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 TomTaylor:
Is a strong tropical storm only several hundred miles off Africa nada to you? That's incredibly impressive to me.


i be impress if it was only 120 hrs out

at 360 hrs iam kinda ROFLOL
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Quoting 954FtLCane:


Nope, at 240 looks further north.


There ain't no Nadine...yet...and I hope there won't be. This thing has tortured us on the Gulf coast for something like two months...or at least it seems like it. The cold front coming down tomorrow should pick up the hot mess and move it east...or north....maybe south...but not west...probably. :)
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Quoting 954FtLCane:


360 and nada....


What is in the Pacific?

Its all fantasy land anyway.
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Quoting MTWX:


Then what is that over off the coast of Africa???


Initializing to far north for it to trek west very far. Of course this is waaayyyy out and to early of course.
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Quoting seminolesfan:
You need to understand the difference between scientific theory and law.

Link


From the webpage:

"Example: It is known that on June 30, 1908 in Tunguska, Siberia, there was an explosion equivalent to the detonation of about 15 million tons of TNT. Many hypotheses have been proposed for what caused the explosion. It is theorized that the explosion was caused by a natural extraterrestrial phenomenon, and was not caused by man. Is this theory a fact? No. The event is a recorded fact. Is this this theory generally accepted to be true, based on evidence to-date? Yes. Can this theory be shown to be false and be discarded? Yes."


About.com apparently doesn't know the working difference between "hypothesis" and "theory". It would be hypothesized that the Tugunska blast was caused by an extraterrestrial explosion. We then test that hypothesis (look for fragments, examine the blast pattern, interview witnesses who saw/heard something, compare what's preserved in Siberia with known impact structures)-- only after we make observations and collect that data can we evaluate that hypothesis.

That's a pretty badly written description of the terminology. I'd give it a C+ at best if one of my geology students submitted that as an assignment (well, they'd get a zero if they brought exactly that webpage, but you get my point...)
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Quoting KEEPEROFTHEGATE:


why do you continue to take cheap shots
i notice you do that a lot


Just my own personal troll.Pinacle of he or she's day is giving my a hard time.Actually kind of sad.
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If Leslie's going to miss Newfoundland to the east, Michael has to get out of the way. It seems like the NHC has Michael farther west than the wundermap has most of the models. Is that because the ECMWF is putting Michael farther west or some other model that's not on the wundermap?
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Quoting 954FtLCane:


192 hrs


GFS please send that storm a little bit more south!
Member Since: October 6, 2007 Posts: 0 Comments: 6424
43. MTWX
Quoting 954FtLCane:


final image at 384 maybe a little homegrown beginning....


When 90L finally gets going!! ;)
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Quoting 954FtLCane:


360 and nada....
Is a strong tropical storm only several hundred miles off Africa nada to you? That's incredibly impressive to me.
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41. MTWX
Quoting 954FtLCane:


360 and nada....


Then what is that over off the coast of Africa???
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final image at 384 maybe a little homegrown beginning....
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Quoting seminolesfan:
You need to understand the difference between scientific theory and law.

Link

Snort! Turns out Newton's Law was wrong. It was corrected by Einstein's Theory. I don't think the difference is as cut and dried as you seem to believe.
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Arrgh! 90L coming back to the Panhandle? Enough with this thing already. Where's my dry ice and silver iodide? I'm going to rent a Cessna 172 and go out and bomb that thing myself. :)
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Quoting TomballTXPride:

The course for what? The course you wish to be on. Not everyone can cater to your specific wishes. We can't talk New England weather all the time, especially when the tropics are active. We can do both you know, especially when they are action systems out there. And GW was not off-topic either in the last blog....fyi.


why do you continue to take cheap shots
i notice you do that a lot
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Fishes only FISHES!!
Member Since: October 6, 2007 Posts: 0 Comments: 6424


360 and nada....
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Quoting hydrus:
No gravity, everything stays because of really tiny suction cups...:)

I heard it was because of invisible gremlins with velcro.

So is 90L gonna do anything or not?
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WTF Nadine is Leslie part II!
Member Since: October 6, 2007 Posts: 0 Comments: 6424


288 hrs.... 12 days and home seems quiet. We may be looking at the end of Cape Verde and back to home cooking with whats looks like some early digging fronts.
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29. MTWX
Looking at the possibility of some significant severe weather for the Northeast tomorrow!

SPC Day 2
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Daily SOI: 14.3
30 Day SOI: -2.1
90 Day SOI: -5.1
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264...
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Thanks DRM. Seems I missed something earlier. Lol. But that's ok. :)
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Quoting ILwthrfan:


The belief in science behind gravity is also very solid an substantial as well...
You need to understand the difference between scientific theory and law.

Link
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Quoting goalexgo:
Does Nadine start moving west at this point? It looks like it to me.


Nope, at 240 looks further north.
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Quoting hydrus:
Greetings.

Hey hydrus! How have you been?
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Quoting 954FtLCane:


216 hrs
Does Nadine start moving west at this point? It looks like it to me.
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Thanks,Dr. Masters,new blog was needed to get us back on course.
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Quoting ILwthrfan:


The belief in science behind gravity is also very solid an substantial as well...
No gravity, everything stays because of really tiny suction cups...:)
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Weather image, nothing to see here...
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10 days.......
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Thanks a bunch Doc! I hated having to do an hourly 'pop-in' to see if we were back to tropical weather talk. Yep, now we are good to go.
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Quoting nigel20:
Thanks Dr. Masters...good morning fellow bloggers.:-)
Greetings.
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216 hrs
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Thanks Dr. Masters...good morning fellow bloggers.:-)
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Quoting seminolesfan:
The belief in the science behind AGW is very solid and substantial. FTFY...


The belief in science behind gravity is also very solid and substantial as well...
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192 hrs
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Mike..
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Quoting GeorgiaStormz:
Thanks Dr Masters

Fellow Bloggers, let us have nothing carry over from the Last blog. :)


Ditto.

I peeped in the door yesterday and last night and immediately slammed it shut each time.
Member Since: October 7, 2005 Posts: 236 Comments: 25249
How about a nice sat pic of the West Pacific...
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nice clean page

thanks doc
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thanx Doc!

Previous blog wasa fun read tho!
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Thank you Dr. Masters.
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Thanks Doc. Wondering if Leslie will ever intensify?


Quoting GeorgiaStormz:



That was once with the first weapon in a giant war.
No garuntees it wouldnt happen in a WWIII if hell broke loose.


But what does that have to do with weather or climate?


Your right politics is a dead street and to each will always have their own. Those line of storms will find a way to miss me again, wonder if the NWS will have back to back busted forecasts. They were calling for 2" of rain today.


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Quoting GeorgiaStormz:
Thanks Dr Masters

Fellow Bloggers, let us have nothing carry over from the Last blog. :)


Agreed!
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well....busy days in the tropics.
Member Since: October 7, 2005 Posts: 236 Comments: 25249
Thanks Dr Masters

Fellow Bloggers, let us have nothing carry over from the Last blog. :)
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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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