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 NoNamePub:
WAHOO - MY AV IS APPROVED


My, but you're easily amused...LOL
Member Since: Posts: Comments:
1321. vince1
Quoting jscs:


You really should stop watching Faux News.

Yes, because the government loves you and only wants the best for you. If you're only getting mainstream news, it's the best antidote for the joke that is MSNBC and CNN much of the time.
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I don't see a TS symbol. i have no idea of what hes looking.
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1319. xcool


betterlook
Member Since: September 26, 2009 Posts: 2 Comments: 15684
IMO...No way td3 will be upgraded.. it looks like she’s losing all her steam.. Storms are collapsing big time…
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Quoting newportrinative:
Storm w this is going to miss S.FL right?

Enough already!!! Asking about airport closings and where the storm is going....
Why are you doing this? At best it's a TS, not a hurricane. Wind and rain so calm down.

Follow what the NHC is saying!!!!!


50mph sustained winds (the forecast max) are not fun, at least not for me. Yes, airports can be closed due to tropical storms. I think you are being a bit harsh and perhaps not fully understanding the implications. I have never understood the "it's only a tropical storm" mentality.
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1315. 10Speed
Quoting StormW:


South FL. is going to be on the "dirty side"


Gads. We were hoping for badly needed rain ... not African dust. :-)
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You know... for a bunch of people that do nothing but make fun of TWC and how wrong they are all the time, you guys sure do watch it a lot. Seems kinda strange to me.
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Quoting cajunroach:
I'm trying to think of a storm that covers the gulf in late july and stays a weak system as per models.


Well, in years to come people may look at similar systems and compare them to TD3 (Bonnie) in 2010 which does just that.

If all of the models are keeping this as a tropical storm, with really none of them developing it into a hurricane... then it will probably remain a tropical storm. Otherwise, at least one of the models would have intensified it further by now.
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Quoting btwntx08:

lower caps plz


That is like someone asking you to use punctuation. :)
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Quoting MrJoeBlow:


It has Sarasota all over it I do think. That XTRP model shows it nice.


****Head in Hands****
XTRAP......SHEESH
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1309. angiest
Quoting tropicfreak:


What site??


WU...
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1308. leo305
Quoting MrJoeBlow:


It has Sarasota all over it I do think. That XTRP model shows it nice.


that's the current motion
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Quoting StormW:


South of Miami, if it makes it that far north.


Hi Storm - how prepared you think we should get here in SE TX?
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Here's more Joe Bastardi.


THURSDAY:
LOOK AT THIS FROM KEY WEST:

...WINDS AND SEAS... AS TROPICAL DEPRESSION THREE APPROACHES...SUSTAINED TROPICAL STORM FORCE WINDS ARE EXPECTED TO BEGIN LATE FRIDAY MORNING. SEAS OF 8 TO 12 FEET FRIDAY MORNING MAY BUILD TO 10 TO 16 FEET BY FRIDAY AFTERNOON.

Now, there is little weather with and south of the center of this. The center is likely to go north of them. It's like what we saw with warnings on the Mexican coast with Alex and TD 2.

I expect wind gusts from Miami to Ft. Pierce to average over 35 knots but I would be surprised if I see one over 20 knots at eyw, when the storm is within 100 miles of them.

Ciao for now.
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LLC according to the RGB appears to be at 22.8N 75.0W... nice blob of convection developing right near the center.
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Wow TWC has a 500++ mile cone of stupidity!! Guess they want to be weatherly correct****
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Quoting BahaHurican:


Now getting some heavier downpours from the expanded band over NP...


Its starting to wrap around.
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Quoting Clearwater1:
Yes, I do see how it's moving, but I am hoping the ridge that is building will turn it more westerly, way before it has a chance to get north enough affect sarasota. I guess we will find out soon enough. Should turn wmw in a three or four hours. imo


It has Sarasota all over it I do think. That XTRP model shows it nice.
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Quoting angiest:


If you look on the main tropical page, the global map has a TS symbol where TD3 is.


What site??
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Quoting louisianaboy444:


Lol i'm getting a headache..I can't wait till this South-Central Florida stuff can be put to bed
South Florida stretches to the keys, so it isn't gonna be put to bed. Still stickin' with my south Dade prediction. Lol.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting angiest:


Did you reload?


YA LIKE 5 TIMES
Member Since: July 21, 2010 Posts: 0 Comments: 1181
Quoting TOMSEFLA:
site has changed map logo to bonnie with ts symbol


Link???
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Now getting some heavier downpours from the expanded band over NP...
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Schrapnel.
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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?
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Time: 19:20:30Z
Coordinates: 22.4167N 75.1167W
Acft. Static Air Press: 988.0 mb (~ 29.18 inHg)
Acft. Geopotential Hgt: 161 meters (~ 528 feet)
Extrap. Sfc. Press: 1006.4 mb (~ 29.72 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 340° at 2 knots (From the NNW at ~ 2.3 mph)
Air Temp: 24.3°C (~ 75.7°F)
Dew Pt: 20.6°C (~ 69.1°F)
Peak (10s) Flt. Lvl. Wind: 3 knots (~ 3.4 mph)
SFMR Peak (10s) Sfc. Wind: 6 knots* (~ 6.9 mph*)
SFMR Rain Rate: 6 mm/hr* (~ 0.24 in/hr*)
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1291. angiest
Quoting chrisdscane:



NOT FOR ME IM SRY


Did you reload?
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Product: Air Force Tropical RECCO Message (URNT11 KNHC)
Transmitted: 22nd day of the month at 18:08Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 306)
Mission Purpose: Investigate second suspect area (flight in the North Atlantic basin)
Mission Number: 2
Observation Number: 08

Mandatory Data...

Observation Time: Thursday, 18:06Z
Radar Capability: Yes
Aircraft Altitude: Below 10,000 meters
Coordinates: 22.1N 75.1W
Location: 151 miles (243 km) to the NNE (18°) from Santiago de Cuba, Cuba.
Turbulence: None
Conditions Along Flight Route: In the clear
Pressure Altitude: 180 meters
Flight Level Wind: From 330° at 13 knots (From the NNW at ~ 14.9 mph)
- The above is a spot wind.
- Winds were obtained using doppler radar or inertial systems.
Flight Level Temperature: 24°C
Flight Level Dew Point: 15°C
Weather (within 30 nautical miles): Shower(s) (continuous or intermittent precipitation - from cumuliform clouds)
Mean Sea Level Pressure (MSLP): 1008 mb (extrapolated)

Optional Data...

Estimated Surface Wind Direction: Bearing was unavailable.
Estimated Surface Wind Speed: 5 knots (~ 5.8 mph)
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1288. lolzzz
Quoting chrisdscane:
GUYS I HAVE BEEN DOWNCASTING THIS THING ALL DAY I JUST GOT BACK FROM GOLF AND I MUST SAY IT IS LOOKING GOOD THERE R NOW SIGNIFICANT SHOWERS ON THE WESTERN SIDE AND IT IS NOW MORE CIRCULAR HURRICANE HUNTERS R FINDING TS WINDS AT ITS CURRENT SPPED ITLL BE HERE EARLY TOOMOROR ATLEAST THATS WHAT I THINK TY AND BYE

lol...
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1285. Drakoen
22.5N 75.2W
Member Since: October 28, 2006 Posts: 57 Comments: 30825
Quoting sammywammybamy:


N.E Quadrant.

Rain and possible tornadoes.

SouthWest Quadrant is typically the least "dirty" side

That would be for a storm moving north. For a storm moving west, the dirty quad would be the NW and the clean quad would be the SE.
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Quoting angiest:


If you look on the main tropical page, the global map has a TS symbol where TD3 is.



NOT FOR ME IM SRY
Member Since: July 21, 2010 Posts: 0 Comments: 1181
1282. Grothar
the big squeeze is going on right now. Will have to wait to see what it does.

Member Since: July 17, 2009 Posts: 71 Comments: 27208
1280. Drakoen
Recon found 1006mb
Member Since: October 28, 2006 Posts: 57 Comments: 30825
1006.0mb was this found
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Quoting MrJoeBlow:


Don't you see how its moving. I seen it go NW and I said yep there right there is going to Sarasota for sure.
Yes, I do see how it's moving, but I am hoping the ridge that is building will turn it more westerly, way before it has a chance to get north enough affect sarasota. I guess we will find out soon enough. Should turn wmw in a three or four hours. imo
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looks like we will have an upgrade at 5PM plenty of TS Winds around 40MPH and very very few 50 MPH wind bards
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1275. angiest
Quoting chrisdscane:


????


If you look on the main tropical page, the global map has a TS symbol where TD3 is.
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Quoting newportrinative:
Storm w this is going to miss S.FL right?

Enough already!!! Asking about airport closings and where the storm is going....
Why are you doing this? At best it's a TS, not a hurricane. Wind and rain so calm down.

Follow what the NHC is saying!!!!!


Lol i'm getting a headache..I can't wait till this South-Central Florida stuff can be put to bed
Member Since: August 29, 2006 Posts: 22 Comments: 1352
Each plane has a different cross wind component, as far as headwind, that's pilot discretion. They do close the airport at a certain windspeed though.
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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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