93L near tropical depression strength

By: Dr. Jeff Masters , 2:31 PM GMT on June 25, 2010

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The first tropical depression of the 2010 Atlantic hurricane season appears imminent in the Western Caribbean, as the areal coverage and intensity of heavy thunderstorm activity associated with the tropical wave (Invest 93L) continue to increase. The storm has developed a surface circulation near 16.5N, 82.5W at 8am EDT, about 100 miles northeast of the Nicaragua/Honduras border. This is far enough from land that development will be slowed only slightly. Satellite loops show a poorly organized system, with only a modest amount of heavy thunderstorm activity near the center. However, the developing storm is affecting the weather across the entire Western Caribbean, and bands of heavy thunderstorms are quickly building over a large region. Pressures at ground stations and buoys all across the Western Caribbean have been falling significantly over the past day (Figure 2.) Water vapor satellite loops show that moist air surrounds 93L, and there is not much dry air to slow down development. There is an upper-level high pressure system a few hundred miles west of 93L, and the clockwise flow air around this high is bringing upper-level winds out of the northwest of about 10 - 15 knots over 93L, contributing to the 10 - 15 knots of wind shear observed in this morning's wind shear analysis from the University of Wisconsin's CIMSS group. Sea Surface Temperatures are very warm, 29 - 30°C. The Madden-Julian oscillation (MJO) currently favors upward motion over the Caribbean, which will act to increase the chances of tropical storm formation this week. The main negative for 93L is a combination of lack of spin and wind shear. Last night's pass of the ASCAT satellite showed a broad, elongated circulation, which will need to tighten up in order for 93L to become a tropical depression. The Hurricane Hunters are scheduled to fly into 93L at 2pm EDT this afternoon to see if a tropical depression has formed.


Figure 1. Morning visible satellite image of the central Caribbean disturbance 93L.


Figure 2. Combined plot of wind speed, wind gusts, and pressure at buoy 42057 in the Western Caribbean. Pressure (green line) has fallen significantly over the past two days, and winds are beginning to increase.

Forecast for 93L
The greatest risk from 93L to the Western Caribbean will be heavy rainfall, and the nation most at risk is Honduras. The counter-clockwise flow of air around 93L will bring bands of rain capable of bringing 4 - 8 inches of rain to northern Honduras over the next two days. Heavy rains of 3 - 6 inches can also be expected in northeast Nicaragua, Cuba, Belize, the Cayman Islands, and Mexico's Yucatan Peninsula. The storm is moving west-northwest at about 10 mph, and this motion is expected to gradually slow over the next five days to about 6 mph. I expect that by tomorrow, 93L should be closer to being directly underneath the upper level high pressure system to its west, which would act to lower wind shear and provide more favorable upper-level outflow. NHC is giving 93L a 70% chance of developing into a tropical depression by Sunday morning, which is a reasonable forecast. The storm will probably be a tropical depression or tropical storm with 40 mph winds when it moves over Mexico's Yucatan Peninsula on Sunday. The storm will probably spend a day or so over the Yucatan, resulting in significant weakening. Once 93L emerges over the Gulf of Mexico, it will take the storm 24+ hours to recover its strength.

A trough of low pressure is expected to swing down over the Eastern U.S. on Monday. If this trough is strong enough and 93L develops significantly, the storm could get pulled northwards and make landfall along the northern Gulf of Mexico coast. This is the solution of the GFDL and HWRF models. If 93L stays weak and/or the trough is not so strong, the storm would get pushed west-northwestwards across Mexico's Bay of Campeche and make landfall along Mexican coast south of Texas, or in Texas. This is the solution of the NOGAPS, ECMWF, and Canadian models. A likely landfall location is difficult to speculate on at this point, and the storm could hit virtually anywhere along the Gulf of Mexico coast given the current uncertainty in its development. The amount of wind shear in the Gulf of Mexico next week is also highly uncertain. There is currently a band of high shear near 30 knots over the Gulf. The GFS model predicts that this band of high shear will lift northwards, keeping low wind shear over the Gulf next week. However, the ECMWF model keeps high shear entrenched over the Gulf of Mexico, which would make it unlikely 93L could intensify into a hurricane. In summary, I give 93L a 60% chance of eventually becoming Tropical Storm Alex, and 10% chance of eventually becoming a hurricane.

Elsewhere in the tropics
A tropical wave a few hundred miles northeast of the northernmost Lesser Antilles Islands is producing a modest amount of heavy thunderstorm activity. This system was designated Invest 94 by NHC this morning, and is passing beneath a trough of low pressure that is generating 30 - 40 knots of wind shear. However, by Sunday, the storm will be in a region of much lower wind shear, and NHC is giving the storm a 10% chance of developing into a tropical depression by Sunday morning. We do have one model, the GFS, which develops the system early next week. The GFS model takes the storm to the northwest and then north, predicting it will be very close to Bermuda on Tuesday.


Figure 3. Hurricane Celia as a Category 4 storm at 20:55 UTC Thursday, June 24, 2010, as captured by NASA's MODIS instrument.

Impressive Hurricane Celia hits Category 5
The first Category 5 hurricane in the Northern Hemisphere this year is Hurricane Celia in the Eastern Pacific. Celia's 160 mph winds make it tied with Australia's Tropical Cyclone Ului as the strongest tropical cyclone in the world so far in 2010. Celia has likely peaked in intensity, and is not expected to threaten any land areas.

Wind and ocean current forecast for the BP oil disaster
East to southeast winds of 5 - 15 knots will blow in the northern Gulf of Mexico today through Tuesday, according to the latest marine forecast from NOAA. The resulting weak ocean currents should push the oil to the west and northwest onto portions of the Louisiana and Alabama coasts, according to the latest trajectory forecasts from NOAA and the State of Louisiana. I would expect Mississippi to have its most serious threat of oil yet early next week as these winds continue. The longer range outlook is uncertain, and will depend upon what 93L does.

Resources for the BP oil disaster
Map of oil spill location from the NOAA Satellite Services Division
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's interactive mapping tool to overlay wind and ocean current forecasts, oil locations, etc.
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

Jeff Masters

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With West winds around 25 plus mph on the weak side of the system one would expect close to TS force winds in the NE quad, at the very least in squalls. Just came on so have not seen what winds the HH was finding there.

I still think this needs to pull a little further away from land to really get going.
Member Since: August 19, 2006 Posts: 0 Comments: 15842
Quoting leo305:


it's likely enhanced by the pressure gradient though =P


I was going to leave the office in Tallahasse and just got locked in by a fierce T-Storm and rain...Gonna wait till it dies down; not related to the "93L effect".....
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Does anyone know what's happened to weather 456, he hasn't been heard from in 5 days?
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2425. cg2916
Quoting Floodman:


That's the rumour...


Oh yeah, forgot, very top secret, very hush hush.
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Quoting JamesSA:
I think it makes sense to get a better fix on where it is going too before ratcheting up the panic level too much.

The HH run should give the models better data to chew on.


Agreed again!
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im out, see what happens in a few hours
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Could somebody post the corresponding mb pressures that collate with mph's?
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Quoting cg2916:
Is 93L closed?


That's the rumour...
Member Since: August 2, 2006 Posts: 10 Comments: 9922
I think this system is going to intensify pretty steadily over the next 2 days
Member Since: March 10, 2010 Posts: 1 Comments: 7818
Quoting TerraNova:
And they just keep coming...




What website can i find those maps
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Quoting CaneWarning:


Taz, please give me your expert opinion on the storm. Thanks.



its a TS for dran sure if not then crow me
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Quoting Stormchaser2007:
More -80C tops coming.



The storm still looks like something you would see in the West Pacific. It looks like a certain typhoon from last year that became a MONSTER later on... I'll try and see if I can find it.
Member Since: July 7, 2008 Posts: 2 Comments: 3237
Quoting cg2916:
Is 93L closed?


Yup
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2414. leo305
Quoting weathermanwannabe:


Happy to see that you did not use the word "rain band"....... :)


it's likely enhanced by the pressure gradient though =P
Member Since: April 17, 2010 Posts: 0 Comments: 1753
2413. cg2916
Miami, is it closed?
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Quoting HurricaneSwirl:


I don't know who you're calling a troll.. but I don't think he meant to put COMPLETELY false information up there.. as he edited his post with tomorrow. He tried to make an unsuccessful funny XD


Hahaha, i was mean, no hard feelings :)
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Quoting Tazmanian:



it sure looks like it but but whats wait and see


Taz, please give me your expert opinion on the storm. Thanks.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
good afternoon everyone. yesterday dr. m said that he didn't think 93L would ever make it to a hurricane. is this still the case?
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2407. Levi32
Quoting Inactivity:
Levi,how long do you think the pressure will continue to fall?


Until landfall in the Yucatan.
Member Since: November 24, 2005 Posts: 635 Comments: 26654
Quoting ShenValleyFlyFish:


A a mouth-full of mushrooms, perhaps?


I was wondering when you would join the party...a mouthful of mushrooms, indeed!
Member Since: August 2, 2006 Posts: 10 Comments: 9922
2405. cg2916
Is 93L closed?
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Quoting leo305:
very strong rain shower came through the miami area.. strong gust of wind too..


Happy to see that you did not use the word "rain band"....... :)
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2403. Levi32
Quoting TerraNova:


Hey Levi, what site do you use for satellite images for Google Earth?


It's found in here
Member Since: November 24, 2005 Posts: 635 Comments: 26654
Quoting TerraNova:


Unsuccessful troll is unsuccessful.


I don't know who you're calling a troll.. but I don't think he meant to put COMPLETELY false information up there.. as he edited his post with tomorrow. He tried to make an unsuccessful funny XD
Member Since: July 7, 2008 Posts: 2 Comments: 3237
2401. leo305
Quoting Stormchaser2007:
More -80C tops coming.



I think that is were the center is, rigth to the NW of that convection..
Member Since: April 17, 2010 Posts: 0 Comments: 1753
2391. he is getting his act together
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This system or ( Alex ) doesn't seem to be headed north-west. It will probably be a tropical depression by the 800 pm advisory, and maybe Alex at 200 am. However it's extrely close to land and seems to be headed due west, unless it changes course, there may not much left of this system it heads toward belize and yucatan.
CIS J.L
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2398. Grothar
Quoting Levi32:
21:15z...mapping the core to hone in on the center better.



I wouldn't want to be one of those poor people who have to look out of those binoculars, outside the plane
Member Since: July 17, 2009 Posts: 71 Comments: 26486
2397. JamesSA
Quoting ATL:

Still think the NHC will stay with a TD to avoid a media panic and due to the fickle history of this system.
I think it makes sense to get a better fix on where it is going too before ratcheting up the panic level too much.

The HH run should give the models better data to chew on.
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Quoting Floodman:


You're a very funny, yet somehow disturbing man...


He is acting a tad strange today isn't he.. and for Patrap.. thats saying something :)
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Quoting Floodman:


Who can tell with bovines?


A a mouth-full of mushrooms, perhaps?
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Quoting Tazmanian:



it sure looks like it but but whats wait and see


It's not Alex yet but it's a strong Tropical Depression on the verge.
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2393. tkeith
Quoting Michfan:
Have to admit that these storms firing up in June doesn't bode well for the later part of the season when the CV season really kicks up.
yep kinda ominous
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Levi,how long do you think the pressure will continue to fall?
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More -80C tops coming.

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Quoting Levi32:
I have a feeling we won't see a vortex message until they map all these west winds and then make one more stab at the center of the beast. After another pass they should know for sure where it is.


Hey Levi, what site do you use for satellite images for Google Earth?
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Quoting Levi32:
I have a feeling we won't see a vortex message until they map all these west winds and then make one more stab at the center of the beast. After another pass they should know for sure where it is.


I agree.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
2388. Patrap
Quoting Floodman:


You're a very funny, yet somehow disturbing man...


Thank you..


Member Since: July 3, 2005 Posts: 426 Comments: 128661
Quoting HurricaneSwirl:


good 'un


Unsuccessful troll is unsuccessful.
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This isn't a TD guys...this data tells me this is a 40mph Tropical Storm IMO
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2385. Michfan
Have to admit that these storms firing up in June doesn't bode well for the later part of the season when the CV season really kicks up.
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2384. gator23
Quoting louisianaboy444:
Tropical Storm Alex needs to change course quickly if it has big plans

Why would you call it that? I thought we had a TS
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2383. Levi32
I have a feeling we won't see a vortex message until they map all these west winds and then make one more stab at the center of the beast. After another pass they should know for sure where it is.
Member Since: November 24, 2005 Posts: 635 Comments: 26654
2382. leo305
very strong rain shower came through the miami area.. strong gust of wind too..
Member Since: April 17, 2010 Posts: 0 Comments: 1753
And they just keep coming...



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Quoting centex:
They will not wait until 8 to reclassify. I'm 99% sure. Never say never.



trust me ...it's not out of the realm of possibility.it may weaken some soon after
interacting with land which will buy the NHC some more time.
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Quoting Patrap:
pssst...

93L
Pull my finger...C,mon


You're a very funny, yet somehow disturbing man...
Member Since: August 2, 2006 Posts: 10 Comments: 9922

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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.