Tropical Storm Isaac Forms in Atlantic

Tropical Storm Isaac Advisory Number 3
Nws National Hurricane Center Miami Fl
500 Pm Ast Tue Aug 21 2012

Summary Of 500 Pm Ast...2100 Utc...Information
Location...15.4n 53.9w
About 500 Mi...810 Km E Of Guadeloupe
Maximum Sustained Winds...40 Mph...65 Km/H
Present Movement...W Or 275 Degrees At 17 Mph...28 Km/H
Minimum Central Pressure...1006 Mb...29.71 Inches

Watches And Warnings
Changes With This Advisory...


Summary Of Watches And Warnings In Effect...

A Tropical Storm Warning Is In Effect For...
* Martinique
* Dominica
* Guadeloupe And The Surrounding Islands...And St. Martin
* St. Kitts...Nevis...Antigua...Montserrat...Anguilla...And Barbuda
* Saba...St. Eustatius...And St. Maarten

A Tropical Storm Watch Is In Effect For...
* British Virgin Islands
* Puerto Rico...Vieques...Culebra...And The U.S. Virgin Islands

A Tropical Storm Warning Means That Tropical Storm Conditions Are
Expected Somewhere Within The Warning Area Within 36 Hours.

A Tropical Storm Watch Means That Tropical Storm Conditions Are
Possible Within The Watch Area...Generally Within 48 Hours.

Interests Elsewhere In Hispaniola And Cuba Should Monitor The
Progress Of Isaac.

Discussion And 48-Hour Outlook
At 500 Pm Ast...2100 Utc...The Center Of Tropical Storm Isaac Was
Located Near Latitude 15.4 North...Longitude 53.9 West.

Isaac Is Moving Toward The West Near 17 Mph...28 Km/H...And This General Motion Is Expected To Continue For The Next Couple Of Days.

On The Forecast Track...The Center Of Isaac Should Move Through The Central Lesser Antilles Wednesday Evening...And Emerge Over The Eastern Caribbean Sea By Thursday Morning.

Reports From An Air Force Reserve Hurricane Hunter Aircraft Indicate
That Maximum Sustained Winds Are Near 40 Mph...65 Km/H...With
Higher Gusts.

Additional Strengthening Is Forecast During The Next 48 Hours.

Tropical Storm Force Winds Extend Outward Up To 45 Miles...75 Km
To The Northeast Of The Center.

The Minimum Central Pressure Just Measured By The Hurricane Hunter Aircraft Is 1006 Mb...29.71 Inches.

Hazards Affecting Land
Wind...Tropical Storm Conditions Are Expected To Reach The Warning Area By Wednesday Afternoon...Making Outside Preparations Difficult Or Dangerous.

Rainfall...Total Rain Accumulations Of 4 To 8 Inches Are Possible
Over The Northern Windward Islands And The Leeward Islands. Total
Rain Accumulations Of 1 To 3 Inches With Maximum Amounts Of 6
Inches Are Possible Over Puerto Rico And The Virgin Islands.

Storm Surge...A Storm Surge Will Raise Water Levels By As Much As 1To 3 Feet Above Normal Tide Levels In The Northern Leeward Islands. Near The Coast...The Surge Will Be Accompanied By Dangerous Waves.

Surf...Dangerous Surf And Rip Current Conditions Will Affect The
Windward And Leeward Islands During The Next Couple Of Days.

Next Advisory
Next Intermediate Advisory...800 Pm Ast.
Next Complete Advisory...1100 Pm Ast.

Forecaster Beven


Tropical Storm Isaac Discussion Number 3
Nws National Hurricane Center Miami Fl
500 Pm Ast Tue Aug 21 2012

An Air Force Reserve Hurricane Hunter Aircraft Investigating The
Depression Reported 44-Kt Flight-Level Winds At 1000 Ft To The
Northeast Of The Center...As Well As Bias-Corrected Sfmr Surface
Winds Estimates Of 35 Kt. The Minimum Central Pressure Was Near
1005 Mb.

Based On These Data...The Depression Is Upgraded To Tropical Storm Isaac.

Despite The Upgrade...The Cyclone Remains Somewhat Disorganized ...With The Low-Level Center Partly Exposed To The North Of The Main Convective Mass.

The Low-Level Center Has Nudged Northward During The Afternoon...But The Longer Term Motion Is 275/15.

Isaac Remains South Of A Deep-Layer Subtropical Ridge That Is Forecast To Remain Intact For The Next 72 Hr...Which Should Keep The Cyclone Moving Generally Westward As Shown By The Tightly Clustered Track Model Guidance.

After That...The Global Models Continue To Forecast A Shortwave
Trough To Dig Southward Over The Southeastern U.S. And The Gulf Of Mexico...Which Is Expected To Weaken The Ridge Across Florida And The Bahamas.

This Should Allow The Cyclone To Turn West-Northwestward And Slow Down Over The North-Central Caribbean Sea And The Greater Antilles.

The Guidance Has Become Less Consistent Since The Previous Advisory.

While The Center Of The Guidance Envelope Has Changed Little... The Ecmwf Has Shifted Well To The Left Of Its Previous Forecast And Now Calls For A Westward Motion After Isaac Passes Hispaniola.

The Gfs Ensembles Have Also Shifted Westward...Although The Ensemble Mean Still Lies Near The Forecast Track.

The New Track Is Nudged A Little To The North Of The Previous Track Before 72 Hr...And Then Is Nudged A Little To The Right Thereafter.

The Track Forecast After 72 Hr Lies Near The Left Edge Of The Guidance Envelope...With Only The Ecmwf Well To The Left Of The Current Forecast. Users Are Cautioned That Five-Day Track Errors Average About 225 N Mi.

Isaac Continues To Experience Some Light Northeasterly Vertical Wind Shear...And It May Not Yet Have Fully Mixed Out The Dry Air That
Has Been Affecting It.

The Shear Is Forecast To Diminish In 12-24 Hr...Which Should Allow Some Strengthening.

That Being Said...The Gfdl And Hwrf Models Have Backed Off On Their Forecasts Of Intensification...And The Ships And Lgem Models Are Also Less Bullish.

Based On This...The New Intensity Forecast Shows A Little Less Strengthening Than The Previous Advisory.

The Intensity Forecast After 72 Hr Has Again Been Reduced Due To The Forecast Track Showing Increased Land Interaction With Hispaniola And Cuba.

Forecast Positions And Max Winds

Init 21/2100z 15.4n 53.9w 35 Kt 40 Mph
12h 22/0600z 15.6n 56.4w 40 Kt 45 Mph
24h 22/1800z 15.9n 59.8w 45 Kt 50 Mph
36h 23/0600z 16.3n 63.1w 50 Kt 60 Mph
48h 23/1800z 16.6n 66.3w 65 Kt 75 Mph
72h 24/1800z 17.0n 71.0w 75 Kt 85 Mph
96h 25/1800z 19.5n 75.0w 75 Kt 85 Mph
120h 26/1800z 21.5n 78.0w 65 Kt 75 Mph...Inland

Forecaster Beven

WTVY-TV 285 N Foster Street Dothan, AL 36303 334-792-3195
Copyright © 2002-2016 - Designed by Gray Digital Media - Powered by Clickability 166964556 -
Gray Television, Inc.