000
WTNT41 KNHC 060241
TCDAT1
TROPICAL DEPRESSION IDA DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112009
1000 PM EST THU NOV 05 2009

SURFACE OBSERVATIONS AND CONVENTIONAL SATELLITE IMAGERY INDICATE
THAT IDA HAS WEAKENED TO A TROPICAL DEPRESSION.  WHAT REMAINS OF THE
DIMINISHING DEEP CONVECTION IS CURRENTLY CONFINED TO NORTHWEST AND
NORTHEAST QUADRANTS.  SOME FURTHER WEAKENING IS LIKELY DURING THE
NEXT 12 TO 24 HOURS AS IDA CONTINUES ON A GENERAL NORTHWARD TRACK
OVER NORTHEASTERN NICARAGUA AND EASTERN HONDURAS. AROUND THE 36
HOUR PERIOD...THE CYCLONE SHOULD EMERGE OVER THE NORTHWEST
CARIBBEAN SEA AND...ASSUMING THE CIRCULATION IS NOT TOO SEVERELY
DISRUPTED BY ITS PASSAGE OVER LAND...THE SYSTEM SHOULD RESTRENGTHEN
INTO A TROPICAL STORM.  HOWEVER...THE GLOBAL MODELS INDICATE ONLY A
MARGINALLY FAVORABLE UPPER-LEVEL WIND ENVIRONMENT OVER THE
REGION...WHICH SHOULD CURTAIL SIGNIFICANT INTENSIFICATION AS IDA
HEADS IN THE GENERAL DIRECTION OF THE YUCATAN CHANNEL.  AFTER IDA
ENTERS THE SOUTHERN GULF OF MEXICO....THE INTENSITY FORECAST IS
HIGHLY UNCERTAIN.  THE LARGE-SCALE MODELS ALL AGREE ON AN
INCREASINGLY STRONG VERTICAL SHEAR ENVIRONMENT DEVELOPING OVER THE
GULF OF MEXICO TOWARD THE END OF THE FORECAST PERIOD.  THE GFDL AND
HWRF MODELS...PARTICULARLY THE FORMER...SHOW SIGNIFICANT
INTENSIFICATION OF IDA IN THE LATTER PART OF THE PERIOD.  IT SHOULD
BE RECALLED HOWEVER THAT THESE MODELS HAVE BEEN KNOWN TO HAVE A
HIGH BIAS IN STRONGLY SHEARED ENVIRONMENTS...AS WAS THE CASE WITH
TROPICAL STORMS DANNY...ERIKA...AND HENRI OF THIS YEAR.
CONSEQUENTLY...THE OFFICIAL WIND SPEED FORECAST LEANS MORE TOWARD
THE WEAKER LGEM AND SHIPS PREDICTIONS.

THE INITIAL MOTION IS ESTIMATED TO BE 330/4...WITHIN THE SOUTHERLY
STEERING FLOW ON THE WEST SIDE OF A WEAK MID-LEVEL RIDGE. WITH THE
EXCEPTION OF FORWARD SPEED DISPARITIES...THE GLOBAL AND REGIONAL
MODELS CONTINUE TO INDICATE A GENERAL NORTH TO NORTH-NORTHWESTWARD
MOTION INTO THE CENTRAL GULF OF MEXICO OVER THE NEXT 4 DAYS.
AROUND THE END OF THE PERIOD...MOST OF THE TRACK GUIDANCE SHOWS A
TURN TO THE RIGHT AS IDA BEGINS TO INTERACT WITH THE WESTERLIES.
THE OFFICIAL FORECAST HAS CHANGED LITTLE FROM THE PREVIOUS ONE AND
IS CLOSE TO THE MODEL CONSENSUS.

THE BIGGEST IMPACT OF THIS SLOW-MOVING SYSTEM DURING THE NEXT DAY OR
SO WILL LIKELY BE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES
CAUSED BY EXTREMELY HEAVY RAIN OVER PORTIONS OF NICARAGUA AND
HONDURAS.

FORECAST POSITIONS AND MAX WINDS

INITIAL      06/0300Z 13.8N  84.1W    30 KT
 12HR VT     06/1200Z 14.4N  84.1W    25 KT...INLAND
 24HR VT     07/0000Z 15.4N  84.2W    25 KT...INLAND
36HR VT     07/1200Z 16.6N  84.5W    35 KT...OVER WATER
 48HR VT     08/0000Z 17.7N  85.0W    40 KT
 72HR VT     09/0000Z 20.3N  86.2W    45 KT
 96HR VT     10/0000Z 23.0N  87.5W    45 KT
120HR VT     11/0000Z 26.0N  87.0W    45 KT

$$
FORECASTER PASCH/ROBERTS

000
WTNT41 KNHC 062045
TCDAT1
TROPICAL DEPRESSION IDA DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112009
400 PM EST FRI NOV 06 2009

THERE HAS BEEN LITTLE CHANGE WITH IDA DURING THE DAY.  SATELLITE
IMAGES STILL SHOW A RATHER ASYMMETRIC SYSTEM...WITH MOST OF THE
SIGNIFICANT BANDING ACTIVITY TO THE NORTH OF THE CENTER.  THE
INITIAL INTENSITY WILL BE MAINTAINED AT 30 KT.  NOW THAT IDA IS
OFFSHORE OVER VERY WARM WATERS...THE SYSTEM HAS A CHANCE TO RE-
INTENSIFY.  THE BEST OPPORTUNITY FOR THE TROPICAL CYCLONE TO
STRENGTHEN IS OVER THE NORTHWESTERN CARIBBEAN SEA...WHERE VERTICAL
WIND SHEAR IS FORECAST TO BE MODERATE BY THE GLOBAL MODELS.  SHEAR
IS LIKELY TO GET RATHER STRONG BY THE TIME THE SYSTEM ENTERS THE
CENTRAL GULF OF MEXICO...WITH COOLER WATERS PRESENT...SO WEAKENING
WILL BE SHOWN AT THAT TIME.  WHILE THE DYNAMICAL GUIDANCE REMAINS
HIGHER THAN THE STATISTICAL GUIDANCE...THERE IS A LITTLE LESS
SPREAD THAN EARLIER.  THE NHC FORECAST SHOWS SLIGHTLY HIGHER WINDS
IN THE CARIBBEAN SEA THAN THE PREVIOUS FORECAST DID...AND REDUCES
THE INTENSITY AT THE END OF THE FORECAST PERIOD.

IDA CONTINUES MOVING TOWARD THE NORTH...360/7.  THE DEPRESSION
SHOULD MOVE TOWARD THE NORTH-NORTHWEST TOMORROW DUE TO SHORTWAVE
RIDGING OVER THE SOUTHEASTERN UNITED STATES.  MOST OF THE MODELS
ARE IN GOOD AGREEMENT ON THE SYSTEM PASSING OVER OR JUST TO THE
EAST OF THE YUCATAN PENINSULA IN A COUPLE OF DAYS.  AFTER IDA
ENTERS THE GULF OF MEXICO...IT WILL LIKELY TAKE A TRACK TOWARD THE
NORTH OR NORTHEAST AS IT BECOMES STEERED BY AN APPROACHING
MID-LEVEL TROUGH.  THE FORECAST TRACK IS VERY COMPLEX IN THE LONG
RANGE WITH SIGNIFICANT UNCERTAINTY IN HOW IDA WILL INTERACT WITH
THAT TROUGH.  MOST OF THE MODELS ARE SHOWING THE CYCLONE
APPROACHING THE NORTHERN GULF COAST...THEN TURNING EASTWARD OR EVEN
SOUTH OF EAST.  A COMPLICATING FACTOR IS THAT IDA WILL LIKELY BE
TRANSITIONING INTO AN EXTRATROPICAL CYCLONE AT THAT TIME...AND THE
GLOBAL MODELS HAVE QUITE VARYING SOLUTIONS FOR THIS TRANSITION.
THE NHC FORECAST IS ADJUSTED NORTHWARD AT THE LONG RANGE...BUT
REMAINS SOUTH OF THE MODEL CONSENSUS. 

IT IS OF NOTE THAT MOST OF THE GLOBAL MODELS ARE SHOWING A LARGE
PRESSURE GRADIENT BETWEEN A HIGH OVER THE SOUTHEASTERN UNITED
STATES AND THE TROPICAL CYCLONE.  THIS COULD CONTRIBUTE TO A LARGE
AREA OF STRONG WINDS OVER THE GULF OF MEXICO NOT DIRECTLY
ATTRIBUTABLE TO IDA.


FORECAST POSITIONS AND MAX WINDS

INITIAL      06/2100Z 15.7N  83.9W    30 KT
 12HR VT     07/0600Z 16.7N  84.1W    30 KT
 24HR VT     07/1800Z 17.9N  84.7W    35 KT
 36HR VT     08/0600Z 19.1N  85.4W    45 KT
48HR VT     08/1800Z 20.6N  86.3W    50 KT
 72HR VT     09/1800Z 24.5N  88.0W    45 KT
 96HR VT     10/1800Z 27.5N  87.5W    45 KT
120HR VT     11/1800Z 27.5N  85.5W    35 KT...EXTRATROPICAL

$$
FORECASTER BLAKE