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 010 
 WTNT42 KNHC 031452
 TCDAT2
  
 HURRICANE KATIA DISCUSSION NUMBER  22
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
 1100 AM AST SAT SEP 03 2011
  
 SEVERAL MICROWAVE OVERPASSES FROM EARLIER THIS MORNING INDICATED
 THAT KATIA IS TILTED...WITH A MID-LEVEL MICROWAVE EYE DISPLACED
 ABOUT 20 N MI NORTH OF THE LOW-LEVEL CENTER. FINAL T-NUMBERS ARE
 DOWN TO T3.5 FROM BOTH SAB AND TAFB...ALTHOUGH CI NUMBERS ARE STILL
 HOLDING AT 4.0. UW-CIMSS ADT ESTIMATES HAVE BEEN DECREASING AND ARE
 NOW T4.1. KATIA WILL BE KEPT AS A HURRICANE FOR NOW...BUT IF TRENDS
 CONTINUE IT COULD ONCE AGAIN WEAKEN TO A TROPICAL STORM LATER
 TODAY.
 
 KATIA IS BEGINNING TO MOVE AROUND THE SOUTHWESTERN PERIPHERY OF A
 MID-LEVEL HIGH LOCATED OVER THE CENTRAL ATLANTIC...AND TOWARDS A
 DEEP-LAYER TROUGH OVER THE WESTERN ATLANTIC.  WITH THE EXCEPTION OF
 THE UKMET...WHICH IS DISREGARDED IN THIS FORECAST...THE MODELS ARE
 IN GOOD AGREEMENT ON MAINTAINING A MOTION OF ABOUT 305 DEGREES AT 9
 TO 10 KT FOR THE NEXT 48 HOURS.  BEYOND 72 HOURS...THE TRACK
 FORECAST BECOMES A LITTLE MORE COMPLEX AND PARTLY DEPENDS ON HOW
 TROPICAL STORM LEE AND U.S. EAST COAST TROUGHING EVOLVE OVER THAT
 TIME.  AS AN EXAMPLE...THE ECMWF DEVELOPS A DEEP-LAYER CLOSED LOW
 OVER THE OHIO VALLEY BY DAY 5 WHILE THE GFS HAS A SHARP TROUGH
 ALMOST READY TO CLOSE OFF OVER NEW YORK AND PENNSYLVANIA.  DESPITE
 THESE DIFFERENCES...BOTH MODELS HAVE SHIFTED TO THE EAST...WITH THE
 GFS BEING THE FASTEST DUE TO THE MORE PROGRESSIVE FLOW.  THE NHC
 TRACK FORECAST IS ALSO SHIFTED TO THE EAST YET STILL LIES TO THE
 WEST OF THOSE USUALLY RELIABLE MODELS.
 
 STRONG SOUTHERLY SHEAR IS AFFECTING KATIA AND IS LIKELY ALLOWING DRY
 AIR TO ERODE THE DEEP CONVECTION ON THE SOUTHERN SIDE.  THIS SHEAR
 IS EXPECTED TO PERSIST FOR THE NEXT 24 HOURS OR SO...DURING WHICH
 TIME NO STRENGTHENING IS INDICATED IN THE FORECAST.  THEREAFTER...
 THE SHIPS MODEL SHOWS THAT UPPER-LEVEL WINDS COULD BECOME MORE
 CONDUCIVE FOR STRENGTHENING...BUT THIS WILL ALL DEPEND ON THE
 LOCATION OF KATIA RELATIVE TO THE DEEP-LAYER TROUGH OR CLOSED LOW
 OVER THE EASTERN UNITED STATES.  THE NHC INTENSITY FORECAST WILL
 CONTINUE TO INDICATE INTENSIFICATION BETWEEN DAYS 2 AND 4...AND IS
 STILL ABOVE THE INTENSITY CONSENSUS AND STATISTICAL MODELS.
 
 IT IS ADVISABLE NOT TO FOCUS ON SLIGHT FORECAST INTENSITY CHANGES
 NEAR THE MAJOR HURRICANE THRESHOLD OF 100 KT SINCE THERE IS VERY
 LITTLE DIFFERENCE BETWEEN A 95- AND 100-KT HURRICANE.  BASED ON THE
 CURRENT FORECAST AND RECENT NHC INTENSITY ERRORS...AT THIS TIME
 THERE IS ROUGHLY A 50/50 CHANCE OF KATIA STILL BECOMING A MAJOR
 HURRICANE DURING THE NEXT 5 DAYS.
 
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  03/1500Z 19.6N  55.8W   65 KT  75 MPH
  12H  04/0000Z 20.3N  57.0W   65 KT  75 MPH
  24H  04/1200Z 21.3N  58.7W   65 KT  75 MPH
  36H  05/0000Z 22.5N  60.4W   70 KT  80 MPH
  48H  05/1200Z 23.7N  62.1W   75 KT  85 MPH
  72H  06/1200Z 26.5N  65.0W   85 KT 100 MPH
  96H  07/1200Z 29.5N  67.5W   95 KT 110 MPH
 120H  08/1200Z 32.0N  69.5W   90 KT 105 MPH
  
 $$
 FORECASTER BERG
  
 
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