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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1421. 900MB
Quoting earthlydragonfly:


I must say if it wasnt for him, KOGate, Patrap, Baha, and too many to list... I would still be asking dumb question... Still do sometimes.


Word! Thx to the well versed regulars!
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Ahhhh, look how little this little ol depression is. Aint it cute...
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1419. Skyepony (Mod)
Average Position Error (nm) for models
model Error Trend 24hr Error 48hr Error 72hr Error Day 4 Error Day 5 Error
OFCL DECREASING 51.9 119.2 95.7 -1 -1
GFDL INCREASING 77.8 154 -1 -1 -1
BAMD CONSTANT 81.2 80.6 73.7 -1 -1
MM5B CONSTANT 82.6 227.5 -1 -1 -1
CMC DECREASING 89.4 152.7 -1 -1 -1
LBAR CONSTANT 107.3 216.3 437.7 -1 -1
AEMN CONSTANT 110.7 115.9 -1 -1 -1
HWRF DECREASING 135 224 341.8 -1
XTRP DECREASING 135.4 257.2 434.9 -1
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Quoting hurrkat05:
THIS SYSTEM IS SLOWLY LOSING OUT ON THE OPPORTUNITY TO BECOME A TROPICAL STORM...IF THIS IS NOT UPGARDED TO TROPICAL STORM BONNIE BY 11PM IT WILL NEVER BE...BONNIE IS LOOKING REALLY RAGGED NOW BECAUSE SHE IS ENCOUNTERING THE DRY AIR AND THE SHEAR IS BEGINNING TO AFFECT HER..THIS MAY BE A RAINMAKER FOR FLA AND THATS ALL IT WILL AMOUNT TO...98L LOOKS BETTER THEN THIS TRIOICAL DEPRESSION RIGHT NOW...I SEE NO REASON TO POSTPONE ANYTHING OUT IN THE GULF CONCERNING OIL OPERATIONS...


Have you looked at the winds recon has found so far near the surface. I can understand your point of view but really,say something when you really mean it I go by what the NHC says(for the most part) and you should too.
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Quoting MrJoeBlow:


You just joking with me or what? I seen it on a map with all the other models. I sorry I can not tell if you joke with me.


NO he was not joking! It is a straight line average!
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1414. Patrap
A Waiting ATCF Images and Graphics from Beacon Tower 1.

Tango,Foxtrot,Oscar..

Over,Rover..?

raleighwx.easternuswx.com/models
Member Since: July 3, 2005 Posts: 426 Comments: 128668
.
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Quoting Hurricanes101:


I am not joking with you, it is not a forecast model


I am now more confuse than ever. Just when I thought I had lurk enough to understand to. So I guess this one don't got Sarasota wrote all over it now.
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We need a new blog now
does anyone else think it's ridiculous that 4mph differential determines the name
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Fresh Update 18Z




Member Since: January 30, 2010 Posts: 0 Comments: 3259
So the GFD2 and the CLIP is ASSUMING that the ridge would move east, even though it isn't forecast to do that right.

I am sorry if I am contributing to the "million dumb questions" I just happen to enjoy learning about these storms.
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Quoting Baybuddy:


StormW after answering his one millionth dumb question.


I must say if it wasnt for him, KOGate, Patrap, Baha, and too many to list... I would still be asking dumb question... Still do sometimes.
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natuarly storms loose alittle t-storms as they organize then regaine it once its "done"
Member Since: July 21, 2010 Posts: 0 Comments: 1177
1405. IKE
Quoting StormW:


Right now, unless it looks better by 5, maybe not. It just tossed out some arc clouds.


If it isn't I may have to pass out some kleenex's for the heart broken on here.
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1404. leo305
Quoting earthlydragonfly:

D-max occurs during the early morning hours before sunrise. Diurnal Max


the moment the sun goes down, this thing should explode like a monster.

Dry air is fading, shear is dropping quickly to almost nothing, and.. waters are HOT. DMIN currently in control, but remember what happened to KATRINA it looked like a weak TS during the day, then became a hurricane at night near SFL.
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Quoting MrJoeBlow:


You just joking with me or what? I seen it on a map with all the other models. I sorry I can not tell if you joke with me.


I am not joking with you, it is not a forecast model
Member Since: March 10, 2010 Posts: 1 Comments: 7823
Quoting Hurricanes101:


XTRAP is not a model, it is just the current motion of the storm drawn out to fit the 5-day forecast period


You just joking with me or what? I seen it on a map with all the other models. I sorry I can not tell if you joke with me.
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1400. Patrap
Quoting RiverSteve:

Storm or Pat

I'm in Central Alabama should I stock up on spam or mustard sardines? jk thanks to both of you for the updates and maps.


Sardine's,.


I don't like Spam


Member Since: July 3, 2005 Posts: 426 Comments: 128668
Quoting moonlightcowboy:
1341. IKE 7:36 PM GMT on July 22, 2010

If that verifies it seems unlikely this goes to Texas. I would think Louisiana or just east.



That's how it's shaping up in the present - subject to change. Even if it's not a bad storm, all Cat'd up - the oil will be dreadful
:(
A Cat WD-40.

Hi, MLC. Good to see ya'.
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Quoting Orcasystems:

Time: 19:19:30Z
Coordinates: 22.4667N 75.15W
Acft. Static Air Press: 988.8 mb (~ 29.20 inHg)
Acft. Geopotential Hgt: 152 meters (~ 499 feet)
Extrap. Sfc. Press: 1006.1 mb (~ 29.71 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 61° at 5 knots (From the ENE at ~ 5.8 mph)
Air Temp: 24.8°C (~ 76.6°F)
Dew Pt: 20.5°C (~ 68.9°F)
Peak (10s) Flt. Lvl. Wind: 6 knots (~ 6.9 mph)
SFMR Peak (10s) Sfc. Wind: 4 knots* (~ 4.6 mph*)
SFMR Rain Rate: 4 mm/hr* (~ 0.16 in/hr*)
Looks like it's still moving towards the NW, that should continue for another 2 maybe 3 hours before resuming WNW motion.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Just drop by for a visit. The latest sat looks like the TD is moving north its forecast points.
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Quoting RainyEyes:
Ok, I am still a newb, despite lurking here for 3 years. This is a question, not a wishcast..but, what is making this storm go west then turn north rather then riding the florida coast straight north to te panhandle. It is avoiding that dry air and ULL but why not just stay east of that and go up the florida coast? can someone explain?
There's a bigh High Pressure ridge in the way.



The westernmost point of it is currently over near TX. Instead of going north across it, TD 3 will go west along it until it gets to the point where it can go around. Then it'll turn N and NE...
Member Since: October 25, 2005 Posts: 19 Comments: 22322
Quoting angiest:


Someone is giving Storm a red stapler?

LOL
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Quoting all4hurricanes:
She looks emaciated bur D-max will fix her up I'm fairly certain we'll have Bonnie at the end of the day

D-max occurs during the early morning hours before sunrise. Diurnal Max
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Oh and TS Gaston when Floods ravaged Richmond(where I'm from.)
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1391. leo305
Quoting MrJoeBlow:
does anybody have a run of the XTRP model? It got a Sarasota exit last I seen it.


that is not a model, that's the current movement
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Quoting Patrap:
Isn't that old now? some were posting 18Z models.
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Quoting MrJoeBlow:
does anybody have a run of the XTRP model? It got a Sarasota exit last I seen it.


XTRAP is not a model, it is just the current motion of the storm drawn out to fit the 5-day forecast period
Member Since: March 10, 2010 Posts: 1 Comments: 7823
1388. angiest
Quoting Baybuddy:


StormW after answering his one millionth dumb question.


Someone is giving Storm a red stapler?
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Quoting Hurricanes12:
This system isn't looking too great, like it was earlier. Is there a reason for this?


Because all tropical systems fluctuate in storm activity. And it is currently entering a low period. It will probably stay a bit lower for a few hours, and then flare back up tonight and look impressive again.

Don't let the slight lack of storms at the moment fool you, though. It's not size, but organization that matters. And right now, storms are starting to wrap around the center. So even though it doesn't look as impressive, it is actually getting better organized, not dying.
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1386. xcool
Patrap old pic
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting ChillinInTheKeys:
Do they now use that icon for a TD?


Yes.....when it changes from an Invest they have that symbol.
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1384. Patrap




Member Since: July 3, 2005 Posts: 426 Comments: 128668
Quoting FSUstormnut:
still have not seen surface winds above 36mph... thats not 40-45mph...
Apparently you haven't been paying attention. About 20 SFMR observations concluded surface winds of 40+ mph, with about 5 of them showing 45mph.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting lickitysplit:
Why does Bonnie seem to suddenly look powerful then, just as suddenly, seems to fall apart and weaken?


just wait till dmax this is the most organized its been
Member Since: July 21, 2010 Posts: 0 Comments: 1177


StormW after answering his one millionth dumb question.
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Storm or Pat

I'm in Central Alabama should I stock up on spam or mustard sardines? jk thanks to both of you for the updates and maps.
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does anybody have a run of the XTRP model? It got a Sarasota exit last I seen it.
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Quoting FSUstormnut:
perhaps 11pm...?


nope 5pm, you must have missed the last hour or so of recon reports, there have been numerous sustained surface winds of TS force recorded
Member Since: March 10, 2010 Posts: 1 Comments: 7823
1376. 900MB
Quoting StormW:


She's tryin' Drak!


Been away from the computer for a few hours (for once), what was the max surface wind on recon? Thx.
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1341. IKE 7:36 PM GMT on July 22, 2010

If that verifies it seems unlikely this goes to Texas. I would think Louisiana or just east.



That's how it's shaping up in the present - subject to change. Even if it's not a bad storm, all Cat'd up - the oil will be dreadful
:(
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Quoting MiamiHurricanes09:
What are the coordinates?

Time: 19:19:30Z
Coordinates: 22.4667N 75.15W
Acft. Static Air Press: 988.8 mb (~ 29.20 inHg)
Acft. Geopotential Hgt: 152 meters (~ 499 feet)
Extrap. Sfc. Press: 1006.1 mb (~ 29.71 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 61° at 5 knots (From the ENE at ~ 5.8 mph)
Air Temp: 24.8°C (~ 76.6°F)
Dew Pt: 20.5°C (~ 68.9°F)
Peak (10s) Flt. Lvl. Wind: 6 knots (~ 6.9 mph)
SFMR Peak (10s) Sfc. Wind: 4 knots* (~ 4.6 mph*)
SFMR Rain Rate: 4 mm/hr* (~ 0.16 in/hr*)
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1373. Patrap
Member Since: July 3, 2005 Posts: 426 Comments: 128668
1372. Greyelf
Quoting TexasHurricane:


Hi Storm - how prepared you think we should get here in SE TX?


Lol...for some reason, I just "heard" Patrap's voice in my head saying...."you should always be prepared". Heh.
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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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