Tropical Storm Isaac, Part 2: Isaac Moving Into The Gulf Of Mexico-Hurricane Warnings For Morgan City, LA/MS/AL & FL Panhandle To Destin, FL

[Srain]

Maybe this has been discussed previously, but the tendency to stall out at around H96 is really close to being over water. If the weak steering flow sagged another 50-100 miles south, seems like the problems for the panhandle could escalate quite a bit. Is this a realistic scenario?

Also, not sure what to make of the post landfall track - GFS, et al NNE vs. the EC NW.

PRELIMINARY EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD

245 AM EDT SAT AUG 25 2012

VALID 12Z WED AUG 29 2012 - 12Z SAT SEP 01 2012

...ISAAC EXPECTED TO MAKE LANDFALL ALONG THE NORTHERN GULF COAST

THIS PERIOD...

USED THE DETERMINISTIC ECMWF FOR THE PRELIMINARY FRONTS AND

PRESSURES FOR DAYS 3 AND 4...SWITCHING TO THE ECENS MEAN

THEREAFTER TO ADDRESS THE UNCERTAINTIES IN SYNOPTIC DETAIL AMONG

THE ARRAY OF GLOBAL MODEL SOLUTIONS. CHOSE TO MANUALLY MODIFY THE

ISOBARS OVER THE DEEP SOUTH NEAR AND AROUND ISAAC TO FIT THE MOST

RECENT NATIONAL HURRICANE CENTER FORECAST...AS OPPOSED TO CHOOSING

A MODEL OF BEST FIT FOR THAT SYSTEM AT THE EXPENSE OF THE FLOW

OVER THE REMAINDER OF THE NATION. IN THIS CASE...THE GFS IS QUITE

CLOSE TO THE OFFICIAL ISAAC FORECAST...BUT DIFFERS ENOUGH FROM THE

OTHER GUIDANCE WITH THE MAIN BAND OF WESTERLIES TO PRECLUDE ITS

WHOLESALE USE.

[wxsmwhrms]

FWIW the GFDL has Isaac as a strong category 2 that passes the Bird's Foot of LA then goes into MS. The HWRF peaks Isaac out as a category 4 then has it about 100 knots making landfall just E of Escambia Bay. The UK is now only the model that shows a more NE motion after landfall, all the other models either stall Isaac or keeping it going NW/NNW.

Also, I think now that we have clearer vis imagery I was a little too quick with the movement on my earlier estimate. I think it's about 20/74 right now.

EDIT: The HWRF actually peaks out just shy of a cat 4.

[phil882]

Omg, love this.

What makes you so bullish Re: the NE Gulf? Scott-- or someone-- posted that map the other day that showed crappy oceanic heat content up there.

Well looks like I'm going to bust bad now because:

1. The storm is being significantly impacted by the land interaction, something I was expecting not to have happen.

2. The storm is interacting with the lee cyclone, which is now located S of cuba (you can see the broad turning on visible imagery). Since the surface circulation of Isaac is disrupted now, its much weaker and no longer the dominant feature in this binary interaction. Thus we should see a track closer to cuba as it remains tied to this broader low-level cyclonic circulation.

Given the current structure and expected track, I'll be shocked if it can get to 85 mph before Florida Landfall. The second landfall is a lot more uncertain mainly because I don't know how long it will take for Isaac to redevelop an inner core. However, I'm obviously not nearly as confident on the intensity as I was just a few hours ago. (track still looks good though).

[David Reimer]

I see that NHC had scheduled an aircraft to be investigating Isaac since 12Z this morning. Did they scrub the mission?

[Srain]

NCEP Operational Status Message

Sat Aug 25 13:32:03 2012 GMT

NOUS42 KWNO 251331

ADMNFD

SENIOR DUTY METEOROLOGIST NWS ADMINISTRATIVE MESSAGE

NWS NCEP CENTRAL OPERATIONS COLLEGE PARK MD

1330Z SAT AUG 25 2012

THE 12Z NAM BEGAN ON SCHD WITH GOOD US/CAN/CARIB UPA

DATA COVERAGE INCL 71 CONUS 14 AK 32 CAN AND 7 CARIB

RAOBS. NO MEX RAOBS WERE AVBL...SDM WILL CONTINUE TO

MONITOR FOR THESE. ALSO 24 DROPSONDE AND 4 700 MB FL

RECON REPORTS VCNTY TS ISAAC WERE AVBL. RAOB RECAP...

DVN.74455 - GROUND EQUIPMENT OUTAGE...CODE 10142.

PNI/91348 - GROUND EQUIPMENT OUTAGE...CODE 10142.

NKX/72293 - DELETED TEMPS 922-906 MB...WET-BULB EFFECT.

VBG/72393 - DELETED TEMPS 934-906 MB...WET-BULB EFFECT.

VPS/72221 - DEL HGTS 200 MB AND UP...HYDROSTATIC ERRORS.

CRITICAL WEATHER DAY STATUS...

CWD IS TO REMAIN IN EFFECT THRU THE COMING WEEK IN SUPPORT OF

MONITORING TS/HCN ISAAC AND POTENTIAL IMPACT ON SE US

AND IN SUPPORT OF THE REPUBLICAN NATL CONV IN TAMPA FL.

STOUDT/SDM/NCO/NCEP

[Srain]

I see that NHC had scheduled an aircraft to be investigating Isaac since 12Z this morning. Did they scrub the mission?

ATLANTIC REQUIREMENTS

1. TROPICAL STORM ISAAC

FLIGHT ONE --TEAL 72

A. 25/1800Z,26/0000Z

B. AFXXX 1609A ISAAC

C. 25/1530Z

D. 20.0N 76.3W

E. 25/1730Z TO 26/0000Z

F. SFC TO 10,000 FT

[David Reimer]

ATLANTIC REQUIREMENTS

1. TROPICAL STORM ISAAC

FLIGHT ONE --TEAL 72

A. 25/1800Z,26/0000Z

B. AFXXX 1609A ISAAC

C. 25/1530Z

D. 20.0N 76.3W

E. 25/1730Z TO 26/0000Z

F. SFC TO 10,000 FT

I swore I saw them have a flight scheduled earlier this morning. I guess my lack of sleep is getting to me. Thanks!

[uofmiami]

And for the day:

000

NOUS42 KNHC 231503

REPRPD

WEATHER RECONNAISSANCE FLIGHTS

CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.

1100 AM EDT THU 23 AUGUST 2012

SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)

VALID 24/1100Z TO 25/1100Z AUGUST 2012

TCPOD NUMBER.....12-096

I. ATLANTIC REQUIREMENTS

1. TROPICAL STORM ISAAC

FLIGHT ONE --TEAL 73 FLIGHT TWO --NOAA 49--

A. 24/1800Z,25/0000Z A. 25/0000Z

B. AFXXX 1209A ISAAC B. NOAA9 1309A ISAAC

C. 24/1630Z C. 24/1730Z

D. 17.5N 71.2W D. NA

E. 24/1730Z TO 25/0000Z E. NA

F. SFC TO 10,000 FT F. 41,000 TO 45,000 FT

FLIGHT THREE --TEAL 71-- FLIGHT FOUR --NOAA 49--

A. 25/0600Z,1200Z A. 25/1200Z

B. AFXXX 1409A ISAAC B. NOAA9 1509A ISAAC

C. 25/0400Z C. 25/0530Z

D. 18.6N 73.5W D. NA

E. 25/0530Z TO 25/1200Z E. NA

F. SFC TO 10,000 FT F. 41,000 TO 45,000 FT

2. SUCCEEDING DAY OUTLOOK: CONTINUE 6-HRLY FIXES. A G-IV

MISSION DEPARTING 25/1730Z AND 26/0530Z.

II. PACIFIC REQUIREMENTS

1. NEGATIVE RECONNAISSANCE REQUIREMENTS.

2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.

$$

JWP

National Hurricane Center

Isn't this the correct Recon schedule for Saturday?

NOUS42 KNHC 241545

REPRPD

WEATHER RECONNAISSANCE FLIGHTS

CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.

1145 AM EDT FRI 24 AUGUST 2012

SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)

VALID 25/1100Z TO 26/1100Z AUGUST 2012

TCPOD NUMBER.....12-097

I. ATLANTIC REQUIREMENTS

1. TROPICAL STORM ISAAC

FLIGHT ONE --TEAL 72 FLIGHT TWO --NOAA 49--

A. 25/1800Z,26/0000Z A. 26/0000Z

B. AFXXX 1609A ISAAC B. NOAA9 1709A ISAAC

C. 25/1530Z C. 25/1730Z

D. 20.0N 76.3W D. NA

E. 25/1730Z TO 26/0000Z E. NA

F. SFC TO 10,000 FT F. 41,000 TO 45,000 FT

FLIGHT THREE --TEAL 74-- FLIGHT FOUR --NOAA 49--

A. 26/0600Z,1200Z A. 26/1200Z

B. AFXXX 1809A ISAAC B. NOAA9 1909A ISAAC

C. 26/0230Z C. 26/0530Z

D. 21.6N 78.6W D. NA

E. 26/0530Z TO 26/1200Z E. NA

F. SFC TO 10,000 FT F. 41,000 TO 45,000 FT

FLIGHT FIVE --TEAL 75--

A. 26/1200Z

B. AFXXX 2009A ISAAC

C. 26/0900Z

D. NA

E. NA

F. SFC TO 30,000 FT

G. SYNOPTIC FLOW/ BUOY DROP MISSION

2. SUCCEEDING DAY OUTLOOK:3-HRLY FIXES 27/0000Z. .

G-IV MISSIONS EVERY 12 HRS. WP-3 BEGIN FLYING

26/2000Z

[turtlehurricane]

Looks like the center is about over the eastern tip of Cuba, not much of a circulation and it's caught up in the Cuban mountains. Basically a mid-level vortex over the convoluted remains of the low level vortex, it'll keep frictionally spinning down until it can get some convection.

http://www.ssec.wisc.../loop_srso.html

[Eyewall2005]

http://philstropical...ndfall-looming/

My first track map for Isaac... I agree that its likely not to be significantly affected by land over the next 12-24 hours. In fact, if Isaac can maintain its formative inner core, this intensity forecast might be on the low side before the first landfall in extreme S Florida. The second landfall timing is tricky since the storm will be slowing down, but a track between Panama City and Pensacola seems like a relatively good bet at this time. I think this has a reasonable shot to be our first US major hurricane landfall in 7 years.

Phil can you update your track?

[winterymix]

Well looks like I'm going to bust bad now because:

Maybe not a bust. If Isaac only nicks Cuba, your generally track

could be fine with perhaps a 10% drop in intensity forecast at

second landfall.

[wxsmwhrms]

Very heavy convective bands pummelling southern Haiti and DR. Going to be a long day there on the SE side of this system.

[Quincy]

Hard to tell, because I can only see the 96hr panel, but the ECMWF has 850mb winds of 101kts at landfall. That mixes down to about 93mph near the surface. (probably maxes a bit higher before landfall)

[das]

1. The storm is being significantly impacted by the land interaction, something I was expecting not to have happen.

2. The storm is interacting with the lee cyclone, which is now located S of cuba (you can see the broad turning on visible imagery). Since the surface circulation of Isaac is disrupted now, its much weaker and no longer the dominant feature in this binary interaction. Thus we should see a track closer to cuba as it remains tied to this broader low-level cyclonic circulation.

Looking at the GOES-14 SRSO Vis, it looks like the lee low might be trying to take over as primary. I'd love to get some pressure and wind vector obs out of the whole eastern island area.

Edited to add: Get your SRSO loops here:

http://www.ssec.wisc.edu/data/1min/index.php?action=view_animation&req_method=nframes_enddate&enddate=20120825&endtime=1540&nframes=100&band=1&res=1&aniwidth=1920&aniheight=1200

Editable params are: frames from 0-600 (300 max for 1km), res is 1km or 4km, band is 1=vis, 2=shortwave IR, 3=WV, 4=longwave IR, 6+ longerwave IR, image pixels max at 2400 x 1372. Put your date and end time and away you go. Get aggressive with size and number of frames on a slow computer and it will bomb your system.

[turtlehurricane]

The swirly radar echoes over the eastern tip of Cuba is probably the center. Visible cloud motions also suggest the center is right about there.

Unfortunately for Isaac that puts it directly over some of the highest peaks in Cuba

[yoda]

12z GFS makes landfall somewhere around AL/MS border at 99 hrs as a pretty strong system... probably just west of Mobile

[wxsmwhrms]

12Z GFS is significantly slower, stronger and left. Nearly gets Isaac to the bird's foot of LA before turning it north to a landfall along the MS/AL state line Wednesday morning.

[SN_Lover]

The swirly radar echoes over the eastern tip of Cuba is probably the center. Visible cloud motions also suggest the center is right about there.

Unfortunately for Isaac that puts it directly over some of the highest peaks in Cuba

you can already see how downsloping is effecting the region nearest to the eye from the high resolution visible satellite dry air can be seen going into the eye. major flash flooding going on in the windward side of the mountains though.

[wxsmwhrms]

12z is a bit farther west at landfall compared to 0z/6z and it really slows down.

It is trending toward the ECMWF in implying that the trough in the east will not be strong enough to pull it east or pick it up. However, the GFS has a tendency to slow things down too much in those situations due to not being strong enough with the ridge to its E. I would guess it would continue on a somewhat faster N motion based on experience with these types of systems.

[PSUBlizzicane2007]

I definitely find it interesting that the 12Z GFS finally has Isaac strengthening a good bit over the northern Gulf. I think it is fair to say between this GFS and what the Euro has constantly been showing...that there is a good chance for RI in the northern gulf.

[yoda]

Hrs 99 to 117 Issac probably moves a total of 50 miles as it sits there and barely moves north

[wxmeddler]

This site says around 100 mph max 10m winds.

[OSUmetstud]

There is some concern of weakening near the coast there given slow movement and upwelling over the north Gulf shelf waters. But that's a long way away.

[Ground Scouring]

I definitely find it interesting that the 12Z GFS finally has Isaac strengthening a good bit over the northern Gulf. I think it is fair to say between this GFS and what the Euro has constantly been showing...that there is a good chance for RI in the northern gulf.

I really, really, really doubt that will occur, given the average to below-average OHC in the region plus the potential for upwelling due to such slow movement. Plus, I am no longer so sure that Isaac will retain enough structure to re-intensify by the time it leaves Cuba...particularly with the LLC becoming detatched from the MLC and remaining over land.

[turtlehurricane]

you can already see how downsloping is effecting the region nearest to the eye from the high resolution visible satellite dry air can be seen going into the eye. major flash flooding going on in the windward side of the mountains though.

The outflow boundaries just south of Cuba also indicate that dry air is present.

[Ian]

There is some concern of weakening near the coast there given slow movement and upwelling over the north Gulf shelf waters. But that's a long way away.

I would say it's more than a slight concern but if the storm is strong enough it might not matter much. More storms than not weaken up there at least recently. There are a lot of unknowns before that though.. if for some reason it holds off big strengthening till the end it could peak and steady state in etc.

[OSUmetstud]

I would say it's more than a slight concern but if the storm is strong enough it might not matter much. More storms than not weaken up there at least recently. There are a lot of unknowns before that though.. if for some reason it holds off big strengthening till the end it could peak and steady state in etc.

yeah, and just as a counterpoint SHIPS has an average of only 5 kt of shear between 18 and 72 hours.

[winterymix]

I would say it's more than a slight concern but if the storm is strong enough it might not matter much. More storms than not weaken up there at least recently. There are a lot of unknowns before that though.. if for some reason it holds off big strengthening till the end it could peak and steady state in etc.

I like the steady state idea. GFS slows it down tremendously and adds a NNW component. Shear should be low near FL/AL landfall and this should balance the lack of latent heat in the north GOM esp. with upwelling. At landfall, the winds will be a lesser factor than 9+ inch rains and spin up tornadoes. My stoopid SIL lives in Spanish Fort, AL hee hee.

[Ian]

yeah, and just as a counterpoint SHIPS has an average of only 5 kt of shear between 18 and 72 hours.

yeah.. that's a wild card, the environment is considerably better than many weakening storms face at least as far as shear. i'd just not want it to slow too much offshore if we're looking for maximum impacts. but i dunno if it'll peak a day early and then ERC etc.. no one does. it's hard to get too worked up over the high end intensity progs near landfall at this point. i know everyone likes to get their intensity thoughts out so they can go back later and back pat but obviously a lot to be worked out still.

[gulfcane]

I really, really, really doubt that will occur, given the average to below-average OHC in the region plus the potential for upwelling due to such slow movement. Plus, I am no longer so sure that Isaac will retain enough structure to re-intensify by the time it leaves Cuba...particularly with the LLC becoming detatched from the MLC and remaining over land.

Where are you getting your information regarding below avg OHC? I saw Dr. Masters mention it which was odd given that is false. I'm wondering if there is some data I am missing because this map from Dr. Ryan Maue shows clearly the above avg OHC in the GOM. If there is other data disputing this, please let me know.