David Reimer Posted August 27, 2012 Share Posted August 27, 2012 TROPICAL STORM ISAAC FORECAST/ADVISORY NUMBER 27 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012 2100 UTC MON AUG 27 2012 CHANGES IN WATCHES AND WARNINGS WITH THIS ADVISORY... THE HURRICANE WARNING FROM THE FLORIDA-ALABAMA BORDER TO DESTIN HAS BEEN CHANGED TO A TROPICAL STORM WARNING. SUMMARY OF WATCHES AND WARNINGS IN EFFECT... A HURRICANE WARNING IS IN EFFECT FOR... * EAST OF MORGAN CITY LOUISIANA TO THE ALABAMA-FLORIDA BORDER... INCLUDING METROPOLITAN NEW ORLEANS...LAKE PONTCHARTRAIN... AND LAKE MAUREPAS A HURRICANE WATCH IS IN EFFECT FOR... * INTRACOASTAL CITY TO MORGAN CITY LOUISIANA A TROPICAL STORM WARNING IS IN EFFECT FOR... * FROM THE ALABAMA-FLORIDA BORDER TO THE AUCILLA RIVER * INTRACOASTAL CITY TO MORGAN CITY LOUISIANA A TROPICAL STORM WATCH IS IN EFFECT FOR... * EAST OF SABINE PASS TO WEST OF INTRACOASTAL CITY LOUISIANA A HURRICANE WARNING MEANS THAT HURRICANE CONDITIONS ARE EXPECTED SOMEWHERE WITHIN THE WARNING AREA. PREPARATIONS TO PROTECT LIFE AND PROPERTY SHOULD BE RUSHED TO COMPLETION. A HURRICANE WATCH MEANS THAT HURRICANE CONDITIONS ARE POSSIBLE WITHIN THE WATCH AREA. 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. TROPICAL STORM CENTER LOCATED NEAR 26.4N 86.2W AT 27/2100Z POSITION ACCURATE WITHIN 15 NM PRESENT MOVEMENT TOWARD THE NORTHWEST OR 305 DEGREES AT 10 KT ESTIMATED MINIMUM CENTRAL PRESSURE 981 MB MAX SUSTAINED WINDS 60 KT WITH GUSTS TO 75 KT. 50 KT....... 50NE 15SE 15SW 50NW. 34 KT.......150NE 150SE 80SW 180NW. 12 FT SEAS..180NE 180SE 180SW 150NW. WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT. REPEAT...CENTER LOCATED NEAR 26.4N 86.2W AT 27/2100Z AT 27/1800Z CENTER WAS LOCATED NEAR 26.1N 85.9W FORECAST VALID 28/0600Z 27.4N 87.5W MAX WIND 70 KT...GUSTS 85 KT. 64 KT... 20NE 0SE 0SW 20NW. 50 KT... 60NE 20SE 20SW 60NW. 34 KT...165NE 150SE 80SW 180NW. FORECAST VALID 28/1800Z 28.6N 89.0W MAX WIND 80 KT...GUSTS 100 KT. 64 KT... 20NE 20SE 0SW 20NW. 50 KT... 60NE 50SE 30SW 60NW. 34 KT...180NE 150SE 80SW 180NW. FORECAST VALID 29/0600Z 29.5N 90.0W...NEAR THE COAST MAX WIND 85 KT...GUSTS 105 KT. 64 KT... 30NE 20SE 10SW 20NW. 50 KT... 60NE 60SE 40SW 60NW. 34 KT...180NE 150SE 80SW 150NW. FORECAST VALID 29/1800Z 30.3N 90.7W...INLAND MAX WIND 75 KT...GUSTS 90 KT. 50 KT... 60NE 60SE 40SW 40NW. 34 KT...180NE 150SE 80SW 110NW. FORECAST VALID 30/1800Z 32.2N 91.8W...INLAND MAX WIND 35 KT...GUSTS 45 KT. 34 KT... 60NE 130SE 30SW 40NW. EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 175 NM ON DAY 4 AND 225 NM ON DAY 5...AND FOR INTENSITY NEAR 20 KT EACH DAY OUTLOOK VALID 31/1800Z 35.9N 92.1W...INLAND MAX WIND 25 KT...GUSTS 35 KT. OUTLOOK VALID 01/1800Z 38.7N 89.3W...INLAND MAX WIND 20 KT...GUSTS 30 KT. REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 26.4N 86.2W NEXT ADVISORY AT 28/0300Z Link to comment Share on other sites More sharing options...
phil882 Posted August 27, 2012 Share Posted August 27, 2012 it should be expected...it's a 90-minute forecast...it should look close to reality (assuming a proper, accurate initialization)...the same satellite images your eyes are ingesting were ingested by the HRRR...90 minutes isn't a lot of time to deviate from the initialization. It becomes more impressive when you realize that the model has to downscale the input data (at 12km resolution from the RAP) to 4km in that same time period. Keep in mind there is no radar coverage over the storm either, so its capturing the features pretty well considering. I am just trying to highlight the utility of using very high resolution models as opposed to other options like the NAM, which still require cumulus parameterizations that preform poorly in the tropics. Link to comment Share on other sites More sharing options...
HKY_WX Posted August 27, 2012 Share Posted August 27, 2012 I was thinking earlier that maybe that band over E Florida could be robbing some of the convection to the East of the center. That coupled with dry air. Hoping that once it sheds that band and we get D Min tonight it will finally get going better. As others have said it looks like an eye may trying to pop on visible with the thinning clouds but Im trying to determine if thats just dry air wrapping itself into the coc. I'm not an expert on hurricane dynamics, but the earlier NHC discussion mentioned the winds concentrated outside of the COC inhibiting strengthening around the eye. THe HRRR could perhaps be keying on that band as being the inhibiting factor. IE, once it dissipates, we could see strengthening or at least a more traditional SAT representation. Link to comment Share on other sites More sharing options...
chris87 Posted August 27, 2012 Share Posted August 27, 2012 It becomes more impressive when you realize that the model has to downscale the input data (at 12km resolution from the RAP) to 4km in that same time period. Keep in mind there is no radar coverage over the storm either, so its capturing the features pretty well considering. I am just trying to highlight the utility of using very high resolution models as opposed to other options like the NAM, which still require cumulus parameterizations that preform poorly in the tropics. i hear you...it does show good performance on "spin-up" considering the lower resolution initial fields.. Link to comment Share on other sites More sharing options...
Superstorm93 Posted August 27, 2012 Share Posted August 27, 2012 NHC has it at 70 mph for the 5pm If this can pop an eye by tonight, we could see quite a show. Link to comment Share on other sites More sharing options...
PSUBlizzicane2007 Posted August 27, 2012 Share Posted August 27, 2012 I think it is safe to say that tonight's diurnal maximum period will be the most important time during Isaac's entire lifetime in determining the final intensity of the system at landfall. Right now, we see Isaac strengthening and getting better organised on satellite and in recon which would put it in a perfect position for RI during the overnight diurnal maximum. Will it take advantage of it? We will have to see. Link to comment Share on other sites More sharing options...
eurojosh Posted August 27, 2012 Share Posted August 27, 2012 NHC has slightly bumped up their forecasted max windspeed from 90 to 100mph on the 1700EST probability table... http://www.nhc.noaa.gov/refresh/graphics_at4+shtml/163340.shtml?table#contents Link to comment Share on other sites More sharing options...
lakeeffectkid383 Posted August 27, 2012 Share Posted August 27, 2012 I'm not an expert on hurricane dynamics, but the earlier NHC discussion mentioned the winds concentrated outside of the COC inhibiting strengthening around the eye. THe HRRR could perhaps be keying on that band as being the inhibiting factor. IE, once it dissipates, we could see strengthening or at least a more traditional SAT representation. Ya its pretty funny because if I cover up the right side of the storm with my hand on my Ipad on vis imagery it looks pretty darn good than I see the right side and it looks pretty bad although the convection wrapping around the center now does look better but theres still a big void of convection from the (developing) core to the west cosst of Florida which I do believe has something to do with that band on E Florida which is probably due to strong convergence, this should die though when the sun sets as picked up by the HRRR. NHC has this thing back up to a Cat 2 at landfall as of the 5pm advisory, Link to comment Share on other sites More sharing options...
PSUBlizzicane2007 Posted August 27, 2012 Share Posted August 27, 2012 Also, I forgot to mention... I'm curious to see that, if Isaac does undergo RI tonight (with a corresponding increase in convection on the east side of the system)... will the momentum on the east side of the system/wrapping of the convection on the right side correspond to a slight shift to the right in forward motion as Isaac moves towards the coast? Link to comment Share on other sites More sharing options...
LocoAko Posted August 27, 2012 Share Posted August 27, 2012 New HRRR run just coming in has some impressive 3-hr pressure falls later http://rapidrefresh....g_t6sfc_f06.png Those pressure falls cannot simply be interpreted as deepening. That is the local pressure tendency at a given point. Most of those pressure falls are due to the storm's movement westward (hence the pressure rises to the east where the storm is currently). You could make the argument that with only 3-4mb/3hr rises on the back end and 5-6mb/3hr falls on the front end that it does show some deepening (my apologies if this is what you meant in the first place - perhaps I'm sensitive from seeing isallobaric maps misused during winter storms ). Link to comment Share on other sites More sharing options...
lakeeffectkid383 Posted August 27, 2012 Share Posted August 27, 2012 I think it is safe to say that tonight's diurnal maximum period will be the most important time during Isaac's entire lifetime in determining the final intensity of the system at landfall. Right now, we see Isaac strengthening and getting better organised on satellite and in recon which would put it in a perfect position for RI during the overnight diurnal maximum. Will it take advantage of it? We will have to see. Not that this thing has become the most beautiful thing to look at but its done a decent job holding its own and even strengthening today even during D Min. This thing was at 990mb at 5am this morning and its now at 981... Tonights D Max will be critical for sure. Link to comment Share on other sites More sharing options...
Superstorm93 Posted August 27, 2012 Share Posted August 27, 2012 The clearing is really wrapping up on SRSO now http://www.ssec.wisc.edu/data/1min/index.php?action=view_animation&req_method=nframes_enddate&enddate=20120827&endtime=2054&nframes=100&band=1&res=4&aniwidth=1280&aniheight=1024 Link to comment Share on other sites More sharing options...
gulfcane Posted August 27, 2012 Share Posted August 27, 2012 Guys, is that curling dimple that can be seen on vis and ir part of dry air entrainment into the core or is it the beginning of the eye taking shape? What your thoughts? Link to comment Share on other sites More sharing options...
EasternUSWX Posted August 27, 2012 Share Posted August 27, 2012 Guys, is that curling dimple that can be seen on vis and ir part of dry air entrainment into the core or is it the beginning of the eye taking shape? What your thoughts? It's an eye. Link to comment Share on other sites More sharing options...
David Reimer Posted August 27, 2012 Share Posted August 27, 2012 Cloud tops have warmed over the past 45 minutes. That might temporarily halt or at least slow this strengthening trend. Link to comment Share on other sites More sharing options...
Dunkman Posted August 27, 2012 Share Posted August 27, 2012 FL winds on this pass through the SE quadrant are 10-15kts. higher than the last pass which was less than 3 hours ago. Link to comment Share on other sites More sharing options...
HKY_WX Posted August 27, 2012 Share Posted August 27, 2012 It's the eye, but there is dry air entrainment. It will probably take several more hours before we see a true eye. Maybe early morning hours. Link to comment Share on other sites More sharing options...
lakeeffectkid383 Posted August 27, 2012 Share Posted August 27, 2012 Still looks like theres some E shear present. Its most noticable on the Far NW side.. http://www.ssd.noaa.gov/PS/TROP/floaters/09L/imagery/rbtop-animated.gif Link to comment Share on other sites More sharing options...
Superstorm93 Posted August 27, 2012 Share Posted August 27, 2012 BIG FWIW, but the new HRRR has a complete convective pattern reorganization taking place tonight. With the developing eye and falling pressures, this may not be so far-fetched. Link to comment Share on other sites More sharing options...
wxmx Posted August 27, 2012 Share Posted August 27, 2012 Last pass at the wind shift was at a lower altitude, indicating that probably it's still deepening Link to comment Share on other sites More sharing options...
Indystorm Posted August 27, 2012 Share Posted August 27, 2012 That forecast increase to 100 mph at landfall is low end category 2. It is also interesting that they are forecasting storm surge in a range of 6-12 feet for se Louisiana and Mississippi. That covers a category 3 surge on the scale as well as category 2. What I mean by this is that although winds may only reach category 2 strength, because of the large geographical extent of the windfield with this storm, the surge may be greater than what would ordinarily be expected of a category 2. Link to comment Share on other sites More sharing options...
Superstorm93 Posted August 27, 2012 Share Posted August 27, 2012 SRSO shows convection developing in the core. Could be game time soon. Link to comment Share on other sites More sharing options...
PSUBlizzicane2007 Posted August 27, 2012 Share Posted August 27, 2012 That forecast increase to 100 mph at landfall is low end category 2. It is also interesting that they are forecasting storm surge in a range of 6-12 feet for se Louisiana and Mississippi. That covers a category 3 surge on the scale as well as category 2. One could probably expect a more cat-3 like surge from a very large landfalling category 2 hurricane in that area. Link to comment Share on other sites More sharing options...
lakeeffectkid383 Posted August 27, 2012 Share Posted August 27, 2012 They just had the president of Plaquemans Parrish on TWC and he said the surge will likley top the levees there by 2-3 feet and he sounds worried that a prolonged surge like this one may weaken the levees significantly as they're not part of the Federal system of levees. Link to comment Share on other sites More sharing options...
andyhb Posted August 27, 2012 Share Posted August 27, 2012 BIG FWIW, but the new HRRR has a complete convective pattern reorganization taking place tonight. With the developing eye and falling pressures, this may not be so far-fetched. That is a very similar appearance to the HWRF and it's more intense verbatims, just FYI. Link to comment Share on other sites More sharing options...
jburns Posted August 27, 2012 Share Posted August 27, 2012 They just had the president of Plaquemans Parrish on TWC and he said the surge will likley top the levees there by 2-3 feet and he sounds worried that a prolonged surge like this one may weaken the levees significantly as they're not part of the Federal system of levees. If the storm follows the projected forecast Plaquemans Parrish would be a good place not to be. It is just to the right of a strengthening hurricane. Link to comment Share on other sites More sharing options...
Nikolai Posted August 27, 2012 Share Posted August 27, 2012 If the storm follows the projected forecast Plaquemans Parrish would be a good place not to be. It is just to the right of a strengthening hurricane. If Isaac strengthens beyond Cat 2 and takes 24 hours to move through the region, there probably won't even be a Plaquemines Parish by Thursday morning. It's barely above sea level as is. Link to comment Share on other sites More sharing options...
lakeeffectkid383 Posted August 27, 2012 Share Posted August 27, 2012 If the storm follows the projected forecast Plaquemans Parrish would be a good place not to be. It is just to the right of a strengthening hurricane. Definitly than you throw in large battering waves on top of the surge along with several inches of rain in an area thats 65% water its a perfect recipie for disaster. Link to comment Share on other sites More sharing options...
David Reimer Posted August 27, 2012 Share Posted August 27, 2012 If Isaac strengthens beyond Cat 2 and takes 24 hours to move through the region, there probably won't even be a Plaquemines Parish by Thursday morning. It's barely above sea level as is. That's speculation and probably needs to be kept in the banter thread. Link to comment Share on other sites More sharing options...
Superstorm93 Posted August 27, 2012 Share Posted August 27, 2012 Towers in the core... Should be an interesting night. Link to comment Share on other sites More sharing options...
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