Science and Technology News

Friday, April 22, 2011

Countdown to Endeavour: When the Weatherwoman Can’t Be Wrong

By Carla Voorhees

Kathy Winters is an Air Force Civilian Meteorologist at the 45th Weather Squadron at Cape Canaveral Air Force Station. She is the Space Shuttle Launch Weather Officer providing weather support to the Space Shuttle Program at Kennedy Space Center as the Launch Team prepares for the 29 April 2011 launch of Endeavour. You can find out more about the 45th Space Wing at their Facebook page.

Shuttle Launch Weather Predictions:
Shuttle launch preparations continue and we are providing both general information about launch weather as well as specific information to the Space Shuttle team. I provide a weather briefing to the Launch Director every morning, and we are already looking ahead at next week’s launch weather. For predictions beyond seven days, we review the Global Forecast System (GFS) long-range model outputs which are updated every six  hours. The meteorological model predictions for time periods beyond five days toggle around quite a bit. On Tuesday weather predictions for April 29th looked bad, but on Wednesday the 00Z and 06Z GFS model runs trended to a more favorable launch day weather prediction. Still, it’s too early to tell. Over the next week, we will watch each model run noting the consistency of the models as we approach launch.  Our first launch forecast will be issued on April 26, three days prior to launch.

Temperature Prediction assists ATK in Determining Solid Rocket Motor Performance:
Nine days before launch, we provide the Marshall Space Flight Center Natural Environments Branch with forecast high and low temperatures for each day up through launch day. This temperature forecast is used by ATK Aerospace Systems to predict the propellant mean bulk temperature, a critical parameter in predicting the solid rocket motor performance during launch. Forecasting temperatures at 60 feet at the Shuttle launch pad is a lot different than forecasting temperatures at the surface away from the coast. Over the next week, we are expecting a lot of southeast winds, and onshore flow means the temperatures will be moderate at the launch pad and will average very close to the coastal water temperature. The high temperature will be several degrees lower than the inland temperatures in this type of situation, and the low temperatures will be several degrees higher. This is why I was wearing a leather jacket during our launch pad tour a couple weeks ago—it gets cool at the launch pad with onshore winds!

For a further explanation of why coastal temperatures are more moderate than inland temperatures, particularly with onshore flow, visit the National Oceanic and Atmospheric Administration.

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