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 Tracker09:
What type of weather should we expect here in miami? 30-40 sustained with very heavy rain??


yep im thinnk the same thing
Member Since: July 21, 2010 Posts: 0 Comments: 1181
Wow. That was ... unexpected... LOL

Thanks Doc. Very comforting to those of us "under the wx", so to speak.

From previous blog...

Quoting stillwaiting:
i have a feeling after recon they'll upgrade to bonnie....
Why have a feeling?

AN AIR FORCE PLANE WILL BE IN THE AREA THIS AFTERNOON AND WILL HELP
TO DETERMINE IF THE SYSTEM HAS BECOME A TROPICAL STORM.

LOL... I doubt the strengthening to cat 1 unless the storm slows down. I can see a movement slightly more north, like S tip of FL as opposed to Srn keys at most.

After that, don't know what to expect. However, I'm not seeing the ULL back far enough away from TD3 to allow for massive strengthening....

Quoting palmbaywhoo:
i am not sure why the bahamas issued warnings so far north with the cone so far south, expecting some significant shifts when recon gets there
Warnings are for the rain, likely. For us, a TS can represent SIGNIFICANT flooding. When Noel went through here, someone drowned in the RAIN flooding (not storm surge).
Member Since: October 25, 2005 Posts: 19 Comments: 22561
HoustonTxGal,

Howdy! I wonder when this blog is going to be packed with SE Texas/LA residents?! Lol
Member Since: June 27, 2010 Posts: 0 Comments: 372


Looks quiet after TD 3 and 98L
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Thanks much.
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moving N. W. is what I thought I was seeing also.
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Quoting A4Guy:
Question-what can cause the storm to relocate it's center closer to or under the heavy convection? Thx.


Shear can cause it and if the sheared MLC can work down to the surface and kick out the old low. Not likely here though, IMO.
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Member Since: July 3, 2005 Posts: 426 Comments: 129089
What type of weather should we expect here in miami? 30-40 sustained with very heavy rain??
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IMO... it really appears to me as if the center is moving almost NW, not WNW.
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Quoting Waltanater:
So they are saying that this will just be a TS in the GOM throughout its life? Are they serious? What is the #1 factor then, that is preventing that "significant intensification" here? Can anyone elaborate on that, in support of NHC of course? Thanks.


NHC says it is the ULL.
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61. IKE
Vorticity south of the north-central GOM at 60 hours on the 12Z GFS....

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We're on a local weather conference call at 1 with NWS Ruskin... They'll give us the straight dope about what to expect here on Florida's west coast.

My anniversary is this Saturday... da missus will be quite upset if our beach plans get rained out!
Member Since: June 20, 2005 Posts: 22 Comments: 1054
Quoting HoustonTxGal:


I too am in Spring.. howdy neighbor!
hELLO Neighbor, I am in Katy
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So they are saying that this will just be a TS in the GOM throughout its life? Are they serious? What is the #1 factor then, that is preventing that "significant intensification" here? Can anyone elaborate on that, in support of NHC of course? Thanks.
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57. IKE
12Z GFS takes it through the Keys....

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Quoting jlp09550:
Latest GHCC imagery animation:
I usually follow the way the clouds/precip is pointing to where I feel storms our headed; so would not this be headed more towards palm beach and north???
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Question-what can cause the storm to relocate it's center closer to or under the heavy convection? Thx.
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Quoting whs2012:


I live in Houston too (near Spring to be exact lol). What do you think about TD3?


I too am in Spring.. howdy neighbor!
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D6X,

Do you think there will be another shift in the models?
Member Since: June 27, 2010 Posts: 0 Comments: 372
Quoting cybergrump:
looking at visible and track point looks like center is north of the point. I also see some convention right on the center.Link


Initial motion from the NHC was uncertain however, it looks to be taking a bit of a steeper angle than 295, that I'll agree with.
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Quoting StonedCrab:
OK. I'm off to Home Depot to buy up all of the generators and plywood, then to Publix to load up on 1800 gallons of water per person per day.

Am I forgetting anything?
dont forget ten loaves of bread
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TD #3 Update w/ Video
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The Motion looks to be west or around 270
Member Since: July 3, 2005 Posts: 426 Comments: 129089
Quoting whs2012:


I live in Houston too (near Spring to be exact lol). What do you think about TD3?
TD3 will bring rain and wind to Texas if it comes to Texas, if it comes in at Lousiana Texas will be on the dry and hot side of the Storm, if you want Hot and Dry weather then be on the West side of a storm
Member Since: July 5, 2009 Posts: 0 Comments: 1348
Quoting Drakoen:
GOES hi-resolution satellite imagery


Looks like a wrap around attempt, hopefully the goalie will stop it.
Member Since: September 6, 2009 Posts: 2 Comments: 3774
Blog Update!

July 22, 2010 - 11:55 AM EDT - Tropical Depression #3 Is Classified - 98L Organizing
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting Patrap:
TD 3 Floater - Rainbow Color Infrared Loop


Pat, do you think that shows a more northerly movement of the COC or just the cloud tops?
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Here is a look at the TCHP map. The loop current is pretty far south this year, so TD3 won't be able to tap into the deepest moisture for more than a few hours as it crosses the Florida straights, at which point it will still be getting eaten by shear and dry air. Then there is a cold patch west of Key West, and then a low-moderate heat potential smack in the middle of the gulf, which should give it at least some moisture to work with. So this definitely doesn't have the heat to rapidly intensify, but it's just enough that if the wind and dry air were to die down, it could become a hurricane. This might become more of a possibility if it were to take a more westward track, as there would be slightly greater heat potential on a Houston-like path, while the waters are a bit colder southeast of Louisiana.



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GOES hi-resolution satellite imagery
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Does someone have a link to the MJO forecasts? Per San Juan NWS, MJO will become highly unfavorable begining next week.
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Quoting StonedCrab:
OK. I'm off to Home Depot to buy up all of the generators and plywood, then to Publix to load up on 1800 gallons of water per person per day.

Am I forgetting anything?



Liquor run.
Member Since: July 25, 2006 Posts: 0 Comments: 590
Dr.M this is key short term. And will have long term implications if it happens.

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.
Member Since: September 6, 2009 Posts: 2 Comments: 3774
35. D6X
With the strength of the building ridge to its north, I feel soon to be Bonnie may be nudged further south or take more of a westerly course through the straights or even northern Cuba initially until it begins to round the base of the ridge in a couple of days. The ridge can be seen building south in this sat pic.Link
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looking at visible and track point looks like center is north of the point. I also see some convention right on the center.Link
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Quoting StonedCrab:
LIVE Hurricane Hunter Aircraft Recon Data for Google Earth

Link


hmm.. i cant seen to find the plane route on there anywhere
Member Since: May 30, 2010 Posts: 0 Comments: 111
98L should be TD4 SOON.
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Quoting StonedCrab:
OK. I'm off to Home Depot to buy up all of the generators and plywood, then to Publix to load up on 1800 gallons of water per person per day.

Am I forgetting anything?


Concertina wire and a few Marines to help you keep it...you know...safe
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Latest GHCC imagery animation:
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Question-what can cause the storm to relocate it's center closer to or under the heavy convection? Thx.
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anything can happen guys none of us r anywere near having PHd's like at the nhc so lets just have fun and dont insult people for having an opinion diffrent than urs
Member Since: July 21, 2010 Posts: 0 Comments: 1181
OK. I'm off to Home Depot to buy up all of the generators and plywood, then to Publix to load up on 1800 gallons of water per person per day.

Am I forgetting anything?
Member Since: October 30, 2007 Posts: 0 Comments: 270
good ol subsidence side of storm is always good
Member Since: July 14, 2008 Posts: 1 Comments: 9645
thank you dr masters!
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Finally! Thanks Doc.
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Looks like a bullseye for my neighborhood. Expecting winds 30-40, gusts to 50 late Friday early Saturday.
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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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