TYPHOON 10W KST Advisory Number 1
KST HQ CEBU, PHILIPPINES
Typhoon Cempaka [WP102021]
0900UTC TUE JULY 20 2021
...CEMPAKA MOVING STATIONARY AS A TYPHOON...
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SUMMARY OF INFORMATION
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INITIAL POSITION: 21.4N 112.3E
INITIAL INTENSITY: 70 KTS
GEOGRAPHIC REFERENCE: 119 NM WEST-SOUTHWEST OF HONG KONG
MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 01 KTS
SIGNIFICANT WAVE HEIGHT: 26 FEET
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WATCHES AND WARNINGS
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...ORANGE TYPHOON ALERT...
-CHINA
...SIGNAL NO. 1 - STANDBY SIGNAL...
-HONG KONG
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DISCUSSION
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Cempaka is located 220 km west-southwest of Hong Kong, and has moved northwestward at 2 km/h (1 knot) over the past 6 hours.
Cempaka will make landfall in 12 hours 241 km west-southwest of Hong Kong. After landfall, the system will begin to weaken rapidly due to interaction with the underlying terrain.
An incoming, midlatitude trough will begin to weaken the steering ridge after this time and the weakened Cempaka will begin an equatorward track as a result after 36 hours along an extension of a ridge to the west.
Cempaka will then reenter the warm waters of the South China Sea whereupon it will gradually intensify to 65 km/h (35 knots) in 3 days. Thereafter the system will begin to track initially eastward and then east-northeastward through the remainder of the forecast period as the near-equatorial ridge positioned to the south becomes the dominant steering mechanism.
Despite continue warm sea surface temperatures, TY cempake will struggle to intensify further due to terrain interaction with Hainan and unfavorable (greater than 25 knots) wind shear.
Numerical model track and intensity guidance is in tight agreement over the next 36 hours, however they diverge thereafter due to the timing of the interaction between the incoming midlatitude trough and the steering ridge.
Despite this divergence in model tracks, all member of the JTWC multi-model consensus agree on the southward recurve scenario with subsequent re-entry into the South China Sea and final east to east-northeastward track.
The JTWC forecast track is placed along the mult-model consensus due to the overall agreement in track guidance.
Maximum significant wave height is 7.9 meters (26 feet).
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FORECAST CONE
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NEXT FULL ADVISORY AT 1500UTC TUE JULY 20TH 2021
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INFORMATION FROM THE JOINT TYPHOON WARNING CENTER
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FORECASTER KHAN