000 WTNT41 KNHC 050836 TCDAT1 TROPICAL STORM IDA DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112009 400 AM EST THU NOV 05 2009 THE SATELLITE PRESENTATION OF IDA HAS CONTINUED TO IMPROVE OVER THE PAST FEW HOURS. EARLIER THERE WAS A LARGE EXPANSION OF COLD CLOUD TOPS IN A SYMMETRIC CENTRAL DENSE OVERCAST WHILE IN THE LAST HOUR OR TWO THE COLDEST TOPS HAVE TAKEN ON A MORE BANDED APPEARANCE. DVORAK INTENSITY ESTIMATES AT 0600 UTC WERE 55 KT FROM TAFB AND SAB... HOWEVER AIRCRAFT RECONNAISSANCE FOUND THAT IDA WAS ALREADY THAT STRONG YESTERDAY WHEN IT HAD A MUCH LESS IMPRESSIVE SATELLITE APPEARANCE. THEREFORE...THE INITIAL INTENSITY IS RAISED TO 60 KT FOR THIS ADVISORY. WHILE THERE IS ONLY A SMALL WINDOW FOR ADDITIONAL STRENGTHENING...THE HURRICANE WATCH FOR PORTIONS OF THE COAST OF NICARAGUA REFLECTS THE SMALL CHANCE THAT IDA COULD REACH HURRICANE STATUS AS IS MAKES LANDFALL. AFTER LANDFALL...WEAKENING IS FORECAST AS THE CENTER IS EXPECTED TO REMAIN OVER LAND FOR THE NEXT COUPLE OF DAYS. THE TRACK FORECAST TAKES IDA BACK OVER THE NORTHWESTERN CARIBBEAN SEA AFTER 48 HOURS...AND THE INTENSITY FORECAST SHOWS SOME STRENGTHENING AT 72 HOURS AND BEYOND. HOWEVER ...THERE IS A LARGE DEGREE OF UNCERTAINTY AT THIS TIME RANGE...SINCE IDA MAY NOT SURVIVE LONG ENOUGH TO REACH WATER AGAIN. THE INITIAL MOTION ESTIMATE IS 310/06. THROUGH 48 HOURS THE MULTI-MODEL CONSENSUS IS IN GOOD AGREEMENT WITH THE PREVIOUS FORECAST...AS IDA IS EXPECTED TO TURN NORTHWARD BETWEEN A WEAK MID-LEVEL RIDGE OVER THE NORTH-CENTRAL CARIBBEAN SEA AND A WEAK TROUGH OVER THE SOUTHERN GULF OF MEXICO. BEYOND THAT TIME... MUCH OF THE GUIDANCE HAS SHIFTED WESTWARD WITH LARGE DIFFERENCES IN FORWARD SPEED AS WHATEVER IS LEFT OF IDA INTERACTS WITH A MID-LEVEL TROUGH DIGGING INTO THE NORTHWESTERN GULF OF MEXICO. GIVEN THE LARGE SPREAD IN THE GUIDANCE...A SLOW NORTH-NORTHWESTWARD MOTION IS SHOWN AT DAYS 3 THROUGH 5. THIS IS IN GOOD AGREEMENT WITH THE PREVIOUS FORECAST AND ON THE EASTERN SIDE OF THE GUIDANCE ENVELOPE...WITH THE EXCEPTION OF THE GFDL WHICH IS A FAR EASTERN OUTLIER. THE BIGGEST IMPACT OF THIS SLOW-MOVING SYSTEM WILL LIKELY BE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES CAUSED BY EXTREMELY HEAVY RAIN OVER PORTIONS OF NICARAGUA AND HONDURAS OVER THE NEXT COUPLE OF DAYS. FORECAST POSITIONS AND MAX WINDS INITIAL 05/0900Z 12.8N 83.4W 60 KT 12HR VT 05/1800Z 13.3N 83.9W 45 KT...INLAND 24HR VT 06/0600Z 13.9N 84.3W 35 KT...INLAND 36HR VT 06/1800Z 14.7N 84.6W 30 KT...INLAND 48HR VT 07/0600Z 15.7N 84.8W 25 KT...INLAND 72HR VT 08/0600Z 18.0N 85.5W 35 KT...OVER WATER 96HR VT 09/0600Z 20.0N 86.0W 40 KT 120HR VT 10/0600Z 22.0N 87.0W 45 KT $$ FORECASTER BRENNAN/CANGIALOSI