Tropical Depression Three forms

By: Dr. Jeff Masters , 3:42 PM GMT on July 22, 2010

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Tropical Depression Three has formed over the Bahama Islands, and appears poised to become Tropical Storm Bonnie later today. Satellite images of TD 3 show a modest area of heavy thunderstorms that have slowly increased in intensity and areal coverage this morning. The surface circulation center is exposed to view, thanks to strong upper-level winds out of the southwest that are creating about 20 knots of wind shear. This wind shear is due to the counter-clockwise circulation of air around a large upper-level low pressure system over Florida that is moving west at about the same speed TD 3 is. Water vapor satellite loops show a large area of dry air is associated with the upper-level low pressure system, and this dry air is hindering development of TD 3. The storm is attempting to wrap a curved band of clouds around its center, on its west side. If TD 3 is able to do this, the center will be protected from shear and dry air, and more significant strengthening can occur. Surface observations in the Bahamas and several nearby ships have shown top winds in TD 3 of up to 35 mph, so the storm is close to the 40 mph winds needed to be classified as a tropical storm.


Figure 1. Water vapor satellite image showing dry air (brown colors) associated with the upper-level low over Florida. Image credit: NOAA/NESDIS.

Track Forecast for TD 3
The storm is in a fairly straightforward steering current environment, and TD 3 should progress steadily to the west to west-northwest through Saturday. This will bring the storm ashore over the Florida Keys or South Florida on Friday, and into the Gulf of Mexico on Saturday. The latest set of model runs from 2am EDT (6Z) had the advantage of having data from a flight of the NOAA jet last night, so we have higher confidence than usual in the track of TD 3 over the next two days. The location of TD 3's final landfall along the Gulf of Mexico coast has the usual uncertainties for 3 - 4 days, with the various models calling for landfall somewhere between the upper Texas coast and the Florida Panhandle coast. Given the uncertainties, the move halt operations in the Deepwater Horizon blowout recovery effort are probably wise.

Intensity Forecast for TD 3
The primary detriment to development of TD 3 for the next three days will be the presence of the large upper-level low to its west. As long as this low remains in its present location, relative to TD 3, it will bring wind shear of about 20 knots and dry air into the storm. This will limit the intensification potential of TD 3 to no more than about 10 - 15 mph per day. If the upper-level low slow down a bit, relative to TD 3, more shear will affect the storm, potentially weakening it. Conversely, if the upper-level low picks up speed and pulls away from TD 3, the storm may be able to intensify at a faster rate. None of the computer models is calling for that to happen, but it would not take much of an additional separation between TD 3 and the upper level low to substantially reduce shear and allow TD 3 to intensify into a hurricane on Saturday. I put the odds of TD 3 making it to hurricane strength in the Gulf of Mexico at 20%.

98L
An area of disturbed weather (98L) has developed in the Gulf of Mexico's Bay of Campeche. This system is under a low amount of shear, 5 - 10 knots, and may barely have enough time to organize into a tropical depression before making landfall along the Mexican coast a few hundred miles south of the Texas border on Friday.

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

Next update
I'll have an update between 3 - 4 pm, when the Hurricane Hunters will be in the storm. I'll also speculate on the possible impact the storm will have on the oil spill region.

Jeff Masters

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Quoting Grothar:
If the coordinates of 22.2N and 78.9W are correst, the strong convection has not wrapped around the center yet. It appears that it is trying. How will the jump of the center to the NE affect the current track??????

Problably not much difference as the ridge will strengthen back and cause it to go WNW
Member Since: July 5, 2008 Posts: 0 Comments: 254
Quoting StormW:


Possible it could track closer to you now.


Thanks for the info! :)
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Quoting 69Viking:


It also hasn't moved much while the LLC still continues to move SW, the forecast for intensity and possibly track could change considerably depending on the ever changing dynamics aloft!
You mean the ULL?
Member Since: September 2, 2009 Posts: 130 Comments: 21109
98L has sloppy circulation

Member Since: October 28, 2006 Posts: 57 Comments: 30117
I'd really like to see SFMR on recon right now..
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Quoting weathersp:


Anybody having problems with the HDOB messages? I am getting the sondes and RECCO's but the HDOB track is not showing (and yes thay are sending HDOB messages)
I am not sure what is wrong with it right now. I don't think anyone has been able to see the mission going to 03L
Member Since: July 5, 2008 Posts: 0 Comments: 254
616. xcool
NOW BACK TO WNW
Member Since: September 26, 2009 Posts: 2 Comments: 15648
If the coordinates of 22.3N and 75.9W are correst, the strong convection has not wrapped around the center yet. It appears that it is trying. How will the jump of the center to the NE affect the current track??????

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50% still for 98L
Member Since: March 10, 2010 Posts: 1 Comments: 7486
Quoting AlexEmmett:

OMFG


WSVN will be at the beach showing surfers
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Hey HoustonTxGal - Thankfully Ray Nagin is no longer in office!!!!

I'm getting a little nervous here in La. - looks like we're going to get at least a little something out of this thing.
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Quoting Hurricanes101:


they did not, you should not post information that is incorrect

NHC does not change tracks in intermediate advisories


The track is fine and is not going to shift much closer to Florida follow what the NHC is saying these people are going to freak people out for nothign
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Quoting neonlazer:
http://tropicalatlantic.com/recon/


Anybody having problems with the HDOB messages? I am getting the sondes and RECCO's but the HDOB track is not showing (and yes thay are sending HDOB messages)
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If this storm does what the experts are saying then Bonnie or 97L should not really be a big deal to anyone. Hopefully they are right.
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So is there 3 systems????????????
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We may even see a WSW movement in few days
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so much for 2010 being a bust lmao
Member Since: March 10, 2010 Posts: 1 Comments: 7486
603. unf97
Quoting bohonkweatherman:
I am guessing Lousiana coast, maybe New Orleans?


Somewhere along the Central Gulf Coast, from LA to FL Panhandle. With the subtropical ridge building in as forecasted, I am leaning more toward somewhere from Biloxi - Lake Charles as a target area for this system.
Member Since: September 25, 2007 Posts: 0 Comments: 1193
I guess I'm freeking blind. I do not see a NW movement at all. All I see is a WNW with a hint of NW to it. Ohh well!
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Quoting HoustonTxGal:


OMG, I can here Ray Nagen now...

and we can all say AMEN that he's not the mayor here anymore
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98L ASCAT:

Member Since: October 28, 2006 Posts: 57 Comments: 30117
Quoting MiamiHurricanes09:
With the new coordinates the cone should be shifted northward putting the northern keys in the "center line", however cones aren't released in intermediate advisories.


It also hasn't moved much while the ULL still continues to move SW, the forecast for intensity and possibly track could change considerably depending on the ever changing dynamics aloft!
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They're late with the 2 pm TWO.. 98L looks great. Has 24 hours left over water.
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Quoting Tropicaddict:


I don't see a change at all on the track...where do you see a track change?


There is none, he is giving false info.
Member Since: September 6, 2009 Posts: 2 Comments: 3712
Quoting StormW:


Where are you located?


I live in Pass Christian, MS and work at Stennis Space Center.
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There are lower temps than normal around the upper atmosphere because of lower sunspot activity. This is causing TD to strengthen. There is a new batch of moisture coming up from Eastern Cuba because of the separation of TD3(Bonnie) from the upper level low to the west.
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Quoting extreme236:


I disagree. I don't see why it would take 2 whole days for a circulation to tighten.


We'll see. I'm all up for a good debate. Most of the convection is to the west of the center and moving onshore. That's not going to help it develop. This system is of monsoonal origin and that's why it is taking so long to tighten up.
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Quoting neonlazer:
http://tropicalatlantic.com/recon/


Thanks!
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Quoting ElConando:


You must be one NHC's alternative universe site CHN.


I don't see a change at all on the track...where do you see a track change?
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Quoting tkeith:
3' above normal high tides was the last forecast I read....Could be some coastal flooding.
thanks so much :)
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The TWO would normally be up by now. Has it been shown yet?
Member Since: July 7, 2010 Posts: 0 Comments: 5672
Quoting hurricanedave:
NHC just changed track now into ft lauderdale


You must be one NHC's alternative universe site CHN.
Member Since: September 6, 2009 Posts: 2 Comments: 3712
I would have to pick today to bring my son school shopping. People buying up water and bread here in Houma like mad.
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Quoting StonedCrab:
I'm not getting any dropsonde info since OB 12 west of Ft Myers...anyone else?


nada
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Quoting raggpr:
where in google earth can i watch the hurricane hunters mission? I mean i have been trying to find it in google earth for a while now and couldnt find anything
http://tropicalatlantic.com/recon/
Member Since: July 5, 2008 Posts: 0 Comments: 254
Quoting extreme236:


I disagree. I don't see why it would take 2 whole days for a circulation to tighten.
On satellite 98L looks better organized than 03L. However 03L has a much more defined circulation. Either way I think 98L will be classified soon.
Member Since: September 2, 2009 Posts: 130 Comments: 21109
Quoting nishinigami:
Sorry to be a dense 33 year old here, but could we be possibly looking at some flooding if you live outside of the levee protection system in Plaquemines? (Have not had enough coffee yet, my mind is not working :( )
3' above normal high tides was the last forecast I read....Could be some coastal flooding.
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The tail that just started showing up on satellite is interesting...

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Quoting hurricanedave:
NHC just changed track now into ft lauderdale


they did not, you should not post information that is incorrect

NHC does not change tracks in intermediate advisories
Member Since: March 10, 2010 Posts: 1 Comments: 7486
I can see where the weakness is pulling it NW but once it passes, TD3 is going to zip line it cuz of the ridge in place, Time boys to get outta of the well
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where in google earth can i watch the hurricane hunters mission? I mean i have been trying to find it in google earth for a while now and couldnt find anything
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Darn. I wish I wasn't on vacation....I would've driven to Miami and hung out with Oz.
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Quoting bohonkweatherman:
I am guessing Lousiana coast, maybe New Orleans?


OMG, I can here Ray Nagen now...
Member Since: September 18, 2007 Posts: 0 Comments: 1074
Funny enough... the 2pm position is .4N .1E of the 11am position
Member Since: March 19, 2010 Posts: 0 Comments: 1147

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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.