Tropical Depression Isaac:

[srainhoutx]

Per usual many of us get caught up looking at long range models and tend to overlook real time obs.

Isaac isn't the healthiest looking system at the moment. Interaction with Haiti and Eastern Cuba has taken a toll where it looked for a time last night it was going to retain much of its organization.

The attachment 08252012_1625_goes13_x_ir1km_09LISAAC_50kts-998mb-197N-737W_80pc.jpg is no longer available

[Scott747]

Of note is that area in the Keys that you see in the satellites that popped up last night and has gained notice. Not sure the impacts it will have on Isaac but you hear chatter from some folks out there trying to give reasoning as why that feature would induce a more short term heading towards S Fla/Upper Key or perhaps would also abate any strengthening.

Key West disco -

DISCUSSION... LATEST MID AND UPPER AIR IR IMAGERY OVERLAID WITH
STREAMLINE ANALYSIS DEPICT A SLOWLY ELONGATING NORTH TO SOUTH
ORIENTED TROUGH AXIS ASSOCIATED WITH VERY DRY AIR THAT IS GRADUALLY
PINCHING SOUTHWARD. THE LATEST SATELLITE PRECIPITATION ANALYSIS
FROM NESDIS SHOWS A VORT MAX AND LARGE SCALE LIFT IS CURRENTLY OVER
THE FLORIDA STRAITS...KEYS AND SOUTH FLORIDA...AND IS RESPONSIBLE
FOR NUMEROUS SHOWERS AND SCATTERED THUNDERSTORMS ACROSS THE AREA.
GIVEN SOME REMAINING DRY AIR...STRONG TO SEVERE WIND GUSTS ARE
OCCURRING WITHIN SOME OF THESE SHOWERS AND STORMS. OF COURSE...TO
THE SOUTHEAST OF THAT IS OF COURSE TROPICAL STORM ISAAC. CURRENTLY
THE MAJORITY OF THE THUNDERSTORMS ASSOCIATED WITH ITS VERY LARGE
CIRCULATION ARE LOCATED ACROSS HISPANIOLA AND THE NORTH CENTRAL
CARIBBEAN SEA...WHICH IS DETACHED TO THE SOUTH FROM THIS TROPICAL
SYSTEMS MAIN LOW TO MID LEVEL CENTER...WHICH IS NOW OVER THE
WINDWARD PASSAGE APPROACHING MOUNTAINOUS GUANTANAMO PROVINCE IN
EASTERN CUBA.

[srainhoutx]

I think we can stop the 'who is safe and who is not' banter. Clearly as has been stated on this very forum by Gene, Jeff as well as others, there are a lot of uncertainties and those have been posted repeatedly. Let's get back to the storm at hand and leave the 'Monday Morning quarterbacking' for another time and place...

[biggerbyte]

In essence, while impacts of Isaac west of New Orleans appear unlikely at this time ... there is enough uncertainty beyond Day 3 to warrant paying attention.

I'm not sure I would use unlikely and uncertain in the same sentence. My comment about anything west of NOLA only pertains to the official NHC track for "today". I want to make that very, very clear folks. No one is certain what is going to happen tomorrow and beyond. There are too many possibilities with this system right now, so each day you may get a completely different outlook. Every one in the gulf region should realize this and prepare for those possible track alterations. Again, best bet is to pay attention to our conversations in this forum. But from day to day, to keep every one on the same page, use the official NHC track. Model flip flopping will drive you crazy. Again, folks, if you live in LA, or Texas, check back daily until Isaac is dead and gone.

[jasons2k]

Yes, at one time Katrina into the FL Panhandle seemed like a sure bet...

Issac sure looks ragged* today. A humble reminder of how fragile these systems are. It will be very interesting to see how the next day or so unfolds with the interaction with Cuba....lots of possibilities on the table, even in the short term.

*Edit "ragged" not "raged"

[biggerbyte]

I think we can stop the 'who is safe and who is not' banter. Clearly as has been stated on this very forum by Gene, Jeff as well as others, there are a lot of uncertainties and those have been posted repeatedly. Let's get back to the storm at hand and leave the 'Monday Morning quarterbacking' for another time and place...

LOL!

Who is quarterbacking? Calm down, dude.

Totally agree! We've all made the point clear that there is much uncertainty. Folks, that is our stand.

[wxman57]

All agree on high pressure holding firm over Texas next week with another center east of the U.S. Coast. Weakness is between SE LA and the eastern FL Panhandle. My initial estimate of the western FL Panhandle for final landfall looks good for now. Don't see any threat to Houston.

Wxman57, do you still agree that the high pressure will hold firm over Texas and that you still don't see any threat to Houston?

Pretty strong ridge next Tuesday over the 4-corners area to Texas should keep Isaac well to our east. I'm certainly not going out to buy extra gas for my generator. Not worried in the least.

[srainhoutx]

12Z GFS Ensmble members:

[sambucol]

All agree on high pressure holding firm over Texas next week with another center east of the U.S. Coast. Weakness is between SE LA and the eastern FL Panhandle. My initial estimate of the western FL Panhandle for final landfall looks good for now. Don't see any threat to Houston.

Wxman57, do you still agree that the high pressure will hold firm over Texas and that you still don't see any threat to Houston?

Pretty strong ridge next Tuesday over the 4-corners area to Texas should keep Isaac well to our east. I'm certainly not going out to buy extra gas for my generator. Not worried in the least.

Great news! Thanks!!

[srainhoutx]

BULLETIN
TROPICAL STORM ISAAC INTERMEDIATE ADVISORY NUMBER 18A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
200 PM EDT SAT AUG 25 2012

...CENTER OF ISAAC NOW NEAR THE NORTH COAST OF EASTERN CUBA...


SUMMARY OF 200 PM EDT...1800 UTC...INFORMATION
----------------------------------------------
LOCATION...20.8N 75.3W
ABOUT 40 MI...65 KM N OF GUANTANAMO CUBA
ABOUT 325 MI...525 KM SSE OF NASSAU
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 17 MPH...28 KM/H
MINIMUM CENTRAL PRESSURE...1000 MB...29.53 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A HURRICANE WARNING IS IN EFFECT FOR...
* THE FLORIDA KEYS INCLUDING THE DRY TORTUGAS
* THE WEST COAST OF FLORIDA FROM BONITA BEACH SOUTHWARD TO OCEAN
REEF
* FLORIDA BAY

A HURRICANE WATCH IS IN EFFECT FOR...
* HAITI
* THE FLORIDA EAST COAST FROM GOLDEN BEACH SOUTHWARD TO OCEAN REEF
* ANDROS ISLAND IN THE BAHAMAS

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 EAST COAST FROM SEBASTIAN INLET SOUTHWARD TO OCEAN
REEF
* LAKE OKEECHOBEE

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* CUBAN PROVINCES OF MATANZAS AND CIENFUEGOS
* THE FLORIDA EAST COAST NORTH OF SEBASTIAN INLET TO FLAGLER BEACH
* THE FLORIDA WEST COAST NORTH OF BONITA BEACH TO TARPON SPRINGS

A HURRICANE WARNING MEANS THAT HURRICANE CONDITIONS ARE EXPECTED
SOMEWHERE WITHIN THE WARNING AREA. A WARNING IS TYPICALLY ISSUED
36 HOURS BEFORE THE ANTICIPATED FIRST OCCURRENCE OF TROPICAL STORM
FORCE WINDS...CONDITIONS THAT MAKE OUTSIDE PREPARATIONS DIFFICULT
OR DANGEROUS. PREPARATIONS TO PROTECT LIFE AND PROPERTY SHOULD BE
RUSHED TO COMPLETION.

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 FLORIDA
SHOULD MONITOR THE PROGRESS OF ISAAC.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED
STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE
MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE
FORECAST OFFICE. FOR STORM INFORMATION SPECIFIC TO YOUR AREA OUTSIDE
THE UNITED STATES...PLEASE MONITOR PRODUCTS ISSUED BY YOUR NATIONAL
METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 200 PM EDT...1800 UTC...THE CENTER OF TROPICAL STORM ISAAC WAS
LOCATED NEAR LATITUDE 20.8 NORTH...LONGITUDE 75.3 WEST. ISAAC IS
MOVING TOWARD THE NORTHWEST NEAR 17 MPH...28 KM/H. A GENERAL
NORTHWESTWARD MOTION IS EXPECTED DURING THE NEXT 48 HOURS. ON THE
FORECAST TRACK...THE CENTER OF ISAAC SHOULD MOVE NEAR OR OVER
EASTERN CUBA THIS AFTERNOON...NEAR OR OVER CENTRAL CUBA TONIGHT...
AND MOVE NEAR OR OVER THE FLORIDA KEYS AND THE SOUTHERN FLORIDA
PENINSULA SUNDAY OR SUNDAY NIGHT.

MAXIMUM SUSTAINED WINDS ARE NEAR 60 MPH...95 KM/H...WITH HIGHER
GUSTS. LITTLE CHANGE IN STRENGTH IS EXPECTED THIS AFTERNOON. SOME
STRENGTHENING IS FORECAST TONIGHT THROUGH MONDAY...AND ISAAC IS
EXPECTED TO BECOME A HURRICANE SUNDAY OR SUNDAY NIGHT.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 205 MILES...335 KM
FROM THE CENTER.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000 MB...29.53 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 SOUTHERN BAHAMAS.

WIND...TROPICAL STORM CONDITIONS ARE OCCURRING OVER PORTIONS OF THE
DOMINICAN REPUBLIC AND HAITI...EASTERN CUBA...THE SOUTHEASTERN
BAHAMAS AND THE TURKS AND CAICOS ISLANDS. TROPICAL STORM CONDITIONS
ARE EXPECTED OVER THE CENTRAL BAHAMAS LATER TODAY AND TONIGHT...AND
OVER THE NORTHWESTERN BAHAMAS BY SUNDAY MORNING. HURRICANE
CONDITIONS ARE POSSIBLE ON ANDROS ISLAND ON SUNDAY. TROPICAL STORM
CONDITIONS ARE EXPECTED OVER CENTRAL CUBA BY LATER TODAY AND
TONIGHT. TROPICAL STORM CONDITIONS ARE EXPECTED TO REACH
NORTHWESTERN CUBA AND THE NORTHWESTERN BAHAMAS BY TONIGHT OR
SUNDAY.

HURRICANE CONDITIONS ARE EXPECTED IN THE HURRICANE WARNING AREA IN
SOUTHWEST FLORIDA AND THE FLORIDA KEYS ON SUNDAY...WITH TROPICAL
STORM CONDITIONS EXPECTED BY EARLY SUNDAY. HURRICANE CONDITIONS ARE
POSSIBLE IN THE HURRICANE WATCH AREA IN SOUTHEAST FLORIDA ON
SUNDAY...WITH TROPICAL STORM CONDITIONS EXPECTED IN THE TROPICAL
STORM WARNING AREA IN FLORIDA BY EARLY SUNDAY. TROPICAL STORM
CONDITIONS ARE POSSIBLE IN THE TROPICAL STORM WATCH AREA IN FLORIDA
BY SUNDAY NIGHT OR MONDAY.

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...

SOUTHWEST FLORIDA COAST...5 TO 7 FT
SOUTHEAST FLORIDA COAST AND THE FLORIDA KEYS...1 TO 3 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. FOR INFORMATION SPECIFIC TO YOUR AREA...PLEASE SEE
PRODUCTS ISSUED BY YOUR LOCAL WEATHER SERVICE OFFICE. NEAR THE
COAST...THE SURGE WILL BE ACCOMPANIED BY DANGEROUS WAVES.

SURF...DANGEROUS SURF AND RIP CURRENT CONDITIONS WILL AFFECT
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. PLEASE CONSULT PRODUCTS FROM YOUR
LOCAL WEATHER OFFICE FOR MORE INFORMATION.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...500 PM EDT.

$$
FORECASTER BEVEN

[srainhoutx]

12Z Euro suggest near Ft Walton Beach/Destin area:

The attachment 08252012 12Z Euro NATL_GRD_850mb_096.gif is no longer available

[srainhoutx]

12Z UKMet suggests Florida Panhandle landfall:

[srainhoutx]

MODEL DIAGNOSTIC DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
239 PM EDT SAT AUG 25 2012

VALID AUG 25/1200 UTC THRU AUG 29/0000 UTC


...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...


FINAL 12Z MODEL EVALUATION INCLUDING THE ECMWF

INITIALIZATION ERRORS DO NOT APPEAR TO SIGNIFICANTLY IMPACT THE
LARGE SCALE FORECAST.


...TROPICAL STORM ISAAC...

MODEL GUIDANCE CONTINUES TO INDICATE A TRACK TOWARD THE GULF COAST
OF THE U.S. IN ABOUT 4 DAYS. MID LATITUDE TROUGHING WILL WEAKEN
FROM THE NORTHEAST GULF UP THE EAST COAST OF THE U.S...WHICH
LEAVES ROOM FOR THE TROPICAL CYCLONE TO BE DRAWN UP TOWARD AND
EVENTUALLY INTERACT WITH A BAROCLINIC TROUGH THAT DIGS INTO THE
OHIO VALLEY TO LOWER MISSISSIPPI VALLEY BY THAT TIME. THERE IS
STILL CONSIDERABLE UNCERTAINTY ON THE SUB-SYNOPTIC
SCALE...HOWEVER...AND MODEL RUN TO RUN DIFFERENCES WITH RESPECT TO
THE EXACT TRACK WILL CONTINUE.

THE 12Z UKMET AND ECMWF ARE VERY CLOSE TO THE OFFICIAL TRACK. ONE
OF THE MORE VARIABLE MODELS HAS BEEN THE NAM...BUT OVER THE PAST
FOUR CYCLES IT HAS MOVED ITS TRACK FROM A POSITION WELL LEFT OF
THE OFFICIAL NATIONAL HURRICANE CENTER TRACK...TOWARD SOMETHING
THAT IS BETTER ALIGNED WITH THE OFFICIAL TRACK. THE 12Z NAM
DOES...HOWEVER...BEGIN ITS RUN WITH A NORTHWARD JOG THAT SPREADS
HEAVY RAIN A LITTLE FARTHER NORTHWARD IN FLORIDA ON SUNDAY
COMPARED TO CONSENSUS. THE 12Z GFS REMAINED CONSISTENT WITH ITSELF
AND THE OFFICIAL TRACK THROUGH MONDAY MORNING...BUT IT THEN LEANS
FARTHER WEST INTO THE GULF AFTER 27/12Z...WHICH IS AN IDEA THAT
HAD SUPPORT FROM MANY OF THE 00Z ECMWF ENSEMBLE MEMBERS. THE 12Z
CANADIAN IS EVEN FARTHER WEST. PLEASE REFER TO THE NATIONAL
HURRICANE CENTER FOR OFFICIAL TRACK AND STRENGTH FORECASTS...AND
ADDITIONAL INFORMATION.

[srainhoutx]

The 12Z Euro Ensembles are clustered from SE LA to the Florida Panhandle with a few of the 51 members further W and E as well...

[biggerbyte]

Models are flip flopping as I type this. Interesting to note the westward shift again. Models, or not, I want to express my concerns again for LA. As pointed out earlier on.. Folks from SE Texas to the western Pan Handle of Florida should not take the current forecast for granted. Check every day for changes. The NHC still has the official path, as of today, Saturday, moving over areas east of NOLA. As we all know, and have seen with storms like Ike and Rita, for instance, those last two to three days before landfall can make a huge difference.

[cisa]

I have a wierd feeling about this one, not necessarily for us. I'm just afraid someone on the Gulf Coast is going to be caught off guard. It's going to have to be watched because the forecast is still so fluid. Weekends are notorious for people being busy with other stuff, turning the news on on Sunday night and saying " where did that come from?

[biggerbyte]

Isaac looks rather poor right now.

[biggerbyte]

I have a wierd feeling about this one, not necessarily for us. I'm just afraid someone on the Gulf Coast is going to be caught off guard. It's going to have to be watched because the forecast is still so fluid. Weekends are notorious for people being busy with other stuff, turning the news on on Sunday night and saying " where did that come from?

Agreed!

[srainhoutx]

BULLETIN
TROPICAL STORM ISAAC ADVISORY NUMBER 19
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
500 PM EDT SAT AUG 25 2012

...CENTER OF ISAAC MOVING ALONG THE NORTHERN COAST OF EASTERN
CUBA WITH LITTLE CHANGE IN STRENGTH...


SUMMARY OF 500 PM EDT...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...21.3N 76.0W
ABOUT 120 MI...195 KM E OF CAMAGUEY CUBA
ABOUT 270 MI...435 KM SSE OF NASSAU
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...NW OR 310 DEGREES AT 21 MPH...33 KM/H
MINIMUM CENTRAL PRESSURE...997 MB...29.44 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

A TROPICAL STORM WATCH HAS BEEN ISSUED FOR THE FLORIDA WEST COAST
NORTH OF TARPON SPRINGS TO SUWANNEE RIVER.

THE GOVERNMENT OF THE DOMINICAN REPUBLIC HAS DISCONTINUED THE
TROPICAL STORM WARNING FOR THE DOMINICAN REPUBLIC.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A HURRICANE WARNING IS IN EFFECT FOR...
* THE FLORIDA KEYS INCLUDING THE DRY TORTUGAS
* THE WEST COAST OF FLORIDA FROM BONITA BEACH SOUTHWARD TO OCEAN
REEF
* FLORIDA BAY

A HURRICANE WATCH IS IN EFFECT FOR...
* THE FLORIDA EAST COAST FROM GOLDEN BEACH SOUTHWARD TO OCEAN REEF
* ANDROS ISLAND IN THE BAHAMAS

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* 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 EAST COAST FROM SEBASTIAN INLET SOUTHWARD TO OCEAN
REEF
* LAKE OKEECHOBEE

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* CUBAN PROVINCES OF MATANZAS AND CIENFUEGOS
* THE FLORIDA EAST COAST NORTH OF SEBASTIAN INLET TO FLAGLER BEACH
* THE FLORIDA WEST COAST NORTH OF BONITA BEACH TO SUWANNEE RIVER

A HURRICANE WARNING MEANS THAT HURRICANE CONDITIONS ARE EXPECTED
SOMEWHERE WITHIN THE WARNING AREA. A WARNING IS TYPICALLY ISSUED
36 HOURS BEFORE THE ANTICIPATED FIRST OCCURRENCE OF TROPICAL STORM
FORCE WINDS...CONDITIONS THAT MAKE OUTSIDE PREPARATIONS DIFFICULT
OR DANGEROUS. PREPARATIONS TO PROTECT LIFE AND PROPERTY SHOULD BE
RUSHED TO COMPLETION.

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...THE REMAINDER OF FLORIDA...AND
ELSEWHERE ALONG THE NORTHERN GULF COAST SHOULD MONITOR THE PROGRESS
OF ISAAC.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED
STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE
MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE
FORECAST OFFICE. FOR STORM INFORMATION SPECIFIC TO YOUR AREA OUTSIDE
THE UNITED STATES...PLEASE MONITOR PRODUCTS ISSUED BY YOUR NATIONAL
METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 500 PM EDT...2100 UTC...THE CENTER OF TROPICAL STORM ISAAC WAS
LOCATED NEAR LATITUDE 21.3 NORTH...LONGITUDE 76.0 WEST. ISAAC IS
MOVING TOWARD THE NORTHWEST NEAR 21 MPH...33 KM/H...AND THIS
GENERAL MOTION IS EXPECTED TO CONTINUE DURING THE NEXT 48 HOURS.
ON THE FORECAST TRACK...THE CENTER OF ISAAC SHOULD MOVE NEAR OR
OVER EASTERN CUBA THIS EVENING...NEAR OR OVER CENTRAL CUBA
TONIGHT...AND MOVE NEAR OR OVER THE FLORIDA KEYS AND THE SOUTHERN
FLORIDA PENINSULA SUNDAY OR SUNDAY NIGHT.

MAXIMUM SUSTAINED WINDS ARE NEAR 60 MPH...95 KM/H...WITH HIGHER
GUSTS. STRENGTHENING IS FORECAST DURING THE NEXT 48 HOURS...AND
ISAAC IS EXPECTED TO BE AT OR NEAR HURRICANE STRENGTH WHEN IT
REACHES THE FLORIDA KEYS.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 205 MILES...335 KM
MAINLY TO THE NORTH OF THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE BASED ON HURRICANE HUNTER
AIRCRAFT AND CUBAN SURFACE OBSERVATIONS IS 997 MB...29.44 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 3 TO 5 INCHES ARE POSSIBLE
OVER THE CENTRAL AND SOUTHERN BAHAMAS.

WIND...TROPICAL STORM CONDITIONS ARE OCCURRING OVER PORTIONS OF THE
HAITI...EASTERN CUBA...THE CENTRAL AND SOUTHEASTERN BAHAMAS AND THE
TURKS AND CAICOS ISLANDS. TROPICAL STORM CONDITIONS ARE EXPECTED
OVER THE NORTHWESTERN BAHAMAS BY SUNDAY MORNING. HURRICANE
CONDITIONS ARE POSSIBLE ON ANDROS ISLAND ON SUNDAY. TROPICAL STORM
CONDITIONS ARE EXPECTED OVER CENTRAL CUBA TONIGHT. TROPICAL STORM
CONDITIONS ARE EXPECTED TO REACH NORTHWESTERN CUBA ON SUNDAY.

HURRICANE CONDITIONS ARE EXPECTED IN THE HURRICANE WARNING AREA IN
SOUTHWEST FLORIDA AND THE FLORIDA KEYS ON SUNDAY...WITH TROPICAL
STORM CONDITIONS EXPECTED BY EARLY SUNDAY. HURRICANE CONDITIONS ARE
POSSIBLE IN THE HURRICANE WATCH AREA IN SOUTHEAST FLORIDA ON
SUNDAY...WITH TROPICAL STORM CONDITIONS EXPECTED IN THE TROPICAL
STORM WARNING AREA IN FLORIDA BY EARLY SUNDAY. TROPICAL STORM
CONDITIONS COULD SPREAD NORTHWARD ALONG THE WEST COAST OF FLORIDA IN
THE WATCH AREA BY EARLY MONDAY.

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...

* SOUTHWEST FLORIDA COAST WITHIN HURRICANE WARNING AREA...5 TO 7 FT
* FLA WEST COAST WITHIN WATCH AREA INCLUDING TAMPA BAY...3 TO 5 FT
* SOUTHEAST FLORIDA COAST AND THE FLORIDA KEYS...1 TO 3 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. FOR INFORMATION SPECIFIC TO YOUR AREA...PLEASE SEE
PRODUCTS ISSUED BY YOUR LOCAL WEATHER SERVICE OFFICE. NEAR THE
COAST...THE SURGE WILL BE ACCOMPANIED BY DANGEROUS WAVES.

SURF...DANGEROUS SURF AND RIP CURRENT CONDITIONS WILL AFFECT
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. PLEASE CONSULT PRODUCTS FROM YOUR
LOCAL WEATHER OFFICE FOR MORE INFORMATION.


NEXT ADVISORY
-------------
NEXT INTERMEDIATE ADVISORY...800 PM EDT.
NEXT COMPLETE ADVISORY...1100 PM EDT.

$$
FORECASTER BEVEN

[srainhoutx]

TROPICAL STORM ISAAC DISCUSSION NUMBER 19
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
500 PM EDT SAT AUG 25 2012

THE CENTER OF ISAAC IS CURRENTLY MOVING ALONG THE NORTH COAST OF
EASTERN CUBA. THE SATELLITE APPEARANCE IS SOMEWHAT DISORGANIZED...
WITH THE MAIN CONVECTIVE MASS 50 N MI OR MORE EAST OF THE LOW-LEVEL
CENTER. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT HAS
REPORTED 850 MB FLIGHT-LEVEL WINDS OF 56 KT TO THE NORTHEAST OF THE
CENTER...WITH RELIABLE-LOOKING SFMR SURFACE WIND DATA NEAR 50 KT.
BASED ON THIS...THE INITIAL INTENSITY REMAINS 50 KT. THE CENTRAL
PRESSURE OF 997 MB IS BASED ON A COMBINATION OF AIRCRAFT DATA AND
CUBAN SURFACE OBSERVATIONS.

THE INITIAL MOTION IS NOW 310/18. ISAAC IS CURRENTLY PART OF A
LARGE LOW/MID-LEVEL LOW PRESSURE SYSTEM COVERING THE NORTHWESTERN
CARIBBEAN SEA AND THE ADJACENT LAND AND OCEAN AREAS. THIS LOW
PRESSURE AREA HAS A SECOND VORTICITY CENTER BETWEEN JAMAICA AND THE
CAYMAN ISLANDS...AND FOR THE NEXT 24-36 HR ISAAC AND THIS CENTER
WILL LIKELY ROTATE AROUND EACH OTHER. BASED ON THIS EXPECTATION...
THE FORECAST TRACK SHOWS ISAAC MOVING NORTHWESTWARD FOR 12 HR OR
SO...FOLLOWED BY A TURN TOWARD THE WEST-NORTHWEST. IT IS POSSIBLE
THE STORM COULD MAKE A SHARPER TURN THAN FORECAST...AS THE UKMET IS
SHOWING AN ALMOST DUE WEST MOTION BETWEEN THE FLORIDA KEYS AND CUBA
NEAR THE 36 HR POINT. THE EARLY PART OF THE FORECAST TRACK IS
SHIFTED A LITTLE TO THE LEFT OF THE PREVIOUS FORECAST...BUT STILL
LIES TO THE RIGHT OF THE CONSENSUS MODELS AND THE BULK OF THE
DYNAMICAL MODELS. AFTER 36 HR...ISAAC SHOULD BREAK FREE OF OR
ABSORB THE REST OF THE LOW...WITH THE SUBTROPICAL RIDGE TO THE EAST
BECOMING THE DOMINANT STEERING INFLUENCE. THIS SHOULD ALLOW THE
STORM TO GRADUALLY TURN TOWARD THE NORTHWEST AND NORTH OVER THE
EASTERN AND NORTHERN GULF OF MEXICO...WITH AN EVENTUAL LANDFALL
ALONG THE NORTHERN GULF COAST IN 72-96 HR. WHERE THIS MIGHT OCCUR
IS STILL RATHER UNCERTAIN...WITH THE TRACK GUIDANCE SPREAD BETWEEN
SOUTHEASTERN LOUISIANA AND THE CENTRAL FLORIDA PANHANDLE. THIS PART
OF THE TRACK FORECAST LIES IN THE CENTER OF THE GUIDANCE ENVELOPE
NEAR THE CONSENSUS MODELS AND IS SIMILAR TO THE PREVIOUS FORECAST.

A COMBINATION OF LIGHT WESTERLY VERTICAL WIND SHEAR AND LAND
INTERACTION SHOULD AT LEAST SLOW INTENSIFICATION FOR THE NEXT 12
HR. AFTER THAT...THE SHEAR SHOULD DIMINISH WHILE THE CYCLONE
REACHES OPEN WATER. THIS SHOULD ALLOW ISAAC TO GRADUALLY STRENGTHEN
INTO A HURRICANE NEAR THE FLORIDA KEYS OR OVER THE SOUTHEASTERN
GULF OF MEXICO. THE NEW INTENSITY FORECAST IS SIMILAR TO THE
PREVIOUS FORECAST AND IS NEAR OR A LITTLE ABOVE THE INTENSITY
CONSENSUS. IT SHOULD BE NOTED THAT THE GLOBAL MODELS ARE
FORECASTING A VERY FAVORABLE PATTERN OF UPPER-LEVEL WINDS OVER THE
NORTHERN GULF OF MEXICO BY 72 HR. SHOULD THIS VERIFY AND SHOULD
ISAAC ESTABLISH AN INNER CORE...THE CYCLONE COULD BE SIGNIFICANTLY
STRONGER THAN CURRENTLY FORECAST.

IT IS IMPORTANT NOT TO FOCUS ON THE EXACT TRACK OF ISAAC 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 25/2100Z 21.3N 76.0W 50 KT 60 MPH
12H 26/0600Z 22.6N 78.0W 55 KT 65 MPH
24H 26/1800Z 24.1N 80.6W 60 KT 70 MPH
36H 27/0600Z 25.2N 82.7W 65 KT 75 MPH
48H 27/1800Z 26.5N 84.3W 75 KT 85 MPH
72H 28/1800Z 29.0N 86.0W 85 KT 100 MPH
96H 29/1800Z 31.5N 86.0W 55 KT 65 MPH...INLAND
120H 30/1800Z 33.5N 85.5W 25 KT 30 MPH...INLAND

$$
FORECASTER BEVEN