JPATS Weather - NETC

JPATS AVIATION WEATHER BOOKLET
Turbulence Group
This group is similar to the icing group because it is consists of six characters and follows the
same format. The turbulence group, however, begins with a “5,” and the second digit represents
the turbulence intensity, also from Table 6-6. The turbulence group is used to forecast nonthunderstorm
turbulence (the presence of thunderstorms implies moderate or greater turbulence)
and is also repeated as often as necessary to indicate multiple turbulence layers. The group is
omitted if no turbulence is forecasted. The example below illustrates the decoding of the
turbulence group:
510302
Following the same rules as the icing group, above, one would expect light turbulence from 3000
feet AGL to 5000 feet AGL.
Altimeter Group
This group forecasts the lowest expected altimeter setting in inches of Hg (Mercury) during the
initial forecast period and each subsequent BECMG and FM group (to be discussed shortly) that
follows. TEMPO groups (also to be discussed shortly) do not forecast the QNH group. This
minimum altimeter setting becomes quite valuable when aircraft lose radio communications in
IMC conditions and need a useful altimeter setting for the destination airfield (Figure 6-21).
KNSE TAF 260909 28004KT 9000 HZ SCT020 SCT200 QNH2998INS
Figure 6-21 — TAF Altimeter Group
The “QNH” indicates that 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 Table 6-2 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 Table 6-2, 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.”
Version 3.2/Dec 08 6-19