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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In about 150 miles 93L will have to get its forward speed going because it will enter deeper waters in the Caribbean. There is warm water on the surface, but at depth its a different story. It wont take much to upwell cooler waters and inhibit strengthening.

If it was later in the year I would know for sure the warm waters are at depth too. but its still early.
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1578. JDSmith
Time: 19:11:30Z
Coordinates: 18.1167N 81.8W
Acft. Static Air Press: 977.2 mb (~ 28.86 inHg)
Acft. Geopotential Hgt: 273 meters (~ 896 feet)
Extrap. Sfc. Press: 1008.1 mb (~ 29.77 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 130° at 30 knots (From the SE at ~ 34.5 mph)
Air Temp: 23.3°C (~ 73.9°F)
Dew Pt: 18.0°C (~ 64.4°F)
Peak (10s) Flt. Lvl. Wind: 31 knots (~ 35.6 mph)
SFMR Peak (10s) Sfc. Wind: 34 knots (~ 39.1 mph)
SFMR Rain Rate: 2 mm/hr (~ 0.08 in/hr)

34 knots is just about TS strength.

Looks scary.
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Quoting HaboobsRsweet:
Looking closer at it I think they may have missed the center and there may be a low level low. Might find that west wind when it comes back to the other side of their first track.
You just made a lot of people happy. LOL, watch the blog's spirit come back.
Member Since: September 2, 2009 Posts: 130 Comments: 21111
1574. Levi32
Quoting scottsvb:


Well ECMWF is part right and so is the GFS... it will run into Belieze or Yucitan.. decouple.. midlevel low and moisture move N while the LLC moves into the BOC. Or 93L moves inland slightly further north.. still weakens maybe decouples and moves N then NE towards Florida-Alabama by Tuesday. Too early to see.


That all depends on how well-together the system is before landfall in the Yucatan, and decoupling will be reluctant to take place anyway with an anticyclone over top...little wind shear to help force the LLC out from under the mid-level feature. They just got back together for the first time in days....they will be celebrating for a while.
Member Since: November 24, 2005 Posts: 635 Comments: 26594
1573. IKE
Quoting scottsvb:


Well ECMWF is part right and so is the GFS... it will run into Belieze or Yucitan.. decouple.. midlevel low and moisture move N while the LLC moves into the BOC. Or 93L moves inland slightly further north.. still weakens maybe decouples and moves N then NE towards Florida-Alabama by Tuesday. Too early to see.


I still see 2 scenario's based on the models.....


Quoting Drakoen:
93L is moving to the northwest



I could be wrong about it's movement. Hard to really tell looking at a loop of it.
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Quoting Levi32:
93L is already positioned north of most of last night's and this morning's model runs had it during the first 24 hours, including initialization.


Personally I think 93L needs to be replaced with a wave that understands proper protocol. We simply can't allow this kind of insubordination to go as an example to future invests. ;)
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Looking closer at it I think they may have missed the center and there may be a low level low. Might find that west wind when it comes back to the other side of their first track.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
Quoting Levi32:
93L is already positioned north of most of last night's and this morning's model runs had it during the first 24 hours, including initialization.


That collective groan you hear is from the gulf coast. Soon it will be joined with its anticyclone. When that happens hold onto your hats.
Member Since: June 16, 2010 Posts: 0 Comments: 28
1569. Grothar
Quoting MiamiHurricanes09:
LMAO, ok, 2 hours and 35 minutes until 6 PM. Happy?


Countdown.............! (Chuckle)
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Some people need to understand that it MIGHT decouple or strengthen, nothing is written in stone. Gosh you know it alls! Don't matter if your a MET, you can be wrong!
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Quoting ezcColony:
The enigmas of 93L. West or East? Mild or Beast?



ezcColony....hmmmm

Same letters as you know who! Something to think about.

The image reminds me of an inside joke...
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1565. xcool
93L grown FAST OH SHI
Member Since: September 26, 2009 Posts: 2 Comments: 15648
Quoting scottsvb:


Well ECMWF is part right and so is the GFS... it will run into Belieze or Yucitan.. decouple.. midlevel low and moisture move N while the LLC moves into the BOC. Or 93L moves inland slightly further north.. still weakens maybe decouples and moves N then NE towards Florida-Alabama by Tuesday. Too early to see.
,
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Quoting extreme236:
93L's convection starting to look more symmetric. Could really take off soon.
Agreed. Also looks very large.

Member Since: September 2, 2009 Posts: 130 Comments: 21111
1562. fmbill
Quoting btwntx08:

its still moving around wouldnt bite on that yet


Agreed.
Member Since: May 27, 2008 Posts: 0 Comments: 439
93L's convection starting to look more symmetric. Could really take off soon.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1559. Gorty

I have an in depth update in my blog. Am I still thinking 0% for Alex? Come and see!

http://www.wunderground.com/blog/Gorty/show.html
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1558. Levi32
93L is already positioned north of where most of last night's and this morning's model runs had it during the first 24 hours, including initialization.
Member Since: November 24, 2005 Posts: 635 Comments: 26594
do is look like we may have an upgrade later today ??? everything except the west winds
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I think if there's an immediate threat to land the NHC would issue a special Tropical Disturbance statement upgrading to Tropical Depression 1 status.
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Quoting Grothar:


What is all that about? I don't even understand it. I was responding to MiamiHurricane when he said it was 3 more hours to 6 O'clock. LOL
LMAO, ok, 2 hours and 35 minutes until 6 PM. Happy?
Member Since: September 2, 2009 Posts: 130 Comments: 21111
1553. cg2916
Quoting extreme236:
Just what I thought. The TAFB gave out a T2.0/30kt estimate. Link


SAB only gives a 1.0.
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So far looks like a whole lot of nothing for 93L. I see they felt it was safe enough to drop down to 925mb. Winds are not that impressive and no closed low yet.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
Jeff Masters live now on WWL 870 (NOLA)
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Quoting IKE:
93L is going to run out of time. Looks headed W to WNW to me. Probably got 36 hours to landfall.

Looks like it will spend a day to maybe a day and a half over land.

Maybe this gets to a TS over the GOM my best guess...40-50 mph system.

ECMWF may be correct....burying it in the BOC.


Well ECMWF is part right and so is the GFS... it will run into Belieze or Yucitan.. decouple.. midlevel low and moisture move N while the LLC moves into the BOC. Or 93L moves inland slightly further north.. still weakens maybe decouples and moves N then NE towards Florida-Alabama by Tuesday. Too early to see.
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1549. Levi32
Quoting Grothar:


What is all that about? I don't even understand it. I was responding to MiamiHurricane when he said it was 3 more hours to 6 O'clock. LOL


Oh lol....thought you guys were talking about the recon mission.
Member Since: November 24, 2005 Posts: 635 Comments: 26594
1548. Drakoen
93L is moving to the northwest
Member Since: October 28, 2006 Posts: 57 Comments: 30179
Quoting extreme236:
Just what I thought. The TAFB gave out a T2.0/30kt estimate. Link
As expected, didn't think SAB would keep it at 1.0, guess they aren't impressed.
Member Since: September 2, 2009 Posts: 130 Comments: 21111
1545. Levi32
Quoting StormChaser81:
Water temp to the northeast of the center is not as warm as you would expect in this area of the caribbean. 84 degrees which is not conducive for rapid intensifying.



SSTs are just fine. They are rarely hotter than 30C (86F) down there. What matters is the depth of the warmth, which is insane right now. The heat content is more than past the accepted threshold for rapid intensification.

Member Since: November 24, 2005 Posts: 635 Comments: 26594
1544. Grothar
Quoting Levi32:


ATLANTIC REQUIREMENTS
1. SUSPECT AREA (WESTERN CARIBBEAN)
FLIGHT ONE - TEAL 70
A. 25/1800Z
B. AFXXX 01AAA INVEST
C. 25/1430Z
D. 17.5N 83.0W
E. 25/1730Z TO 25/2200Z
F. SFC TO 10,000 FT


What is all that about? I don't even understand it. I was responding to MiamiHurricane when he said it was 3 more hours to 6 O'clock. LOL
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1542. RJT185
Quoting IKE:
So no TD?

I've got a few extra towels if anyone needs one to wipe away the t e a r s......



priceless! :)
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Quoting CybrTeddy:
Don't see any renumbering, nor have I seen any pure W winds. No TD at 5 pm IMO. Is there going to be a recon tomorrow too?


recon will be in there for another 2-3 hours so they could still find a TD before they leave today

next recon is for 2am tomorrow
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Quoting MrNatural:
Looks like an eye is trying to form. About 75 NW of Puert Lampira Honduras. More than a little ragged. It also seems to be doing a little jog here and there. Still feel that it will follow the path of the tropical wave that preceded it by a few days.


Long way from a eye forming.
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1537. IKE
93L is going to run out of time. Looks headed W to WNW to me. Probably got 36 hours to landfall.

Looks like it will spend a day to maybe a day and a half over land.

Maybe this gets to a TS over the GOM my best guess...40-50 mph system.

ECMWF may be correct....burying it in the BOC.
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Quoting Baltimorebirds:
If they do find a depression will they issue a special advisory or no??


No. Once that happens, Operation Keep It Secret will go into effect, and all satellite imagery indicating a storm has formed will be deleted or sanitized. The hurricane hunters who eye witnessed the data will be given new identities in an unknown South American nation, and bloggers who know about it will be hunted down, captured, and sent to re-education camps. That's just what I heard.
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Just what I thought. The TAFB gave out a T2.0/30kt estimate. Link
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1534. fmbill
Quoting HurricaneHunterGal:
2PM Models are out for 93L


So...TVCN now calls for a more northerly path with a turn toward the east at the end of the model run. Interesting.
Member Since: May 27, 2008 Posts: 0 Comments: 439
Quoting extreme236:


At this point I'd say no. Were close enough to the advisory time.
Well if they find a closed circulation after 5 they might release a special advisory, they might even release one now, not after 4PM though.
Member Since: September 2, 2009 Posts: 130 Comments: 21111
Don't see any renumbering, nor have I seen any pure W winds. No TD at 5 pm IMO. Is there going to be a recon tomorrow too?
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Quoting P451:
Belize Radar could be an interesting page to watch in the coming days.



Thank you for that P451. My daughter is traveling there Monday with a mission group. I am really watching with great interest this area.
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1529. Patrap
The Overall Mean Center has been west of the Comma Shaped Clouds a lot believed was the Coc.

Its a Large Circ and its still trying to build a Warm column,

Its making progress, but slowly as forecasted.

Floater - Visible Loop
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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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