000
WTPZ44 KNHC 212038
TCDEP4
TROPICAL DEPRESSION NINE-E DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP092010
200 PM PDT SAT AUG 21 2010
 
THE AREA OF LOW PRESSURE SOUTH-SOUTHEAST OF THE GULF OF TEHUANTEPEC
HAS BECOME BETTER ORGANIZED TODAY...WITH AN INCREASE IN DEEP
CONVECTION NEAR THE ESTIMATED CENTER LOCATION AND THE DEVELOPMENT
OF MULTIPLE CURVED CONVECTIVE BANDS.  THEREFORE...ADVISORIES ARE
INITIATED AT THIS TIME...AND THE INITIAL INTENSITY IS SET AT 25 KT
IN AGREEMENT WITH THE DVORAK ESTIMATE FROM TAFB AT 1800 UTC.  

ENVIRONMENTAL CONDITIONS APPEAR FAVORABLE FOR AT LEAST STEADY
INTENSIFICATION IN THE SHORT TERM...AS THE DEPRESSION IS SITUATED
BENEATH AN UPPER-LEVEL ANTICYCLONE AND OVER VERY WARM WATERS OF
ALMOST 30C.  BEYOND THE NEXT 24 HOURS OR SO...THE INTENSITY OF THE
CYCLONE WILL BE PRIMARY DETERMINED BY HOW MUCH IT INTERACTS WITH
THE COAST OF MEXICO.  THE CURRENT OFFICIAL FORECAST ASSUMES THE
CENTER WILL REMAIN OFFSHORE AND IS CLOSE TO THE SHIPS MODEL IN THE
SHORT TERM AND FOLLOWS A BLEND OF THE SHIPS AND LGEM LATE IN THE
PERIOD.  

THE DEPRESSION IS CURRENTLY SITUATED IN A WEAK STEERING
ENVIRONMENT...AND SOME ERRATIC MOTION IS POSSIBLE AS THE SYSTEM
DEVELOPS OVER THE NEXT 12 TO 24 HOURS.  BEYOND THAT TIME...THE
GLOBAL MODELS SHOW A DEEP-LAYER RIDGE BUILDING NORTH OF THE
CYCLONE...WHICH SHOULD RESULT IN AN INCREASING WESTWARD MOTION OVER
THE NEXT TWO OR THREE DAYS.  BOTH THE GFS AND UKMET SHOW THE CYCLONE
MOVING ONSHORE...ALTHOUGH THE GFS SHOWS THE DEPRESSION INTERACTING
WITH A SECOND VORTEX DURING THIS TIME THAT NONE OF THE OTHER
GUIDANCE SHOWS.  THE OFFICIAL FORECAST SHOWS A SLOW WESTWARD
MOTION FOR THE FIRST 2 TO 3 DAYS WITH A TURN TOWARD THE
WEST-NORTHWEST AT DAYS 4 AND 5 AS THE RIDGE LIFTS NORTH.  THIS
SOLUTION REPRESENTS A BLEND OF THE GLOBAL MODEL AND ENSEMBLE
GUIDANCE...EXCLUDING THE GFS.  THIS INITIAL TRACK FORECAST HAS
LARGER THAN USUAL UNCERTAINTY DUE TO THE WEAK INITIAL STEERING
PATTERN AND POTENTIAL INTERACTION WITH THE MONSOON FLOW AND LAND. 

GIVEN THE CONSIDERABLE TRACK FORECAST UNCERTAINTY...A TROPICAL STORM
WATCH HAS BEEN ISSUED FOR PORTIONS OF THE COAST OF MEXICO.  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/2100Z 13.9N  93.2W    25 KT
 12HR VT     22/0600Z 13.9N  93.6W    35 KT
 24HR VT     22/1800Z 13.8N  94.5W    40 KT
 36HR VT     23/0600Z 13.7N  95.6W    50 KT
 48HR VT     23/1800Z 13.7N  96.6W    55 KT
 72HR VT     24/1800Z 14.0N  98.5W    65 KT
 96HR VT     25/1800Z 15.0N 101.0W    65 KT
120HR VT     26/1800Z 16.0N 103.5W    65 KT
 
$$
FORECASTER BRENNAN