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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2228. KEEPEROFTHEGATE (Mod)
637

TCCA23 KNHC 251946

STDWCA



SATELLITE TROPICAL DISTURBANCE RAINFALL ESTIMATES

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL

1815 UTC FRI JUN 25 2010





SYSTEM NAME/IDENTIFIER...CARIBBEAN WAVE (AL932010)



MAX RAINFALL

DATE/TIME LOCATION MOTION MEAN LAST

----------- ------------ ------ ------- -------

25/1815 UTC 16.9N 82.9W 315/06 17.7 IN 14.8 IN





LAST RAINFALL DISTRIBUTION...



DISTANCE LEFT OF CENTER RIGHT OF CENTER

------------- --------------- ---------------

0 TO 1 DEGREE 10.8 TO 13.9 IN 4.2 TO 11.6 IN

1 TO 2 DEGREE 10.1 TO 14.8 IN 3.3 TO 7.8 IN

2 TO 3 DEGREE 2.2 TO 12.6 IN 1.4 TO 3.2 IN

3 TO 4 DEGREE 0.1 TO 2.0 IN 0.7 TO 2.1 IN


Member Since: Posts: Comments:
2227. 10Speed
So ....

1. Do they take the chance and name 93L even though it might end up not qualifying for a name by the time the night's out?

2. Do they name it simply because of it's proximity to land?

3. Do they refrain from naming it because of the oil promoted media frenzy that's going transpire as soon as they name it?

4. Do they do their job and follow their own rules regarding naming?
Member Since: Posts: Comments:
2226. IKE
Center looks close to 16.5N/83W to me heading toward Belize...on an almost due west course. After looking at a wide view of the GOM and Caribbean, unless this system changes course, it may not have much real estate over the BOC to intensify....Link
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quite impressive. Looks like the models are right about the size. Hopefully its not the first ever oilcane.
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2224. Levi32
Visible satellite is screaming "TD" at me.
Member Since: November 24, 2005 Posts: 635 Comments: 26569
2223. 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: 421 Comments: 127702
2222. leo305
the HH have to move to 17N the center is up there between 17-18N based on vis satellite..

I mean they found west winds there once before.. so who knows
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starting to look very impressive
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94L not looking so bad either...

-Snowlover123
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I'm not convinced on a TD until I see a vortex message.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
2217. KEEPEROFTHEGATE (Mod)
93L/XX/XX
MARK
16.9N/83.8W
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NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
530 PM EDT FRI JUN 25 2010

AMZ089-260330-
SYNOPSIS FOR CARIBBEAN SEA AND TROPICAL N ATLC FROM 07N TO 22N
BETWEEN 55W AND 65W


.SYNOPSIS...A TROPICAL WAVE ALONG 83W WITH DEVELOPING 1005 MB
LOW PRES ALONG THE WAVE NEAR 16.9N83.2W WILL MOVE W TO NW AND IS
EXPECTED TO REACH THE E COAST OF YUCATAN PENINSULA SAT NIGHT
MOVING ACROSS THE PENINSULA SAT NIGHT AND EARLY SUN
. THE LOW MAY
DEVELOP INTO A TROPICAL CYCLONE TONIGHT OR SAT BEFORE REACHING
THE YUCATAN COAST. FRESH TO STRONG WINDS AND ACTIVE WEATHER WILL
AFFECT THE NW CARIBBEAN TONIGHT THROUGH SAT NIGHT. ANOTHER
TROPICAL WAVE ENTERING THE SE CARIBBEAN...WITH THE N PORTION NOW
AS A TROUGH IN THE NORTHERN PART OF THE TROPICAL N ATLC WILL
MOVE W-NW. POSSIBLE LOW PRES MAY DEVELOP ALONG THE TROUGH THIS
WEEKEND.
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Quoting Tazmanian:



i say its more then a TD right now


YOu do? Thanks Taz!
Good to see you back in the middle of the discussion here!
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Time: 20:44:30Z
Coordinates: 16.5333N 83.4333W
Acft. Static Air Press: 977.4 mb (~ 28.86 inHg)
Acft. Geopotential Hgt: 237 meters (~ 778 feet)
Extrap. Sfc. Press: 1004.3 mb (~ 29.66 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 289° at 4 knots (From the WNW at ~ 4.6 mph)
Air Temp: 24.3°C (~ 75.7°F)
Dew Pt: 18.0°C (~ 64.4°F)
Peak (10s) Flt. Lvl. Wind: 5 knots (~ 5.8 mph)
SFMR Peak (10s) Sfc. Wind: 7 knots (~ 8.0 mph)
SFMR Rain Rate: 0 mm/hr (~ 0 in/hr)
(*) Denotes suspect data
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Quoting bwi:
Pressure dropped over 1mb between passes so far. 1004.3


That is definitely TD strength. Millibars, that is.

-Snowlover123
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Quoting TerraNova:
No update on the FTP site. Link



not yet any way
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Quoting seflagamma:


Hi Skye, You think it is a TD yet?



i say its more then a TD right now
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No update on the FTP site. Link
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2205. KORBIN
Doesn't the heating of the day cause these storms to blow up a bit than dwindle down as it cools?

If there is no is no closed low wouldn't this just constitute a wave that is feeding off the daytime heating?
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Quoting KEEPEROFTHEGATE:


Dang it Keeper! Thats the second time I was just scrolling along then got to your post. And the next thing I knew I'm waking up and minutes had passed. Lol. The lil crystal ball guy is hypnotizing me. Or I need a nap. :)
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Quoting Skyepony:
That pass looked pretty good. Wouldn't be surprised to see it called on that one.


Hi Skye, You think it is a TD yet?
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Quoting iluvjess:


Pardon me, 90% of the posts on here are opinions.


And HH Data is part of the 10% that's not.
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2201. centex
TD classification is not perfect science it's alot of factors and the centers of these are not always very well defined and can be somewhat broad. On a side note, they are under extreme pressure to give max early warning to BP and Obama.
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Quoting Levi32:


I want to see more....these two passes through the core have been very different in the location of the westerly winds. We need a clearer picture of the center. It is very close to a TD though, just about as close as you can get without being one. We just need to know how defined the center is.


IMO, this is probably already a TD... all we need is to have a confirmed Center, like you said... and we hit the jackpot. :)

-Snowlover123
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2199. Levi32
Quoting StormW:


NHC also looks how long it has had persistent organized convection.


Yeah. I believe those particular criteria have been met, but that is one of the more subjective requirements that they make a decision on.
Member Since: November 24, 2005 Posts: 635 Comments: 26569
I am almost willing to bet that the low pressure in this storm will relocate further north due to the interaction with land. This system already has a history of jumping here and there. One more but big time this time could be very likely.
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Quoting tennisgirl08:


Ok - my last point. You don't think that NHC forecasting (with storms in the gulf) are driven at all influenced by oil drilling? Just sayin..


One would like to think not, though he possibility exists
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2196. bwi
Pressure dropped over 1mb between passes so far. 1004.3
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2194. Skyepony (Mod)
That pass looked pretty good. Wouldn't be surprised to see it called on that one.
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Quoting extreme236:


Lol you must have a very broad definition of opinion. I wouldn't really call HH data an opinion...


Pardon me, 90% of the posts on here are opinions.
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2192. hydrus
Quoting gator23:

Not to mention that the Miami area which is one of the most likely places to be effected by a tropical cyclone does not sit on the GOM and is often ignored.
that post was not meant to be rude. These storms bring death and destruction to millions of people. To make a comment like that is ignorant.
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Quoting extreme236:


Probably at least 10-15kt. It depends on how confident they are about the circulation being closed. In all reality, if they don't close this off on this flight, they might wait until the next flight to see if it's closed to classify.
Ok, thanks.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
2189. Levi32
Quoting Snowlover123:


Levi, considering the information from the Hurricane Hunters, is this a TD or not, In your opinion?

-Snowlover123


I want to see more....these two passes through the core have been very different in the location of the westerly winds. We need a clearer picture of the center. It is very close to a TD though, just about as close as you can get without being one. We just need to know how defined the center is.
Member Since: November 24, 2005 Posts: 635 Comments: 26569
Quoting btwntx08:

Link


Thank you.
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Satellite presentation has improved dramatically in the last few hours.
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um, err, uh did i say playing?
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Quoting MiamiHurricanes09:
How strong do the west winds need to be to classify 93L as a TD?


Probably at least 10-15kt. It depends on how confident they are about the circulation being closed. In all reality, if they don't close this off on this flight, they might wait until the next flight to see if it's closed to classify.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
NHC Mission Statement



The NHC mission statement is to save lives, mitigate property loss, and improve economic efficiency by issuing the best watches, warnings, forecasts and analyses of hazardous tropical weather, and by increasing understanding of these hazards. It is important for you to pay attention when you hear alerts, watches, and warnings provided by this official hurricane organization. By listening to information given and the official National Hurricane Center concern behind it, you will be able to make education decisions on preparing for a hurricane, preventative damage, and protecting your family.


http://www.home-weather-stations-guide.com/national-hurricane-center.html
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Looks like they may not find a center...TD might not come until the early morning hours.
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2181. Levi32
Nearly closed low somewhere....but where exactly.

Member Since: November 24, 2005 Posts: 635 Comments: 26569
Quoting MiamiHurricanes09:
How strong do the west winds need to be to classify 93L as a TD?


I never knew that TDs needed to be so organized. Lol.
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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.