PSUBlizzicane2007 Posted August 21, 2012 Share Posted August 21, 2012 Ensemble median track hasn't really changed since Sunday. Obviously, the Euro op is well west of yesterday. That's really interesting. In that case, at some point, one would think to expect some sort of pull back on the Euro towards the right... But maybe not until 00Z or 12Z runs on the 24? Link to comment Share on other sites More sharing options...
LakeEffectKing Posted August 21, 2012 Share Posted August 21, 2012 000 WTNT34 KNHC 212050 TCPAT4 BULLETIN TROPICAL STORM ISAAC ADVISORY NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012 500 PM AST TUE AUG 21 2012 ...AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT FINDS THAT THE DEPRESSION HAS BECOME A TROPICAL STORM... SUMMARY OF 500 PM AST...2100 UTC...INFORMATION ---------------------------------------------- LOCATION...15.4N 53.9W ABOUT 500 MI...810 KM E OF GUADELOUPE MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H PRESENT MOVEMENT...W OR 275 DEGREES AT 17 MPH...28 KM/H MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY... NONE. SUMMARY OF WATCHES AND WARNINGS IN EFFECT... A TROPICAL STORM WARNING IS IN EFFECT FOR... * MARTINIQUE * DOMINICA * GUADELOUPE AND THE SURROUNDING ISLANDS...AND ST. MARTIN * ST. KITTS...NEVIS...ANTIGUA...MONTSERRAT...ANGUILLA...AND BARBUDA * SABA...ST. EUSTATIUS...AND ST. MAARTEN A TROPICAL STORM WATCH IS IN EFFECT FOR... * BRITISH VIRGIN ISLANDS * PUERTO RICO...VIEQUES...CULEBRA...AND THE U.S. VIRGIN ISLANDS 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 ELSEWHERE IN HISPANIOLA AND CUBA SHOULD MONITOR THE PROGRESS OF ISAAC. FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED STATES...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 AST...2100 UTC...THE CENTER OF TROPICAL STORM ISAAC WAS LOCATED NEAR LATITUDE 15.4 NORTH...LONGITUDE 53.9 WEST. ISAAC IS MOVING TOWARD THE WEST NEAR 17 MPH...28 KM/H...AND THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT COUPLE OF DAYS. ON THE FORECAST TRACK...THE CENTER OF ISAAC SHOULD MOVE THROUGH THE CENTRAL LESSER ANTILLES WEDNESDAY EVENING...AND EMERGE OVER THE EASTERN CARIBBEAN SEA BY THURSDAY MORNING. REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INDICATE THAT MAXIMUM SUSTAINED WINDS ARE NEAR 40 MPH...65 KM/H...WITH HIGHER GUSTS. ADDITIONAL STRENGTHENING IS FORECAST DURING THE NEXT 48 HOURS. TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 45 MILES...75 KM TO THE NORTHEAST OF THE CENTER. THE MINIMUM CENTRAL PRESSURE JUST MEASURED BY THE HURRICANE HUNTER AIRCRAFT IS 1006 MB...29.71 INCHES. HAZARDS AFFECTING LAND ---------------------- WIND...TROPICAL STORM CONDITIONS ARE EXPECTED TO REACH THE WARNING AREA BY WEDNESDAY AFTERNOON...MAKING OUTSIDE PREPARATIONS DIFFICULT OR DANGEROUS. RAINFALL...TOTAL RAIN ACCUMULATIONS OF 4 TO 8 INCHES ARE POSSIBLE OVER THE NORTHERN WINDWARD ISLANDS AND THE LEEWARD ISLANDS. TOTAL RAIN ACCUMULATIONS OF 1 TO 3 INCHES WITH MAXIMUM AMOUNTS OF 6 INCHES ARE POSSIBLE OVER PUERTO RICO AND THE VIRGIN ISLANDS. STORM SURGE...A STORM SURGE WILL RAISE WATER LEVELS BY AS MUCH AS 1 TO 3 FEET ABOVE NORMAL TIDE LEVELS IN THE NORTHERN LEEWARD ISLANDS. NEAR THE COAST...THE SURGE WILL BE ACCOMPANIED BY DANGEROUS WAVES. SURF...DANGEROUS SURF AND RIP CURRENT CONDITIONS WILL AFFECT THE WINDWARD AND LEEWARD ISLANDS DURING THE NEXT COUPLE OF DAYS. PLEASE CONSULT PRODUCTS FROM YOUR LOCAL WEATHER OFFICE FOR MORE INFORMATION. NEXT ADVISORY ------------- NEXT INTERMEDIATE ADVISORY...800 PM AST. NEXT COMPLETE ADVISORY...1100 PM AST. $$ FORECASTER BEVEN Link to comment Share on other sites More sharing options...
LakeEffectKing Posted August 21, 2012 Share Posted August 21, 2012 000 WTNT44 KNHC 212051 TCDAT4 TROPICAL STORM ISAAC DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012 500 PM AST TUE AUG 21 2012 AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INVESTIGATING THE DEPRESSION REPORTED 44-KT FLIGHT-LEVEL WINDS AT 1000 FT TO THE NORTHEAST OF THE CENTER...AS WELL AS BIAS-CORRECTED SFMR SURFACE WINDS ESTIMATES OF 35 KT. THE MINIMUM CENTRAL PRESSURE WAS NEAR 1005 MB. BASED ON THESE DATA...THE DEPRESSION IS UPGRADED TO TROPICAL STORM ISAAC. DESPITE THE UPGRADE...THE CYCLONE REMAINS SOMEWHAT DISORGANIZED...WITH THE LOW-LEVEL CENTER PARTLY EXPOSED TO THE NORTH OF THE MAIN CONVECTIVE MASS. THE LOW-LEVEL CENTER HAS NUDGED NORTHWARD DURING THE AFTERNOON...BUT THE LONGER TERM MOTION IS 275/15. ISAAC REMAINS SOUTH OF A DEEP-LAYER SUBTROPICAL RIDGE THAT IS FORECAST TO REMAIN INTACT FOR THE NEXT 72 HR...WHICH SHOULD KEEP THE CYCLONE MOVING GENERALLY WESTWARD AS SHOWN BY THE TIGHTLY CLUSTERED TRACK MODEL GUIDANCE. AFTER THAT...THE GLOBAL MODELS CONTINUE TO FORECAST A SHORTWAVE TROUGH TO DIG SOUTHWARD OVER THE SOUTHEASTERN U.S. AND THE GULF OF MEXICO...WHICH IS EXPECTED TO WEAKEN THE RIDGE ACROSS FLORIDA AND THE BAHAMAS. THIS SHOULD ALLOW THE CYCLONE TO TURN WEST- NORTHWESTWARD AND SLOW DOWN OVER THE NORTH-CENTRAL CARIBBEAN SEA AND THE GREATER ANTILLES. THE GUIDANCE HAS BECOME LESS CONSISTENT SINCE THE PREVIOUS ADVISORY. WHILE THE CENTER OF THE GUIDANCE ENVELOPE HAS CHANGED LITTLE...THE ECMWF HAS SHIFTED WELL TO THE LEFT OF ITS PREVIOUS FORECAST AND NOW CALLS FOR A WESTWARD MOTION AFTER ISAAC PASSES HISPANIOLA. THE GFS ENSEMBLES HAVE ALSO SHIFTED WESTWARD...ALTHOUGH THE ENSEMBLE MEAN STILL LIES NEAR THE FORECAST TRACK. THE NEW TRACK IS NUDGED A LITTLE TO THE NORTH OF THE PREVIOUS TRACK BEFORE 72 HR...AND THEN IS NUDGED A LITTLE TO THE RIGHT THEREAFTER. THE TRACK FORECAST AFTER 72 HR LIES NEAR THE LEFT EDGE OF THE GUIDANCE ENVELOPE...WITH ONLY THE ECMWF WELL TO THE LEFT OF THE CURRENT FORECAST. USERS ARE CAUTIONED THAT FIVE-DAY TRACK ERRORS AVERAGE ABOUT 225 N MI. ISAAC CONTINUES TO EXPERIENCE SOME LIGHT NORTHEASTERLY VERTICAL WIND SHEAR...AND IT MAY NOT YET HAVE FULLY MIXED OUT THE DRY AIR THAT HAS BEEN AFFECTING IT. THE SHEAR IS FORECAST TO DIMINISH IN 12-24 HR...WHICH SHOULD ALLOW SOME STRENGTHENING. THAT BEING SAID...THE GFDL AND HWRF MODELS HAVE BACKED OFF ON THEIR FORECASTS OF INTENSIFICATION...AND THE SHIPS AND LGEM MODELS ARE ALSO LESS BULLISH. BASED ON THIS...THE NEW INTENSITY FORECAST SHOWS A LITTLE LESS STRENGTHENING THAN THE PREVIOUS ADVISORY. THE INTENSITY FORECAST AFTER 72 HR HAS AGAIN BEEN REDUCED DUE TO THE FORECAST TRACK SHOWING INCREASED LAND INTERACTION WITH HISPANIOLA AND CUBA. FORECAST POSITIONS AND MAX WINDS INIT 21/2100Z 15.4N 53.9W 35 KT 40 MPH 12H 22/0600Z 15.6N 56.4W 40 KT 45 MPH 24H 22/1800Z 15.9N 59.8W 45 KT 50 MPH 36H 23/0600Z 16.3N 63.1W 50 KT 60 MPH 48H 23/1800Z 16.6N 66.3W 65 KT 75 MPH 72H 24/1800Z 17.0N 71.0W 75 KT 85 MPH 96H 25/1800Z 19.5N 75.0W 75 KT 85 MPH 120H 26/1800Z 21.5N 78.0W 65 KT 75 MPH...INLAND $$ FORECASTER BEVEN _________________________________________ Quick Navigation Links: Tropical Cyclone Forecasts - Tropical Marine Forecasts - Data Archive Link to comment Share on other sites More sharing options...
EasternUSWX Posted August 21, 2012 Share Posted August 21, 2012 Don't agree with nhc at all. First off 12 hrs to get to 45 mph? Heck recon just found a 60 mph surface wind. Link to comment Share on other sites More sharing options...
HurricaneFrances04 Posted August 21, 2012 Share Posted August 21, 2012 Don't agree with nhc at all. First off 12 hrs to get to 45 mph? Heck recon just found a 60 mph surface wind. I just noticed that. Well, day 5 intensity looks reasonable considering land interaction and current trends. Link to comment Share on other sites More sharing options...
Ed Lizard Posted August 21, 2012 Share Posted August 21, 2012 Ensemble median track hasn't really changed since Sunday. Obviously, the Euro op is well west of yesterday. It could well be a few overly agressive Western outliers with very low pressures amongst the Euro ensemble members skewing the means Westward, but to the casual observer, it looks like the means support the op Euro and a North Central/NE Gulf hit, between surface low position and mean 500 mb heights. Link to comment Share on other sites More sharing options...
Ed Lizard Posted August 21, 2012 Share Posted August 21, 2012 Don't agree with nhc at all. First off 12 hrs to get to 45 mph? Heck recon just found a 60 mph surface wind. Do you mean this? 203400 1513N 05341W 9632 00396 //// +206 //// 210013 013 044 021 01 203430 1514N 05342W 9625 00399 //// +198 //// 226013 014 049 021 05 203500 1515N 05344W 9628 00396 //// +200 //// 225013 014 051 034 01 203530 1516N 05345W 9629 00398 //// +199 //// 201013 014 049 047 05 203600 1517N 05346W 9627 00402 //// +202 //// 184010 015 053 044 01 203630 1517N 05347W 9631 00399 //// +211 //// 246004 008 044 028 05 Notice they don't match flight winds, are flagged, and are in heavy rain? I wouldn't be upgrading to a 50 or 55 knot storm on those.... Link to comment Share on other sites More sharing options...
phil882 Posted August 21, 2012 Share Posted August 21, 2012 Don't agree with nhc at all. First off 12 hrs to get to 45 mph? Heck recon just found a 60 mph surface wind. The SFMR obs were highly rain contaminated in the strong convection south of the center. Notice that the FL winds were not corresponding. I think the NHC forecast is quite reasonable until the system is vertically coupled, which hasn't happened yet. Link to comment Share on other sites More sharing options...
dan88 Posted August 21, 2012 Share Posted August 21, 2012 Don't agree with nhc at all. First off 12 hrs to get to 45 mph? Heck recon just found a 60 mph surface wind. These were found in heavy convection of 20-47mm/hr, where SFMR readings are suspect. Notice the huge jump in SFMR readings as soon as the precip rate jumps (the second to last is rainfall rate, 3rd to last is SFMR readings) 203100 1508N 05333W 9629 00404 0083 +220 +220 193018 022 025 006 01 203130 1509N 05334W 9630 00403 0081 +220 +220 191019 020 027 006 01 203200 1510N 05335W 9621 00408 //// +211 //// 195018 022 028 006 01 203230 1510N 05337W 9629 00400 0079 +230 +230 205017 018 022 007 01 203300 1511N 05338W 9630 00400 0078 +230 +230 210015 017 022 007 01 203330 1512N 05340W 9629 00399 0078 +220 +220 208012 012 028 009 01 203400 1513N 05341W 9632 00396 //// +206 //// 210013 013 044 021 01 203430 1514N 05342W 9625 00399 //// +198 //// 226013 014 049 021 05 203500 1515N 05344W 9628 00396 //// +200 //// 225013 014 051 034 01 203530 1516N 05345W 9629 00398 //// +199 //// 201013 014 049 047 05 203600 1517N 05346W 9627 00402 //// +202 //// 184010 015 053 044 01 203630 1517N 05347W 9631 00399 //// +211 //// 246004 008 044 028 05 203700 1519N 05349W 9625 00401 0075 +230 +230 243003 004 034 019 05 203730 1520N 05349W 9627 00398 0073 +230 +230 258006 007 035 021 01 203800 1521N 05350W 9627 00396 //// +222 //// 287006 007 037 020 01 203830 1523N 05351W 9627 00393 0067 +230 +230 347005 007 036 017 01 203900 1524N 05351W 9632 00387 0066 +230 +230 004007 008 029 015 01 203930 1526N 05352W 9628 00390 0066 +240 +240 000008 008 024 011 01 204000 1527N 05352W 9627 00391 0065 +240 +240 018009 009 020 005 01 204030 1528N 05353W 9630 00390 0065 +230 +230 033009 010 014 006 05 Link to comment Share on other sites More sharing options...
turtlehurricane Posted August 21, 2012 Share Posted August 21, 2012 Don't agree with nhc at all. First off 12 hrs to get to 45 mph? Heck recon just found a 60 mph surface wind. Pressure went up 1 mb so it isn't strengthening for now at least. Link to comment Share on other sites More sharing options...
am19psu Posted August 21, 2012 Share Posted August 21, 2012 It could well be a few overly agressive Western outliers with very low pressures amongst the Euro ensemble members skewing the means Westward, but to the casual observer, it looks like the means support the op Euro and a North Central/NE Gulf hit, between surface low position and mean 500 mb heights. The western outliers make landfall later so they skew the mean. That's why I said median track vs. mean track. Link to comment Share on other sites More sharing options...
EasternUSWX Posted August 21, 2012 Share Posted August 21, 2012 Pressure went up 1 mb so it isn't strengthening for now at least. Certainly looks much better on visible with each update. Still think its at least 45 mph currently. We all know how fast these systems can ramp up under good conditions. Link to comment Share on other sites More sharing options...
dan88 Posted August 21, 2012 Share Posted August 21, 2012 Recon has left for the afternoon, next one is scheduled to take off at midnight. Link to comment Share on other sites More sharing options...
turtlehurricane Posted August 21, 2012 Share Posted August 21, 2012 Certainly looks much better on visible with each update. Still think its at least 45 mph currently. We all know how fast these systems can ramp up under good conditions. Yup it's looking alot better as the sun sets, big convective burst and CDO, with a classic spiral band extending across the western semicircle. The weakening recon measured reflects the the brief decoupling of the center from convection earlier. I wouldn't put hurricane Isaac out of the question by tomorrow morning, this thing is ready to go. Link to comment Share on other sites More sharing options...
CooL Posted August 21, 2012 Share Posted August 21, 2012 Latest frames show strong convection firing and trying to wrap around the north side. Looking healthy now Link to comment Share on other sites More sharing options...
phil882 Posted August 21, 2012 Share Posted August 21, 2012 The ECMWF Ensembles are fairly similar to the OP through 168 hours, including the stronger ridge over Isaac at that period keeping the system further south. The GFS ensembles still have a pronounced weakness which allows Isaac to slide further north. Link to comment Share on other sites More sharing options...
wxsmwhrms Posted August 21, 2012 Share Posted August 21, 2012 The ECMWF Ensembles are fairly similar to the OP through 168 hours, including the stronger ridge over Isaac at that period keeping the system further south. The GFS ensembles still have a pronounced weakness which allows Isaac to slide further north. Yeah, really there is a fair amount of model agreement which would seem to allow better confidence than what one might expect as far as a general idea of how this system will track in the 7-10 day period. Would seem to me like a path toward the W-WNW to near or a bit S of Hispaniola and south of Cuba, then a slowing and turn generally toward the north into the weakness, seems like a very likely scenario. Op EC could be a bit too far west due to its tendency to be overly strong with the ridge - but generally saying the eastern half of the Gulf region as an ultimate impact in 7-10 days seems fairly likely at this point. To be honest, my main surprise with the NHC forecast is that they shifted it a bit more right in later periods. I know there is guidance to their right, but most of it is not very robust guidance (NOGAPS, CMC, GFDL). The GFS and EC and their ensembles all generally shifted west today, and a forecast between the GFS and EC is probably a pretty good guesstimate right now IMO. Certainly looking a lot healthier last couple of hours with strong convective development over the center. Dmax could be very interesting tonight. Link to comment Share on other sites More sharing options...
HurricaneFrances04 Posted August 21, 2012 Share Posted August 21, 2012 18Z GFS so far slightly further north than the 12Z. Also a little stronger. Let the coveted EURO vs GFS battle begin. Link to comment Share on other sites More sharing options...
DopplerWx Posted August 21, 2012 Share Posted August 21, 2012 18z GFS further north, goes under Hispaniola then skirts the eastern coast of Cuba and is heading towards southern Florida @126hr Link to comment Share on other sites More sharing options...
EasternUSWX Posted August 21, 2012 Share Posted August 21, 2012 Yup it's looking alot better as the sun sets, big convective burst and CDO, with a classic spiral band extending across the western semicircle. The weakening recon measured reflects the the brief decoupling of the center from convection earlier. I wouldn't put hurricane Isaac out of the question by tomorrow morning, this thing is ready to go. He looks like he wants to do something evil overnight. Convection keeps on filling in and getting more symmetrical. Link to comment Share on other sites More sharing options...
DopplerWx Posted August 21, 2012 Share Posted August 21, 2012 Miami landfall @138 Link to comment Share on other sites More sharing options...
wxsmwhrms Posted August 21, 2012 Share Posted August 21, 2012 There is no meaningful difference in the track between the 18z and 12Z GFS, at least out through 7 days. Looks like any differences are noise level. The main difference is intensity, the 18Z is quite a bit deeper. Link to comment Share on other sites More sharing options...
PSUBlizzicane2007 Posted August 21, 2012 Share Posted August 21, 2012 Miami landfall @138 The location of the centre of Isaac on that image is over 40 miles south of Miami. Link to comment Share on other sites More sharing options...
Eyewall2005 Posted August 21, 2012 Share Posted August 21, 2012 The location of the centre of Isaac on that image is over 40 miles south of Miami. If it took this track it would put keys and metro dade and broward counties on the dirty side of a potentially dangerous hurricane. Link to comment Share on other sites More sharing options...
JPFLL Posted August 21, 2012 Share Posted August 21, 2012 The location of the centre of Isaac on that image is over 40 miles south of Miami. Yes, that looks to be around Florida City to Everglades City.. southern tip Link to comment Share on other sites More sharing options...
gulfcane Posted August 21, 2012 Share Posted August 21, 2012 Link to comment Share on other sites More sharing options...
turtlehurricane Posted August 21, 2012 Share Posted August 21, 2012 T 3.5 I'd guesstimate with this simple chart (I wish I still had my Dvorak manual to make really accurate measurements), real T numbers always lag though so it's at T2.5 right now according to ADT, which is the way it should be since the maturity of cloud structures tends to precede intensity. Another indicator we might be on our way to a strong TS if trends hold. Link to comment Share on other sites More sharing options...
U_Thant Posted August 21, 2012 Share Posted August 21, 2012 Ok, start throwing the hot dogs at me, but this looks like a rapid development of a legit CDO, that looks like it's already starting to rotate. Not 100% on this, especially given the history of entanglement with SAL, however TPW imagery did indicate that 09L was starting to insulate or surround its center with high PWAT air. FAIL To be honest, It should have been apparent that the SAL wasn't about to just give up the ghost that easily. I'm not usually that prone to the bout of overexcited weenie-ism that I suffered early this morning. Link to comment Share on other sites More sharing options...
U_Thant Posted August 21, 2012 Share Posted August 21, 2012 Thanks, Josh. Still looks like some northward jogs of the center in the last few low light vis images. I think Shredderola is coming more and more into play as eventually having a significant disruptive effect on Isaac. Link to comment Share on other sites More sharing options...
MarkSC Posted August 21, 2012 Share Posted August 21, 2012 It must be difficult for NHC with the only two models showing a strong system in the next 5 days (CMC and NOGAPS) being so unreliable and both showing a strong right turn--out to sea even--whereas the reliable global models keep the storm relatively weak for 5 days, which is possible but seems unlikely given the structure of the storm and the good conditions. No, I'm not predicting it will come to CHS! My money is on a brush with FL and then out to sea or perhaps an OB brush, i.e., the climo favored route. I think the NHC forecast is quite reasonable. I'm just troubled by the lack of model guidance showing the deep system that I think is likely and by the fact that BAM deep, which has been pretty accurate lately, is pretty far right of GFS despite using GFS data. Link to comment Share on other sites More sharing options...
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