90L in the Gulf disorganized; Leslie and Michael weaken

By: Dr. Jeff Masters , 4:27 PM GMT on September 07, 2012

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A partial remnant of Hurricane Isaac off the coast of Louisiana, Invest 90L, was almost torn apart last night by wind shear, but is making a bit of a comeback today. Visible satellite loops and surface observations from buoys and oil rigs in the Gulf show that 90L has an sloppy, elongated surface circulation. The area covered by heavy thunderstorms is relatively modest, and has been pushed to the south side of the circulation center by strong northerly winds that are creating a high 20 knots of wind shear. There is a large amount of dry air that surrounds 90L on all sides that is interfering with development. A hurricane hunter aircraft scheduled to investigate 90L today was cancelled, and has been rescheduled for Saturday afternoon.


Figure 1. Visible satellite image of Invest 90L taken at 11:58 am EDT Friday September 7, 2012.

Forecast for 90L
Wind shear over 90L is predicted to stay in the moderate to high range, 15 - 20 knots, through Saturday morning, then drop to the low range Saturday afternoon through Sunday. Ocean temperatures in the Gulf are 28.5° - 29°C, which is plenty warm enough to support formation of a tropical storm. 90L is essentially stationary this morning, but should begin a slow motion to the east-northeast tonight, in response to the steering flow from a trough of low pressure and its associated surface cold front approaching the Gulf Coast from the northwest. This trough should be capable of pulling 90L to a landfall along the Florida Panhandle or west coast of Florida by Sunday morning. In their 8 am Tropical Weather Outlook, NHC gave 90L a 20% chance of developing into a tropical depression by Sunday morning. I put these odds higher, at 30%.

Leslie weakens to a tropical storm
Tropical Storm Leslie continues to remain nearly stationary to the south of the island of Bermuda, and a NOAA hurricane hunter aircraft found this morning that Leslie had weakened below hurricane strength, to a 70 mph tropical storm. An ocean probe launched by the aircraft found that the ocean temperatures at one location in Leslie were 24.5°C, a full 5°C (8°F) drop from when the storm first reached the area two days ago. Moderate wind shear of 10 - 20 knots due to strong upper-level winds out of the west continue to drive dry air to Leslie's west into the core of the storm. The combined effect of shear and cool waters have eroded away Leslie's core, and the storm has no eyewall, as seen on satellite loops. A NOAA hurricane hunter aircraft will be in the storm tonight, and an uncrewed NASA Global Hawk aircraft finished an HS3 Hurricane Research Mission into Leslie this morning.


Figure 2. Hurricane Leslie as seen by NASA's Aqua satellite at 10:45 am EDT Thursday, September 6, 2012. At the time, Leslie was a Category 1 hurricane with 75 mph winds. Image credit: NASA.

Forecast for Leslie
A strong trough of low pressure approaching the U.S. East Coast should make Leslie start moving to the north at 5 mph by Saturday morning. The models have stayed with their more eastwards solution to Leslie's track, which keeps the threat of Bermuda receiving hurricane-force winds relatively low, since the island is expected to be on the weak (left) side of the storm. If the official NHC forecast verifies, tropical storm-force winds will just graze Bermuda Sunday morning through Sunday evening. According to the latest SHIPS model forecast, the shear is expected to fall to the low category, 5 - 10 knots, by Friday night. Leslie is over warm ocean waters of 29 - 30°C, and once the storm moves away from the large pool of cool waters it has stirred up, the reduction in shear and warm waters should allow the storm to intensify to at least a Category 1 hurricane by Sunday. The latest 11 am EDT NHC wind probability forecast calls for a 30% chance that Leslie will be a Category 2 or stronger hurricane Sunday morning at 8 am EDT, when the storm will be beginning its closest pass to Bermuda. Leslie is a huge storm, and tropical storm-force winds are expected to extend outward from its center 200 - 220 miles by Sunday.

Most of the models indicate Leslie is likely to make landfall in Newfoundland, Canada on Tuesday night or Wednesday morning. However, the models have been trending more to the east with Leslie's track in recent runs, and given the uncertainty in 4-day hurricane forecasts, the storm could very well miss the island, passing to the northeast. Large swells from Leslie are pounding the entire Eastern Seaboard, and are creating beach erosion and dangerous rip currents.


Figure 3. Hurricane Michael as seen by NASA's Aqua satellite at 12:20 pm EDT Thursday September 6, 2012. At the time, Michael was a Category 3 hurricane with 115 mph winds. Image credit: NASA.

Hurricane Michael weakens to Category 2
The only major hurricane of the 2012 Atlantic hurricane season, Hurricane Michael, has weakened, and is now a Category 2 storm with 105 mph winds. Satellite loops show that Michael is still an impressive storm with a well-developed eye, but the storm is not as symmetric, and the eye no longer as distinct as was the case yesterday. Michael is far out over the open Atlantic, and none of the models show that Michael will threaten any land areas during the coming seven days.

Elsewhere in the Atlantic
Most of the reliable computer models are predicting that a new tropical wave moving off the coast of Africa today will develop into a tropical depression by the middle of next week. This wave is predicted to exit Africa too far north to threaten the Lesser Antilles Islands.

Jeff Masters

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Quoting bassis:
Is there a record for a TS being stationary or in one general Lat/Lon?

Isaac was stationary at a higher lat. than Leslie.
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BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE BUFFALO NY
1005 AM EDT SAT SEP 8 2012

THE NATIONAL WEATHER SERVICE IN BUFFALO HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
ALLEGANY COUNTY IN WESTERN NEW YORK
CATTARAUGUS COUNTY IN WESTERN NEW YORK
SOUTHEASTERN ERIE COUNTY IN WESTERN NEW YORK
SOUTHERN LIVINGSTON COUNTY IN WESTERN NEW YORK
SOUTHERN WYOMING COUNTY IN WESTERN NEW YORK

* UNTIL 1100 AM EDT

* AT 1003 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN
EXCESS OF 60 MPH. THESE STORMS WERE LOCATED ALONG A LINE EXTENDING
FROM 7 MILES WEST OF SPRINGVILLE TO 7 MILES SOUTHWEST OF ALLEGANY
PARK...AND MOVING EAST AT 35 MPH.

* SOME LOCATIONS IN THE WARNING INCLUDE...
ALLEGANY PARK...
SPRINGVILLE...
EAST CONCORD...
ASHFORD...
SARDINIA...
CHAFFEE...
ST. BONAVENTURE...
OLEAN...
HINSDALE...
BLISS...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THESE ARE DANGEROUS STORMS. IF YOU ARE IN THE PATH...PREPARE
IMMEDIATELY FOR DAMAGING WINDS...DESTRUCTIVE HAIL...AND DEADLY CLOUD
TO GROUND LIGHTNING. PEOPLE OUTSIDE SHOULD MOVE TO A SHELTER...
PREFERABLY INSIDE A STRONG BUILDING BUT AWAY FROM WINDOWS.

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 300 PM EDT
SATURDAY AFTERNOON FOR WESTERN NEW YORK.
Member Since: August 6, 2011 Posts: 4 Comments: 39123
90L getting convection close to its swirl.
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Quoting bassis:


Ever since Isaac came visiting the Humidity in the Charlotte, NC has been brutal. I pray no poisonous tornado's come with this front but hoping for drier conditions on the other side
yes good luck up there,they say this front is real strong, stay safe
Member Since: August 6, 2011 Posts: 4 Comments: 39123
Quoting Thundercloud01221991:


yeah so now imagine 60-70 mph winds that have already been reported



Yeah I would imagine that kind of wind can really cause havoc up there, even if it doesn't last long. first glance at the radar, those cells don't look severe, however, it doesn't take much for severe weather given very strong winds just off the surface and increasing shear.
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Quoting CybrTeddy:

Weak El Niño will last through February 2013: CPC




will it last that long?
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Quoting LargoFl:
lol, i know what you mean, funny thing with my area, outside of the rain keeping temps sorta down, the cool front will only knock us down a couple of degree's..but hopefully(man i wish)..the humidity would go way down..fat chance of that happening but we can hope.


Ever since Isaac came visiting the Humidity in the Charlotte, NC has been brutal. I pray no poisonous tornado's come with this front but hoping for drier conditions on the other side
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Quoting CybrTeddy:


Here, how about I replace the quote with the post number.



Ok
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Air is really dry over the northeast right now, less than 1 inch of PW in Pennsylvania. Higher moisture than that is going to have to advect quickly for significant thunderstorms. However, st the same time, it doesn't take much moisture to get severe thunderstorms, and sometimes layers of dry air can aid in severe weather, so we'll see.
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Quoting weatherh98:
cool air soon? can i get an amen
Amen.
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Quoting Tazmanian:
There is no weak el niño. This is not a el niño year it nevere was and likey nevere will be

Weak El Niño will last through February 2013: CPC
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Quoting CybrTeddy:
865.

Matthew as I recall developed from a westward tropical wave. Storms that develop like most October hurricanes do generally do so from tail ends of stalled out fronts, usually those take a N-NE path in the Caribbean.


Thanks Teddy. And with how things are going I doubt I will see a track like Matthew. I remember he was suppose to bring rain to my city and when it pass near me it just rain for 10 minutes.
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Quoting Tazmanian:



I wish the admins re move the quote.


Here, how about I replace the quote with the post number.
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Is leslie fully tropical?
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Quoting indianrivguy:


man, that front sure squashed the convection trying to wrap the CoC

coolness would be welcome here, I've been giving my flannels longing looks for a couple weeks.
lol, i know what you mean, funny thing with my area, outside of the rain keeping temps sorta down, the cool front will only knock us down a couple of degree's..but hopefully(man i wish)..the humidity would go way down..fat chance of that happening but we can hope.
Member Since: August 6, 2011 Posts: 4 Comments: 39123
Quoting CybrTeddy:


I have, but people like yesterday continue to quote him, so it's hard not to ignore him. I've already flagged his posts.



I wish the admins re move the quote.
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Is there a record for a TS being stationary or in one general Lat/Lon?
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Quoting washingtonian115:
But the trade winds in the caribbean have been high this year...


Trade winds in the *eastern* Caribbean have been high, you will note that one of the analogues I posted was Hurricane Ida in 2009. That was also an El Nino year, and in November no less. Trade winds in the Eastern Caribbean where very high that year, we didn't see a single tropical cyclone manage to get into the Eastern Caribbean as I recall correctly, the closest was Erika and that died as soon as it reached it.
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cool air soon? can i get an amen
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Quoting LargoFl:


man, that front sure squashed the convection trying to wrap the CoC

coolness would be welcome here, I've been giving my flannels longing looks for a couple weeks.
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Quoting Jedkins01:



It only takes like 40 mph winds to bring trees and power lines down up there though, lol.


yeah so now imagine 60-70 mph winds that have already been reported
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Quoting Tazmanian:




Why not you this put him on ignore and his post will be gone for you this just saying


I have, but people like yesterday continue to quote him, so it's hard not to ignore him. I've already flagged his posts.
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Quoting CybrTeddy:
865.

Matthew as I recall developed from a westward tropical wave. Storms that develop like most October hurricanes do generally do so from tail ends of stalled out fronts, usually those take a N-NE path in the Caribbean.


But the trade winds in the caribbean have been high this year...
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Quoting forecaster1:
It is ok, I am the only one who thinks it is heading west...


The outflow on the NW flank is expanding W. Can't tell about the center
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Isaac wasn't enough for some people...
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865.

Matthew as I recall developed from a westward tropical wave. Storms that develop like most October hurricanes do generally do so from tail ends of stalled out fronts, usually those take a N-NE path in the Caribbean.


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Quoting Thundercloud01221991:
I now have a line of severe storms heading my way..... I am in Rochester, NY..... the line shows 70 knt winds on SRV at less then 1000 ft so I am sure damaging winds are occurring. Also reports have shows power outages and trees down already



It only takes like 40 mph winds to bring trees and power lines down up there though, lol.
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91L at the Cape Verde Islands

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Quoting CybrTeddy:


Will you stop it? I'm sorry, but it is incredible annoying to see you post again and again how these storms are such a bust and a disappointment. Some, heck most of us, myself included, would much rather watch in its prime go right on out to sea and put on an impressive show than run right into land and hurt many, many people like Isaac did. If you don't like these storms, here's a hint - don't bother with them, lurk until one does threaten land. Until then, please stop berating everyone with how 'boring' these storms are.




Why not you this put him on ignore and his post will be gone for you this just saying
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Member Since: August 6, 2011 Posts: 4 Comments: 39123
There is no weak el niño. This is not a el niño year it nevere was and likey nevere will be
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845.

Will you stop it? I'm sorry, but it is incredible annoying to see you post again and again how these storms are such a bust and a disappointment. Some, heck most of us, myself included, would much rather watch in its prime go right on out to sea and put on an impressive show than run right into land and hurt many, many people like Isaac did. If you don't like these storms, here's a hint - don't bother with them, lurk until one does threaten land. Until then, please stop berating everyone with how 'boring' these storms are.
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Quoting washingtonian115:
According to the models we will see at least three more developing waves from Africa.Then I think the activity will cease.The focus will of course turn to the caribbean and Gulf like I suspect.Also watch for developments off the east coast and into the Bahamas.
If that is true Nadine ,Oscar,and Patty will be cape verde storms.
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Quoting Thing342:
Am I the only one who thinks Leslie might not be fully tropical?

It is ok, I am the only one who thinks it is heading west...
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I don't think we'll get good development in the caribbean come October due to the unfavorable conditions.
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Quoting CybrTeddy:
Morning all. 91L looks set for a recurve, but I do hope that we do get a hurricane out of it while doing so as it is no threat other than shipping interests. If it stays weak it *might* go more west than expected but given the high latitude, I find that unlikely.

Judging by the high TCHP, SSTs, and abnormally strong troughs coming down already, I suspect that there is a greater than normal chance of western Caribbean development towards the later end of this month. If that is the case, there is a chance we will see classic Early to late October hurricanes (Paula, Rina, Richard, etc) develop in the SW Caribbean with stalled out fronts.
Do you think we can get tracks like Matthew of 2010 or they will move just north like Paula?
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According to the models we will see at least three more developing waves from Africa.Then I think the activity will cease.The focus will of course turn to the caribbean and Gulf like I suspect.Also watch for developments off the east coast and into the Bahamas.
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Member Since: August 6, 2011 Posts: 4 Comments: 39123
Hi Adrian. Do you see a normal October in terms of tropical activity forming in the Western or SW Caribbean or with the Weak El Nino,things may be below average for that month?
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Member Since: August 6, 2011 Posts: 4 Comments: 39123
............gee just got back from palm harbor, all along alt-19, every dip in the road is under water,these rain squalls hold alot of water alright..drive safely out there..and PUT the damn lights on LOL...
Member Since: August 6, 2011 Posts: 4 Comments: 39123
Morning all. 91L looks set for a recurve, but I do hope that we do get a hurricane out of it while doing so as it is no threat other than shipping interests. If it stays weak it *might* go more west than expected but given the high latitude, I find that unlikely.

Judging by the high TCHP, SSTs, and abnormally strong troughs coming down already, I suspect that there is a greater than normal chance of western Caribbean development towards the later end of this month. If that is the case, there is a chance we will see classic Early to late October hurricanes (Paula, Rina, Richard, etc) develop in the SW Caribbean with stalled out fronts.
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Quoting CaribBoy:


Feel free to say and think what you want. We need that rain badly. AND AS REGARDS TWAVES, WHERE DO YOU SEE AT LAST ONE THAT IS ABLE TO BRING US RAIN IN THE MDR? WHERE?????!


At the beginning of the season, all the systems go south of Guadeloupe, and after they go north of the islands, and in the leewards, we never have good systems...Hopely that it will arrive soon...We badly need rain
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Quoting aspectre:
All times in GMT. Derived from NHC_ATCF data for HurricaneMichael for 8Sept.6am
YAU-Liverpool :: CWRW-FourchuHead :: YYT-St.John's :: FLW-Flores

The (bottom) kinked line traces Michael's path on its 2nd day as a Hurricane
The southeesternmost dot on the longest line is H.Michael's most recent position

The longest line is a straightline projection through H.Michaels's 2 most recent positions to its closest approach to a coastline
7Sept.06am: H.Michael had been headed for passage 509miles(819kilometres)West of Flores (left,FLWdumbbell)
7Sept.12pm: H.Michael had been headed for passage over NarrowPond,NovaScotia (left,CWRWblob)
7Sept.06pm: H.Michael had been headed for passage over CapelinCoveLake,NovaScotia (middle,CWRWblob)
8Sept.12am: H.Michael had been headed for passage over WestBerlin (bottom,right,YAUblob)
8Sept.06am: H.Michael was heading for passage 38miles(61kilometres)ENEast of St.John's on its way to passage over St.Lunaire-Griquet, then the Viking L'Anse aux Meadows,Newfoundland

Copy&paste bda, flw-39.845n40.8w, cwrw, 45.63n60.508w, 45.658n60.390w, yau, 44.058n64.575w, yyt-47.893n52.0508w,30.6n40.8w-30.9n40.8w, 30.9n40.8w-31.1n41.0w, 31.1n41.0w-31.3n41.2w, 31.3n41.2w-31.6n41.6w, 31.3n41.2w-44.058n64.575w, 31.6n41.6w-32.0n41.8w, 31.6n41.6w-51.535n55.445w into the GreatCircleMapper for a tree mapping to and other information
The previous mapping for comparison
What the hell does this mean?
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I now have a line of severe storms heading my way..... I am in Rochester, NY..... the line shows 70 knt winds on SRV at less then 1000 ft so I am sure damaging winds are occurring. Also reports have shows power outages and trees down already
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Quoting mcluvincane:
When or will things heat up in the Caribbean?


High pressure will build south over the US early next week with a front stalled in the gomex/carib. Breeding ground for tropics.
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Quoting yonzabam:
Now, if I was writing a global warming disaster movie script, I'd have a big, green derecho rolling through New York in it, with hailstones the size of apples smashing all the windows in the skyscrapers, and Bruce Willis doing his 'our hero' bit.

No idea if derechos will become more frequent in the US as a result of global warming, but its starting to look that way.


I highly doubt GW has anything to do with the derechos. You just can't blame everything that happens in weather patterns or events to GW.
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Am I the only one who thinks Leslie might not be fully tropical?

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Well, I was thinking about Lake Pontchartrain, and I was remembering running lines for Catfish years ago, and it occurs to me that sea level rise will eventually be enough to change the salt content in the lake. It is presently considered "brackish".

Now I wonder at what point will this happen, perhaps in inches or feet of sea level rise, so that the Catfish will no longer be able to live in the lake?

This could cause a massive loss in biodiversity in the private, "inland" fisheries as fresh water and brackish water fish habitats are destroyed.
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Quoting mcluvincane:
When or will things heat up in the Caribbean?
Most likely late September and into October when the activity shifts from Africa to the west.The fronts will start digging down also.
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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.