Tropical Storm FENGSHEN Advisory mar, 12-11

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 26W (TWENTYSIX) WARNING NR 01//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 26W (TWENTYSIX), LOCATED APPROXIMATELY 1166 NM EAST OF WFO GUAM, HAS TRACKED WESTWARD AT 16 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS TD 26W CONTINUES TO IMPROVE IN STRUCTURE WITH EXCELLENT LOW LEVEL BANDING AND DEEP CONVECTION, MAINLY TO THE WEST OF THE LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH GOOD CONFIDENCE BASED ON A 110946Z METOP-C ASCAT PASS SHOWING 25 KNOT WIND BARBS TO THE NORTH AND SOUTH OF THE LLCC. THE INITIAL INTENSITY OF 25 KNOTS IS BASED ON MULTI-AGENCY DVORAK INTENSITY ESTIMATE OF T1.0-1.5 (25 KNOTS) AND THE AFOREMENTIONED ASCAT PASS. ENVIRONMENTAL ANALYSIS SHOWS TD 26W IS EXPERIENCING MODERATELY FAVORABLE VERTICAL WIND SHEAR (15-20 KNOTS) ALONG WITH GOOD UPPER LEVEL DIVERGENCE. SEA SURFACE TEMPERATURES ARE ALSO FAVORABLE (29-30 DEGREES CELSIUS) FOR CONTINUED DEVELOPMENT. TD 26W IS TRACKING WESTWARD UNDER THE INFLUENCE OF THE WEST TO EAST ORIENTATED SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTH.
3. FORECAST REASONING.
   A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE FORECAST
PHILOSOPHY.
   B. TD 26W WILL CONTINUE TO TRACK TO THE NORTHWEST UNDER THE INFLUENCE OF THE AFOREMENTIONED STR. THE STR WILL BE THE PRIMARY STEERING FEATURE THROUGH TAU 72. UPPER LEVEL OUTFLOW AND SEA SURFACE TEMPERATURES ARE ALL CONDUCIVE FOR CONTINUED INTENSIFICATION. THE POTENTIAL FOR RAPID INTENSIFICATION IS CURRENTLY HAMPERED BY MODERATE TO HIGH VWS THROUGHOUT THE FORECAST TRACK.
AS A RESULT, TD 26W IS CURRENTLY EXPECTED TO REACH AN INTENSITY OF 75 KNOTS BY TAU 72. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT WITH A MODEL SPREAD OF 120 NM BY TAU 72. THEREFORE, THERE IS HIGH CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.
   C. AFTER TAU 72, THE STR LOCATED TO THE NORTH WILL ERODE AS A RESULT OF AN APPROACHING MID-LATITUDE TROUGH. TD 26W IS CURRENTLY EXPECTED TO MOVE THROUGH A NEWLY FORMED COL AS IT APPROACHES THE STR AXIS AROUND TAU 96. VERTICAL WIND SHEAR IS EXPECTED TO INCREASE TO HIGH (25-35 KNOTS) DURING THIS TIME PERIOD, LIMITING PEAK INTENISTY TO 95 KNOTS. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT WITH A TRACK SPREAD OF 170 NM BY TAU 120. HOWEVER, RECURVE TIMING REMAINS UNCERTAIN AROUND THE END OF THE FORECAST. THEREFORE, THERE IS OVERALL FAIR CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK, WHICH IS PLACED NEAR THE MULTI-MODEL CONSENSUS. THERE IS A LARGE SPREAD IN INTENSITY GUIDANCE, ESPECIALLY WHEN SHEAR IS EXPECTED TO PEAK. THE JTWC INTENSITY FORECAST IS PLACED NEAR THE CONSENSUS WITH POOR CONFIDENCE.//
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