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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Directly from Dr. M's blog entry today:

"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."
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1428. bappit
Quoting sarahjola:
the nw movement scares me a little as i am in se la. and from my experience when a storm brushes land it jogs to the east. as a west tracking storm the models had it going to mexico/tx. could the nw movement be happening cuz its so close to land? also will this nw movement mean that the potential for land fall on tx/la more likely?


Moving more west than north right now I think.
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1427. Grothar
Quoting A4Guy:


Grothat...that image has yesterday's date/timestamp on it.....


Unless you are on the other side of the International date line, today still is the 25th here! Look again. I just posted from the update.
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Satellite appearance continues to improve with 93L. Having a hard time believing they cant find any strong west winds. Surprising.
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The passes by the HH just go to show that many times when ASCAT appears to show a closed low it really isn't at all. There is no substitute for obs on location. That is why I always tend to lean against calling a closed low unless the sat. pass is crystal clear.
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Quoting ezcColony:


Within 12 hours, the anticyclone will be directly above this system. It will get that surface low development it needs for sure.


If I had a dime for every time I heard this in the last three days, I'd be able to quit my day job.
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1422. Levi32
Member Since: November 24, 2005 Posts: 635 Comments: 26647
1421. 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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1420. xcool
93l nw wt--
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1419. Patrap
Quoting Floodman:


You know, when you modify that loop to show only the first and the last frame it appears the motion is more WNW


rock it

..always a winna
Member Since: July 3, 2005 Posts: 424 Comments: 128275
Quoting JLPR2:
So everyone knows we have 94L too right?

I just dont see it mentioned in the last pages :P


That area has been closed to fishing.
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1416. Patrap
The HH recon Pass will be under NHC Booth Review
Member Since: July 3, 2005 Posts: 424 Comments: 128275
Quoting Patrap:

93L swinging in the Mo..


93L NASA Viewer


You know, when you modify that loop to show only the first and the last frame it appears the motion is more WNW
Member Since: August 2, 2006 Posts: 10 Comments: 9922
Quoting Levi32:
Yeah I don't buy the 12z ECMWF. That's almost ridiculous right there.
Why? Explain your reasoning?
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The models are certainly trending east. I guess that means a stronger storm.
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Quoting Hurricanes101:


system isnt closed

not Alex, or a TD

30 knots is only 35mph anyway
Give it a couple more hours, Recon might have to spend a little more time than expected inside 93L.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
1411. Drakoen
Satellite imagery suggested a closed low but the surface observations from the HH at the present time are not showing those due west winds.
Member Since: October 28, 2006 Posts: 57 Comments: 30490
1410. Max1023
The extremely low synoptic pressure in the NW Caribbean is probably slowing the development of a surface circulation. The convection has not only lowered the central pressure but the outer pressure as well, during the past few days is has mostly been removed from the area of lowest surface pressure. 93L has a 1005mb center embedded in an 1008mb -1009mb area. If the outlying pressure was 1012mb we would probably have a closed low with TS force winds.
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1409. JLPR2
So everyone knows we have 94L too right?

I just dont see it mentioned in the last pages :P
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the nw movement scares me a little as i am in se la. and from my experience when a storm brushes land it jogs to the east. as a west tracking storm the models had it going to mexico/tx. could the nw movement be happening cuz its so close to land? also will this nw movement mean that the potential for land fall on tx/la more likely?
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Quoting Jeff9641:


Alex are you there?


system isnt closed

not Alex, or a TD

30 knots is only 35mph anyway
Member Since: March 10, 2010 Posts: 1 Comments: 7685
Quoting Levi32:
30-knot southeast winds measured right at 17N, 83W.
18:39:00Z 16.983N 83.033W 977.6 mb
(~ 28.87 inHg) 247 meters
(~ 810 feet) 1005.6 mb
(~ 29.70 inHg) - From 136° at 26 knots
(From the SE at ~ 29.9 mph) 22.4°C
(~ 72.3°F) 18.0°C
(~ 64.4°F) )30 knots
(~ 34.5 mph
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting Drakoen:


It is close with the WSW winds. Still need to spend some more time with its surface low and bend the flow sharper.


They might combine that in with the recent ASCAT pass and declare it. We'll see. If not 5 pm, certainly by tomorrow.
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Quoting Drakoen:


It is close with the WSW winds. Still need to spend some more time with its surface low and bend the flow sharper.


Within 12 hours, the anticyclone will be directly above this system. It will get that surface low development it needs for sure.
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Quoting LRandyB:
No. They made one pass south and they are headed back north now. No west winds to speak of and the strongest winds they have encountered at flight level or on the SFMR (which stopped working before they made the center) has been ia breif area in the 25 knot range.

This system is not yet closed.


thats what I thought Randy, thanks
Member Since: March 10, 2010 Posts: 1 Comments: 7685
1400. Patrap
Repost #1288

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: 424 Comments: 128275
Quoting leo305:


the stronger it gets, the further north it will move


Depending on a number of things, but yes, it's tendency will be poleward...the timing of the trof that's supposed to pick it up will be critical, but we're getting ahead of ourselves here...the HH flight has yet to find a clearly defined LLC

I'll admit that 93L has all the makings of a very nasty week in the GOM...
Member Since: August 2, 2006 Posts: 10 Comments: 9922
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.


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Quoting Patrap:



Actually..the ol Lady went to Domelisi's.


Yep, that's our favorite around here. Back to lurking....
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1396. Drakoen
1005.3mb
Member Since: October 28, 2006 Posts: 57 Comments: 30490
Quoting WINDSMURF:
Hey guys,
I need your honest opinion on that wave with a 20% chance of development. I live in south florida and will be away on a trip for two weeks starting next tuesday. Should I be worried? I appreciate your opinion since I am not an expert but realize that some of you really know your stuff. Thanks


What's your zip code?
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1394. xcool
Drakoen /so true.
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THe NHC is putting all interest in NW Caribbean on alert, I would bet a nickel against a bucket of cow manure that this will be classified before the day is through! This is a true tropical cyclone in the making, could turn out to be significant one too in my opinion.
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1392. LRandyB
No. They made one pass south and they are headed back north now. No west winds to speak of and the strongest winds they have encountered at flight level or on the SFMR (which stopped working before they made the center) has been ia breif area in the 25 knot range.

This system is not yet closed.
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usually delay is about 3 hours from what I have read here.
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1390. Levi32
30-knot southeast winds measured right at 17N, 83W.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
1389. Drakoen
Quoting Hurricanes101:
I have yet to find evidence of a closed low, so in my mind as of now we do not have a TD


It is close with the WSW winds. Still need to spend some more time with its surface low and bend the flow sharper.
Member Since: October 28, 2006 Posts: 57 Comments: 30490
1387. jpsb
Quoting Skyepony:
No west wind second time through..
Great news, go west 93L go west!
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Quoting Levi32:
Yeah I don't buy the 12z ECMWF. That's almost ridiculous right there.
Me either.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
New obs in, but we're the recon is located we wouldn't see west winds in a closed circulation. Needs to be in the southern part of the circulation.
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1382. A4Guy
Quoting Grothar:
This is what is called ein Klecks in German:



Grothat...that image has yesterday's date/timestamp on it.....
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Quoting leo305:


it doesn't let me open it


You need to have Google earth installed
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Quoting kmanislander:


If the NW motion holds I don't see any watches until much later in the timeline and then possibly for the N end of the Yucatan and/or Western Cuba. Too early to worry about for now.
Yeah, lets see if it develops first.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
1379. Levi32
Yeah I don't buy the 12z ECMWF. That's almost ridiculous right there.
Member Since: November 24, 2005 Posts: 635 Comments: 26647

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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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