TCAR - Typhoon Committee

TCAR
CHAPTER 5 - RESEARCH FELLOWSHIP TECHNICAL REPORT
KETSANA formed as TD at 00 UTC 25/09/2009
and moved mainly westward for the whole of
its existence. It strengthened into TS intensity at
00 UTC 26/09/2009 and crossed Luzon Island
to the South China Sea. Maintaining westward
motion in the South China Sea it was upgraded
into TY at 06 UTC 28/09/2009 , reaching its
maximum intensity with Vmax of 70 kts and
central minimum of 960 hPa. Turning to SW
direction KETSANA hit Central Vietnam almost
with its maximum intensity on 29/09/2009 then
weakened rapidly into a TD at 06 30/09/2009.
As can be seen from Fig. 14 and Tab.9 the CMA’s
track forecasts also had NW bias and forecasts
from 2009092800 toward the landfall had large
errors when TY KETSANA suddenly turned to
SW then made landfall.
Fig. 14. Track of TY KETSANA (0916) and
forecasts of CMA’s typhoon track prediction
model. Other explanations are similar to those in
Fig.6.
Table 9. Verification for track forecasts of TY
KETSANA (0916) ( position errors, km)
4.10. TY 0917 PARMA
PARMA formed as TD south of Guam at 06
UTC 27/09/2009. At 06 UTC 29/09/2009 it
gained intensity of TS. It move WNW and further
intensified into TY and reached its maximum
intensity with Vmax of 100 kts and central
pressure of 930 hPa in 18 hours later. It moved
NW and hit Northern Luzon Island on 03/10/2009
and remained in this area moving slowly back and
forth for 6 days and weakened into TD. However,
PARMA intensified again into a TS when moving
westward into the South China Sea at 00 UTC
10/10/2009. Moving WNW and crossing Hainan
Island it suddenly gained rapid intensification with
Vmax of 70 kts in the Gulf of Tonkin then it moved
SW and weakened into a TD in sea water. This
TS had very complicated track, intensification
change and lasted for long time (about 2 weeks).
Model track forecasts in Fig. 15 indicated
obvious north bias for almost whole life time of
TY PARMA, especially for the period before and
after hitting Philippines Island. Two first forecasts
starting from 2009092900 and 2009092906
had large errors for +12h and +24h forecasts
2009
Date and time 00 +12h +24h +36h +48h +60h +72h
2009092518 24.7 162.6 210.9 171.3 156.0 111.2 125.8
2009092600 11.1 194.6 108.2 46.3 61.7 67.9 132.3
2009092606 92.2 162.2 147.3 167.1 111.7 92.6 88.8
2009092612 35.0 86.4 78.1 86.2 181.6 320.7 431.9
2009092618 15.4 54.8 39.6 39.0 72.2 193.8 305.8
2009092700 15.4 11.1 46.3 86.9 242.2 325.3 414.8
2009092706 15.4 63.0 44.5 35.0 143.4 175.1 -
2009092712 22.2 64.2 30.8 154.1 196.4 274.4 -
2009092718 10.7 54.6 92.5 162.5 178.2 - -
2009092800 22.2 39.6 123.4 169.8 303.2 - -
2009092806 0.0 81.9 207.1 310.6 - - -
2009092812 15.4 135.3 208.0 310.6 - - -
2009092818 11.1 100.6 239.4 - - - -
2009092900 24.7 172.9 301.6 - - - -
2009092906 0.0 284.0 - - - - -
2009092912 53.6 259.7 - - - - -
2009092918 39.1 - - - - - -
2009093000 99.1 - - - - - -
FCST TIMES 18 16 14 12 10 8 6
Average (km) 29.1 120.5 134.1 145.0 164.7 195.1 249.9
Min (km) 0.0 11.1 30.8 35.0 72.2 67.9 88.8
Max (km) 99.1 284.0 301.6 310.6 303.2 325.3 431.9
293