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 StSimonsIslandGAGuy:
What was the lowest pressure found?


1005mb
Member Since: March 10, 2010 Posts: 1 Comments: 7818
B or E (the infamous "other" option...which would be after 5 AM tomorrow)
Quoting Seflhurricane:
quick poll to ease peoples minds here, when will we finally have TD 1

A) 5pm
B) 11PM
C) 5am
D) Will not develop
Member Since: Posts: Comments:
there going for other pass
Member Since: May 21, 2006 Posts: 5091 Comments: 115239
Quoting WinterAnalystwx13:


The low is about 95% closed...
Recon has yet to investigate the entire COC so I'm not making any conclusions on whether or not the COC is closed. But looking at visible satellite imagery, I would say it is closed not just 95%.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting Seflhurricane:
quick poll to ease peoples minds here, when will we finally have TD 1

A) 5pm
B) 11PM
C) 5am
D) Will not develop


I say 5am because they will wait for recon to go back out and verify the low is closed
Member Since: March 10, 2010 Posts: 1 Comments: 7818
If recon concludes a depression has not formed, NHC will probably wait until tomorrow's recon before beginning advisories unless the presence of a closed LLC becomes totally obvious.
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the HH is not even done yet lol
Member Since: May 21, 2006 Posts: 5091 Comments: 115239
Quoting reedzone:


Sorry, but scottsvb is on my ignore list for a reason, he was very rude to me. A true MET would explain a reason on why you are wrong, not just tell you your wrong and call you a wishcaster. He does that to many on here and I really disrespect him for that.

If you think that defines a true met or not your expectations are too high haha. There are a lot of bitter ones out there that hate to have to explain themselves all the time. Some feel they worked hard enough to be a met so you shoudl just take their word for it. I have been known to do that every once in awhile but it is rare.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
I enjoy this forum precisely because I'm neither a met, like so few here are, nor a clairvoyant, like so many. I am just a curious software engineer who loves trying to understand tropical weather and a bemused observer of the hiliarious vanity and vexation of spirit inherent in social media.
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5 AM SATURDAY
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Afternoon P451! Glad to have you aboard again! :-)
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key element is the west wind, 93L is really looking good
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Quoting ezcColony:


My link. Glad to meet all of you. Come in and say hi.


Oh that's definitely Oz! Welcome back! Only you would direct me to a disgusting political hack attack.
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Quoting reedzone:


Sorry, but scottsvb is on my ignore list for a reason, he was very rude to me. A true MET would explain a reason on why you are wrong, not just tell you your wrong and call you a wishcaster. He does that to many on here and I really disrespect him for that.


We had a discussion some couple of hours ago about a spin to 93L. Are you willing to admit that you were incorrect now that real data has been released that showed no closed low?
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1662. twooks
Quoting Seflhurricane:
quick poll to ease peoples minds here, when will we finally have TD 1

A) 5pm
B) 11PM
C) 5am
D) Will not develop


If not A, I would say B. I can't see it not being a depression today.
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No TD for now folks. Sorry. LOL
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SFMR finding 36 mph winds.

It does appear imo, although that 93L doesn't appear to be closed its a lot tighter than yesterday and could be closed by tonight.
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Quoting TexasHurricane:


Definitely looks to be getting it's act together. Is it a TD yet?

Nope.

It's getting close though.
It appears they're waiting for west winds to wrap around.
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1656. xcool
i'm not leave for no dam storms
Member Since: September 26, 2009 Posts: 2 Comments: 15684
quick poll to ease peoples minds here, when will we finally have TD 1

A) 5pm
B) 11PM
C) 5am
D) Will not develop
Member Since: Posts: Comments:
Winds stronger in front right sector as expected...another sign that there is probably a closed low. I think they will find it when they head back through the midpoint.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
Quoting IKE:


He's a met. Are you? I'm not.


Sorry, but scottsvb is on my ignore list for a reason, he was very rude to me. A true MET would explain a reason on why you are wrong, not just tell you your wrong and call you a wishcaster. He does that to many on here and I really disrespect him for that.
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Quoting Hurricanes101:


I do find it kind of funny how many posts were omg TD by recon, we have even have a TS

and yet they dont even find a closed low lol


Well, the ASCAT stuff was very convincing.
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1649. Levi32
Quoting RyanFSU:
I updated the GFDL wind speed swath maps to include the inner two nests. The coarse 1x1 degree stuff is pretty ugly and considering the GFS global model operates at roughly 40 km, not a useful intensity aid.

Here is an example for 93L ... the rest can be found on my FSU page -- > Link



Nice. Thanks Dr. Maue.
Member Since: November 24, 2005 Posts: 635 Comments: 26654
Quoting Hurricanes101:


I do find it kind of funny how many posts were omg TD by recon, we have even have a TS

and yet they dont even find a closed low lol


I thought it was funny, too. But sometimes it is hard not to get ahead of oneself.
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Lets allow the Hurricane Hunters to finish flying through the system and collecting all the data before jumping to conclusions. They still have another couple hours and need to complete their classic X pattern through the system, so we will know all we need to know to make any conclusions within the next couple hours.

In analyzing satellite imagery though, it would be surprising to see the Hurricane Hunters not find a closed surface low. Convection is really turning around a common center in the lower levels and surface pressures continue to get slightly lower hour by hour it seems. Something else I noted in viewing satellite imagery is the development of spiral "arms" on the western and eastern side of the system. This further supports a closed defined low level circulation as the system is drawing in convection and moisture from all directions now.
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Quoting RyanFSU:
I updated the GFDL wind speed swath maps to include the inner two nests. The coarse 1x1 degree stuff is pretty ugly and considering the GFS global model operates at roughly 40 km, not a useful intensity aid.

Here is an example for 93L ... the rest can be found on my FSU page -- > Link



Thank you!
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1645. xcool
lmao
Member Since: September 26, 2009 Posts: 2 Comments: 15684
"Potential" is the key word, homey. All that potential has been there, and we dont even have a TD (yet). 93L will be a Cat 2 at best, IMO. It has taken entirely too long to develop, and will be weakened significantly when it strikes the Yucitan (or Belieze).
Quoting RecordSeason:
1560:

<880mb potential minimum pressure

>165kts potential maximum wind

That'd annihilate whatever it hit. Send an entire state back to the stone age.
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Quoting Skyepony:
Looks like AF302 is done with 93L but doesn't look like the are going home either. Maybe stashing it in the Caribbean for the night? or checking out that wannabe low level swirl..


I do find it kind of funny how many posts were omg TD by recon, we may even have a TS

and yet they dont even find a closed low lol
Member Since: March 10, 2010 Posts: 1 Comments: 7818
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1639. Levi32
Quoting 900MB:


If this gets a tad more organized, I can't help but wonder if it may drift towards those warmer ssts off the coast. It will be a good test of my "path of least resistance" theory.


A system this weak won't be attracted to the warmer water because the surface ocean temperature is for all practical purposes uniform across the western Caribbean, and a tropical depression or tropical storm won't be upwelling anything colder than that. In other words, the system isn't strong enough to even need the really deep warmth. The shallow layer will fuel it just fine for now. It won't run for something that's too big for it to eat.
Member Since: November 24, 2005 Posts: 635 Comments: 26654
Great to hear ya Pat!!! You done learned Spud some meteorology
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1636. xcool
WinterAnalystwx13 .NW MOVE
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting Skyepony:
Looks like AF302 is done with 93L but doesn't look like the are going home either. Maybe stashing it in the Caribbean for the night? or checking out that wannabe low level swirl..


They're suppose to be there too 6, they're coming around for another pass
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1634. RyanFSU
I updated the GFDL wind speed swath maps to include the inner two nests. The coarse 1x1 degree stuff is pretty ugly and considering the GFS global model operates at roughly 40 km, not a useful intensity aid.

Here is an example for 93L ... the rest can be found on my FSU page -- > Link

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1633. IKE
Talking about waterspouts on WWL, my son saw 2 off of the Florida panhandle a couple of days ago.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting ATL:

Yep. Confusing the hell out of the radio host ;)
Doesn't take much to confuse this host. He don't know squaddoosh about tropical cyclones.
Member Since: August 3, 2005 Posts: 10 Comments: 5610
Quoting Drakoen:
Anybody can claim to be a meteorologist here


I am not a meteorologist, but i did stay in a Holiday Inn Express last night.

Back to lurking :)
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1630. Skyepony (Mod)
Looks like AF302 is done with 93L but doesn't look like the are going home either. Maybe stashing it in the Caribbean for the night? or checking out that wannabe low level swirl..
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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.