000
WTPZ41 KNHC 151441
TCDEP1

TROPICAL DEPRESSION ONE-E DISCUSSION NUMBER   1
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP012013
800 AM PDT WED MAY 15 2013

THE EASTERN NORTH PACIFIC HURRICANE SEASON HAS WASTED NO TIME
GETTING STARTED.  THE LOW PRESSURE SYSTEM THAT WE HAVE BEEN
MONITORING SOUTH OF THE MEXICAN COAST BECAME BETTER ORGANIZED
OVERNIGHT...AND A NEARLY UNBROKEN BAND OF DEEP CONVECTION NOW WRAPS
AROUND THE SOUTHERN AND WESTERN SIDE OF THE CIRCULATION.  DVORAK
INTENSITY ESTIMATES HAVE INCREASED AND ARE NOW T2.0 FROM TAFB AND
T1.5 FROM SAB...SO THE SYSTEM IS BEING DESIGNATED AS A 30-KT
TROPICAL DEPRESSION.

THE CURRENT MOTION ESTIMATE IS 280 DEGREES AT 10 KT.  THE DEPRESSION
IS SITUATED ON THE SOUTHWESTERN PERIPHERY OF A MID-LEVEL RIDGE THAT
EXTENDS FROM THE BAY OF CAMPECHE SOUTHWESTWARD OVER THE PACIFIC
WATERS.  EVEN THOUGH A MID-LEVEL TROUGH IS LIKELY TO AMPLIFY IN THE
VICINITY OF CALIFORNIA IN THE COMING DAYS...THE DEPRESSION IS SO
FAR SOUTH THAT ANY EFFECTS ON STEERING SHOULD BE MINIMAL.  A
NORTHWESTWARD MOTION IS POSSIBLE IN 4 TO 5 DAYS ONCE THE SYSTEM
REACHES THE WESTERN END OF THE RIDGE.  THERE IS SOME DISAGREEMENT
AMONG THE GLOBAL MODELS TOWARD THE END OF THE FORECAST PERIOD...BUT
THE OFFICIAL FORECAST IS CLOSER TO THE SOLUTIONS THAT SHOW A
STRONGER SYSTEM...SPECIFICALLY THE GFS...BAM MEDIUM...AND BAM DEEP.

THE DEPRESSION IS EMBEDDED IN A ZONE OF UPPER-LEVEL DIFFLUENCE TO
THE EAST OF THE SUBTROPICAL JET...AND IT WILL BE TRAVERSING THE
WARMEST WATERS OF THE EASTERN NORTH PACIFIC OVER THE NEXT FEW DAYS.
THIS SHOULD SUPPORT STRENGTHENING FOR AT LEAST THE NEXT 3 TO 4 DAYS
BEFORE THE SYSTEM REACHES STRONG UPPER-LEVEL WESTERLIES AND
APPROACHES COOLER WATERS.  SINCE CONDITIONS APPEAR FAVORABLE...IT
SEEMS REASONABLE THAT THE DEPRESSION SHOULD AT LEAST BE ABLE TO
KEEP UP WITH A CLIMATOLOGICAL INTENSIFICATION RATE.  THE OFFICIAL
FORECAST THEREFORE SHOWS FASTER STRENGTHENING AND A HIGHER PEAK
INTENSITY THAN SHIPS AND LGEM SINCE THE CLIMATOLOGY-PERSISTENCE
MODEL SHIFOR IS HIGHER THAN EITHER OF THOSE TWO MODELS.

FORECAST POSITIONS AND MAX WINDS

INIT  15/1500Z  8.2N 103.6W   30 KT  35 MPH
 12H  16/0000Z  8.6N 105.3W   35 KT  40 MPH
 24H  16/1200Z  9.1N 107.3W   45 KT  50 MPH
 36H  17/0000Z  9.5N 108.9W   55 KT  65 MPH
 48H  17/1200Z 10.0N 110.4W   65 KT  75 MPH
 72H  18/1200Z 11.5N 113.0W   70 KT  80 MPH
 96H  19/1200Z 13.0N 115.5W   65 KT  75 MPH
120H  20/1200Z 15.5N 117.0W   55 KT  65 MPH

$$
FORECASTER BERG

TROPICAL STORM ALVIN DISCUSSION NUMBER 5
NWS NATIONAL HURRICANE CENTER MIAMI FL EP012013
800 AM PDT THU MAY 16 2013

ALVIN APPEARS TO HAVE DEGRADED IN STRUCTURE OVERNIGHT. INFRARED
SATELLITE IMAGERY AND SCATTEROMETER DATA INDICATE THAT THE
CIRCULATION HAS HAD DIFFICULTY SEPARATING FROM THE ITCZ...AND THE
LOW-LEVEL CENTER IS LIKELY LOCATED ON THE WESTERN EDGE OF THE DEEP
CONVECTION. THE INTENSITY IS BEING HELD AT 45 KT BASED ON THE
EARLIER ASCAT DATA...BUT SATELLITE ESTIMATES SUGGEST THAT ALVIN
COULD BE A BIT WEAKER.

ALTHOUGH THE HISTORICALLY TWO BEST GLOBAL MODELS...THE GFS AND
ECMWF...HAVE HAD SOME DISAGREEMENT ON ALVIN...EACH APPEARS TO HAVE
BEEN RIGHT TO SOME DEGREE. THE GFS HAD A BETTER HANDLE ON
GENESIS...BUT THE ECMWF MAY HAVE BEEN RIGHT THAT ALVIN WOULD NOT
STRENGTHEN SIGNIFICANTLY. AS OPPOSED TO YESTERDAY...THE SHIPS
GUIDANCE NOW INDICATES THAT 15 TO 20 KT OF VERTICAL SHEAR WILL
AFFECT ALVIN DURING THE NEXT FIVE DAYS...AND NEITHER OF THE
STATISTICAL MODELS NOW SHOWS THE CYCLONE REACHING HURRICANE
STRENGTH. THE PROSPECTS FOR SIGNIFICANT INTENSIFICATION APPEAR TO
BE DWINDLING...AND THE OFFICIAL FORECAST ESSENTIALLY HOLDS THE
INTENSITY STEADY FOR THE NEXT 48 HOURS. A MORE PRONOUNCED INCREASE
IN WESTERLY SHEAR SHOULD BEGIN A DEFINITE WEAKENING TREND BY DAY
3...AND ALVIN COULD DEGENERATE TO A REMNANT LOW NEAR THE END OF THE
FORECAST PERIOD. NEEDLESS TO SAY...THERE IS STILL LOW CONFIDENCE IN
THE INTENSITY FORECAST.

SINCE THE OFFICIAL INTENSITY FORECAST HAS BEEN LOWERED...THE NHC
TRACK FORECAST HAS BEEN SHIFTED A BIT FARTHER SOUTH AND WEST WITH
THE ASSUMPTION THAT LOWER-LEVEL FLOW WILL HAVE A GREATER INFLUENCE
ON STEERING. THE TRACK MODELS ARE IN BETTER AGREEMENT ON THE
GENERAL DIRECTION TODAY ALTHOUGH THERE IS STILL A SPEED
DISCREPANCY...ESPECIALLY BETWEEN THE GFS AND ECMWF.

FORECAST POSITIONS AND MAX WINDS

INIT 16/1500Z 9.4N 107.7W 45 KT 50 MPH
12H 17/0000Z 9.9N 108.8W 50 KT 60 MPH
24H 17/1200Z 10.7N 110.5W 50 KT 60 MPH
36H 18/0000Z 11.2N 112.3W 50 KT 60 MPH
48H 18/1200Z 11.6N 113.6W 50 KT 60 MPH
72H 19/1200Z 13.0N 116.0W 45 KT 50 MPH
96H 20/1200Z 13.5N 118.5W 30 KT 35 MPH
120H 21/1200Z 13.5N 120.5W 25 KT 30 MPH...POST-TROP/REMNT LOW

$$
FORECASTER BERG