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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NOAA Has Slewed TD 3 Floater to The Keys View


Floater - RGB Color Infrared Loop
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Quoting StormW:
Hot off the press!

TROPICAL DEPRESSION THREE SYNOPSIS ISSUED 12:10 P.M. JULY 22, 2010


Thanks Storm!
You're OK, I don't care what JFV says about you.
Member Since: October 30, 2007 Posts: 0 Comments: 270
This is not a knock on the NHC, but I don't have alot of confidence in the forecasted strength of this system or its ultimate landfall. This morning at 7am this was an invest that had a 20% chance of becoming a Tropical Storm within 48 hours and one hour later became a depression with a 100% chance of becoming a TS. If this system is able to wrap around and shield itself from dry air it could become a Hurricane before hitting Florida. Also the tracks of these weak systems can be very hard to predict. I wouldn't be surprised to see a shift to the right in the forecasted path once new data and coc location are plugged into the models.
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Quoting scott39:
Thank you Storm, Where would you put your track a little right of the NHC?
Gulf Coast Land Fall
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165. xcool
expect a model shift to rigth imo
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Quoting FLdewey:
You guys are not helping the Floridacaster thing.

I'm not a meteorologist, but I DID stay at a Holiday Inn Express last night.


You should have stayed at Motel 6? They leave the light on for ya?
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Quoting StormW:
Hot off the press!

TROPICAL DEPRESSION THREE SYNOPSIS ISSUED 12:10 P.M. JULY 22, 2010


Thank you Senior Chief...

v/r

Jon
Member Since: January 7, 2007 Posts: 0 Comments: 40
Not looking good for Louisiana as far as oil and/or stress for the people of Terrebonne, Plaquemines, and St. Bernard parishes.
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Good afternoon all. Been reading for 5 years, but had no reason to clutter the blog! Although I'm in Pa., all my family are in Fla. a mile from the Gulf, and in Grand Cayman. So I've been through the last 7 years of stress vicariously.
My question is, do we have any gauge to determine how much effect a given system has deep down where the well cap is? Is there a significant threat of turbulence at that depth? Thanks.
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Quoting StormW:
Hot off the press!

TROPICAL DEPRESSION THREE SYNOPSIS ISSUED 12:10 P.M. JULY 22, 2010
Thank you Storm, Where would you put your track a little right of the NHC?
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If Central Florida was expected to get 35 to 45 mph winds, we would be under a Tropical Storm Warning as well, but we are not... So Matt Makens is wrong... NWS Melbourne not calling for more than 20 mph winds even at the coast... so 15 mph in Orlando.
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Hello I would like to say

I concur at this time with the NHC forecast track

Who am I?
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Quoting Jeff9641:


Yep, I expect a model shift to the Mia/FLL area this afternoon.
Same here. I expect a shift to the right at 5PM, I would put the "center line" of the cone over Homestead.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Well, I'm in HOuston and I have learned after riding out Katrina in MS and then Rita and Ike here in the Houston area... Keep the gas cans full and have the beens and franks stocked up! LOL
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Quoting StormW:
Hot off the press!

TROPICAL DEPRESSION THREE SYNOPSIS ISSUED 12:10 P.M. JULY 22, 2010


You picked up that weakness too ;-/

Nice analysis.
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Quoting Bonz:
I do have one beef with the NHC, listing obscure places as the beginning/end points of watches/warnings. I've lived here almost thirty years and had no idea where "Golden Beach" is; I had to look it up. Saying "Miami-Dade County" would have *more* than sufficed.
I was about to add that part of the reason why TS warnings are up for Grand Bahama even though TS force winds may not be likely there is that it's the breakpoint for NW Bahamas....
Member Since: October 25, 2005 Posts: 19 Comments: 22101
150. IKE
If you believe the 12Z GFS...Texas gets nothing from TD3. Not saying it's true, but that's what it shows.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
I agree with HoustonTxGal - since Katrina I always come to this site for storm info - I refuse to be caught off guard again!! (ok so I knew K was coming, I just assumed it would wobble out of the way like Ivan did the year before).

Anyways I am not confident in the strength forecast - the Gulf waters are WAY too warm not to be at least at Cat 1, maybe even Cat 2 storm. Nevertheless, I have decided not to panic - yet. Let's see how long this lasts hahaha.
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147. xcool
98L WOW
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To Bonz "I do have one beef with the NHC, listing obscure places as the beginning/end points of watches/warnings. I've lived here almost thirty years and had no idea where "Golden Beach" is; I had to look it up. Saying "Miami-Dade County" would have *more* than sufficed."

Agreed, also...the SPC does the exact same thing with watch boxes.

From a point 70 miles NNE of Enid, OK to 55 SE of Whoknows, KS.
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145. xcool
TD continues to get better organized
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Quoting Detrina:
I have a smart beagle, he didn't go to meteorology school or anything but he is a pretty quick thinker...he has relocated ALL of his toys (35 of them) to higher ground..from the flat basket on the floor, in the livingroom to the middle of the guest bedroom bed. Never seen him do that...Perhaps he knows something we don't?


I know what you mean. My Labs used to hide under the house when the in-laws came to visit.
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Quoting Tracker09:
What type of weather should we expect here in miami? 30-40 sustained with very heavy rain??

Probably about right but best prepare for more...
Don't forget Bonnie will be over the Gulf Stream for at least several hours with all that warm water
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Quoting AllStar17:


Then what is this? An error?


They launch from MS, then fly to the storm. They drop the dropsondes along the way.
Member Since: October 30, 2007 Posts: 0 Comments: 270
Quoting btwntx08:
that radar range is abit too far south 98L is abit north and east then that
1) it's the best we've got for now, as the closer site at Holguin is offline [has been for a while, dunno why].

2) TD3/Possible Bonnie is supposed to track this way as the day progresses, so eventually Camaguey is likely to give some good views, esp. if the centre stays as far south as implied by early tracks.
Member Since: October 25, 2005 Posts: 19 Comments: 22101
Quoting cheetaking:
Take a look at the steering map. As the pressures in the storm drop, it will tend to take a more westerly course.

So if it stays a weak TD/TS, it will likely end up on the southern Louisiana coast. A 55-60mph TS will likely end up around Houston, and if it can reach hurricane strength, it could end up as far south as Chorpus Christi.






Good observation... I am in Houston and Im filling the gas jugs tomorrow.. ready for a generator driven bbq with the neighbors!!!
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139. Bonz
Hey StormW, you need to put a "not" in this sentence in your blog. "I would see no reason that this is upgraded to Tropical Storm Bonnie..."
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In analyzing some satellite imagery just recently, it seems like deep convection is building over the circulation center of TD 3 early this afternoon and attempting to expand. In addition, for the first time in the system's history, it would appear a weak anticyclone has begun to build over the center which has allowed for convection to not only persist, but build. I would not be surprised to see this be Tropical Storm Bonnie when Hurricane Hunters reach the storm.

Now, when you look at satellite imagery, notice the higher cloud motion preceding the storm. Note how the clouds seem to be on a general WNW to NW motion. This is a very good indicator as to the direction this storm will take in the next 24 to 48 hours. That is why I believe that this storm will take a track somewhat north of the current track and closer to mainland South Florida.
Member Since: April 14, 2007 Posts: 8 Comments: 5169
Quoting FLdewey:
New model run is out...



:-D

LOL LOL LOL Too funny... :)
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Take a look at the steering map. As the pressures in the storm drop, it will tend to take a more westerly course.

So if it stays a weak TD/TS, it will likely end up on the southern Louisiana coast. A 55-60mph TS will likely end up around Houston, and if it can reach hurricane strength, it could end up as far south as Chorpus Christi.



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131. IKE
Looks like the ULL is beginning to move away from TD3...Link
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting FLdewey:


Does he have a squeaky ant toy?


LOL! :)
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128. Bonz
I do have one beef with the NHC, listing obscure places as the beginning/end points of watches/warnings. I've lived here almost thirty years and had no idea where "Golden Beach" is; I had to look it up. Saying "Miami-Dade County" would have *more* than sufficed.
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Quoting bjdsrq:





omg...on a serious note... animals are very smart at picking up on storms.
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The problem for TD 3 is the ULL will be pumping dry air into the system. Upper level conditions are far more important than SST's. The ULL needs to book on out of there if TD 3 is to become more of a potent storm for the GOM. After TD 3 and 98L the Atlantic looks to be quiet for a while. There are too many ULL's with dry air spinning around the Atlantic basin. I think most of the waves coming off Africa would be a shoe in for development if it wasn't for that.
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NHC has plenty of time to ramp up the storm if needed, its the first update of its life.
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Are all the models counting on the ULL to stay with Bonnie, thus slowing development? Or are they counting on shear in the GOM from another source?
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According to all the tracks (nhc and WU) this thing is projected to stay off of most land, why are they only projecting a tropical storm? Is it because of the lows and will they really have that big of an impact on intensity even though this thing will be tracking across warm waters?
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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.

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