Tropical Remnant Chantal

[Scott747]

 

NHC says no thanks tonight for westward bendy track into FL -- http://www.nhc.noaa.gov/graphics_at3.shtml?5-daynl?large#contents

 

 

You sound like the other boards that are all up in arms because the track doesn't show a westward bend. Have you thought that maybe that 'bend' is outside the forecast range?

[wxmeddler]

Lopsided..

[phil882]

The convective appearence in this diurnal max is horrible right now. I'm not sure Chantal will survive today, even less Hispaniola.

[HurricaneJosh]

You sound like the other boards that are all up in arms because the track doesn't show a westward bend. Have you thought that maybe that 'bend' is outside the forecast range?

The 5 am EDT forecast track now shows a nudging to the W. Interesting that the Day-5 forecast has a strengthening, 50-kt cyclone heading for the SE USA-- almost implying a hurricane threat.

But first it needs to get through the next couple of days. I agree with Phil-- it looks like crap right now. On the other hand, it often seems that the weaker, looser circulations seem to do better with Shredderola-- perhaps because they have less to lose.

[phil882]

The 5 am EDT forecast track now shows a nudging to the W. Interesting that the Day-5 forecast has a strengthening, 50-kt cyclone heading for the SE USA-- almost implying a hurricane threat.

But first it needs to get through the next couple of days. I agree with Phil-- it looks like crap right now. On the other hand, it often seems that the weaker, looser circulations seem to do better with Shredderola-- perhaps because they have less to lose.

 

The radar certainly indicates there is a robust vorticity maxima, its simply moving too fast to maintain a good closed circulation on the earth relative frame... note that the winds at Barbados are still easterly even though the Chantal is nearly due north of the island. 

 

[HurricaneJosh]

The radar certainly indicates there is a robust vorticity maxima, its simply moving too fast to maintain a good closed circulation on the earth relative frame... note that the winds at Barbados are still easterly even though the Chantal is nearly due north of the island.

Lolz, lame.

The radar signature ain't bad, though.

[phil882]

Again this is similar to Ernesto on many levels, but there are some key difference that will be telling if the storm does not survive later today:

 

1. Ernesto's mass field was larger while traversing the Lesser Antilles (pressure was a good 4-5 hPa lower than Chantal's)

2. More anticyclonic outflow over Ernesto (just displaced a little south of the llc before it entered the Caribbean)

3. Somewhat slower forward motion after it entered the Caribbean.

 

I think the vortex associated with Chantal is more fragile than Ernesto's so it will be interesting to see if it can hold together today. This period between 50-70W is often where many weak TCs dissipate as they run into a wall of vertical wind shear as the low-level jet in the Caribbean ramps up. July and August are the climatological peak in low-level easterly flow in the Caribbean. 

[HurricaneJosh]

Again this is similar to Ernesto on many levels, but there are some key difference that will be telling if the storm does not survive later today:

 

1. Ernesto's mass field was larger while traversing the Lesser Antilles (pressure was a good 4-5 hPa lower than Chantal's)

2. More anticyclonic outflow over Ernesto (just displaced a little south of the llc before it entered the Caribbean)

3. Somewhat slower forward motion after it entered the Caribbean.

 

I think the vortex associated with Chantal is more fragile than Ernesto's so it will be interesting to see if it can hold together today. This period between 50-70W is often where many weak TCs dissipate as they run into a wall of vertical wind shear as the low-level jet in the Caribbean ramps up. July and August are the climatological peak in low-level easterly flow in the Caribbean.

Please clarify which Ernie you're talking about-- cuz I know it wasn't the sexy, angry little 2102 Ernie:

[phil882]

Definitely last year's Ernesto... they both looked very similar at this latitude and longitude in their lifetime. The issue here is that Ernesto's environment was becoming more favorable with time, while I think the opposite is going to prove true with Chantal. 

[HurricaneJosh]

Definitely last year's Ernesto... they both looked very similar at this latitude and longitude in their lifetime. The issue here is that Ernesto's environment was becoming more favorable with time, while I think the opposite is going to prove true with Chantal.

Gotcha. I forget that Ernie struggled for most of its lifetime and only really cranked right before landfall. But, boy, did it crank. the 2012 incarnation really broke the Ernie Curse.

Anyhoo, back to Chantal...

[phil882]

Gotcha. I forget that Ernie struggled for most of its lifetime and only really cranked right before landfall. But, boy, did it crank. the 2012 incarnation really broke the Ernie Curse.

Anyhoo, back to Chantal...

 

For fun... here is what Ernesto looked like when it was crossing the Lesser Antilles

 

 

But just a mere 24 hours later (There wasn't any substancial westerly flow in front of Ernesto so it was just a matter of convection developing to establish the outflow).

 

 

Lets see what Chantal can do. 

[HurricaneJosh]

For fun... here is what Ernesto looked like when it was crossing the Lesser Antilles

 

But just a mere 24 hours later (There wasn't any substancial westerly flow in front of Ernesto so it was just a matter of convection developing to establish the outflow).

 

Lets see what Chantal can do.

Wow-- pretty cool. Thanks for the trip down Memory Lane. I guess there is hope for Chantal.

[phil882]

Recon is interesting this morning... pressure down to 1002.3 hPa extrapolated, Flight level winds at 65 knots with uncontaminated SFMR at 51 knots... but no confirmation yet of a closed circulation... just a sharp wave axis. Not surprising given the NW/SE pass being conducted and another inbound leg will be needed to confirm.

 

EDIT: looks like they simply missed the center and had to track back west to get a good pass... some decent 15-20 knot westerly winds on the southern side of the circulation... despite the IR apparence, Chantal has actually intensified. 

[phil882]

I mean there is clearly a llc... but it won't show up well on recon given the very fast forward motion. 

 

[Scott747]

6z parallel HWRF -

 

 

[metalicwx366]

Many unflagged flight level winds of 70-75kts from recon. The hurricane force surface winds were most likely invalid. Even with the disorganized appearance on satellite, this thing is nearing hurricane intensity.

[phil882]

Many unflagged flight level winds of 70-75kts from recon. The hurricane force surface winds were most likely invalid. Even with the disorganized appearance on satellite, this thing is nearing hurricane intensity.

 

SFMR winds confirm that these flight level winds aren't really mixing down to the surface... still though the storm has intensified a bit... probably around 50-55 knots im line with the highest non rain contaminated SFMR obs (53 knots)

 

Nice high-res radar animation out of Martinique this morning showing a pretty well defined vortex. 

 

[wxsmwhrms]

A 75 mph borderline tropical wave. 

The radar loop out of Martinique and recon data show pretty clearly that this is not a "borderline tropical wave," but a decently developed tropical storm.  The rapid forward motion of the system is going to reduce the strength and amount of westerly ground-relative flow on the south side of the vortex.

[MarkSC]

Strange intensity forecast. Almost ideal conditions in the Bahamas and yet slow weakening?

[ams30721us]

Winds up on the 11 AM advisory. Chantal is flying through the Islands at nearly 30 mph!

 

11:00 AM AST Tue Jul 9
Location: 14.4°N 61.5°W
Moving: WNW at 29 mph
Min pressure: 1006 mb
Max sustained: 60 mph

[ams30721us]

Strange intensity forecast. Almost ideal conditions in the Bahamas and yet slow weakening?

Global models continue to show a weak reflection of a system through the Bahamas. Not a ton of support as of now for a much stronger system. Euro continues to not be onboard for a stronger system also.

[Derecho!]

Strange intensity forecast. Almost ideal conditions in the Bahamas and yet slow weakening?

 

Avila doesn't think they will be ideal. He's a pretty dedicated anti-weenie, though.

 

THE UPPER-LEVEL WINDS ARE FORECAST TO REMAIN UNFAVORABLE IN THE AREA OF THE BAHAMAS FOR

SIGNIFICANT DEVELOPMENT

[MarkSC]

Avila doesn't think they will be ideal. He's a pretty dedicated anti-weenie, though.

 

THE UPPER-LEVEL WINDS ARE FORECAST TO REMAIN UNFAVORABLE IN THE AREA OF THE BAHAMAS FOR

SIGNIFICANT DEVELOPMENT

That's what I don't get.  Dual outflow channels and a retrograding low to its west should be pretty good IF Chantal can survive that long. 

[phil882]

Winds up on the 11 AM advisory. Chantal is flying through the Islands at nearly 30 mph!

 

11:00 AM AST Tue Jul 9

Location: 14.4°N 61.5°W

Moving: WNW at 29 mph

Min pressure: 1006 mb

Max sustained: 60 mph

 

 

Global models continue to show a weak reflection of a system through the Bahamas. Not a ton of support as of now for a much stronger system. Euro continues to not be onboard for a stronger system also.

 

The thing is, this storm in the mid and upper-level sense is still very poorly organized. There isn't really an outflow pattern and its about to run into upper level westerlies which will only increase the vertical wind shear over the system. The storm is moving to the WNW at 29 mph! Thats insane for a closed circulation in the deep tropics. If the cyclone doesn't get the mid and upper level portions of its circulation better organized, its game over when it gets to Hispaniola. Low level circulations can't exist when the mountains are higher than 850 hPa. Thus, its the job of the mid-level vortex to carry the storm through the higher terrain where a vortex can spontaneously spin up via vortex stretching on the leeward side. If there isn't a well organized mid-level center, the storm will dissipate. See Emily 2011. 

 

The latest discussion by Alvia sums my thoughts up best.

 

CHANTAL IS RACING TOWARD THE WEST-NORTHWEST OR 295 DEGREES AT 25

KNOTS. I AM SURPRISED THE SYSTEM EVEN HAS A CLOSED CIRCULATION

MOVING AT THAT SPEED. CHANTAL IS BEING STEERED BY A RATHER STRONG

EASTERLY FLOW SOUTH OF THE SUBTROPICAL RIDGE OVER THE WESTERN

ATLANTIC. HOWEVER...AS THE STORM MOVES OVER THE EASTERN CARIBBEAN

AND HISPANIOLA...THE HIGH TO THE NORTH IS FORECAST TO WEAKEN AND

THE CYCLONE SHOULD TURN MORE TOWARD THE NORTHWEST WITH A DECREASE IN

FORWARD SPEED. BY DAY 4 AND 5 THE STERING CURRENTS WILL BE WEAK AND

CHANTAL WILL PROBABLY MOVE VERY SLOWLY IN THE VICINITY OF THE

NORTHWESTERN BAHAMAS. THE OFFICIAL FORECAST IS SIMILAR TO THE

PREVIOUS ONE AND IS BASICALLY ON TOP OF THE MODEL CONSENSUS.

FORECAST POSITIONS AND MAX WINDS

INIT 09/1500Z 14.4N 61.5W 50 KT 60 MPH

12H 10/0000Z 15.8N 65.0W 55 KT 65 MPH

24H 10/1200Z 17.4N 68.5W 60 KT 70 MPH

36H 11/0000Z 19.3N 71.5W 35 KT 40 MPH...INLAND

48H 11/1200Z 21.3N 73.6W 35 KT 40 MPH

72H 12/1200Z 24.5N 76.0W 45 KT 50 MPH

96H 13/1200Z 26.5N 77.0W 45 KT 50 MPH

120H 14/1200Z 27.5N 78.0W 40 KT 45 MPH

$

FORECASTER AVILA

[wxsmwhrms]

That's what I don't get.  Dual outflow channels and a retrograding low to its west should be pretty good IF Chantal can survive that long. 

Just looking at the GFS upper level wind forecast, upper level winds don't seem to become particularly favorable in the area until 120 hours and later.

[wolfpackmet]

Looks like 12z GFS has Chantal hug southern Hispaniola coast line and weakening into Cuba.  So many factors going against this storm: speed, shearing and land interaction with subsidence of northerly winds over tall mountains. 

[thewxmann]

Strange intensity forecast. Almost ideal conditions in the Bahamas and yet slow weakening?

 

Not really ideal, it's going to be under an ULL. As wxsmwhrms alluded to, conditions aren't becoming favorable until the day 5+ period.

[Ed Lizard]

Not really ideal, it's going to be under an ULL. As wxsmwhrms alluded to, conditions aren't becoming favorable until the day 5+ period.

 

 

I'll be wishcasting for that left turn of the remnant low a little further South than 12Z GFS, maybe Northeast Gulf could be favorable.

 

Heat potential is low, but how much TCHP would a TS or, fingers crossed, low end hurricane need?

 

[TropicalAnalystwx13]

BULLETIN
TROPICAL STORM CHANTAL INTERMEDIATE ADVISORY NUMBER 7A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL032013
200 PM AST TUE JUL 09 2013

...A LITTLE STRONGER CHANTAL MOVING RAPIDLY AWAY FROM THE LESSER
ANTILLES AND INTO THE EASTERN CARIBBEAN SEA...

SUMMARY OF 200 PM AST...1800 UTC...INFORMATION
----------------------------------------------
LOCATION...14.8N 62.7W
ABOUT 335 MI...540 KM SE OF SAN JUAN PUERTO RICO
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...WNW OR 295 DEGREES AT 29 MPH...46 KM/H
MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES

[phil882]

 

Outflow boundaries going out ahead of Chantal indicative of some dry air in the near term for Chantal... the pressure has been really oscillating the last few passes between 1005-1010 hPa, mainly due to the storm occasionally wrapping up supercellular like convection on its north and east quadrants  However, Martinique radar shows the center now running ahead of this convection. There is still convection off to the storms NW due to the aforementioned outflow boundary, but honestly Chantal looks less organized than yesterday despite the increase in winds. I'd place the chances of dissipation at or before Hispaniola above 50% right now.