000 WTPZ43 KNHC 192039 TCDEP3 TROPICAL DEPRESSION THIRTEEN-E DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132011 100 PM PST SAT NOV 19 2011 THE LOW-LEVEL CENTER OF THE AREA OF LOW PRESSURE SOUTH OF THE MEXICAN COAST HAS BECOME BETTER DEFINED DURING THE DAY...AND A 1645 UTC ASCAT PASS INDICATES THAT THE SYSTEM IS PRODUCING WINDS OF AT LEAST 30 KT. IT COULD BE ARGUED THAT THE ASSOCIATED CONVECTION IS NOT ALL THAT INTENSE...BUT IT IS JUST DEEP AND ORGANIZED ENOUGH FOR SAB AND TAFB TO PROVIDE DVORAK ESTIMATES OF 25 AND 30 KT... RESPECTIVELY. THE SYSTEM IS THEREFORE BEING DESIGNATED AS A TROPICAL DEPRESSION WITH AN INTENSITY OF 30 KT. THE DEPRESSION IS CURRENTLY LOCATED TO THE SOUTH OF A MID-LEVEL RIDGE THAT EXTENDS FROM THE SOUTHWESTERN GULF OF MEXICO WEST-SOUTHWESTWARD ACROSS SOUTHERN MEXICO...AND IT HAS AN INITIAL MOTION OF 280/10 KT. AS WOULD BE EXPECTED FOR NOVEMBER...A BROAD BUT DEEP MID/UPPER-LEVEL TROUGH EXTENDS WEST OF THE U.S./MEXICAN COAST TO ABOUT 140W WITH THE MID-LATITUDE WESTERLIES EXTENDING DOWN TO 16N. EVEN THOUGH A VIGOROUS CLOSED MID-LEVEL LOW IS EXPECTED TO DIG SOUTHWARD ALONG THE CALIFORNIA COAST OVER THE NEXT COUPLE OF DAYS...THE SUBTROPICAL RIDGE IS EXPECTED TO BUILD AND EXPAND WESTWARD AT THE SAME TIME. THIS SHOULD INDUCE THE DEPRESSION ON A WEST TO WEST-NORTHWESTWARD COURSE WITH A NEARLY CONSTANT FORWARD SPEED THROUGH THE NEXT FIVE DAYS. WITH THE EXCEPTION OF THE HWRF...WHICH SHOWS A MORE POLEWARD MOTION BEYOND DAY 3...THE TRACK GUIDANCE IS TIGHTLY CLUSTERED...AND THE OFFICIAL FORECAST IS VERY CLOSE TO THE MODEL CONSENSUS TVCE. THE THERMODYNAMIC ENVIRONMENT NEAR THE DEPRESSION MAY NOT BE IDEAL FOR CONVECTIVE DEVELOPMENT SINCE THE SYSTEM MOVED OVER COOL WATERS AND THROUGH A REGION OF DRY AIR RESULTING FROM A GAP WIND EVENT OVER THE GULF OF TEHUANTEPEC. HOWEVER...THE SYSTEM IS MOVING TOWARDS A MORE CONDUCIVE ENVIRONMENT...AND DEEP CONVECTION SHOULD BEGIN TO SLOWLY FILL IN OVER THE CIRCULATION. VERTICAL SHEAR IS EXPECTED TO BE RELATIVELY LIGHT THROUGH THE FORECAST PERIOD...SO STEADY STRENGTHENING IS EXPECTED. THERE IS SOME DIVERGENCE BETWEEN THE SHIPS AND LGEM GUIDANCE BEYOND 24 HOURS...WITH THE SHIPS SHOWING MORE AGGRESSIVE INTENSIFICATION. GIVEN THE UNCERTAINTY IN HOW MUCH THE THERMODYNAMIC ENVIRONMENT WILL IMPROVE...THE OFFICIAL INTENSITY FORECAST LIES CLOSER TO THE LGEM MODEL. BASED ON HISTORICAL RECORDS...TROPICAL DEPRESSION THIRTEEN-E IS THE LATEST-FORMING TROPICAL CYCLONE IN THE EASTERN NORTH PACIFIC BASIN SINCE TROPICAL DEPRESSION TWENTY-TWO-E IN 1987...WHICH FORMED ON NOVEMBER 24. IF IT BECOMES A TROPICAL STORM...IT WOULD BE THE LATEST-FORMING NAMED STORM SINCE HURRICANE WINNIE IN 1983...WHICH FORMED ON DECEMBER 4. FORECAST POSITIONS AND MAX WINDS INIT 19/2100Z 10.0N 101.0W 30 KT 35 MPH 12H 20/0600Z 10.2N 102.5W 35 KT 40 MPH 24H 20/1800Z 10.9N 104.5W 40 KT 45 MPH 36H 21/0600Z 11.4N 106.8W 45 KT 50 MPH 48H 21/1800Z 11.6N 109.0W 50 KT 60 MPH 72H 22/1800Z 12.0N 113.0W 60 KT 70 MPH 96H 23/1800Z 12.5N 118.0W 65 KT 75 MPH 120H 24/1800Z 13.5N 122.5W 55 KT 65 MPH $$ FORECASTER BERG