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2017 Impact Stories

September 2017

Hurricane Maria - September 2017

What Happened?
The radar in San Juan, Puerto Rico was destroyed by Hurricane Maria as it made landfall as a Category 4 hurricane.

GSL’s impact:
GSL’s experimental HRRRx forecast model continued to produce predictions of the movement, winds, precipitation, and path of Hurricane Maria after the loss of the San Juan NWS radar.

The experimental HRRR-Caribbean was assimilating the San Juan radar data until that radar went down. Satellite cloud data was also assimilated, as it is for all RAP/HRRR domains and was able to continue to produce valuable forecasts.
September 2017

Hurricane Irma

What Happened?
Hurricane Irma held sustained top winds of 185 mph for 37 hours.

GSL’s impact:
GSL launched a special set of HRRRX runs with a Caribbean domain that produced new 36-hour forecasts every 3 hours. The 36 hour HRRRX forecasts accurately predicted Hurricane Irma’s location within a half county and captured the timing and landfall over Marco Island, Florida at 2pm on Sunday, September 10, 28-hours in advance.

GSL also wrote the software that allows NWS forecasters to manipulate the Storm Surge Watch Warning areas that ultimately create this graphic.

August 2017

Hurricane Harvey

What Happened?
  • Hurricane Harvey is the wettest tropical cyclone on record in the contiguous United States.
  • As of August 29, 2017 record-breaking rainfall amounts of 5-61” were recorded.
  • Harvey’s location and slow movement caused unprecedented amounts of rainfall.
GSL Impact:
  • GSL-developed HRRRX forecast model accurately predicted the Houston, Texas area could receive up to 40” of rain by Sunday morning, August 27, 2017.
  • The HRRRX accurately predicted the rainbands that stalled over the Houston, and later Beaumont areas. Larger-scale models kept the heaviest rains near the remnant eyewall with Harvey.
  • HRRRX accurately predicted the path of Hurricane Harvey before it made landfall


What Happened?
On a typical clear August day in the Great Plains, maximum downward shortwave radiation from the sun occurs about noon. But if the sun is blocked partially for a few hours and completely for a few minutes, how will this affect temperature near the surface? Or to low-level winds? What impact will this drop in radiation have on existing weather, such as thunderstorms in progress? Current operational weather forecasting models are not equipped to represent the eclipse and its effect on the weather.

Researchers at the NOAA Global Systems Division (GSL) and the Cooperative Institute for Research in Environmental Sciences (CIRES) have adapted an eclipse algorithm to use with their experimental version of the 3-km High-Resolution Rapid Refresh (HRRR) model. The algorithm, developed by a University of Barcelona team and shared by NCAR with the Weather Research and Forecasting community model, computes the degree of obscuration of the solar disk at each model grid point. Based on this calculation, the model modifies the incoming solar radiation, which impacts the heating of the earth and, subsequently, the weather.

GSL Impact:

The eclipse and state-of-the-art weather models like the HRRR offer a rare opportunity to compare conditions of the atmosphere with and without the eclipse, and see how it interrupts processes in the atmospheric boundary layer from coast-to-coast.

tornado-2017.pngMay 2017

Elk City, OK Tornado Path

What Happened:

As severe weather brewed in the Texas panhandle late in the afternoon of May 16, NOAA’s National Weather Service forecasters alerted residents in parts of weather Oklahoma about the potential for large hail and damaging tornadoes that evening, particularly in the area around Elk City.

Ninety minutes later, a dangerous, rain-wrapped EF2 tornado struck the small town. It killed one, injured eight, and destroyed about 200 homes and more than 30 businesses.
Normally, meteorologists issue warnings based on radar depictions or spotter reports. By then, a tornado could be minutes from touching down.

This time, the NWS issued an additional advisory for parts of four counties in southwest Oklahoma stating “...a high probability that tornado warnings will be issued.”

This unusual step was prompted by output from an experimental forecast model based on GSL’s experimental hourly-updating regional analysis and prediction system - a spinoff of GSL’s High Resolution Rapid Refresh severe weather forecast model now in operation at all 122 NWS forecast offices.

Impacts on the public and the economy:
  • 90 minute lead-time for estimated tornado path
  • One fatality
  • Eight injuries
  • 200 homes destroyed
  • 30 businesses destroyed
GSL’s Impact:
GSL’s experimental version of the High-Resolution Rapid Refresh Ensemble regional analysis and prediction system honed in on the location and path of potentially tornadic supercell thunderstorms hours before they began to impact the public.