591 
 WTNT44 KNHC 082042
 TCDAT4
  
 TROPICAL DEPRESSION NINE DISCUSSION NUMBER   1
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092013
 500 PM AST SUN SEP 08 2013
  
 SATELLITE IMAGES INDICATE THAT THE LOW PRESSURE SYSTEM BETWEEN THE
 CAPE VERDE ISLANDS AND THE WEST COAST OF AFRICA HAS DEVELOPED
 ENOUGH CONVECTIVE ORGANIZATION TO BE DESIGNATED AS A TROPICAL
 DEPRESSION.  THE INITIAL INTENSITY IS SET AT 25 KT BASED ON DVORAK
 ESTIMATES OF T2.0 FROM TAFB AND T1.5 FROM SAB.  THE LOW-LEVEL
 CENTER APPEARS TO BE ON THE EASTERN EDGE OF THE DEEP CONVECTION DUE
 TO A LITTLE BIT OF NORTHEASTERLY SHEAR.
  
 THE INITIAL MOTION ESTIMATE IS 270/9 KT.  THE DEPRESSION IS LOCATED
 TO THE SOUTH OF A LARGE MID-TROPOSPHERIC ANTICYCLONE CENTERED NEAR
 THE AZORES...AND THE CURRENT WESTWARD MOTION IS EXPECTED TO
 CONTINUE FOR ANOTHER 36 HOURS OR SO.  AFTER THAT TIME...THE
 ANTICYCLONE IS FORECAST TO WEAKEN WHILE A CLOSED MID/UPPER-LEVEL
 LOW DEVELOPS NEAR THE CANARY ISLANDS AND A RIDGE BUILDS WESTWARD
 FROM AFRICA.  THIS PATTERN WILL ALLOW THE DEPRESSION TO TURN RATHER
 SHARPLY TO THE NORTH-NORTHWEST AFTER 48 HOURS AND CONTINUE THAT
 TRAJECTORY THROUGH THE END OF THE FORECAST PERIOD.  SURPRISINGLY...
 THE LARGEST SPREAD AMONG THE TRACK GUIDANCE OCCURS WITHIN THE FIRST
 48 HOURS OR SO...BUT THE MODELS SEEMS TO CONVERGE BY 72 HOURS.  THE
 NHC OFFICIAL TRACK FORECAST IS CLOSE TO THE MODEL CONSENSUS FOR
 MUCH OF THE FORECAST.
  
 A MOIST AIR MASS...WARM WATERS...AND RELATIVELY LIGHT SHEAR SHOULD
 ALLOW THE DEPRESSION TO STRENGTHEN AT LEAST GRADUALLY DURING THE
 NEXT FEW DAYS.  HOWEVER...SOME OF THE MODELS...MAINLY THE
 STATISTICAL-DYNAMICAL GUIDANCE...ARE FAIRLY AGGRESSIVE WITH THE
 INTENSIFICATION RATE AFTER 24 HOURS.  SHIPS AND LGEM HAVE TENDED TO
 HAVE A HIGH BIAS THIS HURRICANE SEASON...SO THE OFFICIAL FORECAST
 IS KEPT A BIT LOWER.  THE FORECAST DOES...HOWEVER...ANTICIPATE THE
 CYCLONE BECOMING A HURRICANE BY 72 HOURS.
  
 GIVEN THE FORECAST...AND THE UNCERTAINTY WITH HOW BIG THE WIND FIELD
 WILL GET ONCE THE DEPRESSION BECOMES A TROPICAL STORM...A TROPICAL
 STORM WARNING HAS BEEN ISSUED FOR THE SOUTHERN CAPE VERDE ISLANDS.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  08/2100Z 13.1N  20.7W   25 KT  30 MPH
  12H  09/0600Z 13.2N  22.1W   30 KT  35 MPH
  24H  09/1800Z 13.5N  24.3W   35 KT  40 MPH
  36H  10/0600Z 13.9N  26.5W   40 KT  45 MPH
  48H  10/1800Z 14.5N  27.9W   55 KT  65 MPH
  72H  11/1800Z 17.5N  29.5W   70 KT  80 MPH
  96H  12/1800Z 21.0N  31.0W   70 KT  80 MPH
 120H  13/1800Z 23.5N  32.5W   65 KT  75 MPH
  
 $$
 FORECASTER BERG