Guiding rescue helicopters

New NCAR tool highlights weather conditions for emergency medical flights

May 31, 2013 | For several years, NCAR has provided an experimental tool for helicopter rescue pilots who must decide quickly whether weather conditions are safe enough to attempt a low-altitude flight. Now the NCAR team has made key upgrades to the Helicopter Emergency Medical Services (HEMS) tool that will enable it to be more widely used in rescue situations.

 The HEMS Tool already provides important information for rescue pilots. It gives users a seamless graphical compilation of reported and forecasted winds, visibility, clouds, temperatures, and radar data for the continental United States.

 But HEMS is particularly notable in that it creates an “intelligent interpolation” of low-altitude visibility and ceilings (the height of the lowest cloud layer) between observation stations by using algorithms that take into account the terrain, forecasting models and technical assessments. That allows users to view an area as small as 5 kilometers by 5 kilometers anywhere in the country and get actual or estimated data about its visibility and cloud heights. In addition, it presents the data measured in feet above ground level (AGL) instead of mean sea level (MSL), which is usually used by pilots, but less useful to those who only fly at low altitudes.

HEMS tool website
HEMS enables rescue pilots to view atmospheric conditions, including ceiling, visibility, wind speed, and icing potential, at various altitudes above ground level. (Image courtesy Arnaud Dumont.)

 Since its creation in 2006, HEMS has been available on an experimental site hosted by NCAR. The original version of HEMS is expected to become an approved flight planning tool supported by the National Oceanic and Atmospheric Administration (NOAA) later this year, increasing its visibility to those engaged in emergency evacuations.

 The program’s updated version, which will be available on NCAR’s site, will allow users to track visibility and ceiling trends in order to better determine if conditions are improving or deteriorating.  It will also add important topographical data such as contoured elevation lines and enable users to locate landmarks to help with navigation, such as heliports or hospitals. 

 Some 900 to 1,200 pilots and other users view the free HEMS tool daily, showing that it fills an important need, says Arnaud Dumont, a senior software engineer in NCAR’s Research Application Laboratory, which developed the application. “Other tools didn’t provide high enough resolution and didn’t show conditions exactly where they were flying to pick somebody up.”

 HEMS was developed at the request of the Federal Aviation Administration (FAA) after a 2006 review of rescue helicopter crashes revealed that a lack of detailed weather information was often a factor. While good weather information is usually available near airports and large cities, no data are available for many other areas.

 Without that information, the FAA found, helicopter rescue pilots have too often flown from safe conditions on takeoff into unanticipated areas of poor visibility, resulting in crashes into obstacles or terrain. The goal of HEMS is to reduce these incidents by providing more accurate information when and where it is needed.


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The University Corporation for Atmospheric Research manages the National Center for Atmospheric Research under sponsorship by the National Science Foundation. Any opinions, findings and conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.