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 btwntx08:
ok are we expecting an intermeddate update??
Yes, next advisory is at 8 PM EDT (7 PM CDT).
Member Since: September 2, 2009 Posts: 130 Comments: 21193
I'm quoting one page per comment and I am just not keeping up at all.
Member Since: August 30, 2008 Posts: 8 Comments: 2835
we sould all flood overe too the nhc site update in a few
Member Since: May 21, 2006 Posts: 5091 Comments: 115122
Wow it looks massive in size for a TD!
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Quoting RyanFSU:
Using my new and improved inner-nest (0.083 degree) GFDL map code, I produce some cooler plots of active storms... Quite the impressive development towards the end of the forecast cycle Link


Thanks! Definitely bookmarked that one.
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I dont know... but thinking that with that burst of convection near/over the LLC, we may have TS by 8pm... if not, definitely 11pm.
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3322. Drakoen
Usually we see black in the West Pacific where the tropopause is higher allowing cloud tops to extend further into the atmosphere. Truly incredible TD1 can do this and produce such nice spatial area of this dense convection.
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3321. HadesGodWyvern (Mod)
btwntx08 11:41 PM GMT on June 25, 2010
ok are we expecting an intermeddate update??


yes since TS Warnings are issued.
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Quoting KoritheMan:
First signs of a CDO?

Indeed.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
3319. uplater
Quoting Drakoen:


Around 50,000ft


Must be an awe-inspiring sight, inside the HH
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looks like mode runs take this too LA now
Member Since: May 21, 2006 Posts: 5091 Comments: 115122
Quoting errantlythought:


That damn hot tower is the size of JAMAICA. O_o
Lol.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting atmoaggie:

Didn't seem we would have a lot...though HWRF's shift is interesting, 00 Z is where it's at, IMHO.


Agreed. but not buying it. The GFS Ensemble looks more realistic.
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Quoting MiamiHurricanes09:
Last image of the day, notice that massive hot tower.



That damn hot tower is the size of JAMAICA. O_o
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Satellite image seems to move West
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GFDL 18z 114 hours

Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting KEEPEROFTHEGATE:
EMPTY SPACE CREATED

EmptySpaceCaster
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Quoting cyclonekid:
...FIRST TROPICAL DEPRESSION OF THE ATLANTIC SEASON FORMS IN THE
WESTERN CARIBBEAN...

Images made by cyclonkid
6pm EDT Graphics Update





The NHC forecast significantly reduces its forward motion between day 3 and 5. This will give it a chance to strengthen steadily while the shear subsides.

Quoting RecordSeason:
Huge surface low under a huge anticyclone.

Going to be a hurricane tomorrow, if not over night, IMO.


Its sheer size may prevent it from rapid strengthening. Ike 2008 was similarly large and failed to become a major hurricane in the Gulf yet had the surge of a cat. 5.

Quoting Tazmanian:
am hoping TD 1 makes it too cat 3


What, and that it stalls in the Gulf for six days, depletes all the warm water in the western Gulf before fizzling out, and destoys all the oil platforms? Sign me up. :P

Quoting Tazmanian:
will the good new is that the oil will be gone from the gulf


No, it will be dispersed, sent into the coast from Louisiana to the Panhandle, and some of it may even enter the Gulf Stream. Not good.
Member Since: August 30, 2008 Posts: 8 Comments: 2835
Quoting RyanFSU:
Using my new and improved inner-nest (0.083 degree) GFDL map code, I produce some cooler plots of active storms... Quite the impressive development towards the end of the forecast cycle Link



Ouch. Looks like Hurricane Isidore track, only much stronger after leaving the Yucatan.
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3308. xcool
RyanFSU thanks alot.
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3307. KORBIN
That picture sure looks like a TS to me- Miami!

This one is looking like it might be the resilient one we have watched for days.
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Quoting RyanFSU:
Using my new and improved inner-nest (0.083 degree) GFDL map code, I produce some cooler plots of active storms... Quite the impressive development towards the end of the forecast cycle Link


oy, I don't think I like your product...at least not it's answer, ATM.
Member Since: August 16, 2007 Posts: 6 Comments: 12461
Quoting RyanFSU:
Using my new and improved inner-nest (0.083 degree) GFDL map code, I produce some cooler plots of active storms... Quite the impressive development towards the end of the forecast cycle Link





OMG THE MODE RUNS IS BEING A DOOMCASTR
Member Since: May 21, 2006 Posts: 5091 Comments: 115122
3304. Drakoen
Quoting RyanFSU:
Using my new and improved inner-nest (0.083 degree) GFDL map code, I produce some cooler plots of active storms... Quite the impressive development towards the end of the forecast cycle Link



Nice graphics there Ryan
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Quoting atmoaggie:

Didn't seem we would have a lot...though HWRF's shift is interesting, 00 Z is where it's at, IMHO.


I am of the opinion that operational recon does not add that much to the models. SFMR and Tail Doppler Radar are not used, so you basically get an accurate position and pressure, along with a windfield shape. Now the Gulfstream IV flights help significantly. Just my own opinion.
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3301. centex
Ever notice that best blogers are absence when we need them? I guess trying to protect there ranking.
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3300. IKE
Quoting Twisterman555:
IKE, looks like Vivian Brown was wrong. Haha.


LOL...I hear ya. TWC:(
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Not to mention the radiosondes...heck, the radiosondes launched at Memphis could have an impact.
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First signs of a CDO?

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Last image of the day, notice that massive hot tower.

Member Since: September 2, 2009 Posts: 130 Comments: 21193
3296. Drakoen
Quoting uplater:


I wonder how high those towers reach?


Around 50,000ft
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Quoting uplater:


I wonder how high those towers reach?
with all due respect, I think thats "High Enough" if you know what I mean....

Taco :o(
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3294. RyanFSU
Using my new and improved inner-nest (0.083 degree) GFDL map code, I produce some cooler plots of active storms... Quite the impressive development towards the end of the forecast cycle Link

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IKE, looks like Vivian Brown was wrong. Haha.
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3292. Drakoen
Quoting atmoaggie:

Didn't seem we would have a lot...though HWRF's shift is interesting, 00 Z is where it's at, IMHO.


I agree
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Quoting TropicalNonsense:


i dont think there was recon. atleast not the upper air stuff yet.

this is why you cannot trust the models right now. they will be all over
the Gulf Coast until the newer data is input after a IV Flight.
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Quoting atmoaggie:

Didn't seem we would have a lot...though HWRF's shift is interesting, 00 Z is where it's at, IMHO.


Agreed.
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3289. uplater
Quoting HadesGodWyvern:


orange is -90C, right?


I wonder how high those towers reach?
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Quoting nrtiwlnvragn:


Some, but not enough to make much of a difference.

dropw
Dropwinsonde
1
1


recco
Flight level reconnaissance aircraft data
14
6


Link

Didn't seem we would have a lot...though HWRF's shift is interesting, 00 Z is where it's at, IMHO.
Member Since: August 16, 2007 Posts: 6 Comments: 12461
dos any of the mode runs take right overe BP?
Member Since: May 21, 2006 Posts: 5091 Comments: 115122
3286. KEEPEROFTHEGATE (Mod)
Quoting ShenValleyFlyFish:


Easy fix for that. If you can't, get the site to do it for you. IGNORE
all posts have been removed empty space created
Member Since: July 15, 2006 Posts: 171 Comments: 53841
Quoting nrtiwlnvragn:


Some, but not enough to make much of a difference.

dropw
Dropwinsonde
1
1


recco
Flight level reconnaissance aircraft data
14
6


Link


Then we shouldn't pay attention to any of them yet.
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Quoting KoritheMan:


i dont think there was recon. atleast not the upper air stuff yet.
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Quoting Tazmanian:



and takeing the oil with it


Yep.
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Quoting KoritheMan:
Does anybody know if the 18z models were fed recon data?


Some, but not enough to make much of a difference.

dropw
Dropwinsonde
1
1


recco
Flight level reconnaissance aircraft data
14
6


Link
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Quoting KEEPEROFTHEGATE:
EMPTY SPACE CREATED
Who?
Member Since: September 2, 2009 Posts: 130 Comments: 21193
3279. KEEPEROFTHEGATE (Mod)
WUEST enjoy that lollipop
Member Since: July 15, 2006 Posts: 171 Comments: 53841

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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.