Forecast for 92L: dissipation by Friday

By: Dr. Jeff Masters , 2:17 PM GMT on June 16, 2010

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A low pressure system about 700 miles east of the Lesser Antilles Islands, Invest 92L, was near tropical depression status early this morning, but is currently weakening. Infrared satellite loops show the disturbance's heavy thunderstorm activity has decreased markedly in the past few hours, with the cloud top temperatures warming noticeably, indicating that 92L's thunderstorms are no longer pushing as high into the atmosphere. Water vapor satellite loops show that the storm is surrounded on all sides by dry air, though there is a region of moister air in front of it that 92L will encounter on Thursday. Wind shear as diagnosed by the University of Wisconsin is near 20 knots, though the SHIPS model is diagnosing the shear at a higher 25 - 30 knots. This high shear is pushing 92L's heavy thunderstorm activity to the east side of the center of circulation, and the center will probably become exposed to view late this morning. Had 92L been able to maintain the heavy thunderstorm activity it had early this morning for 12 or so hours, it could have been classified as a tropical depression. However, classification as a TD requires persistent heavy thunderstorm activity, typically interpreted to mean 12 hours of consistent heavy thunderstorm activity, and 92L did not meet that criterion.


Figure 1. Morning satellite image of Invest 92L. Image credit: NOAA.

The forecast for 92L: dissipation
Wind shear is the main story in the forecast for 92L, as a band of very high wind shear of 20 - 50 knots lies to the northwest of the storm. The current expected track of 92L carries it into this band of high wind shear, and the SHIPS model (based on the GFS model) is predicting that the shear will remain in the 25 - 30 knot range through Friday. Other models predict higher shear levels. It is likely that the high shear, combined with the dry air surrounding the storm, will destroy 92L by Friday. The National Hurricane Center is giving 92L a low (10% chance) of developing into a tropical depression by Friday morning, and this is a reasonable forecast. It is likely that 92L will bring heavy rain showers and wind gusts up to 35 mph on Friday to the Lesser Antilles Islands. I don't expect 92L to be organized enough to cause flooding problems to any of the islands in its path. None of our reliable global computer models develop 92L into a tropical depression. The rest of the tropical Atlantic is quiet, and none of the reliable computer models is calling for tropical cyclone development in the Atlantic over the next seven days.

Is the formation of 92L a harbinger of an active hurricane season?
According to the Hurricane FAQ, Goldenberg (2000) found that during the period 1944 - 1999, formation of a named storm in the tropical Atlantic south of 22°N and east of 77°W during June and July was a harbinger of at least an average season, and in many cases an above average season. The formation of a storm in this region during June or July is one factor the NOAA and Colorado State University seasonal hurricane forecast teams have used in the past as a predictor for an active season in their early August forecasts. Now, 92L didn't make it to named storm status, though it was pretty close to being a tropical depression. However, the near-formation of 92L into a tropical depression, is, in my mind, a clear harbinger that we can expect a severe hurricane season this year. It's very rare to have a development like 92L in that portion of the tropical Atlantic this early in the season. The lower than average wind shear and higher than average SSTs that helped 92L get organized are more likely than not to carry over into the main portion of hurricane season, giving us a much more active hurricane season than normal.


Figure 2. Synthetic Aperture Radar (SAR) image of the oil spill taken at 7:51 am EDT Tuesday June 15, 2010, by the Canadian Radarsat-1 satellite, operated by MDA GeospatialServices of Richmond, Canada. A large amount of oil was present on the Florida Panhandle coast near Pensacola, and was headed east towards Panama City. 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.

Oil spill wind and ocean current forecast
Light and variable winds less than 10 knots will blow in the northern Gulf of Mexico for the next five days, according to the latest marine forecast from NOAA. The winds will tend to have a westerly component for the most part, which will maintain a slow (1/4 mph) eastward-moving surface ocean current that will transport oil eastwards along the Florida Panhandle coast, according to the latest ocean current forecast from NOAA's HYCOM model. These winds and currents may be capable of transporting oil east past Panama City, Florida to Cape San Blas by Monday. Oil will continue to threaten the coasts of Louisiana, Alabama, and Mississippi for the remainder of the week as well, according to the latest trajectory forecasts from NOAA and the State of Louisiana. The long range 8 - 16 day forecast from the GFS model indicates a typical summertime light wind regime, with winds mostly blowing out of the south or southeast. This wind regime will likely keep oil close to the coastal areas that have already seen oil impacts over the past two weeks.

NOAA has lauched a great new interactive mapping tool that allows one to overlay wind forecasts, ocean current forecasts, oil location, etc.

Oil spill resources
My post, What a hurricane would do the Deepwater Horizon oil 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 has lauched a great new interactive mapping tool that allows one to overlay forecasts and oil location observations
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

I'll have an update on Thursday.

Jeff Masters

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Very late TWO...
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414. MTWX
Afternoon all. Had some wicked storms here yesterday afternoon!! I see our invest is getting the crap kicked out of it, but just doesn't know how to just stay down... LOL
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Quoting StSimonsIslandGAGuy:


So.....it's around 4 pm where the wave is now.

Thanks Levi.


Yes, so naturally the pressure will be lower, but I was more attracted to the closed isobar.
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Quoting StormW:
Good afternoon all!


And good afternoon Storm :)
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Quoting Hurricanes101:


The mid-level feature is what I was looking at earlier; I think if 92L is going to stand any chance to survive, it may have to work that mid-level vortex down the surface


It's not dominant though and is now floating off within the upper flow. It will be dissipated by the end of the day.
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Quoting Levi32:
92L's low-level center has decoupled from the mid-level vortex associated with the MCC from last night. One can also see the outflow boundaries to the west of the system where dry air has collapsed thunderstorms. The outflow boundaries are produced when downdrafts of collapsing thunderstorms hit the ocean surface and spread outwards. This is a sign of dry air at work. The decoupling of the low and mid-level centers is a sign of wind shear at work.



The mid-level feature is what I was looking at earlier; I think if 92L is going to stand any chance to survive, it may have to work that mid-level vortex down the surface
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Quoting debbykat:
levi i don't believe i guaranteed anything in my post..i just made a statement that i personally believe.is that ok with you .debby


So did the other guy....that's all I'll say about that.
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Quoting StSimonsIslandGAGuy:


1011 mb! It's a category 5 wave!

I need to remember when diurnal pressure variation is in the tropics, when it is highest and lowest.


Lowest at approximately 4am and 4pm local time, and approximately highest at 10am and 10pm local time.
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92L's low-level center has decoupled from the mid-level vortex associated with the MCC from last night. One can also see the outflow boundaries to the west of the system where dry air has collapsed thunderstorms. The outflow boundaries are produced when downdrafts of collapsing thunderstorms hit the ocean surface and spread outwards. This is a sign of dry air at work. The decoupling of the low and mid-level centers is a sign of wind shear at work.

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Quoting StormW:
Good afternoon all!
hi storm
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.
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397. IKE
11 A.M. UPDATE: OKALOOSA ISLAND — Tar balls, “hard, pliable and sticky” were washing up on the beach at Okaloosa Island Wednesday morning.

Public Safety Director Dino Villani called what was found “the worst we have seen” in Okaloosa County from the Deepwater Horizon oil spill but added “it’s certainly not as bad as it could be.”


From here.
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Quoting debbykat:
alex will not rear his ugly head until middle july..the shear and the dry air rule the atlantic and caribbean right now and will for quite a while...debby


I disagree. With the GFS and NGPS lowering shear across the Caribbean, and with the ECMWF suggesting activity later in its run we could easily see something. I'm not sure where you getting that dry air from. MJO's return should moisten things up alot.
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I don't see 92L making much forward speed now, looks almost stationary, gotta a feeling 92L might just be nuisance and troublemaker down the road for some.
Member Since: April 29, 2007 Posts: 0 Comments: 7506
Thanks for all the answers.
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Quoting hooptie1964:
I'm not sure I understand the shear forecasts and actual conditions. If someone could answer I'd appreciate it.

The el nino causes more shear, nuetral causes less shear, and la nina causes even less shear. Is this correct?

Currently, we are in a nuetral state heading rapidly (?) towards la nina, but shear in the Atlantic, Carribean and Gulf is high enough to restrict development of any storms.

These two statements don't seem to go together so I'm not sure what I'm missing.

Is shear lower than average for this time of year but it is just too early for development or are "things" not going according to general rules?

This question brought to you by a geotechnical engineer who has very limited knowledge in weather. Thanks.


The atmosphere has a delay to respond to changes in the ocean. The further decrease shear according to the current neutral conditions.
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389. IKE
NHC will be RIP-ing soon on 92L. I see no low-level circulation anymore.
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Quoting WinterAnalystwx13:
I think Invest 92L will take much of this path:




if 92L have this way,we'll have some pain with Alex...
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Quoting hooptie1964:
I'm not sure I understand the shear forecasts and actual conditions. If someone could answer I'd appreciate it.

The el nino causes more shear, nuetral causes less shear, and la nina causes even less shear. Is this correct?

Currently, we are in a nuetral state heading rapidly (?) towards la nina, but shear in the Atlantic, Carribean and Gulf is high enough to restrict development of any storms.

These two statements don't seem to go together so I'm not sure what I'm missing.

Is shear lower than average for this time of year but it is just too early for development or are "things" not going according to general rules?

This question brought to you by a geotechnical engineer who has very limited knowledge in weather. Thanks.


What you said is true, but even at below-normal levels for this time of year, wind shear is still too strong on average to allow a lot of storms to form in the month of June, which is one of the reasons why it is the least active month of the season. Below-average shear doesn't always mean it is favorable for development. If wind shear is climatologically 30 knots east of the Caribbean at this time of year, and is 10 knots below normal, that is still 20 knots of shear over 92L which is enough to kill it at this point.
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Quoting WinterAnalystwx13:


I ask for your pardon? I thought it was 2010...
Yes, what's the problem?
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Yes, shear is high in portions of the Atlantic right now, but that is not uncommon for this early in the season. By the time we reach the heart of the season, and probably within the next month, shear will have dropped considerably. Actually for this time of year the basin as a whole, shear is below average.

Quoting hooptie1964:
I'm not sure I understand the shear forecasts and actual conditions. If someone could answer I'd appreciate it.

The el nino causes more shear, nuetral causes less shear, and la nina causes even less shear. Is this correct?

Currently, we are in a nuetral state heading rapidly (?) towards la nina, but shear in the Atlantic, Carribean and Gulf is high enough to restrict development of any storms.

These two statements don't seem to go together so I'm not sure what I'm missing.

Is shear lower than average for this time of year but it is just too early for development or are "things" not going according to general rules?

This question brought to you by a geotechnical engineer who has very limited knowledge in weather. Thanks.
Member Since: Posts: Comments:
Quoting hooptie1964:
I'm not sure I understand the shear forecasts and actual conditions. If someone could answer I'd appreciate it.

The el nino causes more shear, nuetral causes less shear, and la nina causes even less shear. Is this correct?

Currently, we are in a nuetral state heading rapidly (?) towards la nina, but shear in the Atlantic, Carribean and Gulf is high enough to restrict development of any storms.

These two statements don't seem to go together so I'm not sure what I'm missing.

Is shear lower than average for this time of year but it is just too early for development or are "things" not going according to general rules?

This question brought to you by a geotechnical engineer who has very limited knowledge in weather. Thanks.


Development in the open Atlantic in the general area of disturbance 92L is not normal this early in the season. Usually you don't see anything develop out there in that area until around late July. Shear is overall below average for this time of year when judging the whole Atlantic basin as a whole. However shear is still high enough where disturbance 92L is and in conclusion is destroying 92L's circulation and stopping 92L from developing along with dry air to it's northwest as well. So to answer your question it's not surprising 92L is having a hard time trying to form because like I said formation out there in the Atlantic is unusual this early in the season. The Gulf, Caribbean and near the east coast/Bahamas is where development is favored for this time of the season.

So yes shear is below average but it's still too high to allow the disturbance to develop and it is too early in the season to really see any development out there.

As far as my knowledge goes I believe neutral is probably the worst out of the three bringing the worst seasons and ideal conditions.
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Quoting Hurricanes101:


agreed
Quoting Drakoen:
Why you guys would bother wasting your time with someone that claims to be a meteorologist and then blatantly disrespects people is beyond me. The quoting doesn't help others who have that user on ignore.
I'm sorry. I ask for your pardon.
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Quoting Drakoen:
Why you guys would bother wasting your time with someone that claims to be a meteorologist and then blatantly disrespects people is beyond me. The quoting doesn't help others who have that user on ignore.


agreed
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Why you guys would bother wasting your time with someone that claims to be a meteorologist and then blatantly disrespects people is beyond me. The quoting doesn't help others who have that user on ignore.
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373. IKE
Quoting hooptie1964:
I'm not sure I understand the shear forecasts and actual conditions. If someone could answer I'd appreciate it.

The el nino causes more shear, nuetral causes less shear, and la nina causes even less shear. Is this correct?

Currently, we are in a nuetral state heading rapidly (?) towards la nina, but shear in the Atlantic, Carribean and Gulf is high enough to restrict development of any storms.

These two statements don't seem to go together so I'm not sure what I'm missing.

Is shear lower than average for this time of year but it is just too early for development or are "things" not going according to general rules?

This question brought to you by a geotechnical engineer who has very limited knowledge in weather. Thanks.


That's what it is for now.
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Low shear and high moisture content in the air must make two tropical depression into a tropical storm soon.
Member Since: Posts: Comments:
I'm not sure I understand the shear forecasts and actual conditions. If someone could answer I'd appreciate it.

The el nino causes more shear, nuetral causes less shear, and la nina causes even less shear. Is this correct?

Currently, we are in a nuetral state heading rapidly (?) towards la nina, but shear in the Atlantic, Carribean and Gulf is high enough to restrict development of any storms.

These two statements don't seem to go together so I'm not sure what I'm missing.

Is shear lower than average for this time of year but it is just too early for development or are "things" not going according to general rules?

This question brought to you by a geotechnical engineer who has very limited knowledge in weather. Thanks.
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Quoting ryang:
Can anyone post the link to the 12z NOGAPS?


12z NOGAPS
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367. amd
Technical Paper on WindSat

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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.