65th IHC Booklet/Program (pdf - 4.9MB) - Office of the Federal ...

Forecasting Rapid Intensification of Tropical Cyclones in the Western North Pacific Using
TRMM/TMI 37 GHz Microwave Signal
Tie Yuan 1 , Haiyan Jiang 1 , and Margaret Kieper 2
(tyuan@fiu.edu)
1 Department of Earth & Environment, Florida International University; 2 Private Consultant
The prediction of rapid intensification (RI) of tropical cyclones has always been a great
challenge in tropical weather forecasting. Compared with the progress in RI forecast in the
Atlantic and Eastern North Pacific, there are few works in RI forecast in the Western North
Pacific. Following Margie Kieper’s subjective forecast method using the 37 GHz color product
developed by the Naval Research Laboratory (NRL) to predict the onset of RI, we have
developed an automated detection method, 37 GHz ring pattern RI index, to identify the cyancolor
ring pattern around the center of tropical cyclones from the Tropical Rainfall Measurement
Mission (TRMM) Microwave Imager (TMI) 37 GHz observations (please see the abstract by
Jiang et al. in the same conference). In this study, this ring pattern RI index is applied to the 12-
yr TRMM Tropical Cyclone Precipitation Features (TCPFs) database to investigate the
probability of improving RI forecast in the Western North Pacific. The result shows that the
probability of detection (POD) of RI for storms reaching tropical storm intensity in the Western
North Pacific is about 63%. Furthermore, it is found that the greater the intensity of tropical
cyclones is, the larger the POD. The PODs are 40%, 75%, and 100% for tropical storms,
typhoons, and super typhoons, respectively.
Our technique uses the 37-GHz ring feature in the storm’s inner core, therefore it counts the
effects of storm internal processes on intensity change. However, large-scale environmental
conditions are the controlling factors of intensity change. We plan to use the environmental
factors such as SST and wind shear to screen out those ring cases with unfavorable
environmental conditions. The work is underway to generate environmental RI index similar to
STIPS using the ECMWF INTERIM reanalysis data. The environmental RI index will be
incorporated into the 37 GHz ring pattern RI index to further advance the RI forecast skill in the
Western North Pacific.
Session 11 – Page 6