90L heads for North Carolina, drenches Bermuda; oil spill changing little

By: Dr. Jeff Masters , 2:54 PM GMT on May 24, 2010

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An extratropical low pressure system (90L) between the Bahamas and Bermuda is moving north-northwest towards North Carolina and is close to tropical storm strength. Last night's ASCAT pass saw a large area of 35 mph winds to the north and east of the center, and buoy 41048 to northeast of 90L's center was seeing sustained ENE winds of 36 mph, gusting to 43 mph this morning. Bermuda is seeing some heavy weather from this storm, with winds blowing at 35 mph on the west end of the island, and the Bermuda radar showing an area of moderate to heavy rain moving over the island. Seas are running 5 - 10 feet in the outer waters of Bermuda today, and are expected to increase to 10 - 14 feet tonight before diminishing on Tuesday.


Figure 1. Visible satellite image of 90L this morning.

Strong upper-levels winds out of the west are creating about 25 knots of wind shear over 90L, but the shear has been gradually decreasing over the past day. Visible satellite loops show that 90L does not have a well-defined surface circulation. The main thunderstorm activity is in a large curved band to the north and northeast of the center. This band is several hundred miles removed from the center, which is characteristic of subtropical storms. I expect that 90L will continue to grow more subtropical in nature today through Wednesday as the shear continues to fall. Sea surface temperatures are near 25°C today and will fall to 23 - 24°C on Tuesday. This is warm enough to support a subtropical storm, but probably not a tropical storm. On Wednesday, 90L will be nearing the warm waters of the Gulf Stream, and SSTs will warm again, to the 24 - 25°C range. This is still pretty cool for a tropical storm, and I expect 90L will never become fully tropical. To understand the difference between a tropical and subtropical storm and why we care, see my subtropical storm tutorial.

The SHIPS model predicts that shear will fall to the medium 10 - 20 knot range by Tuesday. A large amount of dry air to 90L's southwest associated with the upper-level trough of low pressure on top of the storm, as seen on water vapor satellite loops , will hamper transition of 90L to a subtropical or tropical storm. The system will move slowly towards the Southeast U.S. coast over the next two days, making its closest approach to the coast on Wednesday, when most of the models indicate the center will be 200 - 400 miles southeast of Cape Hatteras, North Carolina. All of the major models currently predict that 90L will not make landfall, but will move slowly eastward out to sea on Thursday, when a trough of low pressure moving across the Eastern U.S. picks up the storm. There presently isn't much to be concerned with about this storm, as it appears that it will remain offshore and will become, at worst, a 40 - 50 mph subtropical storm. The National Hurricane Center (NHC) is giving 90L a medium (30% chance) of developing into a depression or tropical/subtropical storm. Wunderbloggers Weather456 and StormW have more on 90L.

Western Caribbean disturbance
A small region of disturbed weather has developed in the Western Caribbean, off the east coast of Nicaragua. Moisture is expected to increase across in this area in the coming days, and by Saturday, the GFS and NOGAPS models predict that shear will drop low enough to permit the possible development of a strong tropical disturbance or tropical depression. This storm would then move northeastward over eastern Cuba early next week. The other models keep the shear high in the Caribbean all week, and do not show anything developing. Thus, the Western Caribbean bears watching later this week, but the conditions appear marginal for development.

Moderate risk of severe weather today in northern Plains
The Storm Prediction Center has placed western Nebraska and portions of South and North Dakota under their "Moderate" risk for severe weather today. They warn that "a couple of strong and possibly long-track tornadoes appear possible given the forecast scenario." Keep an eye on the activity today with our Severe Weather Page.

Major oil threat continues for the coast of Louisiana
Light winds are expected to prevail across the northern Gulf of Mexico all week, resulting in continued oiling threats to the Louisiana shoreline from the mouth of the Mississippi River westward 150 miles, according to the latest trajectory forecasts from NOAA. There is no longer a flow of oil moving southwards towards the Loop Current, and the oil that did move southwards last week was mostly entrained into a counter-clockwise rotating eddy attached to the northern boundary of the Loop Current. Synthetic Aperture Radar (SAR) imagery over the weekend showed that most of this oil has dispersed, and very little of this oil is now visible from space (Figure 2.) Imagery from NASA's MODIS instrument and from NOAA aircraft did not show any oil in the Loop Current headed towards the Florida Keys over the weekend, so that is good news. NOAA comments that there may be some "scattered tar balls" in the Loop Current headed towards the Florida Keys. I expect these scattered tar balls have completed the full loop of the Loop Current and are now headed east towards the Keys, and will pass the Dry Tortugas and Key West sometime Wednesday - Saturday. My guess is that the oil and its accompanying plume of toxic dispersants will be too thin and scattered to cause significant problems in the Keys.


Figure 2. Synthetic Aperture Radar (SAR) image of the oil spill taken at 11:41am EDT Saturday May 22, 2010, by the European Envisat-1 satellite. Only scattered patches of oil are evident in the counter-clockwise rotating eddy on the northern boundary of the Loop Current. A small amount of oil appears to be in the Loop Current, and is moving southward. Image credit: Center for Southeastern Tropical Advanced Remote Sensing, University of Miami Rosenstiel School of Marine and Atmospheric Science. SAR images have a resolution of 8 - 50 meters, and can be taken through clouds and precipitation.

Future threats to the Keys
Mostly offshore winds are expected this week over the northern Gulf of Mexico, thanks to the approach of the 90L storm along the Southeast U.S. coast. It is uncertain if these winds will be strong enough to push oil southward into the Loop Current, though at least one ocean trajectory model does show this occurring. As I discussed in my post Wednesday, the Loop Current is very unstable right now, and is ready to cut off into a giant clockwise-rotating eddy, an event that occurs every 6 - 11 months. At least one ocean model (the Global HYCOM model from the HYCOM consortium) is predicting that such an eddy will form this week. In the event a Loop Current Eddy does break off, it would create a rotating ring of water 250 miles in diameter to the south of the oil spill. Oil moving southwards would tend to enter the giant eddy and circulate around it, not threatening any land areas. Roffer's Ocean Fishing Forecast Service has a nice discussion on the possibility of the Loop Current cutting off into a Loop Current Eddy. Keep in mind, though, that during the first month that a Loop Current Eddy forms, it exchanges a considerable amount of water with the Loop Current. Thus we can expect that a portion of any oil moving southwards into a Loop Current Eddy will find its way into the Loop Current and move past the Florida Keys.

Oil spill resources
My post Wednesday with answers to some of the common questions I get about the spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA trajectory forecasts
Deepwater Horizon Unified Command web site
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Surface current forecasts from NOAA's HYCOM model
Synthetic Aperture Radar (SAR) imagery from the University of Miami

I'll be back with a new post Tuesday morning.

Jeff Masters

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Quoting cg2916:


The thing is too broad, it might not be able to re-gain the convection it lost. Of course, unless ANOTHER low forms under the convection. What low are we on, now, 4?

I lost count at 10.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
Quoting extreme236:


Its possible, but I'd say its gonna be one or the other...either the EPAC or Caribbean.

Yea I agree, one or the other. I am leaning EPAC for now but part of me wants to see something interesting and watch it come across to the other side.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
Quoting Stormchaser2007:
One of the larger areas of vorticity I have seen in a while.



The thing is too broad, it might not be able to re-gain the convection it lost. Of course, unless ANOTHER low forms under the convection. What low are we on, now, 4?
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Quoting cg2916:


Well, have the models say EPAC and the other have says Carib. Maybe it'll literally split in half and form two systems, one in each basin.


Its possible, but I'd say its gonna be one or the other...either the EPAC or Caribbean.
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Quoting pottery:
You nearly caused mr a permanent heart stoppage with that post LOLOLOL
Was off the blog for a little while, came back and saw that, and shouted
unmentionable words.
Please be more considerate in future....
heheheheh


ROFL, same here!
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Quoting HaboobsRsweet:
I am interested in the blob that could be 91L. It has a chance to be the first EPAC storm but has a higher shot to come over to the carb and be the first Atlantic storm haha. So the first challenge is what side will it form up on? lol


Well, half the models say EPAC and the other half says Carib. Maybe it'll literally split in half and form two systems, one in each basin.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Quoting cg2916:
456, you've been quiet, say something!


sometimes humility is a man's best friend
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One of the larger areas of vorticity I have seen in a while. (For a disturbance of course)

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Quoting reedzone:
This was an awesome looking Subtropical Storm

You nearly caused me a permanent heart stoppage with that post LOLOLOL
Was off the blog for a little while, came back and saw that, and shouted
unmentionable words.
Please be more considerate in future....
heheheheh
Member Since: October 24, 2005 Posts: 0 Comments: 24929
Blog just got quiet...
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Once 90L gets out of the way, as Kman noted this morning, sheer will drop a bit and we should all be looking down in the SW Caribbean/Central America region going into June in accordance with climatology in June..
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I am interested in the blob that could be 91L. It has a chance to be the first EPAC storm but has a higher shot to come over to the carb and be the first Atlantic storm haha. So the first challenge is what side will it form up on? lol
Member Since: May 20, 2009 Posts: 0 Comments: 1640
666. StormW

Good evening.

It's a good thing you aren't the superstitious type...

CRS

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456, you've been quiet, say something!
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Quoting HaboobsRsweet:
Dont get me wrong, 90L is still an impressive storm but I think it will come up just short of sub trop status. I do think it will get real close and we are walking a tight rope.


Just like last year's first 90L.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Quoting stormhank:
Whats the current shear values across atlantic basin?? anyone have a link to the shear charts site??


Here.

Quoting Stormchaser2007:
Pretty obvious that something is brewing in the EPAC with that kind of cloud signature.



Impressive.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Dont get me wrong, 90L is still an impressive storm but I think it will come up just short of sub trop status. I do think it will get real close and we are walking a tight rope.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
Quoting reedzone:
This was an awesome looking Subtropical Storm



If that system was around today it would probably have been considered tropical. It seems the definitions for systems have changed and broadened a bit over time.
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Quoting Stormchaser2007:
Pretty obvious that something is brewing in the EPAC with that kind of cloud signature.



yea and based on what I am seeing, the general motion is to the north and east into the Caribbean
Member Since: March 10, 2010 Posts: 1 Comments: 7874
Quoting stormhank:
decent wave comin off africa...seeing decent waves in May prob a harbinger of whats to come ...Link


I just now realized it's been forever since we've watched blobs roll off Africa. But you're right, it looks like a strong, nice-looking wave. Thing is, it might run into South America.

Quoting VAbeachhurricanes:


Setting up? storms cant plan to wait to set up... its been trying to and has been ripped apart. it almost completely separated from the convection if not for a small strip of thunderstorms, its never going to look good.


Well, ask 456. Plus, that'll change when the shear drops and it gets over the warm Gulf Stream.

Quoting reedzone:
This was an awesome looking Subtropical Storm



For a second, I was like, "That can't be 90L, right?"
Member Since: December 21, 2007 Posts: 13 Comments: 3046
EPAC System


90L
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting HaboobsRsweet:

Got to stick with the forecast. No reason to change sides yet. Still doing what I expected it to do too. Tomorrow is going to tell a lot. It could go either way.


Fair enough
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www.wwltv.com CBS NOLA NEWS LIVE
Member Since: July 3, 2005 Posts: 428 Comments: 129910
Member Since: September 10, 2007 Posts: 0 Comments: 11557
Quoting Weather456:


The fat lady is singing early. That is bold statement for something that isn't even reached its full potential.

Got to stick with the forecast. No reason to change sides yet. Still doing what I expected it to do too. Tomorrow is going to tell a lot. It could go either way.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
Pretty obvious that something is brewing in the EPAC with that kind of cloud signature.

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Whats the current shear values across atlantic basin?? anyone have a link to the shear charts site??
Member Since: September 8, 2005 Posts: 0 Comments: 1386
Quoting CycloneOz:
There is a system just north of I-40 in Texas that is currently under a tornado warning.

If Taco did go southwest from Enid...he might be pretty close to this thunderstorm.

We hope he's uplinked soon...

That cell is headed towards Woodward, OK. That is probably going to be his best opportunity to intercept a tornadic cell in OK this evening.

SPC states that the wind shear over C OK is not conducive for super-ell development this evening.
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This was an awesome looking Subtropical Storm

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654. xcool
lol weather456
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting cg2916:


Well, it's currently setting up right now, and it's not supposed to look good. That way, once 90L is out of the shear, it'll be ready to organize, gain convection, and then look good.


Setting up? storms cant plan to wait to set up... its been trying to and has been ripped apart. it almost completely separated from the convection if not for a small strip of thunderstorms, its never going to look good.
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652. IKE
Last Update: 24-MAY-2010 5:07pm EDT

An area of low pressure continues to spin a few hundred miles northeast of the Bahamas. The storm center was located near 28 north, 71 west as of late afternoon Monday. Ships in the area are reporting the lowest pressure to be around 1008 millibars. The storm is causing an area of rain and thunderstorms mainly north and east of the center of low pressure, which is affecting Bermuda.

Over the next couple of days, this storm system will track slowly to the west-northwest. It will remain over waters just warm enough that it likely will gain some tropical characteristics. For now, upper level winds are not particularly favorable for further development as westerly winds are causing shear. However, these unfavorable upper level winds likely will relax over the next couple of days. Should the storm pass over the warmer waters of the Gulf Stream, the storm will have a better chance to become tropical in nature. If this occurs, the first storm name for the 2010 season is Alex.

Whether or not the storm becomes a tropical system, the storm will cause rain, gusty winds and perhaps thunderstorms along the Carolina coastline Wednesday night into Thursday. Also, the East Coast will have rough surf and a high rip current risk from Florida's Space Coast all the way north to Long Island starting on Tuesday and lasting through at least Thursday. After that, the storm will track northeastward, pushed away by another storm system moving into the eastern part of the nation. It is possible that the storm directly impacts Bermuda while on its way out to sea.

By AccuWeather.com Senior Meteorologist Frank Strait
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decent wave comin off africa...seeing decent waves in May prob a harbinger of whats to come ...Link
Member Since: September 8, 2005 Posts: 0 Comments: 1386
Quoting MiamiHurricanes09:
Plans may need to be changed:

May 27th - 72 Hours



That just looks like a TS: .
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Quoting HaboobsRsweet:

depends whos forecast haha. I guess that statement goes both ways. It is doing exactly what I thoughht it would and come up just short of sub trop.


The fat lady is singing early. That is bold statement for something that isn't even reached its full potential.
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Quoting HaboobsRsweet:
I am jumping on the 91L bandwagon and also agree that is where Alex will probably form.


Yup, me too, although it might become Bonnie, if 90L takes the spot. 90L has TS winds at the moment, and it should get better when it hits the Gulf Stream.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Quoting Stormchaser2007:


Im actually more inclined to development in the Caribbean now that I have see about eight consecutive shear forecasts from the GFS that show very low shear in the Caribbean developing in about three days and lasting for about 90% of the run.

In my opinion, this is where Alex could form.
I'm going to go on a limb and say that's where Bonnie will form. Guess we'll see if I will end up regretting this decision.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting scott39:
456 whats your thoughts on a possible 91L in the Carib?


I am watching. I got one monitor on 90L and the next on the SW Caribbean. The SW Caribbean is becoming a TC breeding ground. Something is going to spin up, just don't know exactly what but I suspect that a broad area of low pressure is developing over CA as we speak. Now the energy can consolidate in either the EPAC or SW Caribbean. Regardless of this, I am thinking the area will drift north and while this is occurring, the overhead ridge shifts north in tandem, providing low shear and pushing the subtropical jet to north of 20N.

Heavy rains for Central America occurring all week. Flooding concerns are possible.
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Quoting stormpetrol:
I hope all is clear in the Cayman & Belize area on May 27, don't want any weather to interfere or interrupt my travels plans to Belize!
Plans may need to be changed:

May 27th - 72 Hours

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting cg2916:


Once that thing gets into the Gulf, it should get ripped by shear, although I haven't seen the recent shear models.


Its not forecasted to get into the Gulf, moves NE through Cuba and the Bahamas and out to sea; following 90L and all the other mess
Member Since: March 10, 2010 Posts: 1 Comments: 7874
Quoting HaboobsRsweet:
I am jumping on the 91L bandwagon and also agree that is where Alex will probably form.


I agree with us getting 91L, if you look at the visible loop of that area you will see a very noticeable set up. This kind of cloud pattern more often than not leads to a named system either in the EPAC or the Caribbean
Member Since: March 10, 2010 Posts: 1 Comments: 7874
Quoting MiamiHurricanes09:
GFS 18z 120 Hours. Notice the 1005 MB low in the NW Caribbean/GOMEX entrance.



Once that thing gets into the Gulf, it should get ripped by shear, although I haven't seen the recent shear models.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Sub-tropical storms for the most part dont usually look that good anyway
Member Since: March 10, 2010 Posts: 1 Comments: 7874
I am jumping on the 91L bandwagon and also agree that is where Alex will probably form.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
Quoting HaboobsRsweet:

depends whos forecast haha. I guess that statement goes both ways. It is doing exactly what I thoughht it would and come up just short of sub trop.


While true, those who said it would become a STS said it would not do so until Tuesday, so even in their forecasts it is still not a named system today
Member Since: March 10, 2010 Posts: 1 Comments: 7874
Quoting VAbeachhurricanes:


i hope you know im being sarcastic, due to the fact thats its may 24th and people are freaking out about this storm... see it on satellite? looks so bad, its going to be dropped.


Well, it's currently setting up right now, and it's not supposed to look good. That way, once 90L is out of the shear, it'll be ready to organize, gain convection, and then look good.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Quoting Hurricanes101:


So basically 90L has been doing exactly what has been forecasted and the chances of Subtropical development are still the same as they were 4 days ago?

depends whos forecast haha. I guess that statement goes both ways. It is doing exactly what I thoughht it would and come up just short of sub trop.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
636. xcool
Miami .true.and NGP TOO
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting Weather456:


Correct. The only thing 90L remains stagnant in - is its organization.


The funny thing about all of this is that it has been said, by you, Levi and others from the beginning that development would not occur before Tuesday at the earliest and likely not before 90L got to the Gulf Stream

So really those of us who have been watching 90L since it was first designated on Friday, knew it would not be a named system at this point.
Member Since: March 10, 2010 Posts: 1 Comments: 7874
456 whats your thoughts on a possible 91L in the Carib?
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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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