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 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.
Member Since: August 14, 2010 Posts: 10 Comments: 16854
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.
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When or will things heat up in the Caribbean?
Member Since: June 2, 2010 Posts: 0 Comments: 1339
This Cold Front is monstrous, the temperature is not supposed to get out of the 70s at my house tomorrow, down from 93-94F yesterday.
And it is going to be in the mid-50s at night.

I have to go to swim practice, i may be back in time to track the best of the severe weather with you guys.

Everybody up there stay safe and keep your cameras rolling if you see anything.
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Quoting CaribBoy:


.... boring


Most capeverde cyclones recurve.
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Leslie moving west?

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Quoting hurricane23:


Conditions still look rather favorable out there for this to develope into possibly another hurricane in time. In terms of threat i just dont see any substantial ridge that will drive it westward for a prolonged period of time.


.... boring
Member Since: October 6, 2007 Posts: 0 Comments: 6164
Quoting bassis:


???


They need rain badly
Member Since: June 2, 2010 Posts: 0 Comments: 1339
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Quoting washingtonian115:
They claim all they want is "rain" from these tropical systems but we all know they want a cat 2 or higher to come for them..You can get rain and gusty winds from a tropical wave.So why don't you all just ask for that?.


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?????!
Member Since: October 6, 2007 Posts: 0 Comments: 6164
Quoting hurricane23:


Conditions still look rather favorable out there for this to develope into possibly another hurricane in time. In terms of threat i just dont see any substantial ridge that will drive it westward for a prolonged period of time.
The wave that comes after it may need to be watched as the models show that having a more southern route and the ridge building back in.
Member Since: August 14, 2010 Posts: 10 Comments: 16854
Quoting GeoffreyWPB:
We have 91L.

I'm always late to the party.


That's another boring fish, you havent missed anything
Member Since: October 6, 2007 Posts: 0 Comments: 6164
Quoting GeoffreyWPB:


Conditions still look rather favorable out there for this to develope into possibly another hurricane in time. In terms of threat i just dont see any substantial ridge that will drive it westward for a prolonged period of time.
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Quoting bassis:


???
They claim all they want is "rain" from these tropical systems but we all know they want a cat 2 or higher to come for them..You can get rain and gusty winds from a tropical wave.So why don't you all just ask for that?.
Member Since: August 14, 2010 Posts: 10 Comments: 16854
Quoting bassis:


???


lol I'm waiting for her too!! Wayyyyyyyyyyyyy to warm and dry here. JUST BORING..
Member Since: October 6, 2007 Posts: 0 Comments: 6164
Quoting wxmod:


I know keeper. It ain't lookin too great. It appears, actually, to be looking worse than anyone predicted. And now two tropical systems are headin for Greenland.
The ice shelves in the Antarctic are also breaking up and drifting off at an alarming rate, along with many of the freshwater glaciers held in place by the sheets.

On a side note - Good Morning, bloggers!
Member Since: August 2, 2011 Posts: 0 Comments: 291
When you trust computer models lol :

AT LOWER LEVELS...MODELS SHOW HURRICANE MICHAEL JOINING TROPICAL
STORM LESLIE OR RUNNING AHEAD OF IT AND DISSIPATING TO THE
NORTHEAST IN MID LATITUDE FLOW. A DISTURBANCE NOW NEAR 21 WEST
WILL MOVE WEST BUT VEER NORTH ON THURSDAY. A SECOND DISTURBANCE
ABOUT 1200 MILES SOUTHEAST OF THE FIRST WILL FORM IN THE EASTERN
TROPICAL ATLANTIC AND TURN NORTHWEST ON TUESDAY. THIS WILL CAUSE
THE LOCAL AREA TO REMAIN DRY EXCEPT FOR ISOLATED TO SCATTERED
AFTERNOON SHOWERS AND THUNDERSTORMS...MAINLY OVER THE INTERIOR
MOUNTAINS.
Member Since: October 6, 2007 Posts: 0 Comments: 6164
Quoting zicoille:


Where are you going Nadine? Come in the leewards...we're waiting for you... you can invite all your friends for an incredible september party...


???
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Quoting Grothar:


Where are you going Nadine? Come in the leewards...we're waiting for you... you can invite all your friends for an incredible september party...
Member Since: August 19, 2009 Posts: 0 Comments: 130
BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE BUFFALO NY
912 AM EDT SAT SEP 8 2012

THE NATIONAL WEATHER SERVICE IN BUFFALO HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
NORTHWESTERN CATTARAUGUS COUNTY IN WESTERN NEW YORK
NORTHEASTERN CHAUTAUQUA COUNTY IN WESTERN NEW YORK
ERIE COUNTY IN WESTERN NEW YORK
NIAGARA COUNTY IN WESTERN NEW YORK

* UNTIL 1015 AM EDT

* AT 908 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 8 MILES NORTH OF YOUNGSTOWN TO DUNKIRK...AND MOVING EAST AT 30 MPH.

* SOME LOCATIONS IN THE WARNING INCLUDE...
GRAND ISLAND...
SANBORN...
DERBY...
PENDLETON...
ATHOL SPRINGS...
HAMBURG...
WEST SENECA...
ORCHARD PARK...

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.

&&

LAT...LON 4246 7943 4250 7936 4256 7916 4269 7907
4279 7886 4294 7892 4300 7903 4306 7901
4308 7908 4314 7905 4327 7907 4337 7863
4338 7847 4254 7848 4237 7870 4237 7914
4242 7944
TIME...MOT...LOC 1311Z 273DEG 26KT 4335 7896 4249 7932

$$

THOMAS
Member Since: February 11, 2012 Posts: 83 Comments: 7746
Quoting bassis:
Leslie & Michael are starting to remind me of the pics of Jupiter with those storms that never move. Is this trough coming off the East coast going to finally give Leslie a reason to move

Supposed to. Have to keep watch.
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Quoting Grothar:


I have devised a much better and less expensive method. I just have my niece call me from the NHC when something is coming up.
That would work, too. (I used to work about three blocks from the NHC's HQ on the FIU campus; I'd drive or walk by a few times a day, often fantasizing I knew someone on the inside who'd be willing to tip me off on important events. Alas, that never happened...)
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a href="Photobucket" target="_blank">
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MESOSCALE DISCUSSION 1926
NWS STORM PREDICTION CENTER NORMAN OK
0742 AM CDT SAT SEP 08 2012

AREAS AFFECTED...CNTRL NY AND CNTRL-ERN PA

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 081242Z - 081415Z

PROBABILITY OF WATCH ISSUANCE...95 PERCENT

SUMMARY...A SEVERE THREAT IS EXPECTED TO DEVELOP THIS MORNING FROM
CNTRL NY SWD INTO ECNTRL PA. INITIALLY THIS MORNING...WIND DAMAGE
WILL LIKELY BE THE PRIMARY THREAT BUT A TORNADO THREAT IS ALSO
EXPECTED TO DEVELOP THIS AFTERNOON. WW ISSUANCE WILL LIKELY BECOME
NECESSARY ACROSS THE REGION IN THE MID TO LATE MORNING TIMEFRAME.

DISCUSSION...THE LATEST WATER VAPOR IMAGERY SHOWS A STRONG
UPPER-LEVEL TROUGH OVER THE GREAT LAKES AND OH VALLEY. AHEAD OF THE
SYSTEM...VISIBLE SATELLITE IMAGERY SHOWS BREAKS IN THE CLOUD COVER
ACROSS NY AND CNTRL PA WHERE SFC TEMPS ARE ALREADY IN THE MID 70S F.
IN ADDITION...MODIFYING THE PITTSBURG 12Z SOUNDING PRODUCES NO CAP
BY MID-MORNING SUGGESTING CONVECTION WILL INITIATE AND DEVELOP
QUICKLY AS SFC TEMPS CONTINUE TO WARM. INCREASING INSTABILITY ALONG
WITH STRONG DEEP LAYER SHEAR PROFILES WILL BE FAVORABLE FOR SEVERE
STORM DEVELOPMENT AS A LINE OF STORMS ORGANIZES AND MOVES QUICKLY
EWD ACROSS THE REGION THIS AFTERNOON. ALSO...STRONG LOW-LEVEL SHEAR
SHOULD BE SUFFICIENT FOR TORNADOES WITH DISCRETE CELL ELEMENTS AHEAD
OF THE LINE OR WITH BOWING LINE SEGMENTS.

..BROYLES/MEAD.. 09/08/2012
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Leslie & Michael are starting to remind me of the pics of Jupiter with those storms that never move. Is this trough coming off the East coast going to finally give Leslie a reason to move
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Quoting washingtonian115:
When is this suppose to happen?

It's already started, storms are already strengthening in central and western NY and will continue to push east and get stronger throughout the day. The SPC suggests a derecho is possible/likely.

THE OVERALL SYNOPTIC PATTERN SUGGESTS
THE POTENTIAL FOR A SERIAL-TYPE DERECHO EVENT...CHARACTERIZED BY
WIDESPREAD AND SIGNIFICANT DAMAGING WINDS.
Member Since: February 11, 2012 Posts: 83 Comments: 7746
a href="Photobucket" target="_blank">
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Quoting MAweatherboy1:
Not many changes in the new outlook.



--REGIONAL OUTBREAK OF SEVERE STORMS LIKELY WITH THE POTENTIAL FOR
WIDESPREAD DAMAGING WINDS AND A FEW TORNADOES--
When is this suppose to happen?
Member Since: August 14, 2010 Posts: 10 Comments: 16854
Everyone stay safe today in the warning areas..





...NERN U.S. INTO CAROLINAS...

LATEST NUMERICAL GUIDANCE INDICATES THAT THE MOST SIGNIFICANT
RESPONSE TO ABOVE-MENTIONED SHORTWAVE TROUGH /AS SEEN IN MASS AND
MOISTURE FLUXES AND TIGHTENING HEIGHT GRADIENTS/ WILL DEVELOP FROM
THE LOWER GREAT LAKES THIS MORNING INTO ERN QUEBEC AND NRN NEW
ENGLAND BY AFTERNOON. THE NET RESULT OF THIS PROCESS WILL BE AN
INCREASE IN BOTH LOW-LEVEL MOISTURE /AND RESULTANT INSTABILITY/ AND
VERTICAL SHEAR ACROSS THE MODERATE RISK AREA THROUGH THE PEAK OF THE
DIURNAL HEATING CYCLE.

THE STRONGLY FORCED NATURE OF THIS SYNOPTIC SYSTEM HAS RESULTED IN
REASONABLY GOOD AGREEMENT BY THE CONVECTION-ALLOWING MODELS WITH
REGARD TO STORM EVOLUTION AND DOMINANT MODE. THESE DATA SUGGEST THE
RAPID DEVELOPMENT AND SUBSEQUENT UPSCALE GROWTH OF TSTMS INTO A QLCS
BY LATE MORNING/EARLY AFTERNOON FROM CNTRL NY/PA TO NRN VA. THIS
SCENARIO IS GENERALLY SUPPORTED BY THE 12Z BUF/PIT SOUNDINGS WHICH
REVEALED LITTLE OR NO CAP AND AN ALREADY STRONG DEEP-LAYER WIND
FIELD.

BREAKS IN THE CLOUDS IN CONJUNCTION WITH THE MOIST BOUNDARY LAYER
SHOULD YIELD A MODERATELY UNSTABLE ENVIRONMENT BY AFTERNOON WITH
MLCAPE RANGING FROM AROUND 1000 J/KG OVER NRN PORTION OF MODERATE
RISK AREA...TO 1500-2000 J/KG IN THE SOUTH. WHEN COUPLED WITH 50-60
KT OF DEEP-LAYER SHEAR...SETUP WILL SUPPORT EMBEDDED BOWING/LEWP
STRUCTURES AND SUPERCELLS. THE OVERALL SYNOPTIC PATTERN SUGGESTS
THE POTENTIAL FOR A SERIAL-TYPE DERECHO EVENT...CHARACTERIZED BY
WIDESPREAD AND SIGNIFICANT DAMAGING WINDS.

TORNADO POTENTIAL WILL BE MAXIMIZED DURING THE MID-LATE AFTERNOON
HOURS FROM NERN PA/NRN NJ NWD INTO THE HUDSON VALLEY/WRN NEW ENGLAND
WHERE THE NRN EXTENSION OF STRONGER INSTABILITY ALIGNS WITH A
CORRIDOR OF ENHANCED LOW-LEVEL SHEAR /I.E. EFFECTIVE SRH VALUES OF
200-300+ M2 PER S2/. THE OVERALL TORNADO THREAT MAY BE MODULATED BY
THE ANTICIPATED LINEAR CONVECTIVE MODE AND ASSOCIATED WITH EMBEDDED
MESOCYCLONES AND SHALLOWER MESOVORTICES.

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Not many changes in the new outlook.



--REGIONAL OUTBREAK OF SEVERE STORMS LIKELY WITH THE POTENTIAL FOR
WIDESPREAD DAMAGING WINDS AND A FEW TORNADOES--
Member Since: February 11, 2012 Posts: 83 Comments: 7746
Off topic but there's a huge CME leaving the Sun right now... I highly doubt it's Earth directed since there's no big sunspots facing us... Cool to look at though.

Member Since: February 11, 2012 Posts: 83 Comments: 7746
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We'll be getting a new update from the SPC within 10 minutes. Already some line segments firing up. I haven't seen any warnings yet though.

Member Since: February 11, 2012 Posts: 83 Comments: 7746
looks like isaacs little brother is a gone pecan,bye bye.finally
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Quoting Grothar:


I have devised a much better and less expensive method. I just have my niece call me from the NHC when something is coming up.

I just wait till I see it posted here. Much easier and is free.
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Quoting Neapolitan:
You underestimate me, then; my 'F5' key is as underused as my collection of VHS tapes. No, I'm a software developer; I simply wrote a script that runs in the background to monitor certain pages for changes, then pops up the content of those pages when a change is detected. Constantly hitting the F5 key for updates? That went out with disco...


I have devised a much better and less expensive method. I just have my niece call me from the NHC when something is coming up.
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Click image for September 7, 2012 storm reports.



Four fatalities yesterday in NE Oklahoma from high winds. One, a Missouri truck driver whose semi was blown off the road near Miami. Also two adults and a child in a mobile home near Nowata. As I recall, another fatality occurred in February or March in Pontotoc County from t-storm winds. Not likely tornadoes. Just wind.

Last eve when it came through where I live, that N wind ignited two local grass fires and was gusting strong enough to knock you over. And there was no t-storm present nearby. Just the frontal boundary near as I could tell.
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Quoting GeoffreyWPB:
Grothar, If I didn't have to go to work, I'd give you a piece of my mind. But, then again, that would leave me with very little remaining.


Small minds think alike. We must have been posting at the same time.
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Quoting WeatherNerdPR:

It would be awesome if he became a major again. This thing has not been following the NHC's forecasts. It was originally supposed to be a 45mph TS at best...

That would be awesome, defining everyone. I have to go to the orthodantist and the Metro Airport, I'll see you all later.
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Grothar, If I didn't have to go to work, I'd give you a piece of my mind. But, then again, that would leave me with very little remaining.
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Quoting Dakster:


I have heard that before...


But I didn't say "content of their character"....... :)
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Quoting WeatherNerdPR:

It would be awesome if he became a major again. This thing has not been following the NHC's forecasts. It was originally supposed to be a 45mph TS at best...
And be a remnant low by now.I think Chris should have been a sign earlier in the year that conditions were going to be favorable in that region of the Atlantic when he became a hurricane.
Member Since: August 14, 2010 Posts: 10 Comments: 16854
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Quoting wxchaser97:

It almost seems like he wants to strengthen again, that would be cool.

It would be awesome if he became a major again. This thing has not been following the NHC's forecasts. It was originally supposed to be a 45mph TS at best...
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Quoting Grothar:


Don't feel badly. It is not the speed with which one posts, but the content of their entry that counts.


I have heard that before...
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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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