Tropical Storm KALMAEGI Advisory Thu Sep 11

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 15W (FIFTEEN)
WARNING NR 01//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 15W (FIFTEEN), LOCATED APPROXIMATELY 179 NM
EAST OF YAP, HAS TRACKED WESTWARD AT 15 KNOTS OVER THE PAST SIX
HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A
CONSOLIDATED LOW-LEVEL CIRCULATION CENTER WITH VIGOROUS CONVECTION
ALONG THE WESTERN PERIPHERY. A 101642Z AMSU-B IMAGE FURTHER SHOWS
GOOD CONVECTIVE BANDING ALONG THE NORTHERN AND WESTERN PERIPHERY OF
THE SYSTEM. LOCAL OBSERVATIONS FROM YAP INDICATE A DROP IN PRESSURE
OF 02 MB OVER THE PAST 24 HOURS. UPPER LEVEL ANALYSIS INDICATES
EQUATORWARD OUTFLOW AND MODERATE (20 TO 30 KTS) OF VERTICAL WIND
SHEAR (VWS). INTENSITY IS BASED ON DVORAK INTENSITY ESTIMATES WITH
THE MAJORITY OF AGENCIES AGREEING WITH A MAXIMUM WIND SPEED OF 25
KNOTS. TD 15W IS CURRENTLY TRACKING WESTWARD UNDER THE STEERING
INFLUENCE OF THE SUBTROPICAL RIDGE (STR) POSITIONED TO THE
NORTHEAST OF THE SYSTEM.
3. FORECAST REASONING.
   A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE
FORECAST PHILOSOPHY.
   B. THE MAIN STEERING INFLUENCE OF TD 15W THROUGH TAU 72 IS THE
STR TO THE NORTHEAST. AS THE MAIN STR BREAKS DOWN AND TRAVERSES
SLIGHTLY TO THE EAST, EXPECT THE TD 15W TO SLOW SLIGHTLY IN THE
LATER TAUS BEFORE CONTINUING WESTWARD UNDER THE RE-BUILDING STR. AN
ALTERNATE SCENARIO, FAVORED BY THE NAVGEM SOLUTION, HAS THE STR
RIDGE TO THE EAST OF THE SYSTEM BREAKING DOWN FASTER AND 15W
TURNING TO THE NORTH BETWEEN A SMALL BREAK IN THE RIDGE BY TAU 48.
WHILE ALL MODEL TRACKERS ARE IN GOOD AGREEMENT THROUGH 18Z ON THE
12TH, THERE IS SOME DISAGREEMENT BEYOND THAT POINT. WITH REGARD TO
INTENSITY, GOOD SEA SURFACE TEMPERATURES AND FAVORABLE UPPER-LEVEL
ENVIRONMENT SHOULD ALLOW THE SYSTEM TO INTENSIFY AT AN AVERAGE RATE
THOUGH TAU 72.
   C. IN THE EXTENDED FORECAST THE MODEL SOLUTIONS BEGINS TO
FURTHER DIVIDE, WITH THE GFS TRACKING INTO LUZON AND NAVGEM
BEGINNING A RECURVE SCENARIO BETWEEN A WEAKNESS IN THE STR. THE
FORECAST TRACK IN THE LATER TAUS ALIGNS CLOSELY WITH THE CONSENSUS
OF MODEL GUIDANCE, TRACKING INTO NORTHERN LUZON BY TAU 108. LAND
INTERACTION DURING THIS TIMEFRAME WILL IMPEDE FURTHER
INTENSIFICATION DESPITE FORECASTED GOOD EQUATOR OUTFLOW AND AVERAGE
VWS. THE OVERALL CONFIDENCE IN JTWC TRACK IS LOW DUE TO A SLIGHT
DISPARITY IN MODELS AFTER TAU 48.//
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