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 Patrap:
A Weak Hurricane?

...real tomato catsup Eddie?


Surprised you don't have eddye one ignore.
Member Since: September 6, 2009 Posts: 2 Comments: 3784
Product: Air Force Tropical RECCO Message (URNT11 KNHC)
Transmitted: 22nd day of the month at 16:52Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 306)
Mission Purpose: Investigate second suspect area (in the North Atlantic basin)
Mission Number: 2
Observation Number: 06

Mandatory Data...

Observation Time: Thursday, 16:48Z
Radar Capability: Yes
Aircraft Altitude: Below 10,000 meters
Coordinates: 25.5N 79.3W
Location: 61 miles (98 km) to the ESE (109°) from Miami, FL, USA.
Turbulence: None
Conditions Along Flight Route: In the clear
Pressure Altitude: 7,590 meters
Flight Level Wind: From 120° at 34 knots (From the ESE at ~ 39.1 mph)
- The above is a spot wind.
- Winds were obtained using doppler radar or inertial systems.
Flight Level Temperature: -22°C
Flight Level Dew Point: -29°C
Weather (within 30 nautical miles): Scattered clouds (trace to 4/8 cloud coverage)
400 mb Surface Altitude: 7,570 geopotential meters
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Convection doesn't seem to be wrapping around the center yet.

Member Since: July 17, 2009 Posts: 71 Comments: 27125
why isnt the HH info on my google maps updating?
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Rainfall prediction products:

This doesn't look too bad if this forecast holds. ~1.5" from today through Sat over Miami.

From HPC (Hydrometeorological Prediction Center)

2-day Precip Forecast Thur12z to Sat12z

5-day Precip forecast

I also forgot about the TRMM satellite:

TRMM satellite
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Quoting SFlwxwatcher:
I realize this comment is not directly related to TD#3 so i apologize in advance!
If any of you have an IPhone, can you recommend a good app for tracking tropical weather?
Thanks!!


2 must have apps...

1- Hurricane from Kitty Code
2- Base Velocity Radarscope
Member Since: May 14, 2006 Posts: 8 Comments: 13841
I spoke to the folks earlier and my mom wants it to hit SFL so it doesn't go into the gulf and cause a stink with the spill amongst other things. LOL...
Member Since: September 6, 2009 Posts: 2 Comments: 3784
Recon finding anything yet?
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360. MahFL
"Tropical depression races toward BP's leaky well "

races ? really ?
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311. SFlwxwatcher 4:48 PM GMT on July 22, 2010
I realize this comment is not directly related to TD#3 so i apologize in advance!
If any of you have an IPhone, can you recommend a good app for tracking tropical weather?
Thanks!!

I use Hurricane Software (the free version). Just do a search for hurricane and it will pop up.
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Quoting SFlwxwatcher:


Thanks!


Your Welcome
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Floater - Rainbow Color Infrared Loop
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Quoting MScasinojunkie:
Guys, just putting this out there, dont bite my head off - but what is the likelihood of this becoming a Cat 3 hitting LA/MS??


Very slim chance. Though a weak Hurricane in the gulf seems feasible.
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Recon's latest position:

165200 2523N 07906W 3773 08009 0414 -217 -289 118031 032 /// /// 03
Member Since: September 2, 2009 Posts: 130 Comments: 21194
i think its becoming elongaeded
Member Since: July 21, 2010 Posts: 0 Comments: 1181
I think the current forecast over the GOM is too low.
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I agree Jeff... it looks to track over S Andros- at least in the short term... track is more like 320 vice 295
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Quoting markinthedark:
dont forget ten loaves of bread

and spam!
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Guys, just putting this out there, dont bite my head off - but what is the likelihood of this becoming a Cat 3 hitting LA/MS??
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Quoting stormhunter23:


Link

Top 10 Weather apps for the Iphone


Thanks!
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Member Since: July 17, 2009 Posts: 71 Comments: 27125
Quoting Drakoen:


No the 12z runs. The 12z HWRF, GFDL, CMC, ECMWF, and UKMET.
Oh. I thought you were speaking about the plots.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting java162:


duh!!!!!!
Thanks for pointing out that was a dumb question--the latitude threw me off for a second--we all cant be perfect!
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Some dry air to the west is affecting TD3.
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Quoting SFlwxwatcher:
I realize this comment is not directly related to TD#3 so i apologize in advance!
If any of you have an IPhone, can you recommend a good app for tracking tropical weather?
Thanks!!


Link

Top 10 Weather apps for the Iphone

I have The weather Channel Max, nice little app I recommend to any one.
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Quoting Jeff9641:
TDS 3 is making it's own track right. Definite NW movement at 8 mph heading up the Bahama Chain.
For the time being I would definitely say that 03L is moving towards the NW.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting Bonz:


Most are at work and wouldn't know 'til the local news comes on at 6 tonight anyhow.


Not sure where you work but anytime a storm is possibly going to affect our area in less than 24 hours we get emails at work and sent home early if we need to make preparations. Trust me if it's named a tropical storm most people in South Florida will know before they get home tonight if they have an internet connection and email at their work.
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guys give me ur opinion byt loking at the last few fames it looks like its becoming elongaded
Member Since: July 21, 2010 Posts: 0 Comments: 1181
Quoting MiamiHurricanes09:
You mean 18z runs?


No the 12z runs. The 12z HWRF, GFDL, CMC, ECMWF, and UKMET.
Member Since: October 28, 2006 Posts: 57 Comments: 30727
337. unf97
Good afternoon everyone!

Interesting days ahead tracking TD3!
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Quoting SFlwxwatcher:
I realize this comment is not directly related to TD#3 so i apologize in advance!
If any of you have an IPhone, can you recommend a good app for tracking tropical weather?
Thanks!!


See link at upper right on this page you are looking at.

ie: http://i.wund.com/
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Quoting scott39:
for 97L ?

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It has been raining here since 4:30 this a.m. thanks to 98L. ASOS shows 1.76" here at the scareport. Forget the 10"+ we've had the last month thanks to Alex and that "trough depression". Now here comes Bonnie. Oi vey!

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAKE CHARLES LA
1043 AM CDT THU JUL 22 2010
UPDATED POP/WX GRIDS FOR THIS MORNING BASED ON LATEST RADAR TRENDS AS DRIER AIR SEEN ADVANCING FROM THE EAST IS BEING BEATEN
OUT BY PLENTIFUL TROPICAL MOISTURE FROM THE WAVE OVER THE WRN GULF/BAY OF CAMPECHE. AM HOLDING ONTO FAITH THAT THE DRIER AIR
WILL TAKE OVER BY AFTERNOON...OTHERWISE MAY HAVE TO UPDATE AGAIN TO BUMP UP POPS LATER.
UPDATE OUT SHORTLY.
...
THE HIGHEST RAIN CHANCES ARE EXPECTED SUNDAY AND MONDAY TIMEFRAME. THIS IS IN RESPECT TO THE TROPICAL WAVE THAT HAS BEEN MAKING HEADLINES NEAR HISPANIOLA THIS WEEK. PER NHC TROPICAL WEATHER OUTLOOK...OUR CURRENT THINKING IS THE LOCAL IMPACT WILL BE MAINLY ENHANCED RAIN CHANCES. WIND SHEAR FROM THE UPPER LEVEL LOW NEAR SOUTH FLORIDA IS CURRENTLY HINDERING DEVELOPMENT OF THIS SYSTEM...AND THAT MAY HOLD TRUE AS IT MOVES WEST-NORTHWEST ACROSS THE GULF THIS WEEKEND.

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Quoting ElConando:


Got it, well enjoy your flight anyways.


Thanks
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Quoting Drakoen:


Possible. I want to see what the 12z runs say before I forecast possible landfall area.
You mean 18z runs?
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting btwntx08:
looks like 98L is a td already

Should be AT LEAST 60%.
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Quoting Drakoen:
Latest recon position

25.850N 79.800W
for 97L ?
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If there is any kind of NW movement it looks to only be temporary the ridge looks to build back in...I dont see this hitting the Florida Mainland...
Member Since: August 29, 2006 Posts: 22 Comments: 1352
Quoting cchsweatherman:
In performing my analysis this morning based on satellite imagery, computer model data, and steering pattern, I'm quite confident in a forecast that would see a moderate tropical storm making landfall tomorrow afternoon in Southern Miami Dade county.


Possible. I want to see what the 12z runs say before I forecast possible landfall area.
Member Since: October 28, 2006 Posts: 57 Comments: 30727
Question:

Does the weakness to the North provide a way for the ULL to get farther out in front of the storm?

It seems to me that the weakness will effectively slow the westward motion of the storm some, while the ULL is too far west to feel the affects and should just charge around the high.

Does this make sense? And if so, does that change the intensity forecast at all?

Thanks!
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Nice job StormW
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Quoting ElConando:


Just so people don't freak out he means the HH plane.


LOL, sad isn't it.
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322. Bonz
Quoting 69Viking:


We'll know for sure whenever the Hurricane Hunter flight gets out there today. I'm kind of surprised they waited so long with it's proximity to South Florida and some major populations that need to know the facts of what could be on their doorstep by tomorrow!


Most are at work and wouldn't know 'til the local news comes on at 6 tonight anyhow.
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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.