Meteorological Aerodrome Reports (METARs) — Page 473, Lesson 445

I want to walk you through the next part of the METAR report — the Runway Visual Range, or RVR, and then the weather group. Let's start with the RVR. If the RVR is more than the maximum reportable value of 1500 metres, the code P is used in front of the visibility value. So you'd see something like R30/P1500. The P stands for "plus" — it tells you the RVR exceeds 1500 metres, which is the upper limit of what we can report precisely. On the other end, if the visibility is less than 50 metres, the prefix M is used instead — for example, R30/M0050. The M stands for "minus," meaning the RVR is below 50 metres, the lower limit of reportable values. Now, a letter can sometimes come after the RVR value to indicate any trends the RVR has shown over the last 10 minutes. A U means the visibility has increased by 100 metres or more in the last 10 minutes — for example, R30/1100U. A D shows that visibility has decreased by 100 metres or more in that same time period — R30/1100D. An N added to the visibility group shows that there is no distinct trend observed — R30/1100N. So U for up, D for down, N for no significant change. Let's move to the next section of the METAR — the weather group. This group gives information on the present weather at, or near, the aerodrome at the time of the observation. In our example METAR, we have +SHRA added. That means "heavy showers of rain." The plus sign indicates heavy intensity, SH is the descriptor for showers, and RA is the code for rain. I want to walk you through the table of significant present and forecast weather codes. These codes are organised into qualifiers and weather phenomena. The qualifiers include intensity or proximity, and descriptors. The weather phenomena themselves are broken into precipitation, obscuration, and other phenomena. Let's start with intensity or proximity. A minus sign means light intensity. If there's no qualifier, it means moderate intensity. A plus sign means heavy intensity — or in the case of FC and PO, "well developed." FC is funnel cloud, PO is dust or sand whirls. VC means "in the vicinity" — the weather is near but not at the aerodrome. Next are the descriptors. MI means shallow, BC means patches, BL means blowing, SH means shower or showers, TS means thunderstorms, FZ means freezing or supercooled, and PR means partial — covering part of the aerodrome. Now the precipitation codes. DZ is drizzle, RA is rain, SN is snow, IC is ice crystals — also called diamond dust — PL is ice pellets, GR is hail, GS is small hail — less than 5 millimetres in diameter and/or snow pellets — and UP is unknown precipitation. For obscuration, we have BR for mist, FG for fog, FU for smoke, VA for volcanic ash, DU for widespread dust, SA for sand, HZ for haze, and PY for spray. Then there are other phenomena. PO is dust or sand whirls — dust devils. SQ is squall. FC is funnel cloud or clouds — tornado or waterspout. SS is sandstorm or duststorm. So when you see a weather group like +SHRA in a METAR, you can decode it: the plus is heavy, SH is showers, RA is rain — heavy showers of rain. Every code in that table has a specific meaning, and you'll need to know them to read a METAR correctly.