ATL: CHANTAL - Post-Tropical

[ROCK]

current steering....

http://tropic.ssec.wisc.edu/real-time/d ... oom=&time=

[artist]

[adam0983]

I see an Eye on radar. Just an opinion not a forecast.

[chaser1]

[/quote]Miami NWS forecasts it to dissipate by wed night or thursday.[/quote]

Hey Alexis, you noticed that too I had just read that in our local discussion a short while ago. Though I personally think Chantal's satellite presentation right now looks like "dog-meat through a blender", she's holdin' her own for the moment. Assuming that she makes it south of Hispaniola and then north, will be interesting to see if the upper air conditions will then be conducive for re-intensification over the Florida Straits

[Evil Jeremy]

I see an Eye on radar. Just an opinion not a forecast.

There's no eye.

[robbielyn]

I see an Eye on radar. Just an opinion not a forecast.

There's no eye.

it a clear area dry air

[torrea40]

I see an Eye on radar. Just an opinion not a forecast.

There's no eye.

Yeah eye wall....Hurricane Cat. 1...Maybe

[Aric Dunn]

Dr Jeff Masters did a very long and interesting discussion this afternoon about Chantal.

Unusual Tropical Storm Chantal has strengthened a bit more as it speeds west-northwestwards at 29 mph away from the the Lesser Antilles Islands. Sustained winds of 38 mph, gusting to 52 mph, were observed at Martinique at 10 am AST as the storm passed. However, an automated weather station at the airport measured sustained winds of 60 mph, gusting to 78 mph, according to an official with Meteo-France. The Associated Press reported that Chantal ripped the roofs off of several homes on neighboring Dominica. An Air Force hurricane hunter aircraft measured top winds at their 1,000' flight level of 89 mph at 12:55 pm AST. Top winds seen by the aircraft's SFMR instrument were about 65 mph, in a small area east of Chantal's center. The Hurricane Hunters have departed Chantal, and the next plane is due in the storm at 8 pm EDT. Chantal's winds are unusually high considering the storm's high central pressure of 1006 mb and disorganized appearance on satellite imagery. Chantal is fighting dry air associated with the Saharan Air Layer (SAL), as seen on water vapor satellite loops. This dry air is creating strong thunderstorm downdrafts that are robbing Chantal of moisture and energy. Visible satellite loops show the outflow boundaries of these thunderstorm downdrafts at the surface, spreading to the northwest of Chantal. Martinique Radar shows a large area of heavy rain that is not well-organized, lying mostly to the west of the Lesser Antilles Islands.


An small-scale easterly jet creating high shear in Chantal

Chantal is not very impressive on satellite images, with a modest amount of heavy thunderstorms that are not well-organized. Only a small amount of upper-level outflow is visible. The reason for Chantal's rather disorganized appearance can be found by looking at this morning's balloon sounding from Guadaloupe. This island was just northwest of the center of Chantal when the balloon was launched at 8 am EDT. The sounding showed typical easterly trade winds at the surface of 12 knots (14 mph.) However, the winds rose quickly aloft, with a jet of easterly winds of 35 - 53 knots between 800 - 600 mb (about 7,000 - 15,000'.) But, by the time the ballon hit 500 mb (18,000'), the winds had died down to 15 knots. A change of wind speed from 12 knots to 53 knots and back down to 15 knots from the surface to 500 mb is a tremendous amount of wind shear, which will make it very difficult for a tropical storm to keep the surface center aligned with the upper level center. The traditional measure of wind shear, the difference in wind between 200 mb and 850 mb, was 44 knots in this morning's Guadaloupe sounding, but was a much higher 56 knots from 200 mb to 700 mb. The powerful easterly wind jet was not apparent at any of the other balloon soundings this morning at adjacent islands (Barbados, Puerto Rico, Saint Martin), and demonstrates that there is a lot going on the atmosphere at small scales we cannot see which makes intensity forecasting of tropical cyclones very challenging. Thanks go to Jason Dunion of NOAA's Hurricane Research Division for pointing out this morning's interesting Guadaloupe sounding.

Forecast for Chantal

Chantal will have difficulty intensifying much more before hitting Hispaniola on Wednesday afternoon. In their 11 am EDT wind probability forecast, NHC gave Chantal a 29% chance of becoming a hurricane before hitting Hispaniola. Working against intensification will be the high wind shear from the strong mid-level easterly jet discussed above, plus 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 2 pm EDT Tuesday wind shear forecast from the SHIPS model calls for shear to rise to the high range, 20 - 35 knots, Tuesday night through Friday. On Saturday, when Chantal is expected to be in the Bahamas, moderate wind shear of 10 - 20 knots is predicted. If Chantal survives until Saturday, it will then have the opportunity to re-strengthen. The latest 12Z run of the European model (ECMWF) dissipates Chantal as it crosses Hispaniola. The 12Z run of the American GFS model has Chantal barely surviving.

Chantal's fast west-northwest forward speed of 29 mph will slow to 20 mph by Wednesday morning and then 10 mph by Thursday night, 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 Chantal westwards into the Florida or Southeast U.S. coast, with a possible Sunday landfall.

http://www.wunderground.com/blog/JeffMa ... #commentop

excellent discussion ! hope you all read it as it should quell a lot of miss information running around right now.

[wxman57]

From Jeff Masters' discussion:

"The reason for Chantal's rather disorganized appearance can be found by looking at this morning's balloon sounding from Guadaloupe. This island was just northwest of the center of Chantal when the balloon was launched at 8 am EDT. The sounding showed typical easterly trade winds at the surface of 12 knots (14 mph.) However, the winds rose quickly aloft, with a jet of easterly winds of 35 - 53 knots between 800 - 600 mb (about 7,000 - 15,000'.) But, by the time the balloon hit 500 mb (18,000'), the winds had died down to 15 knots. A change of wind speed from 12 knots to 53 knots and back down to 15 knots from the surface to 500 mb is a tremendous amount of wind shear, which will make it very difficult for a tropical storm to keep the surface center aligned with the upper level center. "

Even though the plane was flying below these levels I wonder if this easterly jet was dipping down to FL at times, producing the quite high FL winds (but not dipping down to the surface)?

[Aric Dunn]

From Jeff Masters' discussion:

"The reason for Chantal's rather disorganized appearance can be found by looking at this morning's balloon sounding from Guadaloupe. This island was just northwest of the center of Chantal when the balloon was launched at 8 am EDT. The sounding showed typical easterly trade winds at the surface of 12 knots (14 mph.) However, the winds rose quickly aloft, with a jet of easterly winds of 35 - 53 knots between 800 - 600 mb (about 7,000 - 15,000'.) But, by the time the balloon hit 500 mb (18,000'), the winds had died down to 15 knots. A change of wind speed from 12 knots to 53 knots and back down to 15 knots from the surface to 500 mb is a tremendous amount of wind shear, which will make it very difficult for a tropical storm to keep the surface center aligned with the upper level center. "

Even though the plane was flying below these levels I wonder if this easterly jet was dipping down to FL at times, producing the quite high FL winds (but not dipping down to the surface)?

maybe but did you miss the part about surface obs on the islands supporting recon?

" Sustained winds of 38 mph, gusting to 52 mph, were observed at Martinique at 10 am AST as the storm passed. However, an automated weather station at the airport measured sustained winds of 60 mph, gusting to 78 mph, according to an official with Meteo-France. The Associated Press reported that Chantal ripped the roofs off of several homes on neighboring Dominica."

[Evil Jeremy]

I see an Eye on radar. Just an opinion not a forecast.

There's no eye.

Yeah eye wall....Hurricane Cat. 1...Maybe

There is no eye, or an eye wall, and this is not a Cat 1. Don't spread false information.

every body here was Wrong...Hummmmmm

About what?

[ROCK]

what mis-information? Chantal does look ragged for a TS....thats pretty obvious. Outflow boundaries coming out from the center is not a sign of organization. That is hurricane 101....

oh I can see the low level center on IR by the way....

[wxman57]

From Jeff Masters' discussion:

"The reason for Chantal's rather disorganized appearance can be found by looking at this morning's balloon sounding from Guadaloupe. This island was just northwest of the center of Chantal when the balloon was launched at 8 am EDT. The sounding showed typical easterly trade winds at the surface of 12 knots (14 mph.) However, the winds rose quickly aloft, with a jet of easterly winds of 35 - 53 knots between 800 - 600 mb (about 7,000 - 15,000'.) But, by the time the balloon hit 500 mb (18,000'), the winds had died down to 15 knots. A change of wind speed from 12 knots to 53 knots and back down to 15 knots from the surface to 500 mb is a tremendous amount of wind shear, which will make it very difficult for a tropical storm to keep the surface center aligned with the upper level center. "

Even though the plane was flying below these levels I wonder if this easterly jet was dipping down to FL at times, producing the quite high FL winds (but not dipping down to the surface)?

maybe but did you miss the part about surface obs on the islands supporting recon?

We've noted along the Texas coast that small low-level jets (out of the south) develop some nights associated with convection to the north. Sometimes these jets briefly dip down to the surface, producing winds of 50-60 mph seemingly out of nowhere. Something similar could have happened as the easterly jet passed Martinique, but that jet may not be representative of Chantal's general circulation.

[floridasun78]

ok let wait untill 5pm update let pro at nhc have say

[ROCK]

From Jeff Masters' discussion:

"The reason for Chantal's rather disorganized appearance can be found by looking at this morning's balloon sounding from Guadaloupe. This island was just northwest of the center of Chantal when the balloon was launched at 8 am EDT. The sounding showed typical easterly trade winds at the surface of 12 knots (14 mph.) However, the winds rose quickly aloft, with a jet of easterly winds of 35 - 53 knots between 800 - 600 mb (about 7,000 - 15,000'.) But, by the time the balloon hit 500 mb (18,000'), the winds had died down to 15 knots. A change of wind speed from 12 knots to 53 knots and back down to 15 knots from the surface to 500 mb is a tremendous amount of wind shear, which will make it very difficult for a tropical storm to keep the surface center aligned with the upper level center. "

Even though the plane was flying below these levels I wonder if this easterly jet was dipping down to FL at times, producing the quite high FL winds (but not dipping down to the surface)?

that is an interesting theory....

[lester]

I see an Eye on radar. Just an opinion not a forecast.

There's no eye.

Yeah eye wall....Hurricane Cat. 1...Maybe

there's no eye or eyewall

[Aric Dunn]

From Jeff Masters' discussion:

"The reason for Chantal's rather disorganized appearance can be found by looking at this morning's balloon sounding from Guadaloupe. This island was just northwest of the center of Chantal when the balloon was launched at 8 am EDT. The sounding showed typical easterly trade winds at the surface of 12 knots (14 mph.) However, the winds rose quickly aloft, with a jet of easterly winds of 35 - 53 knots between 800 - 600 mb (about 7,000 - 15,000'.) But, by the time the balloon hit 500 mb (18,000'), the winds had died down to 15 knots. A change of wind speed from 12 knots to 53 knots and back down to 15 knots from the surface to 500 mb is a tremendous amount of wind shear, which will make it very difficult for a tropical storm to keep the surface center aligned with the upper level center. "

Even though the plane was flying below these levels I wonder if this easterly jet was dipping down to FL at times, producing the quite high FL winds (but not dipping down to the surface)?

maybe but did you miss the part about surface obs on the islands supporting recon?

We've noted along the Texas coast that small low-level jets (out of the south) develop some nights associated with convection to the north. Sometimes these jets briefly dip down to the surface, producing winds of 50-60 mph seemingly out of nowhere. Something similar could have happened as the easterly jet passed Martinique, but that jet may not be representative of Chantal's general circulation.

Agreed, though we wont know for sure... Could probably comb over recon as it descended this morning and see if it ran across the jet.. being that it approached north to south east of dominica

[SapphireSea]

Curiously enough, the ULL just off the coast of FL is heading about 265 to 260 if my eyes are not deceiving me. I wonder if this will affect the shear situation for Chantal at all. It also does not show signs of dissipation which was expected to happen tomorrow at some point. All critical keys on what happens next.

[gatorcane]

From Jeff Masters' discussion:

"The reason for Chantal's rather disorganized appearance can be found by looking at this morning's balloon sounding from Guadaloupe. This island was just northwest of the center of Chantal when the balloon was launched at 8 am EDT. The sounding showed typical easterly trade winds at the surface of 12 knots (14 mph.) However, the winds rose quickly aloft, with a jet of easterly winds of 35 - 53 knots between 800 - 600 mb (about 7,000 - 15,000'.) But, by the time the balloon hit 500 mb (18,000'), the winds had died down to 15 knots. A change of wind speed from 12 knots to 53 knots and back down to 15 knots from the surface to 500 mb is a tremendous amount of wind shear, which will make it very difficult for a tropical storm to keep the surface center aligned with the upper level center. "

Even though the plane was flying below these levels I wonder if this easterly jet was dipping down to FL at times, producing the quite high FL winds (but not dipping down to the surface)?

that is an interesting theory....

Yeah that would make more sense given how ragged and disorganized the system looks on SAT imagery today.

[torrea40]

John Morales said about CHANTEL : It will cycle day..