Turbulence Group - P-3040037

METEOROLOGY FLIGHT PLANNING

CHAPTER ONE

KNSE TAF 260909 28004KT 9000 HZ SCT020 SCT200 QNH2998INS

Figure 1-27 TAF Altimeter Group

The "QNH" indicates sea level pressure is being given. The next four digits indicate the lowest

forecast altimeter setting in inches of Hg (and hundredths), without the decimal. "INS" simply

indicates the unit of measurement is inches. Other standards, such as QNE and QFE, are also

used in different circumstances. QNE is the standard datum plane, 29.92 in-Hg, and some

countries use QFE, the actual station pressure not corrected to sea level. If QFE is set, the

altimeter indicates actual elevation above the field, but does not ensure terrain clearance.

Aircrews must exercise extreme caution if conducting operations at a location using QFE.

International stations report the altimeter in millibars (a.k.a. hectopascals, hPa) and use the letter

"Q" for indicator. For example, "Q1013" indicates a forecast altimeter setting of 1013 millibars.

U.S. civil stations generally will not forecast an altimeter setting.

REMARKS

Various remarks may be appended to the end of the initial forecast period and subsequent change

groups. The contractions listed in Figure 1-11 are used for weather and obstructions to vision,

while the FAA General Use Contractions will be used for other abbreviations.

The abbreviation "VC," also from Figure 1-11, will only be used for air mass weather that is

expected to occur within the forecast area. For example, "VCSHRA W" would indicate that rain

showers are in the vicinity to the west. However, "VC" will not be used for weather expected to

occur within a 5-mile radius of the runway complex, since that is considered to be "at the

station."

Temperature Group

This is an optional group; however, its usage is highly encouraged and should be included to

meet the requirements of local operations, especially for helicopter and VSTOL aircraft, which

require density altitude. The forecast maximum or minimum temperature, depending on the time

of the day, is given in two digits Celsius, using "M" for minus temperatures. This is followed by

the 2-digit hour during which the maximum or minimum is expected to occur. It will be on the

last line of the TAF, unless the forecast was amended.

108.

CHANGE GROUP TERMINOLOGY

The change groups of "FM," "BECMG," and "TEMPO" will be used whenever a change in some

or all of the elements forecasted are expected to occur at some intermediate time during the 24-

hour TAF period. A new line of forecasted text is started for each change group. More than one

change group may be used to properly identify the forecast conditions (Figure 1-28).

AVIATION ROUTINE WEATHER REPORTS AND TERMINAL AERODROME

FORECASTS 1-23