Chapter 3a: Aviation Weather Sources  phenomena may be reported as being precipitation, obscurations, and other phenomena,  such as squalls or funnel clouds. Descriptions of weather phenomena as they begin or end  and hailstone size are also listed in the “Remarks” sections of the report.  [Figure 3-1] Remote Pilot – Small Unmanned Aircraft Systems Study Guide  17  10. Altimeter setting—reported as inches of mercury ("Hg) in a four-digit number group (A2970).  It is always preceded by the letter “A.” Rising or falling pressure may also be denoted in the  “Remarks” sections as “PRESRR” or “PRESFR,” respectively. 9. Temperature and dew point—the air temperature and dew point are always given in degrees  Celsius (C) or (18/17). Temperatures below 0 °C are preceded by the letter “M” to indicate  minus. 8. Sky condition—always reported in the sequence of amount, height, and type or indefinite  ceiling/height (vertical visibility) (BKN008 OVC012CB, VV003). The heights of the cloud bases  are reported with a three-digit number in hundreds of feet AGL. Clouds above 12,000 feet are  not detected or reported by an automated station. The types of clouds, specifically towering  cumulus (TCU) or cumulonimbus (CB) clouds, are reported with their height. Contractions are  used to describe the amount of cloud coverage and obscuring phenomena. The amount of  sky coverage is reported in eighths of the sky from horizon to horizon.  [Figure 3-2]  Figure 3-2.  Reportable contractions for sky condition. Figure 3-1.  Descriptors and weather phenomena used in a typical METAR.