WPAC: LEEPI - Post-Tropical

[Subtrop]

93W INVEST 240902 0000 23.4N 146.3E WPAC 15 1009

[Hayabusa]

ABPW10 PGTW 030600
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/SIGNIFICANT TROPICAL WEATHER ADVISORY FOR THE WESTERN AND SOUTH
PACIFIC OCEANS/030600Z-040600ZSEP2024//
REF/A/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI/030151ZSEP2024//
AMPN/REF A IS A TROPICAL CYCLONE WARNING.//
RMKS/
1. WESTERN NORTH PACIFIC AREA (180 TO MALAY PENINSULA):
A. TROPICAL CYCLONE SUMMARY:
(1) AT 03SEP24 0000Z, TROPICAL STORM 12W (YAGI) WAS LOCATED NEAR
18.3N 119.5E, APPROXIMATELY 238 NM NORTH-NORTHWEST OF MANILA,
PHILIPPINES, AND HAD TRACKED WEST- NORTHWESTWARD AT 12 KNOTS OVER THE
PAST SIX HOURS. MAXIMUM SUSTAINED SURFACE WINDS WERE ESTIMATED AT 40
KNOTS GUSTING TO 50 KNOTS. SEE REF A (WTPN31 PGTW 030300) FOR FURTHER
DETAILS.
(2) NO OTHER TROPICAL CYCLONES.
B. TROPICAL DISTURBANCE SUMMARY:
(1) THE AREA OF CONVECTION (INVEST 93W) PREVIOUSLY LOCATED NEAR
24.7N 147.2E IS NOW LOCATED NEAR 24.7N 147.2E, APPROXIMATELY 321 NM
EAST OF IWO TO. ENHANCED MULTISPECTRAL SATELLITE IMAGERY AND A 030053Z
GMI 89 GHZ MICROWAVE PASS DEPICT DEEP CONVECTION ON THE EASTERN SIDE
OF A WELL DEVELOPED LOW LEVEL CIRCULATION CENTER. A 030030Z ASCAT-B
SCATTEROMETER PASS REVEALS A HIGHLY ASYMMETRIC WIND FIELD WITH 25-30
KNOT WINDS IN THE NORTHEASTERN QUADRANT OF THE LLCC, BUT MUCH LIGHTER
WINDS IN THE REMAINDER OF THE CIRCULATION. ENVIRONMENTAL ANALYSIS
REVEALS FAVORABLE CONDITIONS FOR INTENSIFICATION DUE TO WARM (28-29C)
SSTS, LOW (10-15 KTS) VERTICAL WIND SHEAR, AND GOOD DIVERGENCE ALOFT.
DETERMINISTIC MODELS PROVIDE POOR INDICATION OF A CONSOLIDATION,
INDICATING 93W AS A WEAK CIRCULATION GRADUALLY TRACKING NORTH BUT DUE
TO THE VERY SMALL SIZE OF THE CIRCULATION, THE GLOBAL MODELS ARE NOT
LIKELY HANDLING THE SYSTEM WELL AND MORE DEVELOPMENT THAN CURRENTLY
DEPICTED IS POSSIBLE. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT
18 TO 23 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR
1009 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL
CYCLONE WITHIN THE NEXT 24 HOURS REMAINS MEDIUM.
(2) NO OTHER SUSPECT AREAS.
C. SUBTROPICAL SYSTEM SUMMARY:
(1) THE AREA OF CONVECTION (INVEST 01C) PREVIOUSLY LOCATED NEAR
26.1N 179.5E IS NOW LOCATED NEAR 26.7N 179.3E, APPROXIMATELY 138 NM
SOUTHWEST OF MIDWAY ISLAND. THIS SYSTEM IS CLASSIFIED AS A SUBTROPICAL
DEPRESSION, GENERALLY CHARACTERIZED AS HAVING BOTH TROPICAL AND
MIDLATITUDE CYCLONE FEATURES. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY DEPICTS A HIGHLY ASYMMETRIC CONVECTIVE STRUCTURE, WITH
CONVECTIVE BANDING WRAPPING INTO A BROAD CENTER. A 020141Z ATMS 88.2
GHZ MICROWAVE IMAGE REVEALS FRAGMENTED BANDS DISPLACED OVER THE
EASTERN SEMICIRCLE, WITH A WEAK, BROAD LOW-LEVEL CIRCULATION. A
012130Z ASCAT-C IMAGE REVEALS AN ELONGATED CIRCULATION, WITH A WEAK
CORE AND MAXIMUM WINDS DISPLACED OVER 90NM TO THE NORTH. THE SYSTEM IS
LOCATED UNDER A DEEP SUBTROPICAL TROUGH, WITH LOW TO MODERATE (15 TO
20 KNOTS) VERTICAL WIND SHEAR. MAXIMUM SUSTAINED SURFACE WINDS ARE
ESTIMATED AT 28 TO 33 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED
TO BE NEAR 1004 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT
TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS REMAINS LOW.
(2) NO OTHER SUBTROPICAL SYSTEMS.
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]

Jtwc upgrades to 13w

13W THIRTEEN 240904 0000 27.7N 147.0E WPAC 30 10

[dexterlabio]

Is this the first of the two typhoons shown by the GFS and Euro to form after Yagi? This one seems to be too north, I thought the next one would be the area of convection east of northern Philippines

[xtyphooncyclonex]

Is this the first of the two typhoons shown by the GFS and Euro to form after Yagi? This one seems to be too north, I thought the next one would be the area of convection east of northern Philippines

Yup. It may be somewhere here. 13W isn't even in JMA's warning/forecast map.

[doomhaMwx]

Looks much better organized than ever (although LLCC is partially exposed) and is likely a TS. ASCAT found 35-40 kt winds this morning (00Z JTWC: 25kt / JMA: 30kt), maybe even a tad stronger given the storm's small size.

[doomhaMwx]

JMA upgraded it to TS Leepi at 06Z (one of the rare instances where they didn't issue a gale warning before upgrading).

T2412(Leepi)
Issued at 2024/09/05 07:05 UTC
Analysis at 09/05 06 UTC
Grade TS
Scale -
Intensity -
Center position N33°05′ (33.1°)
E145°50′ (145.8°)
Direction and speed of movement N 15 km/h (9 kt)
Central pressure 1002 hPa
Maximum sustained wind speed near center 18 m/s (35 kt)
Maximum wind gust speed 25 m/s (50 kt)
Radius of 30-kt wind area 110 km (60 NM)

JTWC also revised their 00Z estimate to 35 kts.

13W THIRTEEN 240905 0600 33.1N 145.8E WPAC 30 1004
13W THIRTEEN 240905 0000 32.4N 145.9E WPAC 35 1004
13W THIRTEEN 240904 1800 31.3N 146.4E WPAC 30 1004

[cycloneye]

JMA upgrades tp TS Leepi.

T2412(Leepi)
Issued at 2024/09/05 13:05 UTC
Analysis at 09/05 12 UTC
Grade TS
Scale -
Intensity -
Center position N33°55′ (33.9°)
E145°50′ (145.8°)
Direction and speed of movement N 15 km/h (8 kt)
Central pressure 1002 hPa
Maximum sustained wind speed near center 18 m/s (35 kt)
Maximum wind gust speed 25 m/s (50 kt)
Radius of 30-kt wind area 110 km (60 NM)