150 
 WTPZ45 KNHC 271431
 TCDEP5
 TROPICAL STORM DARBY DISCUSSION NUMBER   4
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
 8 AM PDT TUE JUL 27 2004
  
 SATELLITE IMAGES INDICATE THAT THE CLOUD PATTERN ASSOCIATED WITH
 DARBY IS GRADUALLY IMPROVING. THERE IS A WELL DEFINED CONVECTIVE
 CURVED BAND TO THE WEST AND DEEP CONVECTION NEAR THE CENTER. THE
 UPPER-LEVEL OUTFLOW IS WELL ESTABLISHED AND IT IS MOST PRONOUNCED
 ON THE WESTERN SEMICIRCLE. DVORAK T-NUMBERS FROM TAFB AND SAB
 SUGGEST THAT THE WINDS ARE ALREADY 55 KNOTS. DARBY IS EXPECTED TO
 BE OVER WARM WATERS AND LOW SHEAR FOR THE NEXT 2 TO 3 DAYS.
 THEREFORE...THE CHANCES OF BECOMING A HURRICANE AND THEN FURTHER
 STRENGTHENING ARE HIGH. THIS IS CONSISTENT WITH SHIPS AND GFDL
 MODELS.
  
 DARBY IS MOVING 290 DEGREES AT 12 KNOTS AROUND THE PERIPHERY OF A
 SUBTROPICAL RIDGE WHICH HAS A WEAKNESS TO ITS WEST. THIS PATTERN IS
 FORECAST TO GRADUALLY MOVE WESTWARD AS INDICATED BY MOST OF THE
 GLOBAL MODELS. THIS WOULD ALLOW DARBY TO MOVE WEST OR 
 WEST-NORTHWESTWARD DURING THE NEXT 3 TO 5 DAYS. THE OFFICIAL
 FORECAST IS A LITTLE BIT TO THE SOUTH OF THE MODEL CONSENSUS AS IN
 PREVIOUS FORECASTS. I WAS TEMPTED TO SHIFT THE OFFICIAL FORECAST
 NORTHWARD TO BE IN AGREEMENT WITH THE CONSENSUS BUT I RATHER WAIT
 FOR TODAYS EVOLUTION OF THE CYCLONE TO MAKE A CHANGE IN THE
 FORECAST.
  
 FORECASTER AVILA
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      27/1500Z 13.4N 118.7W    55 KT
  12HR VT     28/0000Z 14.0N 120.5W    65 KT
  24HR VT     28/1200Z 14.7N 123.0W    75 KT
  36HR VT     29/0000Z 15.3N 125.5W    85 KT
  48HR VT     29/1200Z 16.0N 127.5W    85 KT
  72HR VT     30/1200Z 16.5N 131.0W    75 KT
  96HR VT     31/1200Z 17.0N 135.5W    65 KT
 120HR VT     01/1200Z 17.0N 139.5W    65 KT
  
  
 $$