this is not that odd to see further development
Member Since: September 11, 2010 Posts: 1 Comments: 4331
3195. Kyon5
The HH measured 1002 millibars.

Extrap. Sfc. Press: 1002.3 mb (~ 29.60 inHg)
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3194. zampaz
Quoting 3187. Grothar:

What's today's Blobcon Gro?
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Time: 11:59:00Z
Coordinates: 13.9667N 60.2333W
Acft. Static Air Press: 969.9 mb (~ 28.64 inHg)
Acft. Geopotential Hgt: 294 meters (~ 965 feet)
Extrap. Sfc. Press: 1002.8 mb (~ 29.61 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 167° at 8 knots (From the SSE at ~ 9.2 mph)
Air Temp: 23.3°C (~ 73.9°F)
Dew Pt: 22.5°C (~ 72.5°F)
Peak (10s) Flt. Lvl. Wind: 16 knots (~ 18.4 mph)
SFMR Peak (10s) Sfc. Wind: 20 knots (~ 23.0 mph)
SFMR Rain Rate: 2 mm/hr (~ 0.08 in/hr)
(*) Denotes suspect data
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3192. Grothar
Quoting 3177. aislinnpaps:
Good morning, Good afternoon, Good evening, everyone.
A very foggy 75 degrees this morning with a 30% chance of rain and a high expected of 93.

Breakfast is on the sideboard: Omelets made from egg whites, with choice of cheeses, mushrooms, peppers and salsa, whole wheat and regular English muffins with cream cheese and jelly or lox, whole wheat or regular pancakes with fresh fruit or syrup, yogurt, fresh fruit, orange juice and fresh made coffee.


I don't want to be picky, but do you have any decaf?
Member Since: July 17, 2009 Posts: 69 Comments: 25362
3191. LargoFl
Quoting 3184. Neapolitan:
Yes, fun. Power outages; beach erosion; property damage; escalated insurance premiums; inflated food and fuel prices; etc. Yep! A real barrel of laughs!
I am with you on that..we do NOT need this storm anywhere near us right now,ground is saturated,already flooding in some parts even before the storm..........
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Quoting 3174. HurricaneAndre:
Chantal looks to be strengthening against all odds.
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Peak (10s) Flt. Lvl. Wind: 59 knots (~ 67.8 mph)
SFMR Peak (10s) Sfc. Wind: 51 knots (~ 58.6 mph)
SFMR Rain Rate: 2 mm/hr (~ 0.08 in/hr)
(*) Denotes suspect data
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3188. pottery
Good Morning all.

It's a veritable Blob-Fest out in the Atlantic right now.

Showers here overnight, clearing out a little this morning.
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3187. Grothar
Member Since: July 17, 2009 Posts: 69 Comments: 25362
3186. LargoFl
Doc should be on soon to make a new blog, it will be interesting to see His take on this system and where HE thinks its going
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3185. 900MB
Wondering about the hispanola effect and the chance it is overstated in the case of Chantal. If it races last at 26mph wouldn't there be less detrimental effect? Thoughts?
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Quoting 3179. JrWeathermanFL:
Good Morning all! I wouldn't mind if Chantal hit FL. It's about time we get a non-june storm to hit us. The last was Bonne in 2010. Not that we need the rain, but still fun nevertheless to be in a TS.
Yes, fun. Power outages; beach erosion; property damage; escalated insurance premiums; inflated food and fuel prices; etc. Yep! A real barrel of laughs!
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As to Chantal, the forward speed is preventing further organization so we will have to see what happens over the next 48. Post-Haiti may well be the best chance she has to reach high-grade tropical storm status.

Can't help but notice on the big-pic loops that that the three areas of interest, in order from East to West; the African wave, Chantal, and the ULL in the Bahamas are "moving around" the current ridge in the the Central Atlantic...........Follow the ULL and Chantel is headed in that general direction.
Member Since: August 8, 2006 Posts: 0 Comments: 8785

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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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