A category 4 hurricane is threatening the Gulf Coast of the United States and is forecast to make landfall to the east of New Orleans within 72 hours.

Emergency Managers: To guide their evacuation decision and planning process, emergency managers for the City of New Orleans need to acquire from National Weather Service (NWS) Internet data services a subset (area includes the city and evacuation routes) of “Probability of Tropical Storm Force Wind” grids (see image below). These gridded data are needed for the 24 – 48 hour period. Similar data are needed for the probability of hurricane force winds in the 36 – 72 hour period.

Industry: Managers at several wind and petrochemical facilities use their Geographical Information Systems to access NWS data servers and retrieve hourly Probabilistic Storm Surge model forecasts grids (see image below) for the next 3 days. They are using the data to decide if they need to shut down their operations that are vulnerable to coastal inundation. For the wind generation facilities, a high probability of flooding is needed to justify shutting down operations while for the petrochemical sites a relatively small chance of a flooding induced toxic release could cost millions of dollars to clean up.

Weather Forecasters: Forecasters at the Houston forecast office are concerned about unusually high temperatures and humidity forecast in the wake of the hurricane. They have downloaded the latest heat index cumulative distribution function percentiles (see image below) from the National Digital Forecast Database and determined that it is necessary to issue an advisory, but just for sensitive populations.

Using probabilistic forecast data, emergency managers, industry, and operational weather forecasters have come to the realization that although the hurricane was forecast to miss their area, the probability that it could affect residence and industry was high enough to justify the cost of evacuating 500,000 people in eastern New Orleans, closing 3 petrochemical facilities and alerting residence to the possibility of health threatening heat.

-- JohnSchattel - 22 Jan 2010

• Probabilistic Tropical Cyclone Wind Speeds (34 kts):
  
  

• Probabilistic Storm Surge Model Forecast:
  
  

• Apparent Temperature cumulative distribution Functions: