Tropical Storm Isaac Advisory Number 16
Nws National Hurricane Center Miami Fl
1100 Pm Edt Fri Aug 24 2012

Summary Of 1100 Pm Edt...0300 Utc...Information
-----------------------------------------------
Location...17.7n 72.5w
About 65 Mi...100 Km Ssw Of Port Au Prince Haiti
About 245 Mi...395 Km Se Of Guantanamo Cuba
Maximum Sustained Winds...70 Mph...110 Km/H
Present Movement...Nw Or 310 Degrees At 14 Mph...22 Km/H
Minimum Central Pressure...990 Mb...29.23 Inches

Watches And Warnings
--------------------
Changes With This Advisory...

A Hurricane Watch And A Tropical Storm Warning Have Been Issued For All Of The Florida Keys...Including Florida Bay...And For The Coast
Of The Southern Florida Peninsula From Ocean Reef On The East Coast Westward To Bonita Beach On The West Coast.

A Tropical Storm Warning Has Been Issued For The Southeast Florida Coast From North Of Ocean Reef Northward To Jupiter Inlet...And For Lake Okeechobee.

The Government Of The Bahamas Has Issued A Tropical Storm Warning For All Of The Northwestern Bahamas.

A Tropical Storm Watch Has Been Issued For The East-Central Florida Coast From North Of Jupiter Inlet To Sebastian Inlet.

The Cayman Islands Meteorological Service Has Issued A Tropical
Storm Watch For The Cayman Islands.

Summary Of Watches And Warnings In Effect...

A Hurricane Watch Is In Effect For...
* Haiti
* Florida Keys Including The Dry Tortugas
* Florida Bay
* The Florida East Coast From Ocean Reef Southward
* The Florida West Coast From Bonita Beach Southward

A Tropical Storm Warning Is In Effect For...
* Dominican Republic
* Haiti
* Cuban Provinces Of Ciego De Avila...Sancti Spiritus...Villa
Clara...Camaguey...Las Tunas...Granma...Holguin...Santiago De
Cuba...And Guantanamo
* The Bahamas
* Turks And Caicos Islands
* The Florida Keys Including The Dry Tortugas
* The Florida East Coast From Jupiter Inlet Southward
* The Florida West Coast From Bonita Beach Southward
* Florida Bay And Lake Okeechobee

A Tropical Storm Watch Is In Effect For...
* Cuban Provinces Of Matanzas And Cienfuegos
* Jamaica
* The Florida East Coast North Of Jupiter Inlet To Sebastian Inlet

A Hurricane Watch Means That Hurricane Conditions Are Possible
Within The Watch Area...In This Case Within The Next 24 To 36 Hours.

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 In The Remainder Of Cuba And The Remainder Of The Florida Peninsula Should Monitor The Progress Of Isaac.

Discussion And 48-Hour Outlook
------------------------------
At 1100 Pm Edt...0300 Utc...The Center Of Tropical Storm Isaac Was
Located Near Latitude 17.7 North...Longitude 72.5 West.

Isaac Is Moving Toward The Northwest Near 14 Mph...22 Km/H...But Is Expected To Resume A Faster Forward Speed Toward The Northwest Tonight Through Sunday.

On The Forecast Track...The Center Of Isaac Should Make Landfall In Haiti Tonight...Move Near Or Over Southeastern Cuba On Saturday... Move Near Or Over Central Cuba Saturday Night...And Approach The Florida Keys On Sunday.

Maximum Sustained Winds Are Near 70 Mph...110 Km/H...With Higher
Gusts. Little Change In Strength Is Likely Before Landfall...
Followed By Some Weakening As The Center Crosses Haiti And
Southeastern Cuba.

Tropical-Storm-Force Winds Extend Outward Up To 230 Miles...
370 Km...Mainly Northwest And Northeast Of The Center.

Estimated Minimum Central Pressure Is 990 Mb...29.23 Inches.

Hazards Affecting Land
----------------------
Rainfall...Total Rainfall Accumulations Of 8 To 12 Inches...With
Maximum Amounts Of 20 Inches...Are Possible Over Hispaniola.

These Rains Could Cause Life-Threatening Flash Floods And Mud Slides.

Total Rain Accumulations Of 4 To 8 Inches...With Maximum Amounts Of 12 Inches...Are Possible Across Jamaica...The Central And Eastern Portions Of Cuba...The Florida Keys And The Southern Peninsula Of Florida. Total Rain Accumulations Of 2 To 4 Inches Are Possible Over The Central And Southeastern Bahamas.

Wind...Tropical Storm Conditions Are Spreading Over Portions Of The
Dominican Republic And Haiti...With Hurricane Conditions Possible In Haiti. Tropical Storm Conditions Are Expected Over The Southeastern Bahamas And The Turks And Caicos Islands Tonight ...Are Expected Over The Central Bahamas By Saturday Or Saturday Night...And Are Expected Over The Northwestern Bahamas By Sunday. Tropical Storm Conditions Are Expected Over Eastern Cuba By Tonight And Over Central Cuba By Saturday Or Saturday Night.

Tropical Storm Conditions Are Expected To Reach Northwestern Cuba And The Northwestern Bahamas By Saturday Night Or Sunday...And South Florida And The Florida Keys On Sunday.

Hurricane Conditions Are Possible Over The Florida Keys...Florida Bay...And The Southernmost Florida Peninsula By Sunday Evening.

Storm Surge...The Combination Of A Storm Surge And The Tide Will
Cause Normally Dry Areas Near The Coast To Be Flooded By Rising
Waters. The Water Could Reach The Following Depths Above Ground
If The Peak Surge Occurs At The Time Of High Tide...

South Florida Including The Florida Keys...2 To 4 Ft
Hispaniola And Eastern Cuba...1 To 3 Ft
The Bahamas And Turks And Caicos...1 To 3 Ft

The Deepest Water Will Occur Along The Immediate Coast In Areas Of Onshore Flow. Surge-Related Flooding Depends On The Relative Timing Of The Surge And The Tidal Cycle...And Can Vary Greatly Over Short Distances.

Near The Coast...The Surge Will Be Accompanied By Dangerous Waves.

Surf...Dangerous Surf And Rip Current Conditions Will Affect Puerto
Rico...Hispaniola...The Bahamas...The Turks And Caicos...Eastern
And Central Cuba...And The East Coast Of Florida And The Florida
Keys During The Next Couple Of Days.

Next Advisory
-------------
Next Intermediate Advisory...200 Am Edt.
Next Complete Advisory...500 Am Edt.

Forecaster Stewart
_____________________________________________________

Tropical Storm Isaac Discussion Number 16
Nws National Hurricane Center Miami Fl
1100 Pm Edt Fri Aug 24 2012

Satellite Imagery And Reconnaissance Aircraft Data Indicate That The
Circulation And Convective Organization Of Isaac Has Continued To
Improve Since The Previous Advisory. Infrared And Microwave
Satellite Imagery Suggest That An Eye Is Forming...And This Is The
Basis For Increasing The Intensity To 60 Kt.

The Initial Motion Estimate Is 315/12 Based On Recon And Microwave
Fixes. Although The Track Forcast Was Adjusted Slightly To The
Right Through 48 Hours...No Other Significant Changes Were Made To The Previous Advisory Track.

Recent Upper-Air Data And Noaa G-Iv Aircraft Dropsonde Data Indicate The Trough That Has Created The Break In The Subtropical Ridge Across Florida Has Shifted To A Position Just East Of The Florida Peninsula. The 18z Gfs Model... Which Shifted To The Right Of Its 12z Track...Captured This Farther East Position...Whereas The 18z Ukmet And 12z Ecmwf Kept The Trough Across The Western Florida Peninsula Valid At 00z This Evening.

Based On The Gfs Verifying Better Than The Other Models At 00z This
Evening...The Nhc Track Has Been Shifted A Little To The Right.

After 48 Hours...The Ridge Is Expected To Build Back Westward
Across Florida And Keeping Isaac On A Mostly Northwestward Heading Across The Eastern And North-Central Gulf Mexico. The Official Forecast Track Is Close To The Consensus Models Tvca And Tv15 Through 48 Hours...And Then Is A Little To The Right Of Those
Models After That.

With The Inner Core Convection Improving...There Is Still The
Possibility That Isaac Could Reach Hurricane Intensity Before
Reaching Haiti Tonight. The Intensity From 12-24 Hours Will Be
Determined By The Amount Of Land Interaction With Haiti And Eastern
Cuba.

After That...The Slight Eastward Shift In The Forecast Track Is Enough To Place Isaac Over Water Longer Than What Was Indicated In The Previous Intensity Forecast Required An Increase In The Intensity Forecast. The Eastward Track Shift And A Larger Initial And Forecast Wind Field To The North Are What Necessitated The Changes In The Watches And Warnings For Florida.

It Is Important Not To Focus On The Exact Track Due To The
Uncertainties In The Forecast And The Fact That Isaac Has A Large
Area Of Tropical-Storm-Force Winds Associated With It.

Forecast Positions And Max Winds

Init 25/0300z 17.7n 72.5w 60 Kt 70 Mph
12h 25/1200z 19.4n 74.1w 50 Kt 60 Mph
24h 26/0000z 21.7n 76.7w 50 Kt 60 Mph
36h 26/1200z 23.4n 79.4w 55 Kt 65 Mph
48h 27/0000z 24.9n 81.6w 60 Kt 70 Mph
72h 28/0000z 27.1n 84.6w 70 Kt 80 Mph
96h 29/0000z 30.0n 86.5w 80 Kt 90 Mph
120h 30/0000z 32.5n 86.5w 40 Kt 45 Mph...Inland

Forecaster Stewart

_____________________________________________________

Oscar's remarks...

In the last 24 hours there has been more weather model (I.e., computer guidance forecasting) flip flopping than in any political race I have ever seen!

24 hours ago, one of the two best models (ECMWF, or European) had Issac headed to the Louisiana / Texas border.

Now it has Isaac headed to the Mobile area in the last two computer runs (the new Saturday morning runs have not been released yet).

The other tried and true model, the GFS (which did a better job on Tropical Storm Debby than the ECMWF did) had Issac moving between Ft. Walton Beach and Apalachicola.

Now, the GFS has Isaac trending toward Mobile also.

I won't go into all the technical details (not enough time and nearly impossible to do it in less than several thousand words!), but TWO things stick out.

First, we should know by Sunday afternoon if Option 1 will play out - i.e., the move north into southern Florida and then up the east coast (Atlantic) of northern Florida.

Second, the Gulf of Mexico Option - if Isaac goes the Gulf route, then TWO more options appear:

Gulf OPTION 1 - does Isaac trend more NNW toward the panhandle (and even then, is it Ft. Walton Beach or east of Apalachicola?) or;

Gulf OPTION 2 - does the Alabama / Mississippi route espoused by the two best performing weather models this season prove true?

Even before Sunday afternoon arrives, will the weather models find something different? Probably.

Stay informed through the weekend for the latest.