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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Quoting stillwaiting:
i'm thinking a td1 upgrade at 2pm.....
NHC is going to wait for Recon to investigate before making any official calls.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
That would be too funny Pat if it weren't disturbingly true.
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Quoting Skyepony:


Yes, it's so close to 93L, they have been disrupting each other all along.

Oh, that's the wave our local met service was talking about.
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776. xcool
headed WNW
Member Since: September 26, 2009 Posts: 2 Comments: 15620
i'm thinking a td1 upgrade at 2pm.....
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Quoting Hurricanes101:


Id say that is pretty well defined lol
That's a TD right there, possible even a TS.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Just gotta wait for that first Vortex data message.
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Hi,.Im Tony Hayward talking to you from Sweden where Im relaxing and Skiing with my Family.

We at BP have a Hurricane Response Plan Ready to Implement in case of a Hurricane or Tropical Storm Emergency.

Rest assured,..were going to make this right.
Member Since: July 3, 2005 Posts: 420 Comments: 127543
771. Skyepony (Mod)
Quoting weatherwatcher12:
Is that convection SE of Jamaica a separate tropical wave?


Yes, it's so close to 93L, they have been disrupting each other all along.
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Quoting Jeff9641:
We could have a system blow up right before our eyes over the next 24 hours if 93L can stay over water. I am think based on Sat. that this maybe Alex or very close.


I agree, a hurricane is so likely within 12-24 hours.. this thing is just exploding
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Member Since: June 9, 2007 Posts: 4 Comments: 15776
Quoting utilaeastwind:
I am located at 16.10N 86.90W on the island Utila.

Winds are light from the west with light showers this morning.

I expect things to change fairly quickly though. Diving canceled and boats in the lagoon.

Please keep in touch with us if you can.

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Quoting Stormchaser2007:


Wow


Id say that is pretty well defined lol
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765. bwi
25 knot sustained winds at the buoy last hour.
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Recon report of 1009.7 extrapolated surface pressure.
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Quoting Stormchaser2007:


Wow
I spy with my little eyes a closed low.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
761. JRRP
so we have 94L
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AOI
Member Since: October 1, 2007 Posts: 81 Comments: 26511
whats the news on 94L
Member Since: May 21, 2006 Posts: 5091 Comments: 114712
Quoting Skyepony:
Fresh ASCAT


Wow
Member Since: June 9, 2007 Posts: 4 Comments: 15776
Quoting CaneWarning:


I am shocked that they didn't confiscate your halo.


Nope, but they did tell me how to turn them off so I could post them :)
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Mercy i got tooooooooo many tabs open lol
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Quoting HaboobsRsweet:
They are at flight level now so the observations should get interesting.
Now passing through the feeder bands.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
First dropsonde data


Level Geo. Height Air Temp. Dew Point Wind Direction Wind Speed

1013mb (29.91 inHg) Sea Level (Surface) 28.8°C (83.8°F) 26.0°C (78.8°F) 45° (from the NE) 17 knots (20 mph)
1000mb 113m (371 ft) 27.6°C (81.7°F) 25.2°C (77.4°F) 50° (from the NE) 20 knots (23 mph)
925mb 801m (2,628 ft) 22.6°C (72.7°F) 22.2°C (72.0°F) 70° (from the ENE) 19 knots (22 mph)
850mb 1,536m (5,039 ft) 19.2°C (66.6°F) 14.4°C (57.9°F) 80° (from the E) 20 knots (23 mph)
700mb 3,181m (10,436 ft) 10.4°C (50.7°F) Approximately 4°C (39°F) 80° (from the E) 22 knots (25 mph)
500mb 5,910m (19,390 ft) -4.5°C (23.9°F) -8.1°C (17.4°F) 100° (from the E) 17 knots (20 mph)
400mb 7,640m (25,066 ft) -14.1°C (6.6°F) Approximately -19°C (-2°F) 65° (from the ENE) 3 knots (3 mph)

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HH Teal 70 on Station..in the Tube 5 X 5.

Working
Member Since: July 3, 2005 Posts: 420 Comments: 127543
Quoting weatherwatcher12:
Is that convection SE of Jamaica a separate tropical wave?



yes
Member Since: May 21, 2006 Posts: 5091 Comments: 114712
751. Skyepony (Mod)
Fresh ASCAT
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Quoting weatherwatcher12:
New HDOB out and a dropsonde has been dropped.


OK, where to get the real-time sonde stuff?
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Quoting leo305:


Wouldn't be suprised.. I know it's june, but the atmosphere is more late julyish, and Wilma went from a TS to a CAT 5 in a night, not saying this will do that, but the convection that fired up over the center is indicative of a rapidly developing system from here on out

I can see TS maybe but not a hurricane. Plus the storm will have to deal with the Yucatan first. After that look out if it stays together.
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Quoting Hurricanes101:


we dont have a vortex message
Fixed.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Is that convection SE of Jamaica a separate tropical wave?
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746. xcool
93L GET READY OH SHI KABOOM
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting Orcasystems:


Yup :)
They were nice enough to even phone first :)


I am shocked that they didn't confiscate your halo.
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They are at flight level now so the observations should get interesting.
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Winds to the north of 93L are going from the E per recon. That's the direction you'd want with a closed LLC. E winds from the N, W winds from the S.
We get any west winds, expect a renumber.
Member Since: July 8, 2005 Posts: 259 Comments: 23565
Quoting Patrap:
Well dere it goes..

weeeeeeeeeeeeeeeeeeeeeeee.....................


Splash.




lol
Member Since: May 21, 2006 Posts: 5091 Comments: 114712
Quoting SavannahStorm:
No recon data sent for 30 minutes. What's the deal?


17:15:00Z 18.967N 84.717W 712.6 mb
(~ 21.04 inHg) 3,009 meters
(~ 9,872 fee it just updated
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Shouldn't the models produce better information after the data from the HH is entered into them? I think the model run later tonight might be more accurate than what we have now.
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Quoting MiamiHurricanes09:
We got a vortex message and RECCO observation.


we dont have a vortex message
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Quoting ElConando:
692.

This happen to you?


Yup :)
They were nice enough to even phone first :)
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Well dere it goes..

weeeeeeeeeeeeeeeeeeeeeeee.....................


Splash.
Member Since: July 3, 2005 Posts: 420 Comments: 127543
Hey guys can someone answer my new question about Google Earth? How can I set the clouds BEHIND the recon data? I can't see the darn bobs because the clouds are covering it. How do I change up what goes behind what and what covers what?
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We got a dropsonde report and RECCO observation.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting Skyepony:
Hurricane hunters are descending into 93L



I wanna see dem chuck the first sonde Skye and turn on the Radar
Member Since: July 3, 2005 Posts: 420 Comments: 127543
New HDOB out and a dropsonde has been dropped.
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.
Member Since: May 21, 2006 Posts: 5091 Comments: 114712

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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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