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 Orcasystems:


Don't go using logic.. it will confuse half of the people here :)


That word, what does it mean?
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Quoting BahaHurican:
Hey, u r 1 of us... and we all had to ask questions and learn stuff. I like that "pay it forward" stuff; somebody help u understand something, you help somebody else.
Forgot to say u were right about GFS, basically, but CLIP is a statistical model that looks at historical storms and bases its track forecast on that info.
Member Since: October 25, 2005 Posts: 19 Comments: 20695
No TS from iam finding on the recon obs...

VORTEX DATA MESSAGE AL032010
A. 22/19:20:30Z
B. 22 deg 25 min N
075 deg 07 min W
C. NA
D. 29 kt
E. 296 deg 22 nm
F. 024 deg 33 kt
G. 297 deg 24 nm
H. EXTRAP 1006 mb
I. 24 C / 183 m
J. 25 C / 217 m
K. 21 C / NA
L. NA
M. NA
N. 12345 / 01
O. 0.03 / 0 nm
P. AF306 02BBA INVEST OB 14
MAX FL WIND 33 KT NW QUAD 19:12:20Z
SLP EXTRAP FROM BELOW 1500 FT

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Of all of the models, which have proven themselves to be the most accurate?
Member Since: September 18, 2007 Posts: 0 Comments: 1073
Quoting StormW:


Go with both...nothin like variety!


Thanks.... No Joking the reason I stay on here is Opel and Ivan both cost me a bundle up here and was w/o power for weeks. The straight line winds and tornadoes theses things spawn are of course secondary but no less severe.
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Quoting MiamiHurricanes09:
Yep I agree. Any idea on current speed and direction? And are you still thinking southern Miami-Dade county as the landfall location?


I am still sticking with my forecast from earlier with a moderate tropical storm making landfall in Southern Miami Dade county tomorrow afternoon.
Member Since: April 14, 2007 Posts: 8 Comments: 5030
Miami Hurricane: td 3 is not going to hit Miami. You need to stop wishcasting; we all know that you want a tropical storm or hurricane.
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Quoting angiest:


You're welcome, but I'm not a ma'am. :)

I have no idea about your BBQ, as I don't know where Riverview is. What does your local NWS forecast say?


I am sorry I thought you name was angie. Riverview is in Florida.
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Quoting ecflweatherfan:


What happened is they got taken over by NBC.


It was going downhill long before that. They decided to join the mainsteam news media 4-5 years ago in order to expand their audience, but technically oriented folks like us couldn't care less about that.
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Quoting Orcasystems:
The vortex plot puts is a little to the north of track.... basically... its going to go over Zoo's house.
At 2PM the center fix was already north of the cone, now the vortex message is north of the 2PM center fix. So a shift to the right in the 5PM cone seems very likely.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting louisianaboy444:


It is riding along just a hair North of the Forecast track...one wobble westward and it will be back on track..i dont see any big track changes


Don't go using logic.. it will confuse half of the people here :)
Member Since: October 1, 2007 Posts: 81 Comments: 26493
td3 continues to move NW look at the visible and put the forecast points
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Quoting Seflhurricane:
do you live in se florida because your ID name says charlotte which is north of ft myers and there are no watches/warning there yet ??



I live in Southern Lee County near Bonita Springs. Grew up in Charlotte county..
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StormW, ballpark it, please.

Assuming (dreadful seas NHC prediction for sFL) it hits/skirts sFL, survives land interaction, shear, etc, can you estimate a nearer and distant nGOM landfall timelines? Monday? Tuesday? TIA
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Quoting MiamiHurricanes09:
Yep I agree. Any idea on current speed and direction? And are you still thinking southern Miami-Dade county as the landfall location?


It is riding along just a hair North of the Forecast track...one wobble westward and it will be back on track..i dont see any big track changes
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Quoting southfla:
sammywammybammy -- I don't think there is a specific overall wind speed that they use to close down flight operations at an airport. I would think that it isn't just about the planes themselves, but also about working conditions for the ground crew. Good question though, hope someone who knows will answer.


That is correct...airports do close for "high winds." Every certified aircraft has a maximum demonstrated cross-wind speed. But...the real limitation is pilot skill.

v/r

Jon
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Can someone answer me this then..the stronger TD3 gets... more west it will go?
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Quoting cchsweatherman:
Recent satellite imagery shows TD 3 becoming better organized as the circulation center has become even better defined and spiral banding has really become established. In addition, convection has begun to build northeast and southwest of the circulation center as the system continues to become better organized.


I think Hurrkat left because she didn't want to be beaten by the experts.
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Quoting MiamiHurricanes09:
Looking at visible loops it seems to me that 03L is still moving towards the NW, maybe a bit quicker than before.




lets place best it goes north of dade county im betting 20 bucks
Member Since: July 21, 2010 Posts: 0 Comments: 1052
Quoting RainyEyes:
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.
Hey, u r 1 of us... and we all had to ask questions and learn stuff. I like that "pay it forward" stuff; somebody help u understand something, you help somebody else.
Member Since: October 25, 2005 Posts: 19 Comments: 20695
Quoting IKE:


That's true. You see on every system with every updated image.
Yeah but the overall trend is that it is getting much better organized now, due to the significant drop in shear and less dry air.
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The vortex plot puts is a little to the north of track.... basically... its going to go over Zoo's house.
Member Since: October 1, 2007 Posts: 81 Comments: 26493
guys this hit Ignore and Poof
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1491. angiest
Quoting MrJoeBlow:


Thank you ma'am. Now is the BBQ at my house going to get rained out on Saturday night? I live in Riverview.


You're welcome, but I'm not a ma'am. :)

I have no idea about your BBQ, as I don't know where Riverview is. What does your local NWS forecast say?
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1490. NYX
Quoting leo305:


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.


Hesitantly agreeing but hoping that will not happen. I drove through Katrina when it was upgraded to cat 1. Not a pleasant experience but all day we were looking at a hapless looking tropical storm just an hour or two prior to landfall.
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Quoting charlottefl:
Afternoon everyone. I'm currently under a tropical storm warning. Everyone at FPL is on standby mode right at the moment. The structure of TD3 has improved considerably since this morning. Shear looks to have relaxed a lot. Still seems to be fighting dry air some at the moment. I'm thinking this is probably gonna make landfall somewhere in the extreme southern part of the state. Just interested to see what happens from here until landfall as conditions have improved quite a bit.
do you live in se florida because your ID name says charlotte which is north of ft myers and there are no watches/warning there yet ??
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Can anyone tell me if the low pressure is moving away?
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Quoting Seflhurricane:
i also would like to remember those who live in south florida what happened with Katrina it became a depression close to where TD3 is now and quickly gained strengh even though the conditions are not there for a hurricane, i would suggest as a precaution be ready for a strong tropical storm !!



thats true u realy never know
Member Since: July 21, 2010 Posts: 0 Comments: 1052
this is a first on this website.... i'm might be wrong! (I don't think I have ever seen anyone write those words in years on this website)..we might have ts at 5pm... :o)
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Quoting vortextrance:
It's silly not to worry about a TS. Even a weak TS can leave you stranded by the winds and flooding. Its not as exciting but can be every bit as dangerous.

Also, I have seen several disagreements over model reliability. In my opinion they are very reliable on track for the most part. They aren't reliable on intensity. You have to understand why it is the models do or don't intensify a storm. Every storm is different. Sometimes its quite obvious that conditions will be more favorable than a model suggests. In this case it seems the models reasoning for keeping TD3 a TS is sound. Their are several things she would have to overcome to make hurricane status. Not to say it can't happen. There is just nothing to suggest it will.


It is NOT a TS. It is NOT named Bonnie yet.
Member Since: October 30, 2007 Posts: 0 Comments: 270
Quoting hurrkat05:
WH WELL TROPIC FREAK WHY HASNT IT BEEN NAMED YET IM PRIVLIDGED TO ALL THE AND MORE OF INFO YOU HAVE AND I SEE NO REASON TO NAME IT NOW...IF IT DOES GET NAMED IT WILL BE AT THE 11PM ADVISORY AND THEN IT WILL BE A MINIMAL TS..


Dude, give it a rest. You were say rip two days ago. Can't wait till school starts back.
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Quoting hurrkat05:
WH WELL TROPIC FREAK WHY HASNT IT BEEN NAMED YET IM PRIVLIDGED TO ALL THE AND MORE OF INFO YOU HAVE AND I SEE NO REASON TO NAME IT NOW...IF IT DOES GET NAMED IT WILL BE AT THE 11PM ADVISORY AND THEN IT WILL BE A MINIMAL TS..


Lower caps please!!!!
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Quoting StormW:


LMAO IKE!


I generally don't disagree with you, Storm, but based on the countless other TCs I've watched over the years, I don't see how this is not Bonnie by 8PM at the latest; I'd be surprised, in fact, if 40kt-45kt winds aren't found by that time. Then again, I'm just a partial pro, and you're the real deal... ;-)
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The spiral banding has really increased in the last couple of hours. A lot more has been feeding in from the north Cuba coastline. It is almost certainly a tropical storm by now as the Upper Level Low pulls away.
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Quoting cchsweatherman:
Recent satellite imagery shows TD 3 becoming better organized as the circulation center has become even better defined and spiral banding has really become established. In addition, convection has begun to build northeast and southwest of the circulation center as the system continues to become better organized.
Yep I agree. Any idea on current speed and direction? And are you still thinking southern Miami-Dade county as the landfall location?
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting MiamiHurricanes09:
Looking at visible loops it seems to me that 03L is still moving towards the NW, maybe a bit quicker than before.


Same here.
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Afternoon everyone. I'm currently under a tropical storm warning. Everyone at FPL is on standby mode right at the moment. The structure of TD3 has improved considerably since this morning. Shear looks to have relaxed a lot. Still seems to be fighting dry air some at the moment. I'm thinking this is probably gonna make landfall somewhere in the extreme southern part of the state. Just interested to see what happens from here until landfall as conditions have improved quite a bit.
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weather is north of center both dade and broward should experience on and off heavy rains and gusts
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Statement as of 3:45 PM EDT on July 22, 2010

... Flood Watch in effect from midnight EDT tonight through Friday
afternoon...

The National Weather Service in Miami has issued a

* Flood Watch for a portion of South Florida... including the
following areas... coastal Broward... coastal Collier... coastal
Miami Dade... coastal Palm Beach... far South Miami Dade...
Glades... Hendry... inland Broward... inland Collier... inland
Miami Dade... inland Palm Beach... Mainland Monroe... Metro
Broward... Metro Miami Dade and Metro Palm Beach.

* From midnight EDT tonight through Friday afternoon

* tropical depression 3 at 2 PM is located about 425 nm southeast
of Miami. This tropical system will move through the Keys on
Friday. Expected rainfall totals later tonight through Friday will
be around 2 to 4 inches with isolated areas up to 6 inches. The
grounds are near saturation due to the rainfall accumulated
since may. There is some uncertainty in the track and intensity,
and this could change the rainfall amounts across the area.


* Some street and low lying flooding can be expected later
tonight and Friday. There is a possibility for significant
flooding with the possibility of roads becoming impassable and
flood waters entering structures.

Precautionary/preparedness actions...

A Flood Watch means there is a potential for flooding based on
current forecasts.

You should monitor later forecasts and be alert for possible
flood warnings. Those living in areas prone to flooding should be
prepared to take action should flooding develop.
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Storm W.. the stronger TD3 gets... more west it will go?
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i also would like to remember those who live in south florida what happened with Katrina it became a depression close to where TD3 is now and quickly gained strengh even though the conditions are not there for a hurricane, i would suggest as a precaution be ready for a strong tropical storm !!
Member Since: Posts: Comments:

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About JeffMasters

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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