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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Convection becoming very intense near the center now. This won't stay as a TD for long.

Member Since: Posts: Comments:
weatherman12345... Florida can not be ruled out at this time... mainly due to lack of model consensus. Some have this going and making double landfall in Mexico, the eastern-most take it into the FL panhandle. So no one along the Gulf Coast can be ruled out, yet.
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2877. Drakoen
We are going to have to wait till the 00z models to get models with proper initialization and intensity
Member Since: October 28, 2006 Posts: 57 Comments: 30490
2876. Levi32
Quoting tennisgirl08:


Possible. I see that the models are still split 50/50 about the track. I am surprised by that since we now have a defined center.


The center coordinates just came in an hour ago. You won't see those in the models until the 0z runs tonight.
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,Weatherunderground map is wrong , has the depression south of Africa !!
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Quoting MiamiHurricanes09:
Considering current conditions and how it seems to be intensifying quite quickly I wouldn't be surprised to see a 50+ mph tropical storm at 11 PM.
I agree TS by 11pm.
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Quoting HurricaneSwirl:


I'm amazed. It stretches from the extreme western Yucatan to the extreme Western tip of... Haiti!!


Can we say Hurricane IKE......wouldn't that be something.
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2872. Levi32
Quoting Tazmanian:




94L is looking good whats the ch of this becomeing the B storm


Low to moderate....it actually has a better chance than it might look.
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2871. tkeith
Quoting Levi32:
It should be remembered that the US models have a northward bias and TD 1 could easily miss the US altogether and hit Mexico. The ridge doesn't want to leave the SE US and the overall pattern means the trough coming into the east won't be hanging around long before getting kicked right back out. The ridge could easily force this straight WNW into Mexico with a double-landfall for them.
the most plausable scenario...
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2870. KEEPEROFTHEGATE (Mod)
Quoting Floodman:


As well she should have...your grammar and spelling is atrocious...LOL
don't you start
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2869. GWTEX
Quoting ecflweatherfan:
The "I called it" US landfalls need to be saved until it ACTUALLY makes it to the CONUS. Who knows, it may never make landfall in the CONUS. Just because it appears at Day 5 to be aimed at TX, does not mean it will go there. How many times has the cone projected FL, or MS, or AL... or anwhere else for that matter and it go someplace completely different? Lets just wait and see
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2868. JamesSA
If the intensity exceeds expectations the track will trend more east of the current cone of despair.
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Quoting Levi32:
It should be remembered that the US models have a northward bias and TD 1 could easily miss the US altogether and hit Mexico. The ridge doesn't want to leave the SE US and the overall pattern means the trough coming into the east won't be hanging around long before getting kicked right back out. The ridge could easily force this straight WNW into Mexico with a double-landfall for them.


Possible. I see that the models are still split 50/50 about the track. I am surprised by that since we now have a defined center.
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Quoting alaina1085:
TD 1 is in beast mode!! Local met thinks the trough will be strong enuff to pull td 1 more north. This thing will be Alex by tonight.
I agree Alaina, I too think this will be a Hurricane by 8pm tomorrow night.... Theres to much going for it now not to be....

Taco :o(
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too big folks hate to break your bubble, but he aint gonna be a monster, land is coming up he will get even bigger when he comes off and be so big like IKE the winds around the center will never be able to spin up at a fast pace.
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2864. Michfan
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TD-1, very close to becoming Tropical Storm Alex


94L also organizing some.
Member Since: July 8, 2005 Posts: 259 Comments: 24018
2862. Drakoen
Very impressive Tropical Depression:

Member Since: October 28, 2006 Posts: 57 Comments: 30490
Quoting MiamiHurricanes09:
Indeed, and it will keep growing. Look at all the outflow around the system.


I'm amazed. It stretches from the extreme western Yucatan to the extreme Western tip of... Haiti!!
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Quoting MiamiHurricanes09:
Considering current conditions and how it seems to be intensifying quite quickly I wouldn't be surprised to see a 50+ mph tropical storm at 11 PM.
I agree
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2859. Levi32
It should be remembered that the US models have a northward bias and TD 1 could easily miss the US altogether and hit Mexico. The ridge doesn't want to leave the SE US and the overall pattern means the trough coming into the east won't be hanging around long before getting kicked right back out. The ridge could easily force this straight WNW into Mexico with a double-landfall for them.
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Quoting bappit:


She mommed us yesterday.


As well she should have...your grammar and spelling is atrocious...LOL
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2855. DocBen
Careful with the intensity prediction right now. Both Celia and Darby have dramatically exceeded their intensity forecasts. If Alex can get into the hot Gulf intact I think it might undergo rapid intensification and surprise many people.
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Quoting Levi32:
Invest 94L spinning up....

Don't forget about this one. Could be a problem for Bermuda.





94L is looking good whats the ch of this becomeing the B storm
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Quoting RitaEvac:
I said yesterday and I'll say it again... Baton Rouge, LA to Brownsville, TX and boy oh boy oh boy was I right....


i'd say Northern Mexico to Bioxi is under heightened alert right now
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2852. leo305
I still think the center is north of that position, or will re develop there, because the strongest convection is there, plus convergence on visible seems strongest there..
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Quoting alaina1085:
TD 1 is in beast mode!! Local met thinks the trough will be strong enuff to pull td 1 more north. This thing will be Alex by tonight.
Considering current conditions and how it seems to be intensifying quite quickly I wouldn't be surprised to see a 50+ mph tropical storm at 11 PM.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
The "I called it" US landfalls need to be saved until it ACTUALLY makes it to the CONUS. Who knows, it may never make landfall in the CONUS. Just because it appears at Day 5 to be aimed at TX, does not mean it will go there. How many times has the cone projected FL, or MS, or AL... or anwhere else for that matter and it go someplace completely different? Lets just wait and see
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2849. Michfan
Quoting TankHead93:
NOT trying to be a wishcaster or an alarmist, but do any of the experts on this blog feel this has an opportunity to pull a "Wilma" on us? Just here to learn and observe. I ask this due to an eerily reminiscent outflow pattern and central structure before the big "boom" Wilma put on overnight, as well as the ridiculously high TCHP. TIA! ;)


Doubtful. System is too large to spin up that fast at the moment and the low is elongated fron north to south. Wilma at this time was already better structured than this currently is. Its large size means its going to take longer for it to tighten up.
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Per Discussion
THE DEPRESSION IS VERY CLOSE TO TROPICAL STORM STRENGTH...AND
CONDITIONS APPEAR FAVORABLE FOR SOME INTENSIFICATION BEFORE IT
REACHES THE YUCATAN PENINSULA IN A DAY OR SO.
AFTER WEAKENING OVER
LAND...THE CYCLONE COULD REGAIN SOME STRENGTH WHEN IT ENTERS THE
SOUTHERN GULF OF MEXICO. THE OFFICIAL INTENSITY FORECAST IS CLOSE
TO THE DECAY SHIPS MODEL...WHICH INCLUDES THE EFFECTS OF
INTERACTION WITH THE YUCATAN PENINSULA.
Member Since: July 8, 2005 Posts: 259 Comments: 24018
I hate to keep belaboring this point, and I have the utmost respect for the forecasters at the NHC - but they are going to be EXTRA conservative this year because of the oil spill.
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This is one huge TD, I suspect that by 8am tomorrow it will a 60mph TS and taking a more NW/NNW track, this is alarming situation imo.
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Quoting nrtiwlnvragn:


That other GFS at 90 hours



Were do you get these images from?
Member Since: June 10, 2005 Posts: 0 Comments: 323
large circulation will take longer for wind speeds to really pick up. Remember Ike after crossing Cuba, got so damn big it couldnt really spread the winds out, had a cat 4 pressure but cat 2 winds...
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Keeper, I know of the oil that is under the water. It is horrible. I drive to Port Fourchon on a daily basis and drive to Grand Isle once a week. It's bad here. The worst case for us would be for this storm to go to our west. We will have more oil higher into the region.
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2842. Levi32
Invest 94L spinning up....

Don't forget about this one. Could be a problem for Bermuda.

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Quoting MiamiHurricanes09:
TD1 really beginning to intensify, wouldn't be surprised to see a moderate strength TS at 8PM. Notice the banding and the convection expanding.



i swear that picture and Track setup is eerily reminiscent of "Hurricane Wilma"!
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Special SST update:



A 14C band of SSTs has developed within the past two days across the California Current, from the Central Northeast Pacific basin to northern Washington State. Current anomalies contain a small pocket of above-average SSTs near the coast, while -2C cool anomalies prevent the warmer anomalies surrounding the Kuroshio current, northwest of Hawaii from connecting with the warm anomaly near the coast, which would create a cool-warm-cool tripole-like pattern in the EPac, the opposite of the Atlantic. A similar pattern is developing in the Atlantic, and since this is a bit analogous to the pattern observed during the past southern summer with the ENSO anomalies choking the Humboldt and warmth off Brazil choking the Benguela current, I will be watching this phenomenon develop if the need arises.



Current SST anomalies. However, the cold PDO, seen in the cooler-than-normal SSTs in the eastern half of the Pacific, may prevent this scenario from occurring, although there was an area of cooler water off South America even in January and February.



Arctic sea ice extent is dropping off rapidly, and there are three areas of open ocean off the coast of Russia in addition to an area north and west of Banks Island. Now, back to the Atlantic disturbances. Based on the current NHC forecast for TD 1, I predict a strong 60kt TS landfall on Calcasieu Lake, Louisiana.
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TD 1 is in beast mode!! Local met thinks the trough will be strong enuff to pull td 1 more north. This thing will be Alex by tonight.
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TD Alex tonight and Hurrican Alex tomorrow night.
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Quoting Thundercloud01221991:
Recon is done ... do you think they will add an overnight mission?


Yes I'm sure they will.
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Just bring me the rain Alex, bring that breath taking quenching water.

"She tastes like a raindrop"
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2835. GetReal
IMHO the intensity forecast for TD #1 are way to conservative. This system is ONLY 10 mb short of what you would normally see with a Cat 1 hurricane. Look for the wind intensity to pick up over the next few hours, as they catch up flowing into that already low pressure!!!

It is very likely that by tomorrow morning this will be TS Alex, with winds sustained around 65 mph. All the conditions remain favorable for this to bomb anytime over the next 12 to 24 hours. It would not surprise me to see this become a Cat 1 before coming ashore in the Yucatan.

Remember the NHC has a well documented history of under estimating storm intensities. Additionally a more intense system will track more towards the north, than to the west.
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this storm will combine with a boundry line over south texas...
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2833. KEEPEROFTHEGATE (Mod)
Quoting Hurricajun:
Well, I promise that if he does come here to LA, I hope he comes down to Grand Isle. I'll go take his picture while he stands in the oily water.
i don't think you will want to do that a great slurge awaits under the water
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Quoting Weatherkid27:

This thing is MASSIVE
Indeed, and it will keep growing. Look at all the outflow around the system.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
2831. JamesSA
Quoting coffeecrusader:
Call me crazy, but I believe this will be a cane by tomorrow.
It could be. Didn't they already find a 47kt wind? And < 1002mb?
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The current track keeps it away from the high octane which is a good thing.

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Quoting Hurricajun:
Who wants to take a shot at where TWC's Cantore ends up to catch this storm???


I'll take Corpus Christi for 500, Alex...
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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.