Flash Flood Emergencies- Two Extreme
Events in Six Weeks
Jeffry Evans, NWS Houston/Galveston, League City, TX
Lance Wood, NWS Houston/Galveston
Jeffrey Linder, Harris County Flood Control District
Two of the most extreme rainfall events on record in or around the Houston metropolitan area occurred during a six week period in late spring 2016. These historic rainfall events resulted in 12 flooding-related fatalities and the issuance of two Flash Flood Emergency for parts of Harris County and surrounding areas. This presentation will discuss the forecast challenges leading into each event and provide a historical perspective of the rainfall and its impacts.
The first event began early in the morning of April 18th over and just north and west of Houston. A large portion of northwest Harris County received between 10-15 inches of rainfall during the morning hours of the 18th, with over 20 inches falling just to the west in Waller county across headwaters of several major bayous which run through the Houston area. A Flash Flood Emergency (only the second ever from WFO Houston) was issued for northwest Harris County and the ensuing flooding resulted in 8 fatalities, all of which were vehicle related.
History repeated itself a mere 6 weeks later a bit further northwest on May 26-27, 2016. Portions of Washington County recorded over 12 inches of rainfall in a 3-hr period, and the 16.33” measured in 12 hrs at the Brenham ASOS exceeded the 500-yr rainfall period. The intense rainfall produced rapid flash flooding, exacerbated by additional heavy rainfall the next afternoon. This event resulted in 4 more vehicle related fatalities, and the second issuance of a Flash Flood Emergency for a part of Harris County in a six week period, and the third time in 12 months.