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 Patrap:


Classified.

Guy's Po-boy on Magazine made me sign a paper.


I didn't think Guy's had ersters on the menu. If they do, I'm headed that way right now!
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Quoting Hurricanes101:


we need a pure west wind, which they have yet to find


And a stronger west wind.
Member Since: July 7, 2008 Posts: 2 Comments: 3237
trimm caught part of 93L's SE side..
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Quoting stormwatcherCI:
Afternoon. Do you think any watches or warnings for Grand Cayman. I doubt it for the sisters but what do you think about for us ?


Current track would not warrant watches for us. It is already about 100 miles West in longitude.
Member Since: August 19, 2006 Posts: 0 Comments: 15842
1325. Drakoen
Quoting Seflhurricane:
what track you mean the models


The OFCI which is from the NHC
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You can really see the northwesterly motion.

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1323. Patrap
Quoting kmanislander:
The critical thing is that the low is sitting right underneath that deep convection which is not showing any sign of warming cloud tops in the middle of the day. That is a sure sign of a system that is on the upswing.

If the HH does not find a closed low now one will not be many hours away. They will likely stick around for some time if necessary and do runs again in an hour or so. They are close to us and can refuel here with ease.


Dusk and the Low Sun Angle then should be interesting on the Viz Imagery later Kman.
Member Since: July 3, 2005 Posts: 426 Comments: 128767
Quoting CybrTeddy:
From 345° at 6 knots
(From the NNW at ~ 6.9 mph)

Another west wind.


we need a pure west wind, which they have yet to find
Member Since: March 10, 2010 Posts: 1 Comments: 7826
Levi, Is there a correlation between size during the consolidation of 93L and the final storm??
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1319. Drakoen
Quoting Levi32:


Yeah, I didn't expect so many easterlies just south of the center though. Appeared to be more solidly closed than that. I wonder if we'll get a vortex message out of this or if it's too iffy for them.


True. If they don't find some decent west winds they may hold off...
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From 345° at 6 knots
(From the NNW at ~ 6.9 mph)

Another west wind.
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1316. leo305
Quoting sonofagunn:


I think it's large size will prevent it from spinning up too quickly.


tell that to wilma
Member Since: April 17, 2010 Posts: 0 Comments: 1753
Quoting kmanislander:


Typically we look for a T # of 2 for a TD

Take a read of how the Dvorak technique is used and what different T numbers mean

Link
Afternoon. Do you think any watches or warnings for Grand Cayman. I doubt it for the sisters but what do you think about for us ?
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Quoting CybrTeddy:


Good enough for classification imo.


Probably gonna need stronger winds than that out of the west.
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1005 mbs being reported by the Recon.
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Quoting Drakoen:
The official track points at Mexico...
what track you mean the models
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The critical thing is that the low is sitting right underneath that deep convection which is not showing any sign of warming cloud tops in the middle of the day. That is a sure sign of a system that is on the upswing.

If the HH does not find a closed low now one will not be many hours away. They will likely stick around for some time if necessary and do runs again in an hour or so. They are close to us and can refuel here with ease.
Member Since: August 19, 2006 Posts: 0 Comments: 15842
Quoting Levi32:


Well they still have to complete some more passes and get a solid look at the structure of the system, but based on those very weak westerlies with easterlies just to the south, I think they would be hesitant to declare it a TD just yet. Let's see what the next few recon passes show first though.


I was thinking that too, we may not have TD 1 just yet
Member Since: March 10, 2010 Posts: 1 Comments: 7826
Looks like the models are having a hard time handling the trough/high interaction in the Gulf. Should be interesting to see where/ if this storm hits the Yucatan.
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Quoting scott39:
NW and going slow-----Not Good IMO


Then you are probably not going to like the next 48 hours very much. NW motion now as it goes through RI means simply that a more northernly component in its track will become reinforced, allowing more time over open water, which will support further intensification, which will help to reinforce a more northerly component in its track, allowing more time over open water (repeat every hour over the next 48 and you have a serious problem in the gulf.)
Member Since: June 16, 2010 Posts: 0 Comments: 28
Quoting Jeff9641:
93L is going to blow up quick guys I'm telling you. No matter what some say I've seen these storms go from nothing to a major hurricane in 24 hours not saying this will happen but a lot of energy is wraping into this system for some serious strengthening soon.


I think it's large size will prevent it from spinning up too quickly.
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looks like we may have a stronger system in the vicinity of the yucatan penninsula/ channel in the next few days looksing at some observations this system is moving very slow in very very hot water
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1305. leo305
Quoting Jeff9641:
93L is going to blow up quick guys I'm telling you. No matter what some say I've seen these storms go from nothing to a major hurricane in 24 hours not saying this will happen but a lot of energy is wraping into this system for some serious strengthening soon.


Yep exactly what I've been saying, people are putting WAYYY too much emphasis on models..
Member Since: April 17, 2010 Posts: 0 Comments: 1753
Quoting Stormchaser2007:
From 237° at 3 knots
(From the WSW at ~ 3.4 mph)


Good enough for classification imo.
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1303. Levi32
Quoting Hurricanes101:


can they still classify a TD that way?


Well they still have to complete some more passes and get a solid look at the structure of the system, but based on those very weak westerlies with easterlies just to the south, I think they would be hesitant to declare it a TD just yet. Let's see what the next few recon passes show first though.
Member Since: November 24, 2005 Posts: 635 Comments: 26661
Hi to everyone, we might be just around the corner of a wild season.
Latest cmc model shows 93L after 72 hrs at Bay of Campeche and at 126 hrs a TX/MEX event with a heck of a storm.

72 hrs


126 hrs



Link
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1301. Drakoen
The official track points at Mexico...
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Quoting Patrap:


Classified.

Guy's Po-boy on Magazine made me sign a paper.


LOL...get ready fo da $30 oyster poboy, bro
Member Since: August 2, 2006 Posts: 10 Comments: 9922
1298. GBguy88
Quoting reedzone:
Some downcasters on here this afternoon, gotta go.. Should have TD1 or Alex by the time I get back home, which is after 5 p.m. I will have a complete update and show my forecast track and intensity with the system later tonight.



I was told that wishcasting is harmless, but downcasters "gotta go"? That's cockeyed, at best.
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1297. Levi32
Quoting atmoaggie:
Tried to steal a page from the Book of Levi, but alas, how come no one near the coast around there has an anemometer?



LOL
Member Since: November 24, 2005 Posts: 635 Comments: 26661
Quoting kmanislander:


Typically we look for a T # of 2 for a TD

Take a read of how the Dvorak technique is used and what different T numbers mean

Link


Great link Kman, thanks!!
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SAB may have been 1.0 but I wanna see what the TAFB got.
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Quoting CaptnDan142:


It isn't even a TD yet. Anyone that would panic over a comment on a blog, about a system that hasn't become anything yet is just looking for something to panic about. If they don't panic about this, they will find something else.


=)
There's someone out there in panic mode right now probably.
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Now out of the N, should see some NW winds soon.
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1291. Levi32
Quoting Drakoen:


They reported some light westerly winds. The still need to complete the X pattern they do


Yeah, I didn't expect so many easterlies just south of the center though. Appeared to be more solidly closed than that. I wonder if we'll get a vortex message out of this or if it's too iffy for them.
Member Since: November 24, 2005 Posts: 635 Comments: 26661
1290. scott39
Quoting RecordSeason:
I'm about to go to sleep...in the middle of the day.

This storm is a complete waste of time.

T number 1.0...

Pathetic 93L, pathetic.
LOL
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Quoting Levi32:


They did, and even if they hadn't, the east winds west of the center speak to an open circulation, and it's not that far open. It is as close to closed as you could want it.


can they still classify a TD that way?
Member Since: March 10, 2010 Posts: 1 Comments: 7826
1288. Patrap
18z Early Cycle NHC model tracks
Invest93
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)





Dynamic Models (More sophisticated models)




Early Model Wind Forecasts



Member Since: July 3, 2005 Posts: 426 Comments: 128767
Some downcasters on here this afternoon, gotta go.. Should have TD1 or Alex by the time I get back home, which is after 5 p.m. I will have a complete update and show my forecast track and intensity with the system later tonight.
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a slow creeper moving NW only gives it more time to develop in those high SSTs. I agree that we could have TS Alex before, or IF, it scurts the yucatan peninsula. I was still expecting it to head on a more WNW motion. surprised me a bit.
Member Since: July 17, 2008 Posts: 0 Comments: 1242
but some time they do not all ways go by the Dvorak technique
Member Since: May 21, 2006 Posts: 5091 Comments: 115244
1283. xcool


nhc
Member Since: September 26, 2009 Posts: 2 Comments: 15684
1282. Levi32
Quoting Hurricanes101:


well based on the google overlay orca just showed, they have not gotten through the center yet


They did, and even if they hadn't, the east winds west of the center speak to an open circulation, and it's not that far open. It is as close to closed as you could want it.
Member Since: November 24, 2005 Posts: 635 Comments: 26661
1281. Drakoen
Quoting Levi32:


That's what I thought too until seeing the recon obs.


They reported some light westerly winds. The still need to complete the X pattern they do
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Quoting RecordSeason:
I'm about to go to sleep...in the middle of the day.

This storm is a complete waste of time.

T number 1.0...

Pathetic 93L, pathetic.


Well, keep it a short nap or you will miss the upgrade in 2.25 hours.
Member Since: June 16, 2010 Posts: 0 Comments: 28

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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.