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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Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Weather456:


Feeling the effects of the Gulf stream...the lapse rate between warm near surface air and cold air aloft is becoming steep.


Yeah, just took a look at the lapse rates and some other parameters off of the SE coast. Interesting.

Looks like 90L could begin to develop some sustainable convection.


Member Since: June 9, 2007 Posts: 4 Comments: 15718
I agree WWB, tomorrow can't come fast enough.
Member Since: Posts: Comments:
twhcracker, the reason the water is murky and not clear, like say Pensacola, is because of the barrier islands stirring up the sand in the water. Well, years ago the drains from the roads used to go into the sound but they found out how bad that was and stopped that. And yes it is shallow, but that's what you get for a man-made beach. And as for the gambling, well let's just say I'm hanging at the Isle for a week while I work out of Pass Christian. Free rooms, gotta love em'
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1. AN AREA OF DISTURBED WEATHER IS LOCATED JUST TO THE WEST OF CENTRAL
AMERICA. DEVELOPMENT...IF ANY...OF THIS SYSTEM IS EXPECTED TO BE
SLOW TO OCCUR. LOCALLY HEAVY RAINS ARE LIKELY TO SPREAD OVER
PORTIONS OF CENTRAL AMERICA OVER THE NEXT FEW DAYS AS THE SYSTEM
MOVES SLOWLY TOWARD THE NORTHWEST. THERE IS A LOW CHANCE...20
PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.

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1179. eddye
that thing in the e pac if it comes into the carribean it could become a ts or hurricane and hit fl or somewhere else because right know it looks really good i think we could be dealing with a system next week
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This is my coffee in the morning

"I wanna be forever young"

Member Since: July 24, 2005 Posts: 407 Comments: 19076
EPAC disturbance
Member Since: June 9, 2007 Posts: 4 Comments: 15718
Quoting Stormchaser2007:
Looks like 90L is developing some 'popcorn' convection near the center.

Life support?



Feeling the effects of the Gulf stream...the lapse rate between warm near surface air and cold air aloft is becoming steep.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting msgambler:
Good Morning Ike, Weather456, Jeff, P451, WWB, and all others I may have forgotten. Hope everyones day is going great. Beautiful day on the Biloxi Beach, as far as I can tell from my hotel window.


I was swimming at biloxi once, well, standing actually, too shallow to swim, the water was murky and something bumped me and I thought shark! but it was a head of lettuce. The beach at biloxi compared to the beach at destin.... oh my. Biloxi is like a bath that needs draining. But gambling is fun...
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1170. msgambler 8:03 AM EDT on May 25, 2010

Morning to you as well.......Beautiful morning along the Gulf this morning, weather wise,; lets hope the "top kill" works...
Member Since: August 8, 2006 Posts: 0 Comments: 8269
Looks like 90L is developing some 'popcorn' convection near the center.

Life support?

Member Since: June 9, 2007 Posts: 4 Comments: 15718
Quoting msgambler:
Good Morning Ike, Weather456, Jeff, P451, WWB, and all others I may have forgotten. Hope everyones day is going great. Beautiful day on the Biloxi Beach, as far as I can tell from my hotel window.


Morning :)
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1171. IKE
BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1015 UTC...

...SPECIAL FEATURE...

DEEP LAYER CYCLONIC FLOW FROM A TROUGH COVERS THE ATLANTIC OCEAN
TO THE WEST OF 60W. SOME OF THE CYCLONIC FLOW EVEN REACHES INTO
THE NORTHWESTERN CORNER AND NORTH CENTRAL SECTIONS OF THE
CARIBBEAN SEA..TO THE NORTHWEST OF THE LINE FROM THE WINDWARD
PASSAGE TO NORTHERN HONDURAS. A 1006 MB LOW PRESSURE CENTER IS
NEAR 30N72W. A 1007 MB LOW PRESSURE CENTER IS NEAR 29N70W.
THE 24 HOUR FORECAST IS FOR THE 29N70W LOW CENTER TO
DISSIPATE...AND THE 1006 MB LOW PRESSURE CENTER WILL DRIFT
NORTHWESTWARD. SHOWERS AND THUNDERSTORMS ARE FROM 20N TO 25N
BETWEEN 55W AND 58W. BROKEN TO OVERCAST MULTILAYERED CLOUDS ARE
MOVING NORTHEASTWARD...FROM 20N TO 26N BETWEEN 60W AND 70W.
BROKEN TO OVERCAST MULTILAYERED CLOUDS AND POSSIBLE PRECIPITATION
ARE WITHIN 90 NM ON EITHER SIDE OF 26N54W 30N60W BEYOND 32N64W.
THE WIND CONDITIONS IN THE AREA OF THIS BULLETIN ARE LESS
THAN GALE-FORCE AT 25/0600 UTC. GALE-FORCE WIND CONDITIONS ARE
BEING EXPERIENCED IN THE ATLANTIC WATERS TO THE NORTH OF THE
BOUNDARY OF THIS BULLETIN.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Good Morning Ike, Weather456, Jeff, P451, WWB, and all others I may have forgotten. Hope everyones day is going great. Beautiful day on the Biloxi Beach, as far as I can tell from my hotel window.
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1169. IKE
Quoting cyclonekid:

That seems to be a good COC. If it's there I don't know why the NHC won't go ahead and classify this Alex.


Void of convection... 20 or higher knots of shear...dry air...

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting Weather456:


Why single out one model when all show shear decreasing? If development is expected around the 30th, why look at shear now?
LMAO Stop that I'm drinking coffee..... Good morning Aqua
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Quoting Jeff9641:


Yep, IKE I see nothing in the foreseeable future in the Caribbean just tropical moisture moving north into Florida this weekend and next week. To much shear right now to support developement.


Why single out one model when all show shear decreasing? If development is expected around the 30th, why look at shear now?
Member Since: July 24, 2005 Posts: 407 Comments: 19076
In the short term another thing to keep an eye on is the e-pac vs. atlantic basin activity. I am not perfectly clear on the actual relationship between the two and issues related to MJO movement, but we have observed in the past this "inverse" relationship where cyclogenisis slows down on the Atlantic side, when e-pac ramps up and vice versa. My point is that if the e-pac ramps up and churns out a few storms in June, things might stay quieter in the meantime on the Atlantic side until July......I don't have the time to do it but it would be nice to make a comparison of early season activity (June/July) in the Atlantic vs. E-Pac during El Nina years to see if this concept holds water.
Member Since: August 8, 2006 Posts: 0 Comments: 8269


Member Since: July 24, 2005 Posts: 407 Comments: 19076
Aquak9 "posts like that- a lotta blowing air- could tend to create an increase in shear, I suppose..."

lol
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1163. aquak9
Quoting hurricanelover236:
Im telling you shear is not going to drop. I can assure everyone its gonna stay strong most of the season discouraging a lot of activity. this year may very well be no different than last year.I foresee very little action.


posts like that- a lotta blowing air- could tend to create an increase in shear, I suppose...
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Quoting largeeyes:
was really hoping to get some rain from 90L


Where do you live?
Member Since: July 24, 2005 Posts: 407 Comments: 19076
anyone know when the shear will diminish?
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1157. gator23
Quoting hurricanelover236:
Im telling you shear is not going to drop. I can assure everyone its gonna stay strong most of the season discouraging a lot of activity. this year may very well be no different than last year.I foresee very little action.


Proof?
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was really hoping to get some rain from 90L
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Buxton, North Carolina: surf 4-5 ft (shoulder to head)

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Good Morning AM Crew......With the exception of whats left of 90L right now and the disturbance down by Central America, sheer levels currently still too high for development out in the MDR. What bothers me however, is the persistent ridging of the A-B high between Bermuda and the mid-Atlantic. Not sure when it will finally "set" for the Summer but if it does so in this general configuation come the CV season, we will not see a lot of recurvature during the heart of the season until we start getting some stronger trofs which might actually come down later than usual in the Fall due to La Nina conditions........That potential beeline from Africa to the Caribbean and Greater Antilles is certainly not something I am looking forward to.
Member Since: August 8, 2006 Posts: 0 Comments: 8269
Quoting IKE:
Hatteras,NC monthly rain total...3.01 in

Charleston,SC monthly rain total...0.31 in


90L...center looks to me to be near 30N and 72W...


That seems to be a good COC. If it's there I don't know why the NHC won't go ahead and classify this Alex.
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This is old from yesterday, but it hasn't changed.


Information Courtesy: Weather Underground
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Quoting Weather456:


Iggy is a man's best friend on this blog.


But an enemy with storms/hurricanes :)
Member Since: April 29, 2007 Posts: 0 Comments: 7506
1150. IKE
Hatteras,NC monthly rain total...3.01 in

Charleston,SC monthly rain total...0.31 in


90L...center looks to me to be near 30N and 72W...

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting stormhank:
Morning fellow bloggers?? Who said shear isnt going to drop all season and we're going to have another 2009?? I guess NOAA, TSR, Dr. Gray and all the others did all that tropical meterology studying for nothing huh


Iggy is a man's best friend on this blog.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
I think the area of low pressure that the Caribbean has to be aware of is around 10N/85W just off the NW coast of Costa Rica on Epac side slowly moving NNE.
Member Since: April 29, 2007 Posts: 0 Comments: 7506
Quoting Weather456:
90L is feeling the effects of the Gulf Stream.
Thanks for your update. Informative as usual.
Member Since: October 9, 2008 Posts: 0 Comments: 8242
Morning fellow bloggers?? Who said shear isnt going to drop all season and we're going to have another 2009?? I guess NOAA, TSR, Dr. Gray and all the others did all that tropical meterology studying for nothing huh
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90L is feeling the effects of the Gulf Stream.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
00z NOGAPS 120 Hours.

Notice the 1006 MB low in the Caribbean. Also notice a 1005 MB low north of Puerto Rico.

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1143. MahFL
Superweatherman...there is still at least 20 kts of shear over 90L.
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Blog Update

Little change to 90L has it heads towards the Carolinas; Central America flood threat
Member Since: July 24, 2005 Posts: 407 Comments: 19076
90L is trying to pull the thunder storm activity back to the center this morning.... we may just have Alex by tonight if it continues... what do think?... And remember it has not been able to keep it in the center since the beginning... having no shear is help it.... also it on top of the gulf stream.
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Quoting hurricanelover236:
Im telling you shear is not going to drop. I can assure everyone its gonna stay strong most of the season discouraging a lot of activity. this year may very well be no different than last year.I foresee very little action.
Ok????
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Quoting hurricanelover236:
Im telling you shear is not going to drop. I can assure everyone its gonna stay strong most of the season discouraging a lot of activity. this year may very well be no different than last year.I foresee very little action.


you obviously haven't been reading/paying attention to anything on here or in the news in the past 3 months.
Did you know there's an oil spill in the gulf too?
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Quoting Weather456:
I am becoming more confident of an Alma-Arthur scenario.

Morning all
I am too. This system is looking very nice on satellite right now.

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1137. IKE
Water vapor of eastern USA and 90L, which looks in RIP mode....

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Im telling you shear is not going to drop. I can assure everyone its gonna stay strong most of the season discouraging a lot of activity. this year may very well be no different than last year.I foresee very little action.
Member Since: Posts: Comments:

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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.

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