Center Weather Advisory (CWA)

METEOROLOGY FLIGHT PLANNING

CHAPTER THREE

While this is indeed the first SIGMET issued for this phenomenon in the DFW area, it is actually

the fourth issuance for the phenomenon since it met SIGMET criteria, and the previous three

issuances occurred in the SLC area.

While SIGMETs may be issued up to two hours before the onset of any condition forecast to meet

a criterion, note the time in line 1 (Figure 3-5) is the issuance time, not the onset time. The time

indicated in the VALID UNTIL 052100 statement is the SIGMET expiration time. The difference

between the two will not exceed four hours. If it is expected to persist beyond four hours, a

statement to this effect will be included in the remarks of the text. If the conditions do persist

beyond the forecast period, then the SIGMET will be updated and reissued. However, if

conditions end, a SIGMET cancellation will be transmitted.

Center Weather Advisory (CWA)

CWAs are unscheduled in-flight, flow control, air traffic, and aircrew advisory. By nature of its

short lead-time, the CWA is not a flight-planning product. It is generally a nowcast for conditions

beginning within the next two hours. CWAs will be issued:

As supplement to an existing SIGMET, Convective SIGMET, AIRMET, or FA.

2. When an In-flight Advisory has not been issued, but observed or expected weather

conditions meet SIGMET/AIRMET criteria based on current PIREPs and reinforced by other

sources of information about existing meteorological conditions.

3. When observed or developing weather conditions do not meet SIGMET, Convective

SIGMET, or AIRMET criteria; e.g., in terms of intensity or area of coverage, but current Pilot

Weather Reports or other weather information sources indicate existing or anticipated

meteorological phenomena will adversely affect the safe flow of air traffic within the Air Route

Control Center (ARTCC) area of responsibility.

The following example (Figure 3-6) is a CWA issued from the Kansas City, Missouri ARTCC. The

"3" after ZKC indicates this CWA has been issued for the third weather phenomenon to occur for the

day. The "301" in the second line denotes the phenomenon number again (3) and the issuance

number, "01," for this phenomenon. The CWA was issued at 2140Z and is valid until 2340Z.

ZKC3 CWA 032140

ZKC CWA 301 VALID UNTIL 032340

ISOLD SVR TSTM OVER KCOU MOVG SWWD 10KTS

Figure 3-6 CWA Example

AIRMET (WA)

AIRMETs also advise of significant weather phenomena other than convective activity but indicate

conditions at intensities lower than those that trigger SIGMETs. Both are intended for dissemination

to all pilots in the en route phase of flight to enhance safety, and are available for preflight planning,

as well.

SEVERE WEATHER WATCHES, MILITARY ADVISORIES, AND PIREPS

3-13