WPAC: Tropical Depression 13W - Dissipated

[euro6208]

WDPN31 PGTW 220900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 13W (THIRTEEN)
WARNING NR 07//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION (TD) 13W (THIRTEEN), LOCATED APPROXIMATELY 239
NM SOUTHEAST OF TAIPEI, TAIWAN, HAS TRACKED NORTHEASTWARD AT 15 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
SHOWS POCKETS OF DEEP CONVECTION REMAIN BUT THE OVERALL STORM
STRUCTURE HAS CONTINUED TO DETERIORATE. THE LOW LEVEL CIRCULATION
CENTER (LLCC) IS BECOMING DISORGANIZED AND DIFFICULT TO LOCATE. THE
INITIAL POSITION IS PLACED WITH LOW CONFIDENCE AND IS BASED ON A
220641Z 36GHZ GMI MICROWAVE IMAGE WHICH SHOWS EVIDENCE OF WEAK LOW
LEVEL BANDING. THE INITIAL INTENSITY OF 30 KNOTS IS BASED ON A DVORAK
CURRENT INTENSITY (CI) ESTIMATE OF T2.0 (30 KNOTS) FROM PGTW.
ENVIRONMENTAL ANALYSIS SHOWS THAT TD 13W HAS VERY WEAK POLEWARD AND
EQUATORWARD OUTFLOW CHANNELS. HOWEVER, VERTICAL WIND SHEAR REMAINS
FAVORABLE, BETWEEN 10 AND 15 KNOTS. SEA SURFACE TEMPERATURES REMAIN
FAVORABLE, RANGING BETWEEN 29 TO 30 DEGREES CELSIUS. TD 13W IS
TRACKING GENERALLY NORTHWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE
SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTHEAST.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TD 13W WILL CONTINUE TO TRACK GENERALLY NORTHWARD WHILE UNDER
THE INFLUENCE OF THE STR TO THE NORTHEAST. UPPER LEVEL OUTFLOW
SUPPORT WILL CONTINUE TO DIMINISH AS THE LOW LEVEL STRUCTURE ALSO
BECOMES INCREASINGLY DISORGANIZED. TD 13W WILL MAINTAIN AN INTENSITY
OF 30 KNOTS THROUGH TAU 24. AFTER TAU 24 TD 13W WILL TRACK
NORTH-NORTHWESTWARD AROUND THE STR. DYNAMIC MODEL GUIDANCE FORECASTS
A DECREASE IN INTENSITY AFTER TAU 24 AND THAT TD 13W MAY DISSIPATE
JUST PRIOR TO MAKING LANDFALL. DYNAMIC MODEL GUIDANCE IS IN GOOD
AGREEMENT WITH GENERALLY LESS THAN A 100NM SPREAD. THEREFORE, THERE
IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK. THE JTWC FORECAST IS
PLACED NEAR THE MULTI-MODEL CONSENSUS.//
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[euro6208]

[NotoSans]

This may have been a TS but has weakened back to TD now. Surface observations from the Ryukyu Islands suggested that central pressure is now near 998 mb.

[euro6208]

WDPN31 PGTW 222100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 13W (THIRTEEN)
WARNING NR 09//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION 13W (THIRTEEN), LOCATED APPROXIMATELY 143 NM
EAST-SOUTHEAST OF TAIPEI, TAIWAN, HAS TRACKED NORTHWARD AT 12 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY (EIR) SHOWS A DEEP, YET SMALL AREA OF CONVECTION LOCATED TO
THE WEST OF THE LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL
POSITION IS PLACED WITH FAIR CONFIDENCE AND IS BASED ON A
COMBINATION OF THE EIR LOOP RADAR AND OBSERVATIONS FROM
ISHIGAKIJIMA (ROIG) WHICH SUGGEST THE LLCC PASSED VERY CLOSE. THE
INITIAL INTENSITY OF 30 KNOTS IS BASED ON A DVORAK CURRENT INTENSITY
(CI) ESTIMATE OF T2.0 (30 KNOTS) FROM PGTW. ENVIRONMENTAL ANALYSIS
SHOWS THAT TD 13W HAS WEAK EQUATORWARD OUTFLOW CHANNELS AND VERTICAL
WIND SHEAR BETWEEN 10 AND 15 KNOTS. SEA SURFACE TEMPERATURES REMAIN
FAVORABLE, RANGING BETWEEN 28 TO 29 DEGREES CELSIUS. TD 13W IS
TRACKING GENERALLY NORTH-NORTHWESTWARD ALONG THE SOUTHWESTERN
PERIPHERY OF THE SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTHEAST.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TD 13W WILL CONTINUE TO TRACK GENERALLY NORTHWARD WHILE UNDER
THE INFLUENCE OF THE STR TO THE NORTHEAST. TD 13W WILL BRIEFLY
INTENSIFY TO 35 KNOTS BY TAU 12 BEFORE BEGINNING TO SLOWLY WEAKEN TO
BELOW WARNING THRESHOLD BY TAU 48. THIS WEAKENING APPEARS TO BE DUE
TO CONTINUED POOR UPPER LEVEL OUTFLOW AND INCREASED LAND INTERACTION
AS IT SKIRTS THE COASTLINE OF CHINA. DYNAMIC MODEL GUIDANCE SPREAD
IS CONSISTENTLY ABOUT 100 NM BY TAU 24. THE FORECAST TRACK CLOSELY
FOLLOWS BUT IS SLIGHTLY SLOWER THAN CONSENSUS TO ACCOUNT FOR AN
OUTLIER (COAMPS) WHICH ACCELERATES THE TRACK SPEED MORE THAN THE
OTHER MEMBERS. BASED ON THE RELATIVELY LARGE SPREAD BY TAU 24, THERE
IS LOW CONFIDENCE IN THE JTWC FORECAST TRACK.//
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[doomhaMwx]

TD
Issued at 01:00 UTC, 23 July 2018

<Analysis at 00 UTC, 23 July>
Scale -
Intensity -
TD
Center position N27°00' (27.0°)
E123°00' (123.0°)
Direction and speed of movement NNW 30 km/h (15 kt)
Central pressure 1000 hPa

[euro6208]

WDPN31 PGTW 230900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 13W (THIRTEEN)
WARNING NR 11//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION (TD) 13W (THIRTEEN), LOCATED APPROXIMATELY 220
NM NORTH-NORTHEAST OF TAIPEI, TAIWAN, HAS TRACKED NORTHWARD AT 22
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY SHOWS DEEP CONVECTION IS BEING SHEARED TO THE TO THE
SOUTHWEST OF THE EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC)
ASSOCIATED WITH TD 13W. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE EXPOSED LLCC SEEN IN A 230600Z HIMAWARI
VISIBLE SATELLITE IMAGE. THE INITIAL INTENSITY OF 30 KNOTS IS BASED
ON A DVORAK CURRENT INTENSITY (CI) ESTIMATE OF T2.0 (30 KNOTS) FROM
PGTW. ENVIRONMENTAL ANALYSIS REVEALS THAT TD 13W HAS VERY WEAK
POLEWARD AND EQUATORWARD OUTFLOW. MODERATE VERTICAL WIND SHEAR (20
KNOTS) FROM THE NORTHEAST TO THE SOUTHWEST IS SHEARING THE REMAINING
DEEP CONVECTION AWAY FROM THE EXPOSED LLCC. HOWEVER, SEA SURFACE
TEMPERATURES REMAIN FAVORABLE, BETWEEN 29 TO 30 DEGREES CELSIUS. TD
13W IS TRACKING NORTHWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE
SUBTROPICAL RIDGE (STR) WHICH IS LOCATED TO THE NORTHEAST.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TD 13W WILL TRACK TO THE NORTH-NORTHWEST ALONG THE SOUTHWESTERN
PERIPHERY OF THE AFOREMENTIONED STR FOR THE REMAINDER OF THE FORECAST
THROUGH TAU 36. DESPITE FAVORABLE SEA SURFACE TEMPERATURES, TD 13W
WILL CONTINUE TO DECREASE IN INTENSITY DUE TO MODERATE VERTICAL WIND
SHEAR AND WEAK UPPER LEVEL OUTFLOW. DETERIORATING ENVIRONMENTAL
CONDITIONS WILL LEAD TO THE DISSIPATION OF TD 13W BY TAU 36. DYNAMIC
MODEL GUIDANCE IS IN GOOD AGREEMENT WITH A 74NM SPREAD AMONG MEMBERS
AT TAU 24. THEREFORE, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST
TRACK.//
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