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 guygee:
Agreed. But it is still a good source for educational material and research. There are some fairly advanced topics covered in mathematics and science. I am not going to put down Wikipedia, especially when the greedy publishers of scientific literature have the gall to charge $20-$50 per paper.

Academics only get published if they sign away their copyright to those publishers, and they never see a penny of that money...in fact there is often a nominal "page charge", for example it could be something like a couple hundred dollars for every page over five.

Society benefits when cutting-edge scientific knowledge is freely available to the general public. Society does not benefit from the greedy publishers and various scientific societies that leech off of academia.

Academic publishing is a racket.

Wikipedia is great for this blog. I can always check out any Wiki articles to see how well they are sourced.

I wish people would cite their sources on here more often. I generally don't believe anything anyone says on here just because they said it. I learn a lot from the blog, but the face value of everything is just opinion. Citing sources is a big plus. Not everyone does that unfortunately.

The NWS field office web sites are great, too. I'm surprised at the number of people posting questions on here that are readily answered by the local NWS office website.

Time to start the rinse cycle.
Member Since: May 18, 2006 Posts: 10 Comments: 6096
Quoting weatherbro:


yeah but they also say that the flow will veer soon after the front clears. So other then some comfy dewpoints on Tuesday(55-59), the onshore flow will creep them back up Weds onwards.

What we need this time of year is a nice cut-off low off the Carolina's or better yet a post-frontal high to settle in the GOM to keep the cool continental air pumpin. Which I believe a more potent front will do around the 21st!!!
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www.weather.bm
Quoting spathy:


Yes a wink is far better than an evil eye.

What is the drought /rain situation for Bermuda?
Have they been dry this season?


Member Since: September 3, 2008 Posts: 0 Comments: 605
...NOAA HURRICANE HUNTER AIRCRAFT REPORT LESLIE HAS CHANGED LITTLE IN STRENGTH...
11:00 PM AST Fri Sep 7
Location: 27.6°N 62.3°W
Moving: N at 3 mph
Min pressure: 983 mb
Max sustained: 65 mph

...MICHAEL WEAKENS WHILE MOVING SLOWLY NORTHWESTWARD...
11:00 PM AST Fri Sep 7
Location: 31.8°N 41.8°W
Moving: NW at 6 mph
Min pressure: 974 mb
Max sustained: 100 mph
Member Since: March 16, 2012 Posts: 127 Comments: 7959
Quoting spathy:


Sounds like a money making opportunity to me!

I wonder why capitalists arent lining up?

Or are they?
They are sneaky when it comes to be the first to make money.

We dont want people to make money now do we?
That just gives revenue to a spend-aholic Gov.
Truthful sarcasm flag on!
Watching 'Frozen Planet' at the moment and according to the program the countries around the Arctic Circle are scrambling to lay claim to the ground beneath the water...many of the energy companies operating there are using the unprecedented melt to lower their transportation costs.
Member Since: August 2, 2011 Posts: 0 Comments: 291
FORECAST SOUNDINGS FROM NRN NJ NWD THROUGH
THE HUDSON VALLEY SUGGEST TORNADOES ARE POSSIBLE IF DISCRETE
SUPERCELLS CAN EVOLVE AHEAD OF THE MAIN LINE AND WITH CIRCULATIONS
WITHIN THE LINE.


Agree with the SPC on that one. 1500 CAPE, high EHI, high wind shear, strengthening low pressure system. This is coming together for a very significant severe weather outbreak tomorrow. The supercells will pose a major risk for tornadoes, but the squall line itself will produce significant damage across the Northeast.

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Quoting Naga5000:


What I meant is while it can be useful, most professors will not allow it for research or citation purposes. Wikipedia is a handy tool, but I always think of it like our very own version of The Hitchhikers Guide to the Galaxy.


good one.
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Quoting guygee:
I disagree. It can be useful for educational purposes in mathematics. If I can write a proof for the theorem that I am presenting in a Wikipedia article, then what is the problem?

If you mean it is not usable as a citation in the scientific literature, then obviously you are correct.


What I meant is while it can be useful, most professors will not allow it for research or citation purposes. Wikipedia is a handy tool, but I always think of it like our very own version of The Hitchhikers Guide to the Galaxy.
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Quoting winter123:
I think I see a eye! (it had to be said.)


I think you mean a wink.
Anyway, looks like good news for Bermuda.
And now that I've seen those tantalizing pictures would like to visit that island sometime!
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Good evening Blog, Leslie looks awful!
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LinkCheck this out


MESOSCALE DISCUSSION 1922
NWS STORM PREDICTION CENTER NORMAN OK
0824 PM CDT FRI SEP 07 2012

AREAS AFFECTED...AR/FAR SOUTHEAST MO/SOUTHERN IL/WESTERN KY TO WESTERN TN AND NORTHERN MS

CONCERNING...SEVERE THUNDERSTORM WATCH 630...632...

VALID 080124Z - 080300Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 630...632...CONTINUES.

SUMMARY...DAMAGING WINDS WILL REMAIN A CONCERN INTO LATE EVENING WITH AN EXTENSIVE SQUALL LINE FROM SOUTHERN IL/FAR SOUTHEAST MO AND CENTRAL/NORTHEAST AR INTO WESTERN/CENTRAL KY...WESTERN/MIDDLE TN...AND NORTHERN MS. SEVERE THREAT CONTINUES TO QUICKLY WANE ACROSS SEVERE TSTM WATCH 630...WHILE CONTINUING ACROSS 632 UNTIL 05Z...WITH NEWLY ISSUED WATCH 633 TO THE EAST OF WW 632 /UNTIL 07Z/.

DISCUSSION...SOUTHWESTERN HALF OF A 500-MILE EXTENSIVE SQUALL LINE EXTENDS FROM THE WABASH/LOWER OH RIVER VICINITIES OF SOUTHWEST INDIANA/SOUTHERN IL AND FAR SOUTHEAST MO/FAR WESTERN KY SOUTHWESTWARD TO NEAR I-40 IN AR/JUST NORTH OF LITTLE ROCK AS OF 0115Z. A DEGREE OF COOLING HAS OCCURRED POST-SUNSET WELL AHEAD OF THE SQUALL LINE...BUT THE PRE-COLD FRONTAL/SQUALL LINE AIRMASS NONETHELESS REMAINS MOIST /UPPER 60S TO LOWER 70S F SURFACE DEWPOINTS/ AND MODERATELY UNSTABLE. THIS IS ESPECIALLY THE CASE ACROSS MUCH OF KY/FAR NORTHEAST AR INTO TN WITH BOUNDARY LAYER ADJUSTED 00Z OBSERVED SOUNDINGS FROM LITTLE ROCK AND NASHVILLE INDICATIVE OF AS MUCH AS 2000-2500 J/KG MLCAPE.

WHILE THE BOUNDARY LAYER WILL CONTINUE TO COOL AND CINH WILL GRADUALLY INCREASE WITH TIME...THE ORGANIZED NATURE OF THE SQUALL LINE AND AMPLE VERTICAL SHEAR/LARGE SCALE ASCENT WILL HELP MAINTAIN A DAMAGING WIND THREAT SOUTHEASTWARD INTO EASTERN AR AND WESTERN/CENTRAL KY AS WELL WESTERN/MIDDLE TN...AND EVENTUALLY NORTHERN MS/PERHAPS FAR NORTHERN AL THROUGH LATE EVENING/EARLY IN THE OVERNIGHT. THAT SAID...SOME SEVERE HAIL WILL ALSO BE POSSIBLE WITH SEMI-DISCRETE STORMS IMMEDIATELY AHEAD OF THE SQUALL LINE.

..GUYER.. 09/08/2012

LAT...LON 34539361 35839150 38118866 38118722 36568681 34458857 34539361

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Quoting TropicalAnalystwx13:
In addition to tomorrow being a significant wind event for the Northeast United States, the threat for tornadoes also exists, and it is quite high. We've got an intense mid- and low level jet stream intersecting an intense boundary layer that consists of dew points in the 60s and 70s. In addition, a deepening surface low over southeast Ontario should exasperate the shear profiles across eastern New York and Pennsylvania, southern Vermont and New Hampshire, New Jersey, and western Massachusetts. Even though winds back and shift with height...the main scene type should be quasi-linear. This means that, while the squall line will be the significant issue, if supercells form ahead of it, we could have some problems.

All things considered, I'd give portions of the aforementioned area a 10% hatched tornado threat tomorrow.



I agree, it is quite possible they go with the 10% hatched area. Instability is adequate, especially for the Northeast. Also, EHI values could range close to 2 or higher in southern New York, leading to a higher tornado risk. As with most squall lines, they often produce individual cells out ahead of them, though they are isolated, and this, plus a 40 to 50 knot LLJ, and a strengthening MLJ with the low pressure system, this should pose a higher tornado threat than advertised, even within the squall line.
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585. wxmod
For all you geoengineering buffs out there, this satellite photo is interesting because, in the top third of the photo there are contrails that you can barely see (you may not even see them on the blog photo. Trust me, they are there.) In the bottom third of the photo there are the shadows of those contrails plainly visible on the arctic ice. MODIS today

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Quoting GTcooliebai:
If the front clears look for humidity to drop, especially over night into the dawn hours, at least it should be comfortable to sleep at night.


yeah but thay also say that the flow will veering soon after the front clears so other then some comfy dewpoints on Tuesday(55-59), the onshore flow will creep them back up Weds onwards.

What we need this time of year is a nice cut off low off the Carolina's or a post-frontal high to settle the the GOM to keep the continental air pumpin. Which I believe a more potent front will do around the 21st!!!
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583. etxwx
Rains, thunderstorms pummel Visayas, Mindanao
Friday, September 7th, 2012 MANILA, Philippines Thunderstorms pummeled Eastern Visayas and Mindanao as a developing cyclone hovered over the area, the state weather bureau said Friday.

The low pressure area was last seen 380 kilometers east of Surigao, the Philippine Atmospheric Geophysical and Astronomical Services Administration said.

Southern Luzon, Visayas and Mindanao will experience cloudy skies with scattered rain showers and thunderstorms becoming widespread rains over Visayas which may trigger flash floods and landslides.
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Michael
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Quoting percylives:
There it is folks. Link Probably three more years before there is no ice in the Arctic Ocean in the late summer.

Book your Arctic Ocean cruise to be on the first liners to float around on the pole.


Holy hyperbole!
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Quoting Chicklit:

Not like last year, eh Nigel?
Are you getting any rain?

Yeah, we had quite a bit of rain today, but it has been hot and dry otherwise.
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I think I see a eye! (it had to be said.)
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Quoting nigel20:

Hey TA! Do you think we'll see late season development in the western Caribbean?

Not like last year, eh Nigel?
Are you getting any rain?
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Quoting AegirsGal:
It is not usable for any kind of citation, for science, mathematics, literature, etc.

Not academically, yes you're right. But for just checking up on history, background information, it's a terrific resource for us 'laypeople' who are just wanting to know stuff and aren't experts in the field.
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Quoting guygee:
I disagree. It can be useful for educational purposes in mathematics. If I can write a proof for the theorem that I am presenting in a Wikipedia article, then what is the problem?

If you mean it is not usable as a citation in the scientific literature, then obviously you are correct.

I cannot cite Wiki as a source in my graduate studies; however, I use it regularly as a resource for cultural and historical information.
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What effect will it have on Leslie and Michael to track closer to one another as they travel north?
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460 TomTaylor: [inre page10comment451] You post these maps all the time and I honestly have no idea what they mean. Feel free to enlighten me.

Why I do them and a rather lengthy explanation of why I post them in the form they have.
(You can skip the blockquote -- though there's some useful info -- to get to the part about "clockface" compass headings and about time as distance.)
Member Since: August 21, 2007 Posts: 0 Comments: 4860
Quoting BDADUDE:
Cant believe Cantore is here!!


You do know that bodes poorly for Bermuda, right? ;-)
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571. yoboi
Quoting Tazmanian:
90L rip



nah it's still kicking i just got some rain from it
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570. SLU
Quoting CaribBoy:


Though the season remains a bust for my area lol I'm in the Leewards.


Where were you during the 6 hurricanes in 5 years in the late 90's?
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.
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Quoting Chicklit:

Congratulations Nigel

Thanks!
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Quoting TropicalAnalystwx13:
The Atlantic is currently the only basin on the blog hosting tropical cyclone activity. Amazing for the month of September.


But we have 2 named storms and a tropical wave that should be named in a few days. Strange to see no activity everywhere else.
Member Since: March 16, 2012 Posts: 127 Comments: 7959
Quoting Grothar:


Sorry, sar. You know I think you great, and I really enjoy your blogs.

1. I never said the story of Atlantis was true.
2. I've seen the translations from the Egyptian
scrolls.
3.

Gro, I've also seen the Egyptian scrolls...but they were already translated to Greek. The thing is, no one has ever seen the purported original Egyptian scrolls. Plato says he saw the Greek translations bought back by Solon, but Solon never wrote about traveling to Egypt or mentioned the Egyptian scrolls in any of his other writings.

I didn't mean to imply you thought the Atlantis legend was true, since I know you're too smart a guy for that. I'm just not convinved that this legend wasn't made up from whole cloth by Plato. He was kind of known for tall tales. :)

BTW, I think you're great too, and your blogs are much better than my pathetic attempts at writing.
Member Since: October 2, 2004 Posts: 0 Comments: 16324
Yep...somebody is definitely going to have some problems if supercells decide to form ahead of the squall line tomorrow afternoon. A lot of wind shear for strong updrafts capable of supporting a few strong tornadoes.



Member Since: July 6, 2010 Posts: 113 Comments: 32528
The Atlantic is currently the only basin on the blog hosting tropical cyclone activity. Amazing for the month of September.

Member Since: July 6, 2010 Posts: 113 Comments: 32528
West Pacific
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Quoting nigel20:
Jamaica has created history by beating the US 2-1 in international football (soccer) for the first time:-)

Congratulations Nigel
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Jamaica has created history by beating the US 2-1 in international football (soccer) for the first time:-)
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Quoting guygee:
Agreed. But it is still a good source for educational material and research. There are some fairly advanced topics covered in mathematics and science. I am not going to put down Wikipedia, especially when the greedy publishers of scientific literature have the gall to charge $20-$50 per paper.

Academics only get published if they sign away their copyright to those publishers, and they never see a penny of that money...in fact there is often a nominal "page charge", for example it could be something like a couple hundred dollars for every page over five.

Society benefits when cutting-edge scientific knowledge is freely available to the general public. Society does not benefit from the greedy publishers and various scientific societies that leech off of academia.

It has been about a year since I was in college, studying Business and Marketing. At that time, all of my Profs were adamant about staying away from Wikipedia for source material. Using it as a tool for getting published, as required for doctoral level study, seems like a great way to cut down on the costs associated.
Member Since: August 2, 2011 Posts: 0 Comments: 291
Quoting percylives:
There it is folks. Link Probably three more years before there is no ice in the Arctic Ocean in the late summer.

Book your Arctic Ocean cruise to be on the first liners to float around on the pole.


Shell Oil already has.

See comment #4
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Quoting Tazmanian:
90L rip



Not yet!
Member Since: June 26, 2008 Posts: 0 Comments: 421
557. auburn (Mod)
Quoting goalexgo:
I believe the Planfalf numbers are derived from these maps.


Yea..thats it..keep on dreaming...whats the point of this post?hey ya got a link?
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556. txjac
Come on Florida, Louisiana, Mississippi and Alabama foks ...share some rain with Texas ...makes 90L come our way ...dont need it to pull to the NE
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90L rip
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552. beell
wiki even does forecasts!

On September 7, Leslie weakened to a tropical storm but forecast to regain hurricane strength. Also, Leslie appeared likely to miss Bermuda.[152]

Link
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Bermuda Radar
Member Since: September 3, 2008 Posts: 0 Comments: 605

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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.