2016 Impact Stories

Houston Flooding - April 2016

NWS forecasters discussed a heavy rainfall threat at least three days in advance of the “Tax Day Flood” of April, 2016, but it was unclear how much precipitation would fall and where the maximum amount would be.

On April 17, the GSL-developed HRRR weather model predicted a group of almost stationary thunderstorms would drop 15-20 inches of rain in a 12-hour period northwest of Houston, Texas. This was an unprecedented amount of rainfall for a forecast that signaled a potentially historic flooding event. Meteorologists working the night shift at the NWS Weather Prediction Center in College Park, MD saw the HRRR rainfall forecast, and at 10:49 p.m. warned of extreme rainfall totals and life-threatening flash flooding.

What happened?
On April 18 at 1:45 a.m., the NWS Houston/Galveston declared a rare “flash flood emergency.” Officials closed schools, businesses, and government offices to keep residents off the roads. GSL continuously pushes these high-impact weather models to the edge of computing power and scientific understanding, and transitions advances into the operational version used by the NOAA NWS about once each year.

Impacts on the public and the economy:

• Largest non-tropical flood event
• 21,000 square miles covered in flash flood warnings
• 650 flight cancellations, 1100 delays
• 1200 high-water rescues
• Houston city offices, schools closed

Denver Blizzard - March 2016

NWS meteorologists had been watching the evolving snowstorm for days as the GSL-developed weather data and analysis system had been steadily collecting 3 million weather observations each hour. The GSL-developed HRRR short-term high-impact weather model showed early signs that it could be a big event. Every hour as the HRRR weather model produced another forecast based on new data, the forecasters saw something they didn’t like.

What happened?
The NWS upgraded the winter weather advisories in the Denver Metro area to winter storm and blizzard warnings that alerted the public from being exposed to dangerous weather.

Impacts on the public and the economy:

• CDOT - chains required in the Denver metro area for the first time
• Thousands of miles of roadways became hazardous
• 2.8 million people were affected in Denver
• 1,000 flights were canceled
• 190,000 customers were without power
• Businesses, non-essential government were shut-down

GSL’s impact:

GSL developed the tools and weather models NWS forecasters used to monitor the growing storm and issue life-saving blizzard warnings.