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 HurricaneFCast:
171230 2459N 07723W 3775 08025 0434 -201 -255 130031 032 /// /// 03
171300 2458N 07721W 3779 08017 0433 -197 -254 132033 034 /// /// 03
171330 2456N 07719W 3775 08023 0434 -195 -255 134033 034 /// /// 03
171400 2455N 07716W 3776 08023 0435 -193 -256 133035 037 /// /// 03
171430 2453N 07714W 3778 08018 0435 -190 -255 131037 038 /// /// 03
171500 2452N 07712W 3778 08022 0436 -190 -253 133035 035 /// /// 03
171530 2451N 07710W 3775 08027 0437 -194 -250 134033 034 /// /// 03
171600 2449N 07708W 3779 08019 0436 -194 -248 134031 032 /// /// 03
171630 2448N 07706W 3773 08031 0437 -195 -246 135029 030 /// /// 03
171700 2446N 07703W 3779 08020 0437 -194 -244 127029 029 /// /// 03
171730 2445N 07701W 3775 08029 0437 -195 -243 127029 029 /// /// 03
171800 2443N 07659W 3778 08022 0436 -191 -242 128030 031 /// /// 03
171830 2442N 07657W 3775 08028 0437 -189 -241 130030 030 /// /// 03
171900 2441N 07655W 3778 08022 0437 -188 -241 134028 028 /// /// 03
171930 2439N 07652W 3778 08022 0437 -190 -242 137026 028 /// /// 03
172000 2437N 07651W 3775 08025 0436 -192 -241 126025 026 /// /// 03
172030 2435N 07649W 3779 08017 0435 -193 -239 131019 020 /// /// 03
172100 2433N 07648W 3777 08023 0435 -193 -238 132017 019 /// /// 03
172130 2431N 07646W 3778 08020 0435 -193 -238 131015 015 /// /// 03
172200 2429N 07644W 3777 08022 0435 -195 -239 127015 018 /// /// 03


For those who are wondering: 4th column from the right are flight level peak winds (10 second average).. still north of TD3.. Near Nassau at the moment.
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98L is still about 150 miles off shore. Go to the floater and click on "fronts"
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Quoting mfaria101:
Patrap.

Did that wave forcast actually read 9 ft.


U betcha
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Do we have




yet ?
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Quoting Drakoen:


Too little, too late.
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Quoting Patrap:
97L/TD 3 12Z tracks
Access forbidden..lol
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515. xcool
98L TD4
Member Since: September 26, 2009 Posts: 2 Comments: 15675
171230 2459N 07723W 3775 08025 0434 -201 -255 130031 032 /// /// 03
171300 2458N 07721W 3779 08017 0433 -197 -254 132033 034 /// /// 03
171330 2456N 07719W 3775 08023 0434 -195 -255 134033 034 /// /// 03
171400 2455N 07716W 3776 08023 0435 -193 -256 133035 037 /// /// 03
171430 2453N 07714W 3778 08018 0435 -190 -255 131037 038 /// /// 03
171500 2452N 07712W 3778 08022 0436 -190 -253 133035 035 /// /// 03
171530 2451N 07710W 3775 08027 0437 -194 -250 134033 034 /// /// 03
171600 2449N 07708W 3779 08019 0436 -194 -248 134031 032 /// /// 03
171630 2448N 07706W 3773 08031 0437 -195 -246 135029 030 /// /// 03
171700 2446N 07703W 3779 08020 0437 -194 -244 127029 029 /// /// 03
171730 2445N 07701W 3775 08029 0437 -195 -243 127029 029 /// /// 03
171800 2443N 07659W 3778 08022 0436 -191 -242 128030 031 /// /// 03
171830 2442N 07657W 3775 08028 0437 -189 -241 130030 030 /// /// 03
171900 2441N 07655W 3778 08022 0437 -188 -241 134028 028 /// /// 03
171930 2439N 07652W 3778 08022 0437 -190 -242 137026 028 /// /// 03
172000 2437N 07651W 3775 08025 0436 -192 -241 126025 026 /// /// 03
172030 2435N 07649W 3779 08017 0435 -193 -239 131019 020 /// /// 03
172100 2433N 07648W 3777 08023 0435 -193 -238 132017 019 /// /// 03
172130 2431N 07646W 3778 08020 0435 -193 -238 131015 015 /// /// 03
172200 2429N 07644W 3777 08022 0435 -195 -239 127015 018 /// /// 03
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Patrap.

Did that wave forcast actually read 9 ft.
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97L/TD 3 12Z tracks
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Quoting TOMSEFLA:
think the shear is forcing cloud nore nnw but center is becoming exposted as it moves wnw?


looks pretty clear to me that TD 3 is moving WNW-NW and the center is not exposed
Member Since: March 10, 2010 Posts: 1 Comments: 7728
Quoting Patrap:
Were gonna need a Bigger Boat..,Quint


GOM 84 Hour Wave Forecast (using SWAN) Model


Orca is not big enough!! LOL
Member Since: July 17, 2009 Posts: 71 Comments: 26156
Quoting 7544:
this will not be a ts at 2pm imo


based on satelite i agree with you
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i only thought google earth wasnt working for me lol
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Been lurking here for a long time now and finally decided to step in; mainly to say thanks to Dr. Masters, StormW. and all the truly knowledgeable folks who’ve been keeping us informed during hurricane season(s) past and present. My husband & I have lived in the Ft. Myers, FL area along with our sons and their families for 30 yrs. This informative blog has helped us to prepare for bad weather ahead of time, and it looks like we could be in for a little action tonight or Friday. Thanks to you all and keep up the good work.
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03L has the opportunity to strengthen before moving in the Gulf as shear across the Bahamas is becoming favorable.
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Quoting 7544:
this will not be a ts at 2pm imo
Recon still not in there, so a TD at 2PM is likely. At 5PM however is when we'll likely see a TS.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting whs2012:
Local met said the stronger TD3 is the further south it goes, and the weaker it is the further north I goes? I thought it was the opposite. :/


As a *general* rule, stronger storms are steered in a different layer of the atmosphere, where they tend to move further north, but that is not always true.

Lots of experts on here said Ike wouldn't come to Texas because strong storms go north.

Alex was as strong as or stronger than Ike, and also took a westward course.
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03L 12Z GFDL


03L 12Z HWRF
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Quoting 7544:
this will not be a ts at 2pm imo


yea cuz recon is just getting there now, I agree lol

but that looks to be the only reason
Member Since: March 10, 2010 Posts: 1 Comments: 7728
think the shear is forcing cloud nore nnw but center is becoming exposted as it moves wnw?
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Judging by visible imagery, the center of 98L is almost over land.
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495. unf97
Quoting rmbjoe1954:


When the ridge refortifies itself TD3 can change westward ho! The begin turning all the way to Louisianna!


I think the ridge will build back in within the next 12-24 hours, and the system will resume a more W-W/NW motion on its approach toward the SE FL coast.
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494. 7544
this will not be a ts at 2pm imo
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Quoting ElConando:
Anyone have a google earth link with recon? I always loose it for some reason.


http://hhrecon.com/recon/ge/Recon_Data_for_the_Atlantic_Basin.kmz
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Quoting WxLogic:
If we take a look at soundings for MIA you'll notice NE winds aloft signaling a building or eastern edge of the High currently across the C Gulf coast... this tells us the NW component TD3 has should come to and end once it reaches the Nassau region.



Thats fairly North. What do you mean by region?
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491. xcool



12Z

Member Since: September 26, 2009 Posts: 2 Comments: 15675
Quoting Drakoen:


Nice obs


Trying to help some... :)
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Quoting ElConando:


That only works in some situations. I cannot explain it properly so I'll let someone else have the liberty to.


well when Katrina got stronger it came in alignment with another steering current and forced it WSW for a little (wasn't expected because they didn't expect it to intensify so quickly)

I don't know alot about it either, but I actually the stronger system in this case would actually take a more northerly track...
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That would actually but most of dade county on the "strongest" part of the storm wouldn't it?
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Were gonna need a Bigger Boat..,Quint


GOM 84 Hour Wave Forecast (using SWAN) Model
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If TD 3 doesn't run out of time, it will have a window of opportunity according to this.

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Quoting ElConando:


WPB lol? I doubt it gets north of homestead prior to landfall. And That is stretching it. You can some force feed me crow if you are right.
Nah, you're probably right, lol. I'm sticking with my south Dade prediction.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
For those wondering the thinking once TD 3 enters Gomex. From local discussion in DFW. Southwesternly shear transitions to easterly speed shear when the cyclone is over the gulf. With a 50-70 knot jet forecast to develop between ULL and
subtropical high over southeast conus. This should keep depression weakly organized and moving quickly.
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If we take a look at soundings for MIA you'll notice NE winds aloft signaling a building or eastern edge of the High currently across the C Gulf coast... this tells us the NW component TD3 has should come to and end once it reaches the Nassau region.

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Quoting Jeff9641:
TD3 is almost moving NNW now at a dead aim for MIA to West Palm Beach. If this goes to the Keys it would have to start moving WNW right now as it continues to lift up the Bahama Chain.
A turn to the WNW can be expected as the weakness begins to dissipate and the ridge fills in. My current thinking leads me to believe that the COC of 03L will move over southern Miami-Dade county.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting Jeff9641:
TD3 is almost moving NNW now at a dead aim for MIA to West Palm Beach. If this goes to the Keys it would have to start moving WNW right now as it continues to lift up the Bahama Chain.
Quoting Jeff9641:
TD3 is almost moving NNW now at a dead aim for MIA to West Palm Beach. If this goes to the Keys it would have to start moving WNW right now as it continues to lift up the Bahama Chain.


WPB lol? I doubt it gets north of homestead prior to landfall. And That is stretching it. You can some force feed me crow if you are right.
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Agreed, it has been in a out....decoder is not receiving today. If anyone who is getting the date can keep us up to date, that would be appreciated.

Quoting cg2916:
The recon on Google Earth is not working for me.
Member Since: June 28, 2010 Posts: 0 Comments: 706
Quoting Jeff9641:
TD3 is almost moving NNW now at a dead aim for MIA to West Palm Beach. If this goes to the Keys it would have to start moving WNW right now as it continues to lift up the Bahama Chain.


When the ridge refortifies itself TD3 can change westward ho! Then begin turning all the way to Louisianna!
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The recon on Google Earth is not working for me.
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Quoting Jeff9641:
TD3 is almost moving NNW now at a dead aim for MIA to West Palm Beach. If this goes to the Keys it would have to start moving WNW right now as it continues to lift up the Bahama Chain.


remember all storms wooble
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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.