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Coastal Storm Impacting the Northeast U.S.; Severe Thunderstorms in the Plains

A coastal storm will continue to bring high winds and heavy rain which may cause flooding to coastal areas of the Northeast U.S. Tuesday and Tuesday night. Scattered severe thunderstorms associated with large hail, wind damage and isolated tornadoes are expected across parts of the southern and central Plains from late Tuesday afternoon through the evening into the overnight. Read More >

 

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Density Altitude

diagram Density Altitude Concept
diagram

On a hot, muggy day, the air becomes “thinner” or less dense, and its density at a pilot’s location is equivalent to a higher altitude in the standard atmosphere.  It is hazardous to aircraft during takeoff and climb because:

- Aircraft power is reduced. The engine will ingest less air to support combustion.

- Aircraft thrust is reduced.  A propeller will have less "grip" on the air, while a jet engine will will exhaust less mass.

- Lift is reduced.  The thinner air will exert less upward force on the airfoils.

As a result, a longer takeoff and landing roll is required, especially for a fully-loaded aircraft.  After takeoff, the aircraft will have a smaller rate of climb and will have a lower service ceiling.

Density altitude is usually reported at each AWOS/ASOS station in the Remarks section of the METAR, if the value is greater than 1000ft higher than the elevation of the airfield.  Here's an example:

METAR KMSY 291400Z AUTO 18006KT 10SM CLR 28/13 A3001 RMK SLP161 DENSITY ALT 1000FT

 

 

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Density Altitude