Predictability of Tropical Cyclone Genesis in the IPRC Regional Model

1
Predictability of Tropical Cyclone Genesis in
the IPRC Regional Model
Y. Wang1, R. Zhan2, C.-C. Wu3, and Yi Lu3 1IPRC,
2Shanghai Typhoon Institute, 3National Taiwan
University
The predictability of tropical cyclone formation
over the western North Pacific was studied in an
ensemble of four 20-year simulations of the
regions atmospheric circulation during tropical
cyclone season conducted with the IPRC Regional
Model (iRAM). Forced with the same observed sea
surface temperature and lateral boundary
conditions, the ensemble members differed only in
their initial conditions. Analyses show the model
has skill in simulating the number of tropical
cyclones that were observed to form each month,
but the individual simulations have a large
spread. This indicates that the internal
variability in the atmospheric circulation limits
the predictability of cyclone formation in the
western North Pacific. The ensemble mean was
usually more accurate in hindcasting the number
tropical cyclones during each of the 20 years
than any individual realization.  
Left the average number of TCs that formed from
July through October over 20 years in each of the
simulations, in the ensemble mean, and in
observations from the China Meteorological
Agency. Right the same variables but for the 4-
month average for each of the 20 years.