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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I think the NHC will formulate their best track for the time being and when the 00Z model runs have a good handle on this system it may be revised
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Here is the scale: (Keep in mind though that these are general pressure guidelines, Hurricane Charley for example was a strong 4, almost a 5 with a pressure of 941mb at landfall, even though it would appear to be a weaker cat 4 on the scale)




Quoting BradentonBrew:
Could somebody post the corresponding mb pressures that collate with mph's?
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but they may re name it too a name storm
Member Since: May 21, 2006 Posts: 5091 Comments: 115235
Member Since: June 16, 2010 Posts: 0 Comments: 28
IKE can't post 0-0-0 now.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Looks like we have a classification as a TD
Member Since: August 19, 2006 Posts: 0 Comments: 15842
Tropical Depression 1

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2471. cg2916
Quoting nrtiwlnvragn:
AL 01 2010062518 BEST 0 169N 829W 30 1005 TD


TD 1, 35 mph winds, pressure to 1005 MB.
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2470. Levi32
We have TD #1


invest_RENUMBER_al932010_al012010.ren
Member Since: November 24, 2005 Posts: 635 Comments: 26654
So it begins.
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Pressures are falling because of the time of the day so i would not be surprised if the next pass would show the pressure lower
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2467. Patrap
Quoting StormW:
Hey gang...I think the Navy is getting ready to designate it...93L just disappeared off the site.


The Gig is Up.

We have TD #1 In the Atlantic 2010 Season
Member Since: July 3, 2005 Posts: 426 Comments: 128642
Quoting JamesSA:
The highest one I saw posted was 41kts.


We don't know if that was sustained or in a squall though. Sometimes you get a burst of strong winds in one reading after another but they will not use those to classify a system as they are transient winds in a squall line.
Member Since: August 19, 2006 Posts: 0 Comments: 15842
WOOOOOOOOO HOOOOOOOO!

Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting cg2916:


Do you think 93L is closed?
Until it lands in Belize/Yucatan.
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2462. cg2916
Quoting nrtiwlnvragn:
06/25/2010 09:25PM 3,473 invest_RENUMBER_al932010_al012010.ren


YES!!! Finally!
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Quoting Floodman:


I was wondering when you would join the party...a mouthful of mushrooms, indeed!


I was napping. Anything of note happened in the last couple of hrs. See Levi and Drak have declaired a TD. Now if we can just get the NHC and Orca on board it should be official
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2460. HadesGodWyvern (Mod)
http://199.9.2.143/tcdat/tc10/ATL/01L.ONE/
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We have TD 1, but not yet TS Alex
Member Since: March 10, 2010 Posts: 1 Comments: 7816
Hello
Member Since: June 16, 2010 Posts: 0 Comments: 28
Uh oh

invest_RENUMBER_al932010_al012010.ren
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AL 01 2010062518 BEST 0 169N 829W 30 1005 TD
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Quoting nrtiwlnvragn:
06/25/2010 09:25PM 3,473 invest_RENUMBER_al932010_al012010.ren


Wow. There you go.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
2454. cg2916
Quoting Levi32:
Southwest winds....making a perfect circle. The circulation is without a doubt closed.



We have TD1/Alex!!! Finally! Just gotta wait for the renumber.
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Quoting nrtiwlnvragn:
06/25/2010 09:25PM 3,473 invest_RENUMBER_al932010_al012010.ren




YAAAAAAAAAAAAAAAY
Member Since: May 21, 2006 Posts: 5091 Comments: 115235
01L.ONE, TRACK_VIS, 25 JUN 2010 2115Z
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2450. Skyepony (Mod)
Cecila..
CI# /Pressure/ Vmax
6.5 / 917.0mb/127.0kt



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2449. Patrap
Itsa all a lot clearer to many this afternoon.

The Intensity Guidance was spot on all week with the Friday Up tick as it slid wnw into the Western CArribean.

Sweeeeeeeeeeeeeeet.


Early Model Wind Forecasts


Member Since: July 3, 2005 Posts: 426 Comments: 128642
no need for DMIN or D MAX any more this storm is now on its own
Member Since: May 21, 2006 Posts: 5091 Comments: 115235
06/25/2010 09:25PM 3,473 invest_RENUMBER_al932010_al012010.ren
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Quoting Stormchaser2007:


based on the pic, and i know this sounds silly, but is that white spot of deep convection the center?
Member Since: July 17, 2008 Posts: 0 Comments: 1242
2443. JamesSA
Quoting kmanislander:
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.
The highest one I saw posted was 41kts.
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Quoting truecajun:
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?


bumping my post because i have to finish up some work before baby wakes
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2441. Levi32
Southwest winds....making a perfect circle. The circulation is without a doubt closed. The aircraft is turning towards the center. It's going to really find it this time.

Member Since: November 24, 2005 Posts: 635 Comments: 26654
2440. leo305
Quoting weathermanwannabe:


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".....


I know, but when there is a strong low in the carribean and a strong high over florida, winds tend to go up because of pressure gradient in between and that causes those atlantic showers to speed there way onshore with gusty winds!
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2439. uplater
Quoting Stormchaser2007:
More -80C tops coming.



This is pretty impressive at DMIN
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Quoting TerraNova:


Hahaha, i was mean, no hard feelings :)


okay.. I still don't know how I was mistaken for being a troll in the least bit for saying good one in a stupid accent. lol. Maybe I'm being too serious, all of these jokes are going right over my head today lol
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2437. xcool
i see cat 1 come 93l move slow omg
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting CaribbeanIslandStorm:

What website can i find those maps


Here you go. Should open up in Google Earth. If it's satellite images you're looking for see Levi's post or try this.
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I think this system is a tropical storm but they will classify it a TD at first for the matter of persistance they want to see if this level of organization will persist before they give it a name
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Quoting Orcasystems:


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



LMAO
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2432. cg2916
Quoting Hurricanes101:
I think this system is going to intensify pretty steadily over the next 2 days


Do you think 93L is closed?
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Wow, we are all getting so excited over a storm that will make landfall in less than 2 days probably. LOL
Member Since: April 26, 2009 Posts: 3 Comments: 3667
The center is not where many of you think it is. This system is intensifying but not rapidly now. It is still disorganized more than organized. That low is going to pop out somewhere away from land. This system is the most land adverse system I've ever seen.
Member Since: June 16, 2010 Posts: 0 Comments: 28
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

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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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