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 reedzone:
Maybe it's me.. but I can see a new well developed center forming right underneath the new convection, see how it's starting to roll around?

Possible center relocation around 31N 68W


The upper level low is closing in on it, which means it's best chance for transition is TONIGHT! We'll see what happens, but I think a center may form there do to deep convection trying to wrap around that location.


Agreed on the new center forming, but I still think it won't transition till at least this time tomorrow.
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Quoting JamesSA:

It is showing the ROV arms holding on to the valve on the siphon tube.


Oh ya the little straw!
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Quoting AllStar17:


I'd agree.

Hi.
Did you get my email?
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Quoting TampaSpin:
What is BP doing on the Live Video

It is showing the ROV arms holding on to the valve on the siphon tube.
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Quoting stormhank:
I think 90 L is just a soldier scout sampling the atlantic for the on sluaght of drone queen and king storms we're going to deal with this season


I'd agree.
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Quoting Hurricanes101:


They system still has multiple vorticies but the main center it is rotating around appears to be further south and west of your location

Id say around 29.5N 71W

but there are so many circulations embedded into 90L it is hard to tell


Yeah thats the current center, but I would think the new low that forms would like to be tucked in some deeper convection. It's a wait and see..
Member Since: July 1, 2008 Posts: 13 Comments: 7334
528. xcool
Hurricanes101 GUESS keep watching, it
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527. IKE
SYNOPSIS FOR THE SW N ATLC INCLUDING THE BAHAMAS
530 PM EDT MON MAY 24 2010

.SYNOPSIS...BROAD AND ELONGATED AREA OF LOW PRES PERSISTS ACROSS
THE SW N ATLC THIS MORNING CENTERED ALONG 69/70W...WITH MEAN
CENTER NEAR 28N69.5W 1007 MB...AND TROUGH EXTENDING S THEN SW TO
THE WINDWARD PASSAGE. ENTIRE SYSTEM WILL SHIFT NW THROUGH LATE
WED AS CENTRAL LOW PRES REACHES NEAR 32N74W...AND THEN BEGIN TO
SHIFT BACK SLOWLY TOWARD THE E-NE DURING THE LATTER HALF OF THE
WEEK AS A COLD FRONTAL SYSTEM MOVES INTO THE NW ATLC. AN
ASSOCIATED WEAK COLD FRONT WILL DRAG E ACROSS THE NW WATERS THU
REACHING THE CENTRAL BAHAMAS FRI NIGHT.

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Well folks...

With about 15 minutes left until Taco's scheduled broadcast, and having received absolutely no communication from him, I'm led to believe that either he does not have connectivity at his current location, or he's too busy to establish a connection.

So we're going to let the countdown clock expire and begin counting up. We'll trust that Taco makes contact with us as soon as he is able.
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I think 90 L is just a soldier scout sampling the atlantic for the on sluaght of drone queen and king storms we're going to deal with this season
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hey stormhank I think it is
Member Since: June 13, 2009 Posts: 2 Comments: 9553
Spam chaser!!!!

;0
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Quoting reedzone:
Maybe it's me.. but I can see a new well developed center forming right underneath the new convection, see how it's starting to roll around?

Possible center relocation around 31N 68W


The upper level low is closing in on it, which means it's best chance for transition is TONIGHT! We'll see what happens, but I think a center may form there do to deep convection trying to wrap around that location.


They system still has multiple vorticies but the main center it is rotating around appears to be further south and west of your location

Id say around 29.5N 71W

but there are so many circulations embedded into 90L it is hard to tell
Member Since: March 10, 2010 Posts: 1 Comments: 7233
Quoting xcool:
stormhank yeah.


It COULD develop in the Caribbean

That being said based on visible, seems steering is taking this are off to the ENE toward the Caribbean
Member Since: March 10, 2010 Posts: 1 Comments: 7233
Maybe it's me.. but I can see a new well developed center forming right underneath the new convection, see how it's starting to roll around?

Possible center relocation around 31N 68W


The upper level low is closing in on it, which means it's best chance for transition is TONIGHT! We'll see what happens, but I think a center may form there do to deep convection trying to wrap around that location.
Member Since: July 1, 2008 Posts: 13 Comments: 7334
Quoting Ossqss:


straight up or on ice :)



In the shot glass, please. Whatcha got for a chaser?
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Quoting TampaSpin:
What is BP doing on the Live Video

blocking the camera... it's working too.. BP crisis management.
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517. xcool
stormhank yeah.
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Quoting CycloneOz:
Now approaching 30 minutes to Taco's scheduled live broadcast...yet his whereabouts remain an enigma!


straight up or on ice :)

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Quoting CycloneOz:
Now approaching 30 minutes to Taco's scheduled live broadcast...yet his whereabouts remain an enigma!

Most of the action is in NE, SD, ND and MN this afternoon. I already saw 2 tornadoes from 2 different chasers on severestudios.com.
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That area of weather down near central america suppose to develope in carribean??
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Quoting MiamiHurricanes09:
Just send me a mail through that Wu-mail thing. lol.
I agree. Make it public. It is just your opinion and not set in stone so no reason not to publicize it.
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while everyone is eyeing 90L, I'm eyeing that next 100+mph Cane thats going to develop down the road
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Quoting reedzone:
Looking at the northeast side of 90L, some deep storms trying to blow up, I think if 90L get's going, it's gonna be tonight, we'll see.
I agree, it's now or never.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Now approaching 30 minutes to Taco's scheduled live broadcast...yet his whereabouts remain an enigma!
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Looking at the northeast side of 90L, some deep storms trying to blow up, I think if 90L get's going, it's gonna be tonight, we'll see.
Member Since: July 1, 2008 Posts: 13 Comments: 7334
What is BP doing on the Live Video
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506. xcool
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not my employer,
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I just installed an Instant Messanger that you all that use the site will love.....if you get time check it out!
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Someone mentioned to pull up that chordgrass soaked in oil and light the end up and smoke a stogie
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BP enriched,..

If you gotta come and ask me,well..ya resources must be Limited a tad.

Member Since: July 3, 2005 Posts: 414 Comments: 125530
hows those wetlands Pat
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Just follow the Paper Mill smell to Bogalusa,La.
Member Since: July 3, 2005 Posts: 414 Comments: 125530
Quoting StormW:
Just listening to TV...Local Met. Dennis Phillips just mentioned that area over Central America should move into the Caribbean. I think he read my synopsis again.


I saw that too StormW
Member Since: March 10, 2010 Posts: 1 Comments: 7233
Quoting Floodman:


I don't know how much I trust a guy that thinks forestry is a larger industry in Louisiana than Fishing...LOL

Now that I think about it, we do have a bunch of paper mills...I wonder how close they are to one another...

*might have to go check that out*
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If anyone wants winning lotto ticket numbers,

..dont wu-mail me
Member Since: July 3, 2005 Posts: 414 Comments: 125530
Quoting tramp96:

Make it public
-----------------------------------------------

I 3rd that
Member Since: June 13, 2009 Posts: 2 Comments: 9553
Quoting IKE:


It is hot outside.

wunderground shows record high here at 88... i would Love it to cool down to 88! saw some PWS around here top 97.
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the 90L invest should win an award for best looking moisture tail but not so much for a well defined COC. But this system has a lot of potential..
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Quoting masonsnana:
I second that
Quoting masonsnana:
I second that
Just send me a mail through that Wu-mail thing. lol.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting tramp96:

Make it public
I second that
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Quoting MiamiHurricanes09:
If anyone would like to know what's my take on the area that should be moving into the Caribbean later this week please WUmail me.

Make it public
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486. IKE
High in my hometown at a PWS....6 miles from here... 96.3 °F
Member Since: June 9, 2005 Posts: 23 Comments: 37858
485. IKE
Quoting Minnemike:

92 degrees here in Minneapolis too... that ain't right!!


It is hot outside.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
If anyone would like to know what's my take on the area that should be moving into the Caribbean later this week please WUmail me.
Member Since: September 2, 2009 Posts: 130 Comments: 21032

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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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