TCAR - Typhoon Committee

TCAR
CHAPTER 5 - RESEARCH FELLOWSHIP TECHNICAL REPORT
Study on
Improvements in CMA’s Typhoon Track Prediction Model
with Vortex Initialization Scheme
Chatchai Chaiyasaen 1 and Nguyen Thi Minh Phuong 2
1. Thai Meteorological Department (TMD)
4353 Sukhumvit Road, Bangna, Bangkok 10260, Thailand
Tel : 662-7445442, Fax : 662-7445441
Mobile : 081 6461381
Email : chatchai@tmd.go.th
2. National Center for Hydrometeorological Forecast of Vietnam (VNCHMF)
No 4 DANG THAI THAN, HANOI, VIETNAM.
Email : ntmphuong@yahoo.com.au, ntmphuong@hotmail.com
Abstract
In China Meteorological Administration (CMA) a
limited area operational numerical typhoon track
prediction model (LTCM) with axisymmetric
vortex bogus scheme was developed in 1992 and
run operationally since 1996 . Model forecast
results served as guidances for forecasters in
issuing official typhoon track forecasts. Forecast
verification for 1996 – 2002 showed that the
mean position errors are approximately 180 km
and above 350 km for +24h and +48h forecasts,
respectively.
Since that time both model and vortex initialization
scheme are improved continuously for providing
more accurate track forecasts. In 2004 in
CMA the global spectral model (GSM) at T213
resolution with 31 vertical levels (T213L31) named
GMTTP (Global Model for TC Track Prediction)
had been run operationally in paralell with LTCM.
The new forecast system included a number of
improvements in both model and bogus vortex
initialization scheme with vortex asymmetric
component that provided significant improvements
in tropical storm (TS) track prediction accuracy.
The performance of GMTTP for 2004 – 2005
is better than those of LTCM in 14.7%, 14.0%,
16.2% and 23.5% for +12h, +24h, +36h and +48h
forecasts respectively. This TS prediction system
GMTTP was put on operational use in 2004 to
replace LTCM. Next improvement in CMA’s TS
prediction system is improving vortex initialization
by vortex modification and data simulation system
upgrading (the OI system was replaced by the SSI
3-Dvar system). The track forecast verification for
2006 showed that the improved forecast system
reduced average track errors of 12 - 23% in +12h
to 120h forecast periods. The last system had been
put into operational work in 2007 sofar.
This study aimed firstly to analyze some model’s
typhoon track results for typhoons of complicated
tracks in Western North Pacific (WNPAC) during
2006 – 2009 to consider model forecast skills and
to find model’s systematic errors and bias, then
conducting numerical experiments for typhoon
(TY) PARMA (0917) and TY FENGSHEN (0806)
by using CMA’s global spectral model and vortex
initialization scheme with last improvements and
modifications.
1. Introduction
Since 1992 in China Meteorological Administration
(CMA) a limited area operational numerical
typhoon track prediction model (LTCM) with
axisymmetric vortex bogus scheme was
2009
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