Maximum Cloud Tops

CHAPTER FOUR

METEOROLOGY FLIGHT PLANNING

Block 18: Minimum Ceiling

Information regarding the minimum ceiling can be derived quickly from the pictorial

presentation of the Weather Depiction Chart. Additionally, the Area Forecasts (FA) and any

AIRMET Sierras (WA) will also indicate conditions of IFR.

Block 19: Maximum Cloud Tops

The cloud tops indicated in Block 19 are given for clouds located around the aircraft's flight

level. For observed data, maximum tops can be determined from the Radar Summary Chart.

Pilot Reports are also a good source, when they are available. Forecasters may refer to satellite

imagery to determine which observed clouds would be moving into the flight area, thus

providing a forecast of tops. The Area Forecasts (FA) may also be used to provide forecast

information.

Block 20: Freezing Level

To determine the minimum freezing level en route, there are a number of products available to

meteorologists and aircrew. These include observed data from Winds-Aloft Prognostic Charts,

and RADAT information from METARs, plus forecast data from AIRMETs Zulu (WA), Winds-

Aloft Forecasts (FD), and Low Level Significant Weather Prognostic Charts. Recall that the

AIRMET Zulu will always include freezing level information, even when icing is not forecast.

Notice that Blocks 18 through 24 will include a location as part of the information presented in

each box, and that these locations are not required to coincide with each other, to give forecasters

maximum flexibility in describing the weather. For example, while the flight is planned for

NQA to TIK, the minimum ceiling will be found between LIT and TIK, while the maximum

cloud tops should be experienced throughout the route, and the freezing level of 10,500' MSL

extends beyond the route of flight, from Tennessee to Oklahoma.

Block 21: Thunderstorms

Thunderstorms will be one of the patterns most obvious when building an overview of the

weather. Of course, the Radar Summary Chart, as well as national NEXRAD composites and

satellite imagery, give a pictorial view of observed thunderstorm activity. Other sources, such as

the Surface Prognostic Chart, Low Level Significant Weather Prognostic Chart, WW, MWA, and

WST also provide thunderstorm information. A look at any one or more of these can give an

instant indication when thunderstorms are present along the route of flight. Determining the

extent of their severity and coverage, however, will likely be best described during the weather

brief.

Block 21 provides means for communicating all pertinent facets of thunderstorm activity, starting

with any thunderstorm warnings applicable to the route of flight (in addition to Block 11 in Part

I, which is for warnings applicable to the local airfield). Any warnings listed here should also

4-8 FLIGHT WEATHER BRIEFING FORM, DD FORM 175-1