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HEAVY RAIN AND FLASH FLOODS
Old Klang Road, Kuala Lumpur on 6 April 2006
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Malaysian Meteorological Department
14 April
2006
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INTRODUCTION
Heavy rain in the vicinity of Kuala Lumpur on the afternoon of 6 April 2006 caused flash floods over many areas. Thunderstorms and heavy rain of this nature is often accompanied by strong winds and occasionally gusting winds. This type of inclement weather often occurs over the west coast states of Peninsular Malaysia between mid March to early May. This period referred to as the inter-monsoon season is characterized by light variable winds and an unstable atmosphere which favors strong convective activity resulting in thunderstorm and heavy rain in the late afternoons and early evenings. In this report an analyses of the rainfall, satellite and radar imageries during the period of this heavy rain episode is presented .
ANALYSIS OF RAINFALL RECORDED AT METEOROLOGICAL STATIONS
Meteorological stations located in Petaling Jaya and Subang had recorded rainfall between 4.00pm and 6.00pm, however the total amount is little. The Petaling Jaya meteorological station located on the border between Kuala Lumpur and Selangor, recorded 3.6mm and 9.8mm of rainfall at 4.00pm and 5.00pm respectively on 6 April 2006. Whereas Subang station which is located to the west of Kuala Lumpur recorded 0.1mm and 0.6mm of rainfall at 5.00pm and 6.00pm respectively. The meteorological station at KLIA in Sepang did not record any rain between the period 1.00pm and 6.00pm as shown in TABLE 1 below.
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TABLE 1: TOTAL HOURLY RAINFALL (MM) RECORDED AT PETALING JAYA, SUBANG AND KLIA STATIONS ON 06 APRIL 2006
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SATELLITE IMAGERIES ON 06 APRIL 2006
Imageries from MTSAT weather satellite are shown in Appendix A ( Figure 1a, Figure 1b, Figure 1c, Figure 1d, Figure 1e, Figure 1f & Figure 1g ) for the period from 1.10 pm to 7.10 pm on 6 April 2006. Thunder clouds started developing from around 2.00 in the afternoon over the west coast of Peninsular Malaysia from Perak to west Johor. Clusters of thunder clouds indicated by the red color as shown in the Figure 1d, Figure 1e, Figure 1f & Figure 1g in Appendix A shows the intense development of cloud over the Kuala Lumpur area. The Satellite imagery at 7.10pm in Figure 1g shows the rainfall beginning to decrease over the Kuala Lumpur area.
DOPPLER WEATHER RADAR IMAGERIES ON 06 APRIL 2006
Doppler radar imageries observed by the KLIA doppler radar shows in more detail the occurrence of heavy rainfall. The development of thunderstorm starting at 1.30 pm to 6.00 pm on 6 April 2006 is shown in the sequence of radar imageries included in Appendix B ( Figure 2a, Figure 2b, Figure 2c, Figure 2d, Figure 2e, Figure 2f, Figure 2g, Figure 2h & Figure 2i). The development of thunder clouds (indicated by the red and yellow colors) over the Kuala Lumpur and inland areas of Selangor started around 2.30 pm (Figure 2b). These thunder clouds intensified rapidly and extended to cover the entire Kuala Lumpur area from 3.00 pm to 4.00 pm (Figure 2c , Figure 2d & Figure 2e). After that thunderstorm activity began to weaken and by 5.34pm the rain over Kuala Lumpur began to clear up as shown in Figure 2h.
CONCLUSION
The heavy rain and flash flood that occurred over Kuala Lumpur on the afternoon of 6 April 2006 is a result of localised thunderstorm development. Very intense rain occurred over a very short period that caused flash floods to occur over several places in the vicinity of Kuala Lumpur.
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