(c)
 Icing

(d)
 Freezing level

(e)
Turbulence

(f)
 Low level wind shear (LLWS)

(g)
 Strong surface winds G-AIRMETs are snap shots at discrete time intervals as de.ned above. The text AIRMET is the result of the production of the G-AIRMET but provided in a time smear for a 6hr valid period. G-AIRMETs provide a higher forecast resolution than text AIRMET products. Since G-AIRMETs and text AIRMETs are created from the same forecast “production” process, there exists perfect con-sistency between the two. Using the two together will provide clar-

ity of the area impacted by the weather hazard and improve situa-tional awareness and decision making.
Interpolation of time periods between G-AIRMET valid times: Users must keep in mind when using the G-AIRMET that if a 00 hour forecast shows no signi.cant weather and a 03 hour forecast shows hazardous weather, they must assume a change is occur-ring during the period between the two forecasts. It should be taken into consideration that the hazardous weather starts imme-diately after the 00 hour forecast unless there is a de.ned initia-tion or ending time for the hazardous weather. The same would apply after the 03 hour forecast. The user should assume the haz-ardous weather condition is occurring between the snap shots unless informed otherwise. For example, if a 00 hour forecast shows no hazard, a 03 hour forecast shows the presence of haz-ardous weather, and a 06 hour forecast shows no hazard, the user should assume the hazard exists from the 0001 hour to the 0559 hour time period.
Example: See Figure 7-1-8 for an example of the G-AIRMET graphical product.
g. Severe Weather Watch Bulletins (WWs) and Alert Mes-sages (AWWs)
* * * * *
7–1–10 In.ight Weather Broadcasts
a. * * * * * * * *
b. Hazardous In.ight Weather Advisory Service (HIWAS). This is a continuous broadcast of in.ight weather advisories including summarized AWW, SIGMETs, Convective SIGMETs, CWAs, AIRMETs (text [WA] or graphical [G-AIRMET] product), and urgent PIREPs. HIWAS has been adopted as a national pro-gram and will be implemented throughout the conterminous U.S. as resources permit. * * *
1. Where HIWAS has been implemented, a HIWAS alert will be broadcast on all except emergency frequencies once upon receipt by ARTCC and terminal facilities, which will include an alert announcement, frequency instruction, number, and type of advisory updated; for example, AWW, SIGMET, Convective SIG-MET, or CWA.
Example: Attention all aircraft. Hazardous weather information (SIGMET, Convective SIGMET, AIRMET (text [WA] or graphical [G-AIRMET] product), Urgent Pilot Weather Report [UUA], or Cen-ter Weather Advisory [CWA], Number or Numbers) for (geographi-cal area) available on HIWAS, Flight Watch, or Flight Service fre-quencies.
2. * * *Included in the broadcast will be the type of advisory updated; for example, AWW, SIGMET, Convective SIGMET, CWA, etc.
* * * * *
[EDITORIAL NOTE:
SEE NEW FIGURE 7–1–8 AT THE END OF THIS UPDATE.]

7–1–11 Flight Information Services (FIS)
* * * * *
c. * * *
1. * * *
(f) AIRMET text bulletins (WA). * * * * *
7–1–12 Weather Observing Programs
* * * * *
b. * * *
1.
 * * *

2.
 * * *

3.
These real-time systems are operationally classi.ed into

eight basic levels: * * * * *
(e)
 AWOS–3P provides reports the same as the AWOS 3 system, plus a precipitation identi.cation sensor.

(f)
 AWOS–3PT reports the same as the AWOS 3P System, plus thunderstorm/lightning reporting capability.

(g)
 AWOS–3T reports the same as AWOS 3 system and includes a thunderstorm/lightning reporting capability.

(h)
 AWOS–4 reports the same as the AWOS 3 system, plus precipitation occurrence, type and accumulation, freezing rain, thunderstorm, and runway surface sensors.

* * * * *
f. Service Standards. During 1995, a government/industry team worked to comprehensively reassess the requirements for surface observations at the nation’s airports. That work resulted in agreement on a set of service standards, and the FAA and NWS ASOS sites to which the standards would apply. The term “Ser-vice Standards” refers to the level of detail in weather observation. The service standards consist of four different levels of service (A, B, C, and D) as described below. Speci.c observational elements included in each service level are listed in Table 7-1-3.
1.
Service Level D de.nes the minimum acceptable level of service. It is a completely automated service in which the ASOS/AWSS observation will constitute the entire observation, i.e., no additional weather information is added by a human observer. This service is referred to as a stand alone D site.
　
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