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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634. scott39
10:44 PM GMT on May 24, 2010
456 whats your thoughts on a possible 91L in the Carib?
Member Since: June 13, 2009 Posts: 0 Comments: 6912
633. VAbeachhurricanes
10:44 PM GMT on May 24, 2010
http://www.spc.noaa.gov/products/watch/

From Canada to Mexico... Stay safe
Member Since: September 6, 2007 Posts: 0 Comments: 6705
632. MiamiHurricanes09
10:44 PM GMT on May 24, 2010
GFS 18z 120 Hours. Notice the 1005 MB low in the NW Caribbean/GOMEX entrance.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
631. cg2916
10:43 PM GMT on May 24, 2010
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. I think this is where we will see Alex.


I say that has more of a shot at being Alex than 90L, but of course, it is very early.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
630. stormpetrol
10:43 PM GMT on May 24, 2010
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!
Member Since: April 29, 2007 Posts: 0 Comments: 8134
629. VAbeachhurricanes
10:43 PM GMT on May 24, 2010
Quoting cg2916:


I beg to differ...


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.
Member Since: September 6, 2007 Posts: 0 Comments: 6705
628. Cavin Rawlins
10:43 PM GMT on May 24, 2010
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?


Correct. The only thing 90L remains stagnant in - is its organization.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
627. Stormchaser2007
10:42 PM GMT on May 24, 2010
Quoting CybrTeddy:
Most likely going to see 91L in this area..



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.
Member Since: June 9, 2007 Posts: 4 Comments: 15950
626. MiamiHurricanes09
10:42 PM GMT on May 24, 2010
Quoting VAbeachhurricanes:
Probably be a Cat 1 hurricane, and will loop around get into the gulf hit the oil spill become a Cat 5 and hit New Orleans... IMHO of course...
Very interesting opinion you have there buddy, lol.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
625. Cavin Rawlins
10:41 PM GMT on May 24, 2010
90L has till Thursday/Friday to become subtropical. That is a decent amount of time still given.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
624. cg2916
10:40 PM GMT on May 24, 2010
Quoting VAbeachhurricanes:
Probably be a Cat 1 hurricane, and will loop around get into the gulf hit the oil spill become a Cat 5 and hit New Orleans... IMHO of course...


I beg to differ...
Member Since: December 21, 2007 Posts: 13 Comments: 3046
623. Hurricanes101
10:40 PM GMT on May 24, 2010
Quoting Weather456:


It has not change much in organization. It is continues to merge with the shortwave near the East Coast so in terms of set-up, it is doing what it should.


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?
Member Since: March 10, 2010 Posts: 1 Comments: 7874
622. cg2916
10:39 PM GMT on May 24, 2010
Quoting IKE:
18Z GFS @ 126 hours...



Nice system in the Carib.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
621. VAbeachhurricanes
10:39 PM GMT on May 24, 2010
Probably be a Cat 1 hurricane, and will loop around get into the gulf hit the oil spill become a Cat 5 and hit New Orleans... IMHO of course...
Member Since: September 6, 2007 Posts: 0 Comments: 6705
620. Cavin Rawlins
10:38 PM GMT on May 24, 2010
Quoting cg2916:
Hey, 456, is 90L still doing what it's supposed to?


It has not change much in organization. It is continues to merge with the shortwave near the East Coast so in terms of set-up, it is doing what it should.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
619. MiamiHurricanes09
10:38 PM GMT on May 24, 2010
Quoting xcool:
Orange.100% .not red
I wouldn't say "100%". There is always a possibility.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
617. cg2916
10:38 PM GMT on May 24, 2010
Hey, 456, you're back!
Is 90L still doing what it's supposed to?
Member Since: December 21, 2007 Posts: 13 Comments: 3046
616. IKE
10:38 PM GMT on May 24, 2010
18Z GFS @ 126 hours...

Member Since: June 9, 2005 Posts: 23 Comments: 37860
615. cg2916
10:37 PM GMT on May 24, 2010
Quoting reedzone:


If the NHC is smart, they will keep it at code orange do to the fact the windown of development closes in 2 days. Lots of RIPing going on, people need to be patient and let 90L do it's thing.


Yup, I agree with you.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
614. Cavin Rawlins
10:37 PM GMT on May 24, 2010


Civil Air Terminal, BE (Airport)
Updated: 42 min 15 sec ago 22 °C
Light Rain
Humidity: 88%
Dew Point: 20 °C
Wind: 41 km/h / 11.3 m/s from the East

Pressure: 1017 hPa (Steady)
Visibility: 4.0 kilometers
UV: 0 out of 16
Clouds: Scattered Clouds 243 m
Mostly Cloudy 457 m
Overcast 1524 m
(Above Ground Level)
Elevation: 3 m
Member Since: July 24, 2005 Posts: 407 Comments: 19076
613. cg2916
10:36 PM GMT on May 24, 2010
Quoting GeoffreyWPB:
90L...Orange or Yellow later this evening? I see some predicted Red...highly unlikely.
'

Still Orange at 30%, I'd say.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
612. reedzone
10:36 PM GMT on May 24, 2010
Quoting GeoffreyWPB:
90L...Orange or Yellow later this evening? I see some predicted Red...highly unlikely.


If the NHC is smart, they will keep it at code orange do to the fact the windown of development closes in 2 days. Lots of RIPing going on, people need to be patient and let 90L do it's thing.
Member Since: July 1, 2008 Posts: 13 Comments: 7437
611. xcool
10:35 PM GMT on May 24, 2010
Orange.100% .not red
Member Since: September 26, 2009 Posts: 2 Comments: 15684
609. MiamiHurricanes09
10:35 PM GMT on May 24, 2010
Quoting TampaSpin:


Hey Geoff i don't see any chance of Red.....likely will be dropped completely soon IMO!
Not going to happen. Cyclone phase evolution graph showing that 90L is getting close to become warm core. Don't write off 90L yet, wait another 60 hours and then we should know if 90L developed or not.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
608. cg2916
10:34 PM GMT on May 24, 2010
Quoting TampaSpin:


Ya its truly going POOOOOFFFF!


Now, the reason I'm asking 456 is because he said this:

This is supposed to become subtropical, which is different from tropical. It's not supposed to look good yet (plus, it's under shear), because it needs to organize low-wise and circulation-wise, which it was and maybe still is doing, then look better convection-wise. So, if this was supposed to be tropical, then it would not be good, but it's supposed to be subtropical.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
606. MiamiHurricanes09
10:33 PM GMT on May 24, 2010
Quoting GeoffreyWPB:
90L...Orange or Yellow later this evening? I see some predicted Red...highly unlikely.
I'm expecting Orange.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
605. TampaSpin
10:33 PM GMT on May 24, 2010
Quoting GeoffreyWPB:
90L...Orange or Yellow later this evening? I see some predicted Red...highly unlikely.


Hey Geoff i don't see any chance of Red.....likely will be dropped completely soon IMO!
Member Since: September 2, 2007 Posts: 179 Comments: 20448
604. reedzone
10:32 PM GMT on May 24, 2010
I'm one of the few still holding on to 90L, lets not forget that it HAS NOT hit the Gulf Stream yet. I'm giving the window of development still a medium chance as is the NHC. Tonight thru Thursday, after that, it get's swept out to sea.
Member Since: July 1, 2008 Posts: 13 Comments: 7437
603. GeoffreyWPB
10:31 PM GMT on May 24, 2010
90L...Orange or Yellow later this evening? I see some predicted Red...highly unlikely.
Member Since: September 10, 2007 Posts: 0 Comments: 11557
602. MiamiHurricanes09
10:29 PM GMT on May 24, 2010
90L getting close to a symmetric warm core. GFDL 12z.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
601. KeyWestwx
10:29 PM GMT on May 24, 2010
Great oil spill updates on this site! Thank you! Liivng in Key West and being in the vacation home rental company business, I and my co-workers are keeping a watchful eye on the evolution of this story. Though, who every reads this, and they know of anyone that wants to come to the Keys, the beaches have never been cleaner and we have had no effects from the spill. So come on down and visit our beautiful island chain
Member Since: September 20, 2008 Posts: 0 Comments: 293
Quoting MrstormX:


Well if convection starts forming around the time the models indicated then its a 95% chance of being 91L due to the fact models have been consistent with it for a while. Plus look how quick 90L was given invest status.


Well, models have been consistent with it forming, but haven't been consisting on how long it'll form, where, and when.

Also, the reason 90L got invest status so quickly is because it formed super quickly. It looks like the Carib. system is on track to do that, but it has a long way to go, since it is currently so disorganized.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Quoting TampaSpin:


Ya its truly going POOOOOFFFF!

Yes it is, yes it is.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
90L still has a shot to develop

It has not yet hit the gulf stream and really some said it would not develop until tomorrow or Wednesday

I know it is hard to track something that doesn't become a Hurricane in 24-36 hours, but in reality most systems take their time to develop

We will see what happens, but as long as the NHC is still watching, I will be as well.
Member Since: March 10, 2010 Posts: 1 Comments: 7874
Quoting cg2916:
Hey, 456, is 90L still doing what it's supposed to?


Ya its truly going POOOOOFFFF!
Member Since: September 2, 2007 Posts: 179 Comments: 20448
*REPOST*
This is the current position of 90L per the W-Underground main tropical site.
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Quoting HaboobsRsweet:
I see some people are still holding onto 90L. Even the GFS looks like it gave up and just starts pushing it east sooner now.


Some?
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Quoting cg2916:
Yeah, I'd say the Caribbean system could be 91L. I'm not sure, but who knows?


Well if convection starts forming around the time the models indicated then its a 95% chance of being 91L due to the fact models have been consistent with it for a while. Plus look how quick 90L was given invest status.
Member Since: Posts: Comments:
I see some people are still holding onto 90L. Even the GFS looks like it gave up and just starts pushing it east sooner now.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
Hey, 456, is 90L still doing what it's supposed to?
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Back later
Member Since: Posts: Comments:
Yeah, I'd say the Caribbean system could be 91L. I'm not sure, but who knows?
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Quoting stormwatcherCI:
For future reference if I need it how do you delete a post ? TIA


the laugh for today!
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Quoting kmanislander:


Just go to your post and click on the "modify comment" button. You can then either substitute something else or just leave a single letter or punctuation mark. I don't believe it will let you leave a complete blank space.
Thanks and I know you are well aware I really might need that in the future. The way things are shaping up I really don't want to get banned again.
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585. xcool
twhcracker:
better move fast delete itt fast..
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Someone posted this site on here this morning..I hope it doesnt happen..we're in big trouble if it does....Link
Member Since: September 8, 2005 Posts: 0 Comments: 1386

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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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