Microbursts - P-3040075

METEOROLOGY FLIGHT PLANNING

CHAPTER TWO

looking at a NEXRAD display should plan around areas of red on the color-coded scale, as these

are generally considered danger areas and should be avoided.

Wind Shear

A major hazard to aviation is the presence of low-level wind shear and frontline wind shear.

Although wind shear can occur at any altitude, it is particularly hazardous when it develops over

a short period of time within 2000 feet of the ground. The primary concern for aircraft at low

altitudes is a rapid change in wind direction that could affect the aircraft's handling

characteristics. There are several display and data analysis options available to indicate possible

wind shear.

Microbursts

Microbursts are detectable by NEXRAD because of the density gradient of the descending air,

the particulate matter contained therein, or both. However, because of the shallow vertical extent

of the outflow from a microburst, the phenomenon will usually not be detected beyond a range of

20 NM from the radar site.

Satellite Imagery

For general-purpose use, there are two types of satellite imagery available. When combined they

provide a great deal of information about clouds to a pilot. Through interpretation, one can

determine the type and height of clouds as well as the temperature and the thickness of cloud

layers. From this information, the pilot can get a good idea of possible associated weather along

the planned route of flight.

Visible Imagery

One type of imagery is the visible satellite (Figure 2-13). With a visible satellite picture, we are

looking at clouds and the Earth reflecting sunlight back to the satellite sensors. The greater the

reflected sunlight reaching the sensors, the brighter white the object is on the picture. The

amount of reflectivity reaching the sensors depends upon the height, thickness, and ability of the

object to reflect sunlight. Since clouds are much more reflective than most of the earth, clouds

will usually show up white on the picture, especially thick clouds. Thus, the visible picture is

primarily used to determine the presence of clouds and the type of clouds from shape and texture.

Due to the obvious lack of sunlight at night, there are no visible pictures available during this

period.

DATA DISPLAYED ON WEATHER IMAGERY PRODUCTS

2-15