WPAC: 17W - Tropical Depression

[Hayabusa]

91W INVEST 250816 0000 14.7N 113.4E WPAC 15 0

[Hayabusa]

WWJP27 RJTD 170000
WARNING AND SUMMARY 170000.
WARNING VALID 180000.
WARNING IS UPDATED EVERY 6 HOURS.
TROPICAL DEPRESSION 1004 HPA AT 17N 111E NW SLOWLY.

[Hayabusa]

low

ABPW10 PGTW 170600
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/SIGNIFICANT TROPICAL WEATHER ADVISORY FOR THE WESTERN AND SOUTH
PACIFIC OCEANS/170600Z-180600ZAUG2025//
RMKS/
1. WESTERN NORTH PACIFIC AREA (180 TO MALAY PENINSULA):
A. TROPICAL CYCLONE SUMMARY: NONE.
B. TROPICAL DISTURBANCE SUMMARY:
(1) THE AREA OF CONVECTION (INVEST 92W) PREVIOUSLY LOCATED NEAR
20.3N 126.5E IS NOW LOCATED NEAR 21.2N 127.7E, APPROXIMATELY 306 NM
SOUTH OF KADENA AFB. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
AS WELL AS A 170419Z ATMS 88.2 GHZ IMAGE DEPICTS A SLOWLY
CONSOLIDATING AND HIGHLY ELONGATED LOW LEVEL CIRCULATION (LLC),
EMBEDDED WITHIN A REVERSE ORIENTED MONSOON TROF. FLARING CONVECTION
IS FORMING ALONG THE SOUTHEASTERN FLANK OF THE LLC IN THE CONVERGENT
FLOW SOUTH OF THE TROF AXIS. ANIMATED WATER VAPOR IMAGERY INDICATES A
TUTT-CELL POSITIONED APPROXIMATELY 200NM NORTHEAST OF 92W, WHICH IS
IMPARTING NORTHERLY SHEAR OVER 92W AND DRAWING IN DRY MID-LEVEL
ACROSS THE REGION TO THE NORTH OF THE LLC. ENVIRONMENTAL ANALYSIS FOR
THE AREA INDICATES MARGINALLY FAVORABLE CONDITIONS FOR DEVELOPMENT
WITH MODERATE NORTHERLY VERTICAL WIND SHEAR (20 KTS) AND DRY MID-
LEVEL AIR TO THE NORTH, OFFSET BY WARM SEA SURFACE TEMPERATURES (30
C) AND MODERATE EQUATORWARD OUTFLOW ALOFT. GLOBAL MODELS ARE IN GOOD
AGREEMENT THAT 92W WILL TRACK NORTHWARD OVER THE NEXT 24 TO 48 HOURS.
GLOBAL MODELS ARE ALSO IN AGREEMENT THAT 92W WILL VERY SLOWLY
CONSOLIDATE AND ONLY MINIMALLY INTENSIFY OVER THE NEXT COUPLE OF
DAYS, HINDERED BY PERSISTENT DRY AIR AND MODERATE SHEAR MAXIMUM
SUSTAINED SURFACE WINDS ARE ESTIMATED AT 13 TO 18 KNOTS. MINIMUM SEA
LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1008 MB. THE POTENTIAL FOR THE
DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24
HOURS IS UPGRADED TO MEDIUM.
(2) AN AREA OF CONVECTION (INVEST 91W) HAS PERSISTED NEAR 17.3N
111.0E, APPROXIMATELY 165 NM SOUTH-SOUTHEAST OF HAIKOU, CHINA. THE
SYSTEM IS CURRENTLY CLASSIFIED AS A MONSOON DEPRESSION, GENERALLY
CHARACTERIZED AS A LARGE CYCLONIC CIRCULATION, GREATER THAN 600NM
DIAMETER, WITH HIGHER WINDS OVER THE EASTERN PERIPHERY AND A WEAK
CORE OF LIGHT WINDS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
AS WELL AS A 180212Z METOP-C 89 GHZ MICROWAVE IMAGE INDICATE A VERY
BROAD CIRCULATION WITH FRAGMENTED CONVECTIVE BANDING ALONG THE
EASTERN PERIPHERY OF THE CIRCULATION. A 170216Z PARTIAL ASCAT PASS
REVEALS 25 KT WINDS ALONG THE CHINESE COAST TO THE EAST OF HAINAN,
WITH A RADIUS OF MAXIMUM WINDS OF AT LEAST 200NM. THE ASCAT AS WELL
AS THE MSI SUGGEST POCKETS OF ENHANCED ROTATION AND VORTICITY ALONG
WITH ISOLATED AREAS OF ELEVATED WINDS, IN THE NORTHEASTERN CORNER OF
THE CIRCULATION, WRAPPING UP THE EASTERN PERIPHERY. ENVIRONMENTAL
FACTORS FOR THIS SYSTEM ARE MODERATELY UNFAVORABLE WITH MODERATE
UPPER LEVEL VWS (20KTS) AS WELL AS A LACK OF POLEWARD OUTFLOW ALOFT,
OFFSET BY WARM SSTS OF (28-29C). GLOBAL DETERMINISTIC MODELS ARE
CURRENTLY IN AGREEMENT THAT THE AREA OF CONVECTION 91W WILL NOT
CONSOLIDATE AND CONTINUE A SLUGGISH NORTH-NORTHWESTERLY TRACK TOWARDS
HAINAN ISLAND OVER THE NEXT 24 HOURS. FOR HAZARDS AND WARNINGS,
REFERENCE THE FLEET WEATHER CENTER SAN DIEGO HIGH WINDS AND SEAS
PRODUCT OR REFER TO LOCAL WMO DESIGNATED FORECAST AUTHORITY MAXIMUM
SUSTAINED SURFACE WINDS ARE ESTIMATED AT 23 TO 28 KNOTS. MINIMUM SEA
LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1002 MB. THE POTENTIAL FOR THE
DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24
HOURS IS LOW.
(3) NO OTHER SUSPECT AREAS.
C. SUBTROPICAL SYSTEM SUMMARY: NONE.
2. SOUTH PACIFIC AREA (WEST COAST OF SOUTH AMERICA TO 135 EAST):
A. TROPICAL CYCLONE SUMMARY: NONE.
B. TROPICAL DISTURBANCE SUMMARY: NONE.
C. SUBTROPICAL SYSTEM SUMMARY: NONE.//
NNNN

[Hayabusa]

TCFA

WTPN22 PGTW 180030
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
REF/A/JOINT TYPHOON WRNCEN PEARL HARBOR HI/171430Z AUG 25//
AMPN/REF IS TROPICAL CYCLONE FORMATION ALERT (WTPN21 PGTW 171430)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
080 NM EITHER SIDE OF A LINE FROM 19.2N 108.1E TO 21.7N 107.2E
WITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 18 TO 23 KNOTS. METSAT
IMAGERY AT 180030Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 19.4N 108.0E. THE SYSTEM IS MOVING WEST-NORTHWESTWARD AT 16
KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 91W) PREVIOUSLY LOCATED NEAR
17.9N 111.1E IS NOW LOCATED NEAR 19.4N 108.0E, APPROXIMATELY 155 NM
SOUTHEAST OF HANOI. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
DEPICTS DEEP CONVECTION BUILDING OVER A CONSOLIDATING LOW-LEVEL
CIRCULATION CENTER (LLCC), ALSO HAVING CURVED CONVECTIVE BANDING TO THE
SOUTHEAST. A CONTRACTING WIND FIELD AND REDUCTION OF THE RADIUS OF
MAXIMUM WINDS INDICATES THAT A TRANSITION FROM A MONSOON DEPRESSION INTO
A TROPICAL DEPRESSION IS COMMENCING. ENVIRONMENTAL ANALYSIS FOR THE AREA
INDICATES FAVORABLE CONDITIONS FOR DEVELOPMENT WITH LOW VERTICAL WIND
SHEAR (10-15 KTS), WARM SEA SURFACE TEMPERATURES (30-31 C), AND MODERATE
EQUATORWARD OUTFLOW ALOFT. GLOBAL MODELS ARE IN GOOD AGREEMENT THAT 91W
WILL TRACK NORTHWARD OVER THE NEXT 24-36 HOURS. ECENS AND GEFS ENSEMBLE
GUIDANCE SHOW A FAIR AGREEMENT THAT 91W WILL DEVELOP, BUT WITH THE ECENS
MODEL BEING MORE AGGRESSIVE THAN THE GEFS. MAXIMUM SUSTAINED SURFACE
WINDS ARE ESTIMATED AT 23 TO 28 KNOTS. MINIMUM SEA LEVEL PRESSURE IS
ESTIMATED TO BE NEAR 1002 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A
SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS HIGH.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY
190030Z.
4. SEE REF A FOR DETAILS ON A TROPICAL CYCLONE FORMATION ALERT
LOCATED NEAR 21.5N 127.1E.//
NNNN