TCAR - Typhoon Committee

TCAR
CHAPTER 5 - RESEARCH FELLOWSHIP TECHNICAL REPORT
As can be seen from Fig.17, the bogus vortex is
very weakly presented in initial field in comparison
with the observed vortex.
Configuration of experiments is as followings :
(i) Experiment 1 : Operational system
(GMTTP)
BOGUS vortex relocation
(ii) Experiment 2 : Bogus vortex relocation
Partly removing shallow
vortex + bogus vortex
Fig. 18 showed the initial sea level pressure
minimum at 00h for EXP 1 and EXP 2. It can
be seen that the EXP 2 initial sea level pressure
minimum is closer to that of observed vortex.
SLPmin
1010
1000
990
980
970
960
00/19
12/19
00/20
12/20
00/21
12/21
00/22
Date
12/22
00/23
12/23
00/24
12/24
EXP1
OBS
EXP2
Fig. 18 . Initial Sea Level Pressure minimum at
00h for EXP 1 and EXP 2 (19-24 Jun.)
There were 10 track forecasts starting from 00
UTC 20/06/2008 conducted for experiments.
Fig. 19a showed the track forecasts for EXP 1 and
EXP 2 , Fig.19b showed the mean track errors for
EXP 1 and EXP 2.
mean track errors (km)
600
500
400
300
200
100
0
24(10) 48(7) 72(4) 96(3)
Time (h)
NWP
Bogus
Fig.19a. Mean track errors for EXP 1 and EXP 2.
Fig. 19b. The track forecasts for EXP 1 and EXP 2
As can be seen from Fig.19 better presenting TC
bogus intensity in vortex initialization scheme
brought positive effect on TY FENGSHEN’s track
forecasts that led to decreasing the prediction
errors and reducing NE bias (Ma and Qu, 2009).
One of reasons causing inaccurate track forecasts
of TY FENGSHEN is that models and official
forecasts failed to predicted the development and
intensity of subtropical high pressure ridge which
is the large scale environmental flow.
As mentioned in section 3 TS track forecasts
could be improved if in vortex initialization scheme
the environmental flow and the vortex structure
were presented appropriatelly through selecting
correct parameters (Nguyen T. M. Phuong,
2004). Fig.20 showed the TY FENGSHEN track
forecasts issued in operational run by above
mentioned barotropic model in VNCHMF.
2009
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