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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1179. Drakoen
We have to wait until the HH get into the right front quadrant of the system to find out what the winds are in this system.
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Quoting Tropicaddict:


What's that mean Drak??


It means the storm top are punching into the upper atmosphere. A sign of unstable air conditions conducive to convection to build.
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Time: 18:02:30Z
Coordinates: 16.7N 83.1167W
Acft. Static Air Press: 976.8 mb (~ 28.84 inHg)
Acft. Geopotential Hgt: 257 meters (~ 843 feet)
Extrap. Sfc. Press: 1005.8 mb (~ 29.70 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 177 at 4 knots (From the S at ~ 4.6 mph)
Air Temp: 23.3C* (~ 73.9F*)
Dew Pt: 23.3C* (~ 73.9F*)
Peak (10s) Flt. Lvl. Wind: 5 knots (~ 5.8 mph)
SFMR Peak (10s) Sfc. Wind: -
SFMR Rain Rate: -
(*) Denotes suspect data
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1175. Levi32
Quoting atmoaggie:

These surface obs scream pressure deficit...almost has to be some west winds.


(full size...click)


Yeah....WNW winds out of Honduras almost has to mean a closed low. I'm seeing a lot of southerlies in the vicinity of the center though on the latest recon obs.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
exactly chaser81, he has been yelling at people for days and screaming Florida despite evidence against that kind of track

now everyone wants to defend him lmao

whatever, doesn't matter, we will see what happens

my thinking is the consensus is good for now, but that can change
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Quoting kmanislander:


Paloma was one of many that passed through this region and became a major with little warning. I know it's June but the TCHP is like mid August. The NW Caribbean is notorious for exceeding the intensification forecats by wide margins and having 93L take its own sweet time moving is not good.
I honestly would not be surprised seeing 93L develop into a hurricane if it stays over water for more than 48 hours, and it looks like it will if it keeps moving ever so slowly.
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Good afternoon all...i'll be back in a few. Gotta do a bit of analysis and update my site.
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Quoting Thundercloud01221991:
I think we will see them declare it a TD at 5 PM and then a TS at 8 pm


TD @ 5, okay. TS @ 8, no way. It won't spin up that fast. Tomorrow, perhaps and then it better hurry and get big fast because it has to move north to avoid going where StormW has it visiting.
Member Since: June 16, 2010 Posts: 0 Comments: 28
93L currently reminds me of Dolly 2008.

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Quoting Drakoen:
Overshooting tops evident on IR imagery



What's that mean Drak??
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Quoting Levi32:


They found a west wind, light but they still have yet to leave the center. The next set of obs should show us a good batch of west winds if there are any.

These surface obs scream pressure deficit...almost has to be some west winds.


(full size...click)
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Hey Matt, how's it going?

Quoting tornadodude:


at this point it could go anywhere, from mexico to florida
Member Since: December 18, 2006 Posts: 7 Comments: 2686
Quoting Jeff9641:


I think you need to chill! I hope to god this stays away from the Eastern Gulf period with all this oil around. Please go west. I just have a bad feeling about this trough coming down in a few days. I've said this several time today. Pipe down buddy as Luda would say.


Calling for landfall areas is a good way of getting people in a panic.
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1163. bwi
16.833N 83.117W at 1005.4mb lowest on that pass if I'm reading it right.
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Someone asked earlier why they send out two HH. They are collecting significant data ahead of the storm for the oil workers in the gulf they need 5 full days to evacuate all the boats working at the Deep Horizon spot. That doesn’t leave a ton of time if this storm ramps up and heads north…
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Quoting Hurricanes101:


I am chill, you are the one that has Florida in every single comment when it is clear the model consensus keeps it away from Florida


at this point it could go anywhere, from mexico to florida
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Quoting Drakoen:


I agree. There is a lot of TCHP content down there and our ability to forecast to intensity still needs signifcant improvement.


Paloma was one of many that passed through this region and became a major with little warning. I know it's June but the TCHP is like mid August. The NW Caribbean is notorious for exceeding the intensification forecasts by wide margins and having 93L take its own sweet time moving is not good.
Member Since: August 19, 2006 Posts: 0 Comments: 15826
1158. Drakoen
Overshooting tops evident on IR imagery

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Here in the north of the peninsula you can observe different weather
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will it not just die out once it makes land fall which looks to be what its going to do soon?
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Quoting P451:
9HR IR Loop ending 145PM ET



That's not spinning up?? Sorry, I disagree, 93L (TD1) is indeed spinning up today.
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Quoting cyclonekid:
He took a job as the "chief meteorologist" at the NWS in San Antonio, TX.

San Angelo...go west, my son, not San Antonio.
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1151. leo305
Quoting Hurricanes101:


I am chill, you are the one that has Florida in every single comment when it is clear the model consensus keeps it away from Florida


forget the models right now.. most of them don't have it touch a strong TS/Hurricane in the carribean.. so if this does that, what will you say about the models then? Since they forecast a weak TD moving towards the YUCATAN.
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Afternoon everyone!
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wow the last few satellite clips show a REALLY well developed Depression/border line T.S. Alex... wow, if all the convection around were to "suck" in towards the center we would have a monster on our hands...

For the Northern Gulf Coast: We need to pray for the sheer to increase in the gulf if this thing tries to come our way!!!!
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I think we will see them declare it a TD at 5 PM and then a TS at 8 pm
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1147. leo305
Quoting charlottefl:
The Yucatan peninsula is extremely flat, and surrounded by water. It will weaken the system, but odds are against it completely falling apart.



wima although a CAT 4 at landfall, was over the Yucatan for 2 days, and it weakened to a CAT 2
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Quoting jasoniscoolman09:
what happern to Dr. Lyons anyhow.
He took a job as the "chief meteorologist" at the NWS in San Antonio, TX.
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1143. cg2916
Quoting StormW:
Look like a CDO to me:



You can see the COC (try saying that 3 times fast, LOL)!
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CDO =
"CDO" is an acronym that stands for "central dense overcast". This is the
cirrus cloud shield that results from the thunderstorms in the eyewall of a
tropical cyclone and its rainbands. Before the tropical cyclone reaches
hurricane strength (64 kt or 33 m/s), typically the CDO is uniformly showing
the cold cloud tops of the cirrus with no eye apparent. Once the storm
reaches the hurricane strength threshold, usually an eye can be seen in
either the infrared or visible channels of the satellites. Tropical cyclones
that have nearly circular CDO's are indicative of favorable, low vertical
shear environments.

So StormW, are you thinking it's ramping up that quickly?


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Quoting ezcColony:
This system just will not spin up! Incredible!


93L has had many near-life experiences. Thus far, it has not bit the apple.
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Quoting Levi32:


They found a west wind, light but they still have yet to leave the center. The next set of obs should show us a good batch of west winds if there are any.


ah ok
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Quoting reedzone:


Not spin up?? It's spinning up right now, convection around, over the center. Its probably a TD or TS by now. I'm calling for TS. Alex by 5 p.m.


I'll go as far as saying that it is organizing finally. But spinning? No.
Member Since: June 16, 2010 Posts: 0 Comments: 28
1136. Drakoen
Quoting kmanislander:


Depends on the intensity. I was thinking more along the lines that a slow mover over high TCHP might ramp up quicker than forecast and a deeper system will pull up to the N sooner in a weak steering environment.

Several variables out there right now and perhaps a few surprises in store over the next 24 hours.


I agree. There is a lot of TCHP content down there and our ability to forecast to intensity still needs signifcant improvement.
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Quoting Jeff9641:


I think you need to chill! I hope to god this stays away from the Eastern Gulf period with all this oil around. Please go west. I just have a bad feeling about this trough coming down in a few days. I've said this several time today. Pipe down buddy as Luda would say.


I am chill, you are the one that has Florida in every single comment when it is clear the model consensus keeps it away from Florida
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Quoting ClearH2Ostormchaser:
Kman, StormW how are you all. Kman how is paradise. You were right in what you said last night. Looks like all the vegetables are in the pot and the heat is about ready to start cooking.



Paradise is just fine today. Sun coming and going. Throw a bone in the pot won't you LOL
Member Since: August 19, 2006 Posts: 0 Comments: 15826
Latest visible satellite pictures show the circulation really starting to come together, with more thunderstorms building over the center. I say TS at 5.
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1132. cg2916
Quoting leo305:
Do you guys know how to add an avatar to your profile? A display pic?


Go to Wunderground photos, upload a pic, then on the right side of the upload page, there should be something that says "This is a portrait" or something that says portrait, then check "This is my primary portrait".
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1131. JDSmith
Time: 18:00:00Z
Coordinates: 16.8333N 83.1167W
Acft. Static Air Press: 977.0 mb (~ 28.85 inHg)
Acft. Geopotential Hgt: 252 meters (~ 827 feet)
Extrap. Sfc. Press: 1005.4 mb (~ 29.69 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 16° at 6 knots (From the NNE at ~ 6.9 mph)
Air Temp: 24.4°C (~ 75.9°F)
Dew Pt: 24.4°C (~ 75.9°F)
Peak (10s) Flt. Lvl. Wind: 6 knots (~ 6.9 mph)
SFMR Peak (10s) Sfc. Wind: 20 knots (~ 23.0 mph)
SFMR Rain Rate: 0 mm/hr (~ 0 in/hr)
(*) Denotes suspect data


1005.4

There's a barb indicating ~30mph just before the wind completely cuts out and the pressure drops off a cliff.
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Da blob

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The Yucatan peninsula is extremely flat, and surrounded by water. It will weaken the system, but odds are against it completely falling apart.

Edit: That does depend on the speed at which it crosses though. That's assuming it continues at it's current forward speed.

Quoting sarahjola:
isn't it just going to fall apart if it makes landfall. it is a weak system and land would jusst rip it apart right?
Member Since: December 18, 2006 Posts: 7 Comments: 2686

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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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