Tropical Depression Isaac:

[srainhoutx]

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
1000 AM EDT WED AUG 22 2012

VALID 12Z SUN AUG 26 2012 - 12Z WED AUG 29 2012

...HURCN ISAAC MAY IMPACT FL DURING THE D5-D7 TIME PERIOD...


THE MAJOR THREAT DURING THE MEDIUM RANGE TIME FRAME WILL BE WITH
HURCN ISAAC WHICH IS CURRENTLY CHURNING THE WATERS NEARBY THE
LESSER ANTILLES. THE LATEST NHC TRACK SUGGESTS THIS TROPICAL
SYSTEM WILL BE LOCATED JUST EAST OF CUBA BY 25/1200Z WITH A
GENERAL SHIFT TOWARD THE NORTHWEST CARRYING IT NEAR THE FL KEYS BY
27/1200Z. FCST MODELS SUGGEST A WEAKNESS IN THE MID-LEVEL RIDGE
AXIS SHOULD EVENTUALLY LIFT ISAAC TOWARD THE SERN U.S. BY MID-NEXT
WEEK. UNFORTUNATELY...THE CURRENT 06Z/00Z MODEL SUITE HAS A
VARIETY OF SOLNS PRESENTED THEREBY COMPLICATING MATTERS FOR
INTERESTED PARTIES ACRS THE SERN U.S. THE CURRENT TRACK INDICATED
BY THE NHC GENERALLY FOLLOWS THE 00Z GFS/GEFS MEAN THRU D5 WITH
HPC CONTINUING ITS GENERALLY MOTION TOWARD THE NNW INTO CNTRL GA
BY THE END OF THE PERIOD. OF COURSE...PLEASE VISIT THE LATEST
TRACK OF HURCN ISAAC ON THE NHC WEBSITE AT WWW.NHC.NOAA.GOV.

ACRS THE REMAINDER OF THE CONUS...THE MID/UPPER PATTERN WILL
GRADUALLY BECOME MORE HIGH AMPLITUDE IN NATURE BY EARLY NEXT WEEK.
A MEAN NEG ANOMALY SHOULD BE FEATURED JUST TO THE WEST OF BRITISH
COLUMBIA WITH THIS AXIS OF HGT FALLS GRADUALLY SPREADING SERD
TOWARD VANCOUVER ISLAND/COASTAL PAC NW BY 27/1200Z. CONSIDERING
TELECONNECTIONS UTILIZING THIS NEG ANOMALY CENTER...A BROAD AXIS
OF MID-LEVEL RIDGING IS SUGGESTED OVER THE MIDDLE OF THE CONUS
WITH A GENERAL MAX ACRS THE NRN/CNTRL PLAINS. IN THIS OMEGA BLOCK
SIGNATURE...AN ELONGATED TROF AXIS WILL BE IN PLACE ALONG THE ERN
THIRD OF THE U.S. THIS FEATURE IN PARTICULAR WILL PLAY A CRUCIAL
ROLE IN HOW MUCH LATITUDE ISAAC WILL GAIN THROUGHOUT THE MEDIUM
RANGE PERIOD.

LOOKING AT THE DETERMINISTIC/ENS GUIDANCE AS A WHOLE...THE IDEA OF
THIS HIGH-AMPLITUDE PATTERN IS CONVEYED ACRS THE BOARD.
HOWEVER...THE TIMING/STRENGTH OF THE NRN STREAM TROF MOVING THRU
THE TN/OH VALLEYS AND ERN U.S. DOES VARY WHICH HAS IMPLICATIONS OF
THE EVENTUAL PATH OF ISAAC. CURRENTLY...THE 00Z ECMWF/ECMWF ENS
MEAN MAINTAIN A STRONG ENOUGH 500-MB RIDGE TO KEEP THE SYSTEM
SOUTH OF 30N. HOWEVER...THE REMAINING GUIDANCE...ESPECIALLY THE
GFS WHICH HAS MAINTAINED ITS SOLN THE PAST 4 RUNS...INSIST ON
ISAAC BEING DRAWN NWRD. OVERALL...HPC FAVORED A SOLN COMPRISING
THE 00Z GFS/GEFS MEAN WITH SOME COMPLIMENTS FROM THE 00Z UKMET
EARLY ON GIVEN ITS FAVORABLE HANDLING OF THE NRN STREAM.


RUBIN-OSTER

[srainhoutx]

TROPICAL STORM ISAAC DISCUSSION NUMBER 6
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
1100 AM AST WED AUG 22 2012

THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT MONITORING ISAAC
DURING THE NIGHT REPORTED THAT THE INNER CORE WIND FIELD BECAME
DISORGANIZED AFTER 0600 UTC. A COUPLE OF MICROWAVE OVERPASSES
SUGGEST THAT THE CIRCULATION CENTER BECAME ELONGATED DURING THIS
TIME....AND THE CENTER IS NOT READILY APPARENT IN FRENCH RADAR DATA
FROM MARTINIQUE AND GUADELOUPE. THE INITIAL INTENSITY IS HELD AT
40 KT BASED ON AIRCRAFT-REPORTED WINDS NORTH OF THE CENTER. WHILE
THE CENTRAL CORE IS DISORGANIZED...THE OVERALL STRUCTURE OF THE
STORM IS IMPROVING...AS SATELLITE IMAGERY SHOWS A LARGE OUTER BAND
FORMING AROUND THE CENTRAL CONVECTIVE FEATURE.

THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 280/15...AS IT IS UNCLEAR
HOW MUCH OF THE OBSERVED NORTHWARD NUDGE WAS DUE TO RE-FORMATION OF
THE CENTER. OTHER THAN THAT...THERE IS NO SIGNIFICANT CHANGE TO THE
PREVIOUS FORECAST TRACK OR REASONING DURING THE FIRST 48-72 HR OF
THE TRACK FORECAST. THE EAST-WEST ORIENTED SUBTROPICAL RIDGE TO THE
NORTH OF ISAAC ALONG 30N LATITUDE IS FORECAST BY ALL OF THE GLOBAL
MODELS TO REMAIN INTACT ACROSS FLORIDA AND THE SOUTHEASTERN U.S.
DURING THAT TIME. THIS EARLY PART OF THE FORECAST TRACK IS AN
UPDATE OF THE PREVIOUS FORECAST. AFTER THAT TIME...THE RIDGE IS
EXPECTED TO WEAKEN SOMEWHAT AS A MID/UPPER-LEVEL TROUGH MOVES ONTO
THE EASTERN UNITED STATES. THE MODELS DIVERGE ON THEIR FORECASTS
OF THE RIDGE. THE ECMWF DOES NOT BREAK THE RIDGE...AND THUS
FORECASTS A MORE WESTWARD MOTION NEAR OR SOUTH OF CUBA. THE
CANADIAN AND NOGAPS HAVE A LARGE BREAK IN THE RIDGE AND TURN ISAAC
NORTHWARD EAST OF FLORIDA. THE UKMET HAS A BREAK IN THE RIDGE OVER
THE NORTHERN GULF COAST AND MOVES THE CYCLONE OVER THE FLORIDA
PENINSULA. THE GFS SHOWS A BREAK IN THE RIDGE EAST OF FLORIDA...
BUT FORECASTS ISAAC TO BYPASS THE BREAK AND MOVE NEAR THE SOUTHWEST
COAST OF FLORIDA. THIS DECREASED-CONFIDENCE PORTION OF THE
FORECAST TRACK IS SHIFTED A LITTLE WEST OF THE PREVIOUS TRACK TO
LIE NEAR THE CONSENSUS MODELS.

WATER VAPOR IMAGERY AND MICROWAVE TOTAL PRECIPITABLE WATER DATA SHOW
DRY AIR TO THE NORTHEAST OF ISAAC...AND A LACK OF CONVECTION IN
THIS AREA SUGGESTS SOME OF THIS AIR IS ENTRAINING INTO THE CYCLONE.
OTHERWISE...ENVIRONMENTAL CONDITIONS APPEAR FAVORABLE FOR
INTENSIFICATION UNTIL THE CENTER REACHES HISPANIOLA IN ABOUT 48 HR.
AFTER THAT...THE INTENSITY WILL BE DETERMINED BY HOW MUCH TIME ISAAC
SPENDS OVER LAND. THE NEW FORECAST IS SIMILAR TO THE PREVIOUS
FORECAST THROUGH 48 HR...THEN IS REDUCED A LITTLE BASED ON
INCREASED LAND INTERACTION IN THE NEW FORECAST TRACK.

A HURRICANE WARNING WILL LIKELY BE REQUIRED FOR PORTIONS OF THE
DOMINICAN REPUBLIC THIS AFTERNOON. IT SHOULD BE NOTED THAT WHILE
NONE OF THE FORECAST POINTS ARE OVER LAND...THE CYCLONE IS FORECAST
TO MOVE OVER HISPANIOLA AND CUBA FROM 48-96 HR.


FORECAST POSITIONS AND MAX WINDS

INIT 22/1500Z 15.9N 59.3W 40 KT 45 MPH
12H 23/0000Z 16.3N 61.8W 45 KT 50 MPH
24H 23/1200Z 16.8N 64.8W 50 KT 60 MPH
36H 24/0000Z 17.3N 67.8W 60 KT 70 MPH
48H 24/1200Z 17.8N 70.3W 75 KT 85 MPH
72H 25/1200Z 19.5N 74.5W 60 KT 70 MPH
96H 26/1200Z 22.5N 78.5W 60 KT 70 MPH
120H 27/1200Z 25.5N 81.5W 70 KT 80 MPH

$$
FORECASTER BEVEN

[djmike]

Let the trend begin! 11am track is out!!

[wxman57]

Let the trend begin! 11am track is out!!

That would be the trend of the main impact region shifting from the southeast FL peninsula to the SW FL peninsula - not a trend that indicates any threat to the NW Gulf. I think that about the farthest west Isaac may track is the mid FL Panhandle.

[jasons2k]

Here's my $.02 on the issue....

In past years I would agree 100% with Portastorm & others about such information being irresponsible, etc. But I've chnaged my tune now, for a few reasons...
1) It's 2012, not 2008, and even in the last few years we've made some pretty good headway in the modelling.
2) Chances of this headed towards Texas are indeed slim to none with this system. Even if the Euro is right, the furthest west this will go looks to be Louisiana. FL or EGOM look to be a lock at this time.
3) Even IF things did change (and I've been around long enough to know it can and does happen) we have PLENTY of time to adjust still.

I mean really folks, fast-forward to next week: Hypothetically, Let's say it's us and Galveston is under a hurricane warning and mandatory evacuation. Do you think any one in Galveston would stay just because KPRC had said the week before it was going to Florida? Really? After all, most said the same thing about Ike. Do you think by the time they shifted the cone to the west that anyone still cared about what the media was reporting a few days before??

Chill folks, people in Texas are not making life or death decisions just yet.

[srainhoutx]

NCEP Operational Status Message
Wed Aug 22 14:52:00 2012 GMT
NOUS42 KWNO 221451
ADMNFD
SENIOR DUTY METEOROLOGIST NWS ADMINISTRATIVE MESSAGE
NWS NCEP CENTRAL OPERATIONS COLLEGE PARK MD
1451Z WED AUG 22 2012
THE 12Z GFS MODEL HAS STARTED AND IS RUNNING ON TIME.
THE NATIONAL HURRICANE CENTER HAS REQUESTED THE INITIATION OF
SPECIAL 6 HOURLY SOUNDINGS STARTING AT 18Z THU AUG 23 FROM WFO
SAN JUAN AND ALL OFFICES WITHIN THE FOLLOWING STATES:
FLORIDA...GEORGIA...ALABAMA...AND MISSISSIPPI.
HANDEL/SDM/NCO/NCEP

[srainhoutx]

Isaac clearly is not a 'healthy' cyclone at this time. The longer it takes to fully develop, the further W and potentially less influence the approaching trough will have on it, IMO.

[tireman4]

from KPRC http://www.click2houston.com/news/Tropi ... index.html

Aug 22 2012 06:19:24 AM CDT

One thing is almost certain: Isaac is not Houston's storm. While we can never say never, the odds of Isaac hitting the Texas coastline are very slim, so southeast Texas can breath a sigh of relief at this point.

heave a collective sigh, everyone

\

Wow. Just wow. Did Frank say this or did a reporter just put that in the blog?

[tireman4]

Here is my take. This is an weather weenie just talkin....

I will say that Frank ( or whomever wrote this) did say...So Southeast Texas can breath a sigh of relief.....at this point. That is what makes the statement ok in my book. It is not a "never gonna hit", it is a at this time, we are not part of the activity.

[nuby3]

Just watch the storm and see where it goes, and if it comes this way, act accordingly. Pro met or amateur, educated or not, anything anyone says about where this storm will finally make landfall is a total guess at this point. Although, it's fun to try, and input from pro mets is certainly well appreciated and very considered. We all thank you for your time to feed our curiosity.

[biggerbyte]

Agreed, Nuby3. I'll just say one more thing on the subject before moving on. I don't think anyone in here is trying to "hype" this situation. It is what it is. Isaac may never get anywhere near Texas. The fact is, no one knows for sure what is going to happen with Isaac five days from now. It is foolish to believe that a person, pro., or not, or any model can tell you otherwise. Today is today. Today, the models have shifted west from up the spine of Florida, to offshore, Gulf side of Florida. Will we continue to see a westward shift? Maybe! This far out, the models may flip back east again. Watch and it will make you dizzy.

Anyway, I'm not sure how one could applaud another for making the same statement he made four days prior to the landfall of Ike over S.E. Texas. Ike is not going to hit anywhere in Texas, I believe were the words used. This person may end up being correct, just as he could have ended up being correct about Ike. However, I find it highly irresponsible to give the public such a pass without a working crystal ball into the future.

Reality is.. Now we watch and wait. Folks, please follow the NHC forecast. We should be able to trust model output about three days out. Until then, just be wise. You know the routine.

[srainhoutx]

The 12Z Euro is a tad further E this run through hour 120.

Hour 144:

168:

192:

[srainhoutx]

Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 22nd day of the month at 18:19Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 307)
Storm Number & Year: 09L in 2012
Storm Name: Isaac (flight in the North Atlantic basin)
Mission Number: 3
Observation Number: 02
A. Time of Center Fix: 22nd day of the month at 18:02:20Z
B. Center Fix Coordinates: 16°06'N 60°24'W (16.1N 60.4W)
B. Center Fix Location: 86 miles (139 km) to the NE (50°) from Roseau, Dominica.
C. Minimum Height at Standard Level: 1,479m (4,852ft) at 850mb
D. Estimated (by SFMR or visually) Maximum Surface Wind: 35kts (~ 40.3mph)
E. Location of the Estimated Maximum Surface Wind: 71 nautical miles (82 statute miles) to the NW (314°) of center fix
F. Maximum Flight Level Wind Inbound: From 68° at 35kts (From the ENE at ~ 40.3mph)
G. Location of Maximum Flight Level Wind Inbound: 74 nautical miles (85 statute miles) to the NW (314°) of center fix
H. Minimum Sea Level Pressure: 1004mb (29.65 inHg)
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 18°C (64°F) at a pressure alt. of 1,525m (5,003ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 21°C (70°F) at a pressure alt. of 1,525m (5,003ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 17°C (63°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, Wind, Pressure and Temperature
N. Fix Levels (sfc and flt lvl centers are within 5nm of each other): Surface and 850mb
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 5 nautical miles
Remarks Section:
Maximum Flight Level Wind: 35kts (~ 40.3mph) in the northwest quadrant at 17:39:00Z
Maximum Flight Level Temp: 21°C (70°F) which was observed 8 nautical miles to the NW (314°) from the flight level center

[djmike]

Where does Euro finish? Waiting patiently as most if us have filtered computers at work and can't see the pics!

[srainhoutx]

Where does Euro finish? Waiting patiently as most if us have filtered computers at work and can't see the pics!

Roughly SE Louisiana/MS/Mobile, AL ish...

[djmike]

Thank you SRAIN...

[srainhoutx]

TROPICAL STORM ISAAC DISCUSSION NUMBER 7
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
500 PM AST WED AUG 22 2012

SATELLITE...AIRCRAFT...RADAR...AND SURFACE OBSERVATIONS INDICATE
THAT ISAAC HAS A BROAD CENTRAL AREA OF LIGHT WINDS WITH MULTIPLE
VORTICITY MAXIMA EMBEDDED. THE LOWEST PRESSURES ARE IN AN AREA
NEAR GUADELOUPE...WHICH IS USED AS THE CURRENT CENTER SINCE IT HAS
SOME CONTINUITY WITH THE CENTER PREVIOUSLY BEING TRACKED.
HOWEVER...THE MEAN CENTER IS LIKELY TO THE SOUTHEAST OF THE
ADVISORY POSITION. SOME ADJUSTMENT OF THE CENTER POSITION MAY BE
NECESSARY WHEN THE CENTRAL CORE AGAIN CONSOLIDATES. THE INITIAL
INTENSITY IS HELD AT 40 KT...ALTHOUGH THE HURRICANE HUNTER AIRCRAFT
DATA SUGGESTS THIS COULD BE GENEROUS.

THE INITIAL MOTION IS NOW A SOMEWHAT UNCERTAIN 280/19. OTHER THAN
THE CENTER POSITION ISSUES...THERE IS NO SIGNIFICANT CHANGE TO THE
FORECAST REASONING DURING THE FIRST 48 HR OF THE TRACK FORECAST. THE
EAST-WEST ORIENTED SUBTROPICAL RIDGE TO THE NORTH OF ISAAC ALONG
30N LATITUDE IS FORECAST BY ALL OF THE GLOBAL MODELS TO REMAIN
INTACT ACROSS FLORIDA AND THE SOUTHEASTERN U.S. DURING THAT TIME.
THIS EARLY PART OF THE FORECAST TRACK IS SHIFTED A LITTLE TO THE
SOUTH OF THE PREVIOUS FORECAST BASED ON THE OBSERVED POSITION AND
MOTION. AFTER 48 HR...THE RIDGE IS EXPECTED TO WEAKEN AS A
MID/UPPER-LEVEL TROUGH MOVES ONTO THE EASTERN UNITED STATES. THE
GLOBAL MODELS HAVE COME INTO BETTER AGREEMENT SINCE THE LAST
ADVISORY...WITH THE NOGAPS AND CANADIAN MODELS SHIFTING TO THE WEST
AND THE ECMWF TO THE NORTH. HOWEVER...THE ECMWF CONTINUES TO SHOW
A STRONGER RIDGE...AND THUS SHOWS A MORE WESTERLY MOTION THAN THE
OTHER MODELS. THE 72-120 HR PORTION OF THE FORECAST TRACK IS
SIMILAR TO THE PREVIOUS FORECAST AND LIES NEAR THE CONSENSUS
MODELS. THERE REMAINS CONSIDERABLE UNCERTAINTY AS TO WHICH PORTIONS
OF FLORIDA...IF ANY...COULD BE AFFECTED BY ISAAC.

WATER VAPOR IMAGERY AND MICROWAVE TOTAL PRECIPITABLE WATER DATA
CONTINUE TO SHOW DRY AIR TO THE NORTHEAST OF ISAAC...AND A LACK OF
CONVECTION IN THIS AREA SUGGESTS SOME OF THIS AIR IS ENTRAINING
INTO THE CYCLONE AND DISRUPTING THE CONVECTIVE STRUCTURE. GIVEN
THE CURRENT STRUCTURE...THE NEW INTENSITY FORECAST CALLS FOR LITTLE
CHANGE IN STRENGTH FOR THE NEXT 12 HR...FOLLOWED BY INTENSIFICATION
INTO A HURRICANE BY 48 HR SIMILAR TO THE PREVIOUS ADVISORY. AFTER
48 HR...THE MAIN FACTOR CONTROLLING THE INTENSITY IS THE AMOUNT OF
LAND INTERACTION. THIS LOW-CONFIDENCE PART OF THE INTENSITY
FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY BUT ABOVE THE INTENSITY
CONSENSUS.


FORECAST POSITIONS AND MAX WINDS

INIT 22/2100Z 16.0N 61.2W 40 KT 45 MPH
12H 23/0600Z 16.3N 63.6W 40 KT 45 MPH
24H 23/1800Z 16.7N 66.7W 50 KT 60 MPH
36H 24/0600Z 17.2N 69.4W 60 KT 70 MPH
48H 24/1800Z 17.9N 71.6W 70 KT 80 MPH...INLAND
72H 25/1800Z 20.5N 75.5W 60 KT 70 MPH...INLAND
96H 26/1800Z 23.5N 79.5W 60 KT 70 MPH...OVER WATER
120H 27/1800Z 26.5N 82.5W 70 KT 80 MPH

$$
FORECASTER BEVEN

[biggerbyte]

Looking at sat. views today, I don't see how anything tropical can make landfall west of NOLA. Of course, said conditions are subject to change as Isaac draws near. If he were three days out from landfall as of this moment, I'd put him well South, or well East of Houston. Let's see what Thursday looks like.

[jasons2k]

KPRC may have jinxed us after all....some of the trends today and some postings elsewhere suggest that FL/EGOM is certainly not a "lock" by any means. Next week could get very interesting if we are faced with a system in the Gulf and collapsing steering currents.

[jasons2k]

Looking at sat. views today, I don't see how anything tropical can make landfall west of NOLA. Of course, said conditions are subject to change as Isaac draws near. If he were three days out from landfall as of this moment, I'd put him well South, or well East of Houston. Let's see what Thursday looks like.

What are Sat loops telling you other than we have a very weak system with a possible center relocation to the south? Both would indicate a further south and west trend at least in the short term. Long term it's looking like more uncertainty with a possible collapse in the steering currents. There could very well be *just enough* ridging across the SE US, as indicated by the Euro, to steer this on a more westerly drift once in the GOM.