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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Anyone else see the Atmospheric wave on the Jackson MS radar?
Or is it a gust front?
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Good Morning fellow bloggers.

Just checking on 90L, looks to be taking on a comma shape more typical of extratropical or hybrid cyclones. She looks like either she will move out ahead of the front generally to the east or get caught up in the front itself. From the looks of her today with that trailing trough and band of storms, seems inevitable to add to the flooding woes being experienced over most of the FL peninsula.

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Quoting MAweatherboy1:

Oops, my bad... do either of you have a link to ACE numbers?

Link
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Quoting MAweatherboy1:
Leslie hasn't exactly been a pretty storm, but she's stuck around long enough that it won't be long until she passes Isaac for highest ACE level in the Atlantic this year.



She did a few days ago already. :P Though Michael is catching up to her quickly and we might see yet again another winner.
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Quoting MAweatherboy1:

Oops, my bad... do either of you have a link to ACE numbers?
I maintain my own--but there's a running list on Wikipedia: http://en.wikipedia.org/wiki/2012_Atlantic_hurric ane_season. (It's not always accurate or up-to-date, but it almost always is.)
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Quoting AussieStorm:

Both Leslie and Michael have past Isaac in ACE already...


LESLIE
Current wind: 55kts
Max Wind: 65kts
A.C.E: 12.425


MICHAEL
Current Wind: 85kts
Max Wind: 100kts
A.C.E: 11.8675


Isaac
Max Wind: 70kts
ACE = 9.555
Quoting Neapolitan:
But Leslie, with 11.21 ACE units, has already passed Isaac, with 9.4225.

Now, Michael is currently behind Isaac, with 9.3025. But he will jump past Isaac at this mornings 1100 EDT TWO.

Oops, my bad... do either of you have a link to ACE numbers?
Member Since: February 11, 2012 Posts: 79 Comments: 7297
Quoting MAweatherboy1:
Leslie hasn't exactly been a pretty storm, but she's stuck around long enough that it won't be long until she passes Isaac for highest ACE level in the Atlantic this year.

But Leslie, with 11.21 ACE units, has already passed Isaac, with 9.4225.

Now, Michael is currently behind Isaac, with 9.3025. But he will jump past Isaac at this morning's 1100 EDT TWO.

ACE
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Quoting MAweatherboy1:
Leslie hasn't exactly been a pretty storm, but she's stuck around long enough that it won't be long until she passes Isaac for highest ACE level in the Atlantic this year.


Both Leslie and Michael have past Isaac in ACE already...


LESLIE
Current wind: 55kts
Max Wind: 65kts
A.C.E: 12.425


MICHAEL
Current Wind: 85kts
Max Wind: 100kts
A.C.E: 11.8675


Isaac
Max Wind: 70kts
ACE = 9.555
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Member Since: July 17, 2009 Posts: 63 Comments: 23726
CMC 228HR
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HPC day 7 we have a NEW TS
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Leslie hasn't exactly been a pretty storm, but she's stuck around long enough that it won't be long until she passes Isaac for highest ACE level in the Atlantic this year.

Member Since: February 11, 2012 Posts: 79 Comments: 7297
Member Since: July 17, 2009 Posts: 63 Comments: 23726
hammered last night with heavy rains ditches are full and waiting for 90l..e.cen.fl
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There's a nice-looking, low-latitude wave (Pouch 27L) moving westward across Africa, and even exhibiting a bit of cyclonic turning. For now, models don't develop it much, but that may change a few days from now:

P27L
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Showing signs of life again.

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It going to be 84 on Tuesday in WPB = :)!!!!!
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Quoting MAweatherboy1:
Already some decent, but non severe storms out there, about to head into Buffalo. I'll be providing radar images today :)


It's going to be a long day today with both a severe weather event and the tropics.
Member Since: March 16, 2012 Posts: 123 Comments: 7887
WOW that is big!!!

Quoting MAweatherboy1:
Good morning... And happy Saturday! End of the 6z GFS run: Atlantic going wild as a monster trough swings into the NE.

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Already some decent, but non severe storms out there, about to head into Buffalo. I'll be providing radar images today :)

Member Since: February 11, 2012 Posts: 79 Comments: 7297
Quoting MAweatherboy1:
Good morning... And happy Saturday! End of the 6z GFS run: Atlantic going wild as a monster trough swings into the NE.


Good morning MA, I see multiple storms/ t-waves and the GFS has been consistently bring down a pretty strong trough into the Great Lakes and NE.
Member Since: March 16, 2012 Posts: 123 Comments: 7887
Good morning... And happy Saturday! End of the 6z GFS run: Atlantic going wild as a monster trough swings into the NE.

Member Since: February 11, 2012 Posts: 79 Comments: 7297
please do not take your eyes off the road to watch leslie 90l is coming
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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
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*90l cold front combo*..never know what to expect alittle cheese on mind
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Good morning everyone, dry air is still affecting Leslie so I think she will only get back up to a cat1.
Member Since: March 16, 2012 Posts: 123 Comments: 7887
Quoting yonzabam:
Oklahoma derecho kills four. Is this the same system that's headed for the north east? Obviously the reporter's got the wind speed wrong. Those figures might be the forward speed of the system.


NOWATA, Okla. (AP) %u2014 Authorities say four people %u2014 including an infant %u2014 have been killed as thunderstorms swept through northeast Oklahoma.

Nowata County Undersheriff Doug Sonenberg tells KSWO-TV the infant and two adults were killed Friday when heavy winds destroyed a mobile home. They were found in a creek.

The Oklahoma Highway Patrol also reported that Ash Grove, Mo., resident Jimmy King was killed when straight-line winds flipped the semi he was driving onto a cement barrier wall and trapped him inside near Afton.

Troopers say the 70-year-old King was pinned in the wreckage for nearly three hours and died at the scene of massive injuries.

The storms were part of a system that unleashed winds of 25 mph to 35 mph as it moved through the state.






I found this:NOWATA, Okla. (AP) %u2014 Four people, including a young child, were killed when strong winds accompanying severe thunderstorms blew through northeastern Oklahoma, authorities said.

Two adults and a child were killed Friday when straight-line winds destroyed a mobile home in Nowata County, located along Oklahoma's border with Kansas, Undersheriff Doug Sonenberg told KSWO-TV. They were found in a creek.

Authorities didn't identify the three people killed. Sonenberg didn't immediately return calls from The Associated Press early Saturday.

Farther east, straight-line winds flipped a semi onto a cement barrier wall, trapping the driver inside for nearly three hours near Afton in Ottawa County, the Oklahoma Highway Patrol reported. Jimmy King, 70, of Ash Grove, Mo., died at the scene of massive injuries, troopers said.

The storms were part of storm system and cold front that collided with triple-digit temperatures in much of the state on Friday. Wind gusts topping 70 mph were reported at Tinker Air Force Base in Oklahoma City.

Damage to some roofs and a garage also were reported in Nowata County, and tree and power line damage was reported in the Oklahoma City metropolitan area. The winds and storms caused more than 18,100 power outages in western, central and northeastern Oklahoma.

The heavy winds propelled grass fires across the area, and Osage County Undersheriff Lou Ann Brown told the Tulsa World that four people had to be evacuated. Crews were able to slow most of the blazes, and rainfall was expected to assist with the efforts, Brown said.

In just an hour at Tulsa International Airport, the temperature dropped from 101 degrees to 78 degrees.

Marianne McGovern, a legal assistant, said the winds caused her downtown Tulsa office building to sway Friday afternoon.

"You sit here and you feel like you're on a ship kind of," she said. "Everybody was coming out in the hall saying, 'Did you feel that?

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Oklahoma derecho kills four. Is this the same system that's headed for the north east? Obviously the reporter's got the wind speed wrong. Those figures might be the forward speed of the system.


NOWATA, Okla. (AP) — Authorities say four people — including an infant — have been killed as thunderstorms swept through northeast Oklahoma.

Nowata County Undersheriff Doug Sonenberg tells KSWO-TV the infant and two adults were killed Friday when heavy winds destroyed a mobile home. They were found in a creek.

The Oklahoma Highway Patrol also reported that Ash Grove, Mo., resident Jimmy King was killed when straight-line winds flipped the semi he was driving onto a cement barrier wall and trapped him inside near Afton.

Troopers say the 70-year-old King was pinned in the wreckage for nearly three hours and died at the scene of massive injuries.

The storms were part of a system that unleashed winds of 25 mph to 35 mph as it moved through the state.



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Quoting JLPR2:
September 21st, Georges 14th anniversary in Puerto Rico.

If "Oscar" where hundreds of miles to the south, it would be deja-vu. XD


This could happen, a hurricane never follow the other remember that!
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NW florida here. scattered storms moving in from the gulf currently. the circulation is inching closer to the panhandle.

I know shear was forecast to fall into the low range tomorrow. with the convergence of the cold front systems and the circulation i think that there will be some good rains setting up across the middle to eastern gulf coast during the daytime tomorrow.
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719. JLPR2
Not bad, showing some signs of life.

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Currently around Sydney there is hazard reduction burns. Smoke from the burns is showing up on radar.


Click image to view loop.
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CONUS


Australia


WPAC




Live streaming cam
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Looks like tomorrow may be a bit crazy...



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Quoting lobdelse81:

Though as in recent years, we've all seen where those Caribbean systems end up- into Mexico or buried into Central America as a result of that persistent Texas death ridge. I hope it goes away soon for a long time. Those folks could use a nice soaking from a tropical system. Tired of hearing about drought for them.


But there has also been a weakness between the western Atlantic ridge and the central plains ridge, which could allow for a system to sneak up toward the northern Gulf Coast or Florida. This weakness was not there in 2010.
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Quoting NJcat3cane:
anyone think todays squall line thats gonna come threw south new jersey much later today (tomorrow ha) will be worse then the derencho? here in the atlantic city area thats talked about much more then any other storm espically "thunder storm" in quite a while..lots of damage and all that bad stuff..dont need another day like that.....BUT im off tomorrow so bring it on


It's less likely to be a derecho and more likely to be a squall line which bows out along certain sections of the line. 850mb/750mb/500mb winds aren't aligned along the length of the squall line and the surface low will be curving north into Canada quickly too so areas like south jersey where the storms will move through later in the event most of the dynamics and stronger winds aloft wil have moved by. Thats not to say there won't be severe weather in south jersey, just less likely than areas further north, closer to the surface low
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Oh well . thats weather. im out for the night. Ill see where 90fai(L) is in the morning.
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Quoting KoritheMan:


Considering October is right around the corner, where the high becomes weaker anyway, I wouldn't be surprised. Still the potential for a big threat coming up out of the Caribbean, which happened even in 2010 (Karl and Matthew). In addition, our focus shifts toward peninsular Florida in October and November.

Though as in recent years, we've all seen where those Caribbean systems end up- into Mexico or buried into Central America as a result of that persistent Texas death ridge. I hope it goes away soon for a long time. Those folks could use a nice soaking from a tropical system. Tired of hearing about drought for them.
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Quoting lobdelse81:

Is our Bermuda High pretty much bitting the dust for the rest of the season? What a big turn-around compared to how strong it was earlier in the year.


Considering October is right around the corner, where the high becomes weaker anyway, I wouldn't be surprised. Still the potential for a big threat for something coming up out of the Caribbean, which happened even in 2010 (Karl and Matthew). In addition, our focus shifts toward peninsular Florida in October and November.
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Quoting KoritheMan:


At this point it should more or less become absorbed by the front. A little rain should develop, but overall it's a harmless mass of nothing.

Is our Bermuda High pretty much bitting the dust for the rest of the season? What a big turn-around compared to how strong it was earlier in the year.
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Quoting Invest80Lurk:


well im here in the panhandle and would like a little something from it rain wise. "I" was a bit of a letdown. Dont mistake that for wishing for a storm as i am not. just moisture.


Well sad to report, but you're probably not getting it. Even if the shear lets up as some of the models are saying, a strong subsident airmass will follow this cold front, which is a little strong for this time of year.
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Quoting KoritheMan:


At this point it should more or less become absorbed by the front. A little rain should develop, but overall it's a harmless mass of nothing.


well im here in the panhandle and would like a little something from it rain wise. "I" was a bit of a letdown. Dont mistake that for wishing for a storm as i am not. just moisture.
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Quoting islandgirls:


I've read many of your complaints about you not getting any rain and not having the "joy or excitement" of having a storm come your way. Caution: BE CAREFUL WHAT YOU WISH FOR! A nice juicy big one may just decide to pay you a visit. I hope that if/when it comes it does not find you hiding under your bed.

Just to let you know: Your complaints don't bother me though. Keep looking for the prize. I'm looking too, we need rain here in Antigua.


I wished for Isaac because I hadn't had a hurricane since Gustav. My wallet is paying for it now, though. >.>
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Quoting Invest80Lurk:
Hey all. new guy here...glad to be apart of this...90L, 25mph, why is this thing still classified? based on that criteria, i just passed gas that i will call 91L..haha just like 90L it also had no convection. anyway even if/when it makes land fall do you guys think it will have any rain associated?


At this point it should more or less become absorbed by the front. A little rain should develop, but overall it's a harmless mass of nothing.
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The rest of September should be active as far as Hurricanes go but it looks like most if not all of them will recurve out to sea. If Florida gets hit with a Hurricane this year it's going to happen in October.
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Hey all. new guy here...glad to be apart of this...90L, 25mph, why is this thing still classified? based on that criteria, i just passed gas that i will call 91L..haha just like 90L it also had no convection. anyway even if/when it makes land fall do you guys think it will have any rain associated?
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Quoting CaribBoy:


Go to hell Pre 91L fish


I've read many of your complaints about you not getting any rain and not having the "joy or excitement" of having a storm come your way. Caution: BE CAREFUL WHAT YOU WISH FOR! A nice juicy big one may just decide to pay you a visit. I hope that if/when it comes it does not find you hiding under your bed.

Just to let you know: Your complaints don't bother me though. Keep looking for the prize. I'm looking too, we need rain here in Antigua.
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.