000
WTPZ42 KNHC 170833
TCDEP2
 
TROPICAL STORM GREG DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP072011
200 AM PDT WED AUG 17 2011
 
DEEP CONVECTION ASSOCIATED WITH THE DEPRESSION HAS BEEN INCREASING
IN INTENSITY AND COVERAGE DURING THE PAST SEVERAL HOURS. SATELLITE
INTENSITY ESTIMATES ARE A UNANIMOUS 35 KT FROM ALL AGENCIES AT 0600
UTC. IN ADDITION...A SHIP REPORTED WINDS OF 35 KT JUST TO THE NORTH
OF THE ESTIMATED CENTER AT 0300 UTC. BASED ON THESE DATA...THE
INITIAL WIND SPEED IS INCREASED TO 35 KT...WHICH MAKES THE CYCLONE
TROPICAL STORM GREG.

THE LOW-LEVEL CENTER OF GREG HAS BEEN DIFFICULT TO LOCATE...BUT
USING THE AFOREMENTIONED SHIP OBSERVATION IT APPEARS TO BE A LITTLE
TO THE NORTH OF THE PREVIOUS TRACK. THE TROPICAL STORM IS MOVING
WEST-NORTHWESTWARD AT 14 KT TO THE SOUTH OF A STRENGTHENING
MID-LEVEL HIGH CENTERED OVER THE SOUTHWESTERN UNITED STATES. A
SLIGHT TURN TOWARD THE LEFT WITH SOME INCREASE IN FORWARD SPEED IS
FORECAST DURING THE NEXT DAY OR SO AS GREG MOVES DIRECTLY SOUTH OF
THE HIGH. GLOBAL MODELS ARE IN AGREEMENT IN SHOWING THE RIDGE
WEAKENING ON FRIDAY DUE TO A TROUGH MOVING OVER THE U.S. WEST
COAST. THIS PATTERN SHOULD CAUSE THE CYCLONE TO SLOW DOWN IN THE
LONGER RANGE. THE NEW OFFICIAL FORECAST IS A LITTLE NORTH OF THE
PREVIOUS ONE FOR THE FIRST COUPLE OF DAYS AND THEN LIES VERY NEAR
THE PREVIOUS TRACK. THIS FORECAST IS A LITTLE FASTER AND TO THE
SOUTH OF THE MULTI-MODEL CONSENSUS...LEANING TOWARD THE GFS AND
ECMWF MODELS.

GREG IS CURRENTLY IN AN ENVIRONMENT OF MODERATE NORTHEASTERLY
SHEAR...SEA SURFACE TEMPERATURES OF ABOUT 30C...AND A RELATIVELY
MOIST ATMOSPHERE. DURING THE NEXT TWO TO THREE DAYS...THE SHEAR IS
EXPECTED TO SLACKEN AND SEA SURFACE TEMPERATURES ALONG THE FORECAST
TRACK GRADUALLY LOWER BUT REMAIN ABOVE 26C. THESE CONDITIONS
SUPPORT INTENSIFICATION...AND THE OFFICIAL FORECAST IS AT THE HIGH
END OF THE GUIDANCE DURING THIS PERIOD. GREG IS EXPECTED TO MOVE
OVER SUB 26C WATERS AND INTO A MORE STABLE ATMOSPHERE IN ABOUT
THREE DAYS...AND THAT SHOULD INDUCE A STEADY WEAKENING TREND. 
    
FORECAST POSITIONS AND MAX WINDS
 
INIT  17/0900Z 15.8N 102.2W   35 KT  40 MPH
 12H  17/1800Z 16.6N 104.5W   45 KT  50 MPH
 24H  18/0600Z 17.4N 107.7W   55 KT  65 MPH
 36H  18/1800Z 18.0N 110.5W   65 KT  75 MPH
 48H  19/0600Z 18.4N 112.6W   70 KT  80 MPH
 72H  20/0600Z 19.1N 115.8W   70 KT  80 MPH
 96H  21/0600Z 20.0N 118.0W   55 KT  65 MPH
120H  22/0600Z 20.5N 120.5W   40 KT  45 MPH
 
$$
FORECASTER CANGIALOSI