NOWCASTING PROBLEM IN A NOWCASTING PROBLEM IN A SUBTROPICAL AREA WITH COMPLEX SUBTROPICAL AREA WITH COMPLEX TERRAIN: LESSON LEARNED FROM A TERRAIN: LESSON LEARNED FROM A

FLASH FLOOD CASEFLASH FLOOD CASE

WSN05, Toulouse France, September 2005WSN05, Toulouse France, September 2005

Ben Jong-Dao JouDepartment of Atmospheric Sciences

National Taiwan University

Pacific Ocean

Asia Continent

East Asia Monsoon

Pacific Ocean

Taipei basin viewed from Taipei basin viewed from south.south.

Wu-Lai

Hsin-Dien

Mu-ZaiNTU

Precipitation pattern

Sounding at Panchiao (46692) and hodographSounding at Panchiao (46692) and hodograph

Composite maximum reflectivity at 3 kmComposite maximum reflectivity at 3 km

Local wind analysis

SW

NW SE

NE

NW

SE

Concluding SummaryConcluding Summary the complex terrain in the northern Taiwan plays a subtle role the complex terrain in the northern Taiwan plays a subtle role

in controlling the organization, propagation, and development in controlling the organization, propagation, and development of the severe multi-cellular thunderstorm systems in the area. of the severe multi-cellular thunderstorm systems in the area.

We have demonstrated, in this case study, that the importance We have demonstrated, in this case study, that the importance of Doppler radar and mesonet in revealing the important mesoof Doppler radar and mesonet in revealing the important mesoscale features and also the mesoscale processes associated witscale features and also the mesoscale processes associated with the formation and the propagation of this complex storm systh the formation and the propagation of this complex storm system. em.

It is not clear, however, which process(es) is (are) more importIt is not clear, however, which process(es) is (are) more important under different environmental conditions. Possibly due to tant under different environmental conditions. Possibly due to the fast growth of the metropolitan area of Taipei city and possihe fast growth of the metropolitan area of Taipei city and possibly due to the global warming, the damages caused by these sebly due to the global warming, the damages caused by these severe rainstorms in the great area of Taipei (an area of approxivere rainstorms in the great area of Taipei (an area of approximately 3,000 km2 with a population of 6 million) has been incrmately 3,000 km2 with a population of 6 million) has been increased dramatically in the last 10 years. eased dramatically in the last 10 years.

In order to improve the forecast capability and to mitigate the In order to improve the forecast capability and to mitigate the damages caused by these short-term localized severe rainstordamages caused by these short-term localized severe rainstorms, a very short term nowcasting system is needed. To establisms, a very short term nowcasting system is needed. To establish a workable forecast system, a comprehensive observational ah a workable forecast system, a comprehensive observational and numerical simulation study is needed in order to get a bettend numerical simulation study is needed in order to get a better understanding of all these complicated mesosacle processes ir understanding of all these complicated mesosacle processes in complex terrain environment of northern Taiwan.n complex terrain environment of northern Taiwan.