Tropical Depression TWENTY-E

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TROPICAL DEPRESSION TWENTY-E DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP202009
200 PM PDT THU OCT 15 2009
 
CONVENTIONAL SATELLITE IMAGERY...DATA FROM THE ASCAT
SCATTEROMETER...AND SHIP REPORTS INDICATE THAT THE LOW PRESSURE
AREA CENTERED SOUTH OF MEXICO HAS ACQUIRED SUFFICIENT ORGANIZED
CONVECTION AND CIRCULATION TO BE DESIGNATED A TROPICAL DEPRESSION. 
THE ASCAT DATA SHOWED MAXIMUM WINDS NEAR 30 KT ABOUT 60 N MI
NORTH-NORTHEAST OF THE CENTER...WHICH IS IN GOOD AGREEMENT WITH
SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB.  THE CIRRUS
OUTFLOW IS CURRENTLY GOOD IN ALL DIRECTIONS.
 
THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 305/11.  THE DEPRESSION
IS ON THE SOUTH SIDE OF A LOW/MID-LEVEL RIDGE EXTENDING FROM MEXICO
WESTWARD OVER THE PACIFIC.  THE LARGE-SCALE MODELS FORECAST THIS
FEATURE TO PERSIST FOR THE NEXT 48-72 HR...AND THIS SHOULD STEER
THE DEPRESSION WEST-NORTHWESTWARD AT A SLIGHTLY SLOWER FORWARD
SPEED.  AFTER THAT TIME...THE RIDGE IS FORECAST TO WEAKEN AS A
MID/UPPER-LEVEL TROUGH DEVELOPS OVER THE WESTERN UNITED STATES. 
THE TRACK GUIDANCE DIVERGES DURING THIS TIME.  THE HWRF AND GFDL...
WHICH ARE ON THE RIGHT SIDE OF THE GUIDANCE ENVELOPE...TURN THE
CYCLONE TO THE NORTH OR NORTHEAST BY 120 HR...WITH THE GFDL
FORECASTING THE CENTER TO BE NEAR SOUTHERN BAJA CALIFORNIA.  THE
NOGAPS...CANADIAN...AND UKMET ARE ON THE OTHER SIDE OF THE
ENVELOPE...AND SHOW A SLOW WEST-NORTHWESTWARD MOTION AFTER 72 HR. 
THE GFS AND ECMWF ARE IN BETWEEN THESE EXTREMES...WITH 120 HR
POSITIONS JUST SOUTH OR SOUTHWEST OF SOCORRO ISLAND.  THE FORECAST
TRACK COMPROMISES BETWEEN THESE EXTREMES...WITH THE TRACK IN BEST
AGREEMENT WITH THE TVCN CONSENSUS MODEL FOR THE FIRST 72 HR AND
WITH THE GFS/ECMWF THEREAFTER.
 
THE DEPRESSION IS EMBEDDED IN A LIGHT VERTICAL WIND SHEAR
ENVIRONMENT OVER VERY WARM WATER...AND THE LARGE-SCALE MODELS
FORECAST THIS TO CONTINUE THROUGH AT LEAST 72 HR.  ALL GUIDANCE IS
FORECASTING SIGNIFICANT AND RAPID STRENGTHENING DURING THE NEXT
72-96 HR...WITH THE HWRF FORECASTING THE CENTRAL PRESSURE TO FALL
BELOW 900 MB.  THE RAPID INTENSIFICATION INDEX OF THE SHIPS MODEL
INDICATES A 60 PERCENT CHANCE OF 30 KT OR MORE INTENSIFICATION
DURING THE NEXT 24 HR.  THE INTENSITY FORECAST THUS CALLS FOR FAST
STRENGTHENING...WITH THE DEPRESSION BECOMING A TROPICAL STORM BY
12 HR...A HURRICANE IN ABOUT 36 HR...AND A MAJOR HURRICANE IN ABOUT
72 HR.  THE INTENSITY FORECAST IS SIMILAR TO THE SHIPS AND
INTENSITY CONSENSUS MODELS.  THERE IS A CHANCE THAT THE CYCLONE
COULD STRENGTHEN FASTER THAN CURRENTLY FORECAST.

THE INITIAL RADII OF 12 FT SEAS ARE BASED ON TWO SHIP REPORTS
130 AND 170 N MI FROM THE CENTER IN THE EASTERN SEMICIRCLE.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/2100Z 12.1N  97.0W    30 KT
 12HR VT     16/0600Z 12.6N  98.2W    40 KT
 24HR VT     16/1800Z 13.0N  99.7W    55 KT
 36HR VT     17/0600Z 13.4N 101.3W    65 KT
 48HR VT     17/1800Z 13.9N 103.3W    80 KT
 72HR VT     18/1800Z 15.0N 108.0W   100 KT
 96HR VT     19/1800Z 17.0N 111.5W   110 KT
120HR VT     20/1800Z 19.0N 112.5W   115 KT
 
$$
FORECASTER BEVEN
 
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