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Chantal Strengthening as it Plows Through the Lesser Antilles Islands

By: Dr. Jeff Masters, 1:41 PM GMT on July 09, 2013

Tropical Storm Chantal is strengthening as it speeds west-northwestwards at 26 mph through the Lesser Antilles Islands. At 6:22 am AST, St. Lucia recorded a wind gust of 54 mph. Sustained winds of 38 mph, gusting to 52 mph, were observed at Martinique at 10 am AST. An Air Force hurricane hunter aircraft is in the storm, and measured top winds at their 1,000' flight level of 80 mph at 8:41 am AST, about 20 miles north of the center. Top winds seen by the aircraft's SFMR instrument were about 60 mph, and it is likely that NHC will bump up Chantal's top winds to at least 60 mph in their 11 am advisory. Barbados Radar shows a large area of heavy rain that has organized moderately well into low-level spiral bands affecting much of the central Lesser Antilles Islands. Chantal is not very impressive on satellite loops, though, with only a modest amount of heavy thunderstorms that are not well-organized. Only a small amount of upper-level outflow is visible. Chantal is fighting dry air associated with the Saharan Air Layer (SAL), as seen on water vapor satellite loops. Moderate wind shear of 15 - 20 knots is driving dry air into the storm. Ocean temperatures are fairly warm, at 28°C.


Figure 1. Latest satellite image of Chantal.


Figure 2. Barbados weather radar image of Chantal taken at 9:14 am AST on Tuesday, July 9, 2013. Chantal's center was located between St. Lucia and Martinique. Image credit: Barbados Met Service.

Forecast for Chantal
Chantal will likely continue to intensify before hitting Hispaniola on Wednesday afternoon. In their 5 am EDT wind probability forecast, NHC gave Chantal a 23% chance of becoming a hurricane 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. Interaction with the high mountains of Hispaniola and high wind shear may be able to destroy Chantal by Thursday. The 8 am EDT Tuesday wind shear forecast from the SHIPS model calls for shear to rise to the high range, 20 - 30 knots, as the storm approaches and crosses Hispaniola on Wednesday and Thursday. On Friday and Saturday, when Chantal is expected to be in the Bahamas, lower moderate wind shear of 15 - 20 knots should allow for re-intensification of the storm--if it survives interaction with the high mountains of Hispaniola, Puerto Rico, and Eastern Cuba. The latest 06Z run of the GFS model dissipates Chantal as it crosses Hispaniola, though the 00Z run done 6 hours earlier had the storm surviving. 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.

Chantal's fast west-northwest forward speed of 26 mph will slow to 20 mph by Wednesday afternoon and then 10 mph by Thursday afternoon, as the storm "feels" the presence of a trough of low pressure over the U.S. East Coast. This trough will steer Chantal to the northwest and then north-northwest across Hispaniola and into the Bahamas. The trough of low pressure pulling Chantal northwards is expected to lift out the the northeast over the weekend, leaving Chantal behind off the coast of Florida. High pressure will likely build in, potentially forcing an intensifying Chantal westwards into the Florida or Southeast U.S. coast, with a possible Monday landfall.

Jeff Masters

Hurricane

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

Quoting 493. Skyepony:
Same ASCAT pass but in coastal winds mode..


Maybe working to surface I am seeing that too.
THIS HAZARDOUS WEATHER OUTLOOK IS FOR WEST CENTRAL AND SOUTHWEST
FLORIDA.

.DAY ONE...TODAY AND TONIGHT.

...THUNDERSTORM IMPACT...
SCATTERED MAINLY AFTERNOON AND EVENING THUNDERSTORMS ARE EXPECTED
AGAIN TODAY. THE STRONGEST STORMS WILL BE CAPABLE OF PRODUCING HEAVY
RAINFALL...GUSTY WINDS...AND FREQUENT LIGHTNING.

...RIVER FLOOD IMPACT...
A COUPLE OF AREA RIVERS REMAIN ABOVE FLOOD STAGE. ANY ADDITIONAL
RAINFALL COULD CAUSE A FURTHER INCREASE IN WATER LEVELS AND MORE
PRONOUNCED FLOODING ALONG THE RIVERS.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

...THUNDERSTORM IMPACT...
SCATTERED MAINLY AFTERNOON AND EVENING THUNDERSTORMS ARE EXPECTED
EACH DAY. THE STRONGEST STORMS WILL BE CAPABLE OF PRODUCING HEAVY
RAINFALL...GUSTY WINDS...AND FREQUENT LIGHTNING.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS SHOULD MONITOR THE WEATHER AND SELF ACTIVATE IF NEEDED.

$$

JELSEMA
Quoting 463. weatherh98:
She's entering the east Caribbean... I guess you could say she has one foot in the grave


John Hope rule does not apply.

He used to say, "If it hasn't developed before it reaches the eastern Caribbean it usually won't until it reaches the western Caribbean."

This storm was named a day and a half ago.


Chantal is entering 29C water. In about 3 hours it's entire convection in the NE quadrant will be over 29C water, so I would expect strengthening since everything else is staying about the same.

Key West
NEXRAD Radar

Base Reflectivity 0.50° Elevation
Range 248 NMI

Per the most recent WV loop frames, there might be some slight repositioning of the coc going on with Chantal. That convection that was previously over Montinique is trying to wrap around the NW quadrant into the coc as the dry air is being mixed out of the back-end of the storm:

Link

Either that, or, the convection is outrunning the coc and the storm is starting to fall apart for the moment.

Take your pick.
Quoting 486. moonlightcowboy:


GTCC, starting to make sense now?
Good call, but do you think part of that has to do with land interaction causing Chantal to stay weak? I was expecting this strength to hold on up until landfall which was why I was basing my reasoning on the northward turn. I also was looking at the ULL over Bahamas carving out a weakness in the ridge. I think the high is winning :D
Whew, glad I wasn't alone with the NCEP page issues, lol. But if the 12Z has shifted left for it's Hispaniola track, that's the first time in 3 days it's stopped shifting eastward. Not too surprising there would be adjustments given the difficulty pinpointing the track of a system flying so fast, even at 24-36 hrs out...

Got to fly myself, good day all.
Quoting 506. weathermanwannabe:
Per the most recent WV loop frames, there might be some slight repositioning of the coc going on with Chantal. That convection that was previously over Montinique is trying to wrap around the NW quadrant into the coc as the dry air is being mixed out of the back-end of the storm:

Link

Either that, or, the convection is outrunning the coc and the storm is starting to fall apart for the moment.

Take your pick.


When looking at weaker storms like this, it's almost impossible to determine a center location using water vapor.
So recon found the storm to be still closed and it's even stronger wind wise?
Quoting 494. moonlightcowboy:


LARGER SFC MAP IMAGE


Look closely at the 1016mb isobar.

(Again, from yesterday):

My experience has always been that no storm, even the stronger ones, can push through 1016mb of high pressure. They can bend it, push up against it, but ultimately have to find a way around it. And, I think this will be the case with Chantal along about the vicinity of St Lucia or possibly Guadaloupe (in that area), and that's when it will turn more west around the ridge looking for an escape route poleward.


Will that escape route run the edge of the 1016mb line?
Quoting 499. JDSmith:
Can anyone explain why frame rates are so poor on the East Atlantic/west coast of Africa satellite loop? That is in comparison to all the other loops that are available in the atlantic....


It's because the east Atlantic imagery comes from a different satellite. The East Atlantic imagery comes from METEOSAT satellite & The rest of the Atlantic imagery comes from GOES-east (which is currently GOES13) satellite.
Western Atlantic - Visible Loop

click image for Loop

click Loop to ZOOM

Area in the Bahamas looks interesting, but that's about it. Looking at surface flow, low level clouds are still moving mostly east to west underneath it. The ULL has made a little progress towards the surface, but still not even close. Should run out of time as it will phase with a passing upper trough in the next couple of days.

Wow! Likely now Super Typhoon Soulik

Quoting 505. GetReal:


Wow. Every scenario shows a left hook, regardless of track or timing.
JeffMasters has created a new entry.
Quoting opal92nwf:
I'm not trying to be nit-picky on exactly where Chantal is going to go. For all we know it could skirt Hispaniola and be relatively unhindered. A lot of the models have been downplaying it from the beginning, but Chantal just keeps proving them wrong and being more robust and resilient. I am watching this situation and mentally preparing for a hurricane situation on the Florida coast.

So it just makes no sense to say THIS FAR OUT, that Chantal will be insignificant or be no problem for Florida at all. It's so far away, that what the current forecast is in the long term will almost definitely turn out to be different.

Most of us know about the MJO (Madden–Julian oscillation) cycle. I have come to the conclusion, after many yers on this blog, that we have the JMBO (Jeff Master Blog oscillation) cycle. Living in the South and all, I pronounce it like "Jimbo". The JMBO is a very sensitive cycle that reacts in nanoseconds to every new model, HH flight, satellite picture, JB twitter post, or generalized anxiety. The cycle normally goes from "We're all gonna die!" to "This isn't going to be that bad" to "The whole thing is going to fall apart with X hours". The cycle repeats itself about every eight hours. The cycle seems to have speeded up some with Chantal. I'm thinking of writing a research paper on this phenomena to see if I can't snag me some kind of Nobel prize. :-)
Quoting 500. Patrap:




ACK!!!!


Come on. You and I both keep AM radios and packs of batteries in our "Hurricane" - kits. I even have a hand crank AM/FM with a cell-phone charger on it. What did the scouts say; 'be prepared'.....?
Quoting 510. Bluestorm5:
So recon found the storm to be still closed and it's even stronger wind wise?


That is an affirmative.
Statement as of 10:13 AM EDT on July 09, 2013



The Flood Warning continues for
the Myakka River at Myakka River State Park
* until further notice
* at 09 am Tuesday the stage was 7.6 feet
* flood stage is 7.0 feet
* the river will continue to fall to a stage of 7.5 feet by .
* Impact... at 8.5 feet... most of Myakka State Park is closed.
* Impact... at 8.0 feet... the Main Park Road floods.
* Impact... at 7.0 feet... trails... picnic areas... and parking lots flood.
* Flood history... this crest compares to a previous crest of 8.1 feet on Jun 30
2012.



Fld observed forecast 8am
location stg stg day time Wed Thu Fri Sat sun

Myakka
Myakka rive 7 7.6 Tue 09 am 7.5 7.4 7.3 7.2 7.1

Quoting 490. tj175:


They are the worst one of all. Leave it up to WSVN channel 7 to scare the hell out of South Floridians


Totally bypassing that station for the next week!
Quoting 509. MississippiWx:


When looking at weaker storms like this, it's almost impossible to determine a center location using water vapor.


Yup.......The storm is moving so fast past the islands that it is hard to discern the exact location at the moment relative to the loops with the convective burst clouding what is going on underneath.
Quoting 510. Bluestorm5:
So recon found the storm to be still closed and it's even stronger wind wise?


The circulation is closed, but there is only like one quadrant of an eye-wall-like feature, so it has a lot of work to do to become a hurricane. The strongest wind was in 1 cell in the band near the CoC in the NE quadrant.
12z and 00z runs are typically the most reliable, as they ingest data from actual soundings from weather balloons. The 06z and 18z are usually less accurate. 
Quoting washingtonian115:
I suspect comments like these today "it's the end of the line" only fr the other runs of the GFS to pick her back up.12z is one of the most unreliable runs any way.

The recon is still out there.
propane full car tank full ecen fl.
Pressure continuing to drop. Pressure now at 1006 MB it has gradually came down for the past 2 centerfixes.
Steady light rain in Palm Beach gardens FL
The GFS now has two cut off lows. the second of which wraps in whatever Chantal becomes, and brings it ashore.
New Blog again!!!!!!!!!!!!!!!!!!
Hey Cowboy!

You know I am prepared! Good to see you!
Quoting 480. moonlightcowboy:


BFox! :) That is some good-looking avatar you got there! Hope you're well, and prepared for this season. Looks like a doozie.
Quoting 242. JRRP:
ALERTA DE HURACAN PARA EL SUR DE REP.DOM
ENGLISH please!
How do you add the hurricane hunters overlay to Google Earth? Thank you in advance.
537. vis0

Quoting 311. VAstorms:
Why does everyone feel the need to re-post bulletins? Once is plenty.

i agree, yet an idea...

WXU should try (not now, when weather is quite...R) to program an ICON for bulletins.

If member "x" posts a bulletin, then i try to post
the same bulletin the icon appears showing
how many have posted that bulletin * its original posted link.

Just as when one "FAVs" a comment you see the members that
have favored that comment on the fav icon drop around
menu.
The criteria is that a program checks word for word
plus bulletin time stamp.
If it is a repeat that user gets a thank you, but its already up + bulletin icon. The drop around menu showing the others might
be too much for servers so that's optional.

The thank you is in case the re poster doesn't know (i.e. a youngster) that has interest in weather. One doesn't want a youngster or someone with an interest in science to be feeling left out by a needed rejection notice. Its the job of those that know or are teachers to make science INCLUSIVE and enjoyable.

Here is my raggedy looking icon taken w/o permission from a
nice looking icon from a Toshiba
site and edited to look like a 2 headed pin.
image host

Free Image Hosting by imgbox.com
Original icon here (not linking directly to be safe), http://ts2.mm.bing.net/th?id=H.4737590507407797&am p;pid=15.1&w=126&h=151&p=0
SAR2401 - JIMBO - I love it! Please let me overreact to that now.