Tropical depression forming over the Bahamas

By: Dr. Jeff Masters , 1:29 PM GMT on July 22, 2010

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A tropical wave (Invest 97L) over the eastern Bahama Islands has developed a closed circulation at the surface, and has become a tropical depression or tropical storm. Here is the text of the Special Tropical Weather Outlook from NHC at 8:25am EDT today:

Visible satellite images and observations from the Bahamas indicate that the area of low pressure in the southeastern Bahamas has become better organized and a closed circulation has formed. Advisories on a tropical depression or a tropical storm will be initiated at 11 am EDT...1500 UTC today. This advisory will likely include tropical storm watches and warnings for portions of the Bahamas and southern Florida.

Satellite images of 97L show a modest area of heavy thunderstorms that have slowly increased in intensity and areal coverage this morning. Water vapor satellite loops show a large area of dry air lies to the west of 97L, over Florida. This dry air is associated with a large upper-level low pressure system that is moving west at about the same speed 97L is. The counter-clockwise flow of air around the upper low is bringing about 20 knots of wind shear to 97L. Surface observations in the Bahamas and several nearby ships have shown top winds in 97L 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 97L
The storm is in a fairly straightforward steering current environment, and 97L 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 97L over the next two days. The location of 97L'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 97L
The primary detriment to development of 97L 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 97L, it will bring wind shear of about 20 knots and dry air into the storm. This will limit the intensification potential of 97L to no more than about 10 - 20 mph per day. If the upper-level low picks up speed and pulls away from 97L, the storm may be able to intensify at a faster rate. None of the computer models is calling for that to happen, but it is possible. I put the odds of 97L 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.

I'll have an update after NHC releases their 11am advisory package.

Jeff Masters

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Its unbelievable, around this time yesterday it was poorly disorganized, now I wake up to a TD.
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Quoting CybrTeddy:


Thats the norm for this time of year.


True although it could be enhanced more with this tropical feature, it should bring down the temperatures down to the low 90s.
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This is my only day off this week, and my only day off the past 2 weeks...

Looks like I picked a good day!
Member Since: May 30, 2010 Posts: 0 Comments: 111
Quoting aquak9:


weel if you're in my back yard, it's easy- just look up!

Keeper it was so cool!! I ran out there and it looked like a big jet with the big round plate on top- SO COOL!!!

lol. im in mobile so i never get to see any of that.
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cat 3 before slipping near the keys....maybe right over them...then onto the oil spill....

model is too far left...it will be a Biloxi to Panama City event. if it hits east of New Orleans...we will be bathed in oil, here in Alabama.....uggh
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@59
Hahaha!
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64. IKE
Quoting hurrkat05:
just like i been saying bonnie can't intensify with the low to the west and the shear 30-40 knots..also the dry air thats going to be sucked into the system will disrupt bonnie.....bonnie will be no more then a weak tropical storm and as long as the shear stays around dr i have to disagree with you i give bonnie no chance of becoming a hurricane in the gom...


See post #40.
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remember not to focus so much on the center when its a tropical storm, weak storms worst weather is usually displaced well n and e of center, not like in a well organized hurricane where the most intense part is right around the eye wall. That being said it will just be like when we get strong afternoon storms just probably with a bit more frequency.
Member Since: August 16, 2008 Posts: 0 Comments: 81
Quoting clwstmchasr:


I guess I should have said the core of the storm. I do think we'll get the northern periphery with 20-30 mph winds and rain.

true the core will probably miss this part of FL.
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hurrkat05 is never right anyway. If you listen to him you get what you deserve.
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looks like the center is developing nicely
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doh, deleted cause of my stupidity
Member Since: May 30, 2010 Posts: 0 Comments: 111
Thanks, Doc!

And oh, well, just peachy.
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Quoting sporteguy03:

not so sure on that....
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
427 AM EDT THU JUL 22 2010
THIS HAZARDOUS WEATHER OUTLOOK IS FOR WEST CENTRAL AND SOUTHWEST
FLORIDA.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

...THUNDERSTORM IMPACT...
A TROPICAL FEATURE IS EXPECTED TO MOVE THROUGH THE REGION WITH
INCREASING CHANCES FOR SHOWERS AND THUNDERSTORM FRIDAY INTO
SATURDAY. THE MAIN HAZARDS MAY BE STRONG GUSTY WINDS...DEADLY
LIGHTNING...AND HEAVY RAINS.


Thats the norm for this time of year.
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Quoting StormW:
97L / 98L SYNOPSIS ISSUED 9:30 A.M. JULY 22, 2010


Thank you Storm! Where do we find those dynamic and statistical models you post and also, how often are models updated, as needed or should we check them so often or what?
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Quoting FLdewey:
Thank goodness we have that high pressure center in extreme S Florida to keep it away.



bwaahhahaha
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Quoting CJ5:
Dude, this is what you said less than 12 hours ago. You have no credibility and are useless in a this tropical discussion.



Oh, wait..now it is a "short lived" storm. What happened to RIP? Jeez....




Well said. Pure bittercasting.
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Quoting FLdewey:
Thank goodness we have that high pressure center in extreme S Florida to keep it away.

I am surprised 97L is not heading east back towards the open Atlantic....That is a face only a mother could love.
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Quoting kputerman26:
how do you get those tracks on google earth and the hurricane hunters


weel if you're in my back yard, it's easy- just look up!

Keeper it was so cool!! I ran out there and it looked like a big jet with the big round plate on top- SO COOL!!!
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Quoting aquak9:
(runs thru the door, slips, crashes sideways into the wall)

i hate these hyper-jumps

gambler I did answer you in the previous wormhole
I saw it before the warp flash, thank you.
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Quoting clwstmchasr:
I think Tampa is in the clear once again. The storm would have to move NW to get up into our region. Dr. M says that the storm will move W to WNW through the FL straights.

not so sure on that....
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
427 AM EDT THU JUL 22 2010
THIS HAZARDOUS WEATHER OUTLOOK IS FOR WEST CENTRAL AND SOUTHWEST
FLORIDA.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

...THUNDERSTORM IMPACT...
A TROPICAL FEATURE IS EXPECTED TO MOVE THROUGH THE REGION WITH
INCREASING CHANCES FOR SHOWERS AND THUNDERSTORM FRIDAY INTO
SATURDAY. THE MAIN HAZARDS MAY BE STRONG GUSTY WINDS...DEADLY
LIGHTNING...AND HEAVY RAINS.
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Quoting aquak9:
woo-hoo!!! I just saw a NOAA jet with the big round thing on top heading east!!
thats a good thing
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Thnx Doc
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how do you get those tracks on google earth and the hurricane hunters
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40. CJ5
Dude, this is what you said less than 12 hours ago. You have no credibility and are useless in a this tropical discussion.

Quoting hurrkat05:
this low will not develop like is aid yesterday it has to many things against...shear is its #1 enemy..so all you people n he gulfcoast can rest easy the most you are going to get out of this is some much needed rain..i said bonnie will not form until at least august 10...this shear and dry air wil rule the tropics for the next 2 weeks..so people no need to get all ecited about something this weekend regardless of what the models say...the models have been out shopping on this one...


Oh, wait..now it is a "short lived" storm. What happened to RIP? Jeez....


Quoting hurrkat05:
dr would you kindly let these guys know we have a short lived tropical storm on our hands because of the 30-40 knots of shear she will be going into...lol people are saying this is going to be a cat 3 lol how is it going to get pass this shear dr...please educate them...plus the dry air pocket over florida another fly in the mix...thanks...
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Thanks for the update, Doc.

The ULL should continue to shear TD3 and limit intensification as it moves WNW over the Gulf. Due to dry air ahead and persistent shear, development will be slow.

My concern is that storm system moving now through the upper Midwestern states. If TD3 continues moving WNW toward La/MS/Al landfall, it's arrival timing should coincide with the storm system moving down from the North. If timing is right, TD3 moving just South of the storm system could lead to rapid intensification of TD3 just before landfall.

On the other hand, collision of the TD3 with the frontal boundary near La/Ms/Al coast might just cause very heavy rainfall and regional flooding.
Member Since: April 28, 2008 Posts: 0 Comments: 354
As part of the oil recovery Fleet, I can attest to the need to evacuate vessels and personnel from DWH spill site. The combination
of 98-L to our SW and the ridge to our North
had winds and seas running 15-25 kts and 4-8
feet respectively. After consult with several
Forecasting experts, including NHC, the decision was made to insure our safety. Looks
like it was a good call. Regardless of the final track and intensity of TD 3, the area will have high wind and waves through at least
Sunday. Thanks Doc for your usual clarity.
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With that upper level low moving west, the shear should drop significantly thru the day allowing for Bonnie to take off.
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woo-hoo!!! I just saw a NOAA jet with the big round thing on top heading east!!
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Just an FYI to anyone expecting a MAJOR shift in any model runs.. The BAM models DID have the correct coordinates (21.6N, 74.4W) at the 12Z runs. That being said, there could still be a slight shift as models handle more organized systems better, and the steering level will be a bit deeper and more certain... However, I still wouldn't expect a South Florida landfall.. The ridge is just so strong, and the weakness that has been allowing it to inch northward disappears and the ridge grows stronger as (Future) Bonnie approaches Florida.. It will be forced almost due west as it approaches Florida, and if it doesn't gain latitude now, it will likely sweep through the keys and into the GOM... That's my observation, but time will tell.
Member Since: April 20, 2007 Posts: 7 Comments: 1482
Mike if the 06z plots are correct this will bring possibly a windy day with scattered showers to sfl. Nothing really to get overly concerned about across the mainland. The keys on the other hand could get some signficant weather from this.
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TD3 Tracks


AOI

AOI

AOI

AOI

Landfall Points

TS BUSTED FORECAST ALIBI
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Hey. 9:32. I knew I should have checked over here... anyway, I think I'll go out and buy a few gallons of water early instead of later today as I had planned. The "named storm" at 11 a.m. might spook a few pple here... lol
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Quoting MiamiHurricanes09:
03L



extremely cold cloud tops starting to take shape
Member Since: May 30, 2010 Posts: 0 Comments: 111
Meanwhile.. developing TD in the BOC.

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Thanks Storm for your blog, very informative and easy for the "want to learn weathercaster" to understand!!
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Thx Doc... interesting. Took a break and now 97L (now TD3) already took advantage of the little favorable conditions it has to organize into a TD.
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03L


Member Since: September 2, 2009 Posts: 130 Comments: 21194
Hi Dr Jeff,
thank you for the update and a new blog thread!
Could you possibly put up a new one every few hours since ths one will probably explode shortly? LOL j/k... thanks.


I see our little system is now getting the "all clear" to start developing... and another one in BOC...

I will continue to be watching as much as I can.

Be nice to each other....no name calling!
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Thanks Dr Masters
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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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