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 MrJoeBlow:


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.


XTRP is not a model-only a straight line reference point- if you will. Or as the crow flies. This is coming from a newbie person.
Someone will correct me if my thinking is not close.
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Hopefully this works.
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Looking at visible loops it seems to me that 03L is still moving towards the NW, maybe a bit quicker than before.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
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.
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1467. angiest
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.


CLIP is not a model either. :) (Well, not a sophisticated one at least) It basically looks at where storms in that area have gone historically this time of year, and assumes no other influences. They use it as a way of verifying the other sophisticated models.
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Does it look just terrific, no, but better than this morning? I think so.
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1461. 900MB
Actually looks better to me since there is convection on the West side of the storm.
Is recon over? What's the recap on recon, or reconcap?
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AOI
Member Since: October 1, 2007 Posts: 81 Comments: 26511
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.
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Quoting louisianaboy444:
Does the 4PM Advisory come out at 4PM Eastern Time?


4PM Central, 5PM EST
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Quoting dolphingalrules:


do you really think that bonnie shifted north..
yes it has i expect the track to shift north
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Does the 4PM Advisory come out at 4PM Eastern Time?
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1453. IKE
Quoting cheetaking:
And the cycle continues... now we have everyone saying "it's dying! It better get organized fast!" since it's losing storms, and then tonight as soon as the storms flare back up it will be another "OMG rapid intensification!"

It seems like I see this on just about every single up-down cycle of thunderstorm activity.


That's true. You see on every system with every updated image.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting Dropsonde:
I have run some loops and I have no idea what anyone is talking about who says that this storm looks poor as compared to earlier in the day. It has gained convection over its center, which was exposed earlier today... those high cloud tops that showed up this morning were displaced to the east of the true center. It has taken on a cyclonic structure instead of the "structure" it had earlier of the partially exposed LLC and blob of convection displaced to the east. The convection is building right where it needs to be now, around 22.4N 75W, which is over the center... not in some easterly blob that would only steal energy away.
I agree
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Quoting Seflhurricane:
looks like based on the current movement the forecast track will be shifted north looks like a Miami-Dade county Direct hit and exit near bonita beach on the florida west coast, i really dont think we will have winds above 60 MPH and maybe in gusts .


do you really think that bonnie shifted north..
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Tropical Depression 03L




--------------------------------------------------------------------------------
UW-CIMSS Automated Satellite-Based
Advanced Dvorak Technique (ADT)
Version 8.1.1
Tropical Cyclone Intensity Estimation Algorithm


Current Intensity Analysis




UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 22 JUL 2010 Time : 184500 UTC
Lat : 22:12:08 N Lon : 75:43:04 W


CI# /Pressure/ Vmax
2.6 /1004.0mb/ 37.0kt


Final T# Adj T# Raw T#
2.6 2.7 2.7

Latitude bias adjustment to MSLP : +0.0mb

Center Temp : +17.2C Cloud Region Temp : -3.9C

Scene Type : SHEAR (0.38^ TO DG)

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : OFF
Rapid Dissipation Flag : OFF
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1449. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15626
looking at info from recon TD 3 can be upgraded if the NHC wants too plenty of 40 MPh Winds to the NW of the center based on goggle earth
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Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 22nd day of the month at 19:43Z
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: 14
A. Time of Center Fix: 22nd day of the month at 19:20:30Z
B. Center Fix Coordinates: 22°25'N 75°07'W (22.4167N 75.1167W)
B. Center Fix Location: 171 miles (276 km) to the NNE (16°) from Santiago de Cuba, Cuba.
C. Minimum Height at Standard Level: Not Available
D. Estimated (by SFMR or visually) Maximum Surface Wind: 29kts (~ 33.4mph)
E. Location of the Estimated Maximum Surface Wind: 22 nautical miles (25 statute miles) to the WNW (296°) of center fix
F. Maximum Flight Level Wind Inbound: From 24° at 33kts (From the NNE at ~ 38.0mph)
G. Location of Maximum Flight Level Wind Inbound: 24 nautical miles (28 statute miles) to the WNW (297°) of center fix
H. Minimum Sea Level Pressure: 1006mb (29.71 inHg) - Extrapolated
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 24°C (75°F) at a pressure alt. of 183m (600ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 25°C (77°F) at a pressure alt. of 217m (712ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 21°C (70°F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Not Available
M. Eye Shape: Not Available
N. Fix Determined By: Penetration, Radar, Wind, Pressure and Temperature
N. Fix Levels (sfc and flt lvl centers are within 5nm of each other): Surface and 1,500 feet
O. Navigation Fix Accuracy: 0.03 nautical miles
O. Meteorological Accuracy: 0 nautical miles
Remarks Section:
Maximum Flight Level Wind: 33kts (~ 38.0mph) in the northwest quadrant at 19:12:20Z
Sea Level Pressure Extrapolation From: Below 1,500 feet
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting tropicfreak:



are the hh in 98L too?
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Quoting sammywammybamy:
THIS JUST IN

FLOOD WATCH HAS BEEN ISSUED FOR SOUTH FLORIDA

JUST CAME OVER THE EMERGANCY BRODCASTING SYSTEM

FLOOD WATCH
NATIONAL WEATHER SERVICE MIAMI FL
345 PM EDT THU JUL 22 2010

...FLOOD WATCH IN EFFECT FOR ALL OF SOUTH FLORIDA FROM MIDNIGHT
TO 5 PM EDT FRIDAY...

FLZ063-066>075-168-172>174-232100-
/O.NEW.KMFL.FA.A.0004.100723T0400Z-100723T2100Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
GLADES-HENDRY-INLAND PALM BEACH-METRO PALM BEACH-COASTAL COLLIER-
INLAND COLLIER-INLAND BROWARD-METRO BROWARD-INLAND MIAMI DADE-
METRO MIAMI DADE-MAINLAND MONROE-COASTAL PALM BEACH-
COASTAL BROWARD-COASTAL MIAMI DADE-FAR SOUTH MIAMI DADE-
345 PM EDT THU JUL 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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Member Since: September 2, 2009 Posts: 130 Comments: 21091
And the cycle continues... now we have everyone saying "it's dying! It better get organized fast!" since it's losing storms, and then tonight as soon as the storms flare back up it will be another "OMG rapid intensification!"

It seems like I see this on just about every single up-down cycle of thunderstorm activity.
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Quoting angiest:


XTRP is eXTRaPolation of the last two center fixes. They just connect them with a straight line and then extend the line out through 5 days with time points based on current forward speed.


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


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.


He's a troll, a moron and a disgrace to himself. Hopefully, people just start ignoring him.
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Quoting Dropsonde:
I have run some loops and I have no idea what anyone is talking about who says that this storm looks poor as compared to earlier in the day. It has gained convection over its center, which was exposed earlier today... those high cloud tops that showed up this morning were displaced to the east of the true center. It has taken on a cyclonic structure instead of the "structure" it had earlier of the partially exposed LLC and blob of convection displaced to the east. The convection is building right where it needs to be now, around 22.4N 75W, which is over the center... not in some easterly blob that would only steal energy away

finnaly some1 smart
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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.


Oh, me too. Mainly i just listen. It's the people asking if it is going to cancel Juniors pool party tomorrow...etc
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at lest the TDs and TS are looking way better the last year
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Quoting hurrkat05:
LEO I THINK YOU NEED TO LEARN HOW TO READ SHEAR MAPS...


You should know how to read shear tendency maps!
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Quoting chrisdscane:


lol r u blind she finally has significant showers on the west and hurricane hunters r reporting ts winds lol huhhhh


Where do you see TS winds? I'm watching the dropsondes, and I havent seen them.
Member Since: October 30, 2007 Posts: 0 Comments: 270
look for a WSW movement down the road folks
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Why do they call it the XTRAP model if it is not a model?
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MrJoeBlow.. XTRP is not a model, it is the current movement of the storm.
Member Since: September 18, 2007 Posts: 0 Comments: 1073
Quoting Greyelf:


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


That is so funny! I hear Patrap too...lol
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Quoting Greyelf:


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


yeah, i know....just wondering if it is us or sw la more in the line of fire...
Member Since: July 2, 2009 Posts: 0 Comments: 2811
1427. angiest
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.


XTRP is eXTRaPolation of the last two center fixes. They just connect them with a straight line and then extend the line out through 5 days with time points based on current forward speed.
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Quoting NoNamePub:
Whats the Navy Site . . . Lost all my favorites when I moved!


Link
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1425. JamesSA
Quoting Hurricanes101:


I am not joking with you, it is not a forecast model
But when a hurricane is moving in a straight line XTRP is ALWAYS right. ;-)
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1402....no he's not joking...that is a line that says..."This is where it'll go if it keeps moving in this EXACT direction the duration of it's life".
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I have run some loops and I have no idea what anyone is talking about who says that this storm looks poor as compared to earlier in the day. It has gained convection over its center, which was exposed earlier today... those high cloud tops that showed up this morning were displaced to the east of the true center. It has taken on a cyclonic structure instead of the "structure" it had earlier of the partially exposed LLC and blob of convection displaced to the east. The convection is building right where it needs to be now, around 22.4N 75W, which is over the center... not in some easterly blob that would only steal energy away.
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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.