FORECASTING COURSE SPECI CODING

Presentation Objectives After this presentation session you will be able to: Understand the criteria used in the issue of special reports (SPECI) Apply the criteria in order to issue SPECI

SPECIs (special reports) are to be issued under the following weather conditions: - When a deterioration of one weather element is accompanied by an improvement in another element, a single selected special report shall be issued; it shall then be treated as a deterioration report. A SPECI representing a deterioration of one weather element and an improvement in another element should be disseminated immediately after the observation. A SPECI representing a deterioration in conditions should be disseminated immediately after the observation. A SPECI representing an improvement in conditions should be disseminated, if necessary, to indicate the conditions prevailing at the end of that 10-minute period.  

SURFACE WIND CRITERIA When the mean surface wind direction has changed by ≥ 60° from that given in the latest report, BUT the mean speed before and/or after the change must be ≥ 20 km/h (10kt). When the mean surface wind speed has changed by 20 km/h (10kt). Variation from the mean surface wind speed (gusts) has increased by ≥ 20 km/h (10kt) from that given in the latest report, BUT the mean speed before and/or after the change being ≥ 30 km/h (15kt)

Wind direction and/or speed Ave wind speed change of ≥ 10kts 1 36 = 360 270 = 27 180 = 18 09 = 090 01 =010 05 = 050 04 = 040 02 = 020 03 = 030 06 = 060 10 = 100 11 = 110 08 = 080 07 = 070 340 = 34 12 = 120 13 = 130 230 = 23 290 = 29 14 = 140 350 = 35 280 = 28 16 = 160 15 = 150 17 = 170 260 = 26 250 = 25 240 = 24 220 = 22 210 = 21 200 = 20 300 = 30 310 = 31 330 = 33 320 = 32 190 = 19 Variation between gusts and ave wind speed is ≥ 10kts The ave wind speed before and or after being ≥ 15 kts 2 Ave wind direction change of ≥ 60° The ave wind speed before and or after being ≥ 10 3

HORIZONTAL VISIBILITY CRITERIA When the visibility changes to or passes 800, 1 500 or 3 000m 5 000 m, in cases where significant numbers of flights are operated in accordance with the visual flight rules When the RUNWAY VISUAL RANGE changes to or passes 150, 350, 600 or 800m  

Horizontal visibility Horizontal visibility is deteriorating AND passes through the following… A deterioration Using RVR Runway Visual Range 150m 350m 600m 800m 800m 1500m 3000m 5000m Horizontal visibility Using eyes & visibility markers An improvement Horizontal visibility is improving AND changes to or passes through the following

CLOUD AMOUNT CRITERIA When the amount of cloud below 450 m (1 500 ft) changes from Less than FEW, FEW or SCT …… to …… BKN or OVC or BKN or OVC …… to ……SCT or FEW or less than FEW.

Cloud amount 7/8 6/8 5/8 8/8 BKN OVC SCT or less BKN or OVC or from 4/8 SCT or less BKN or OVC or from OVC or BKN SCT or less Cloud cover changes from … … … Cloud base ≤ 1500 ft

CLOUD BASE HEIGHT CRITERIA When the height of the lowest cloud layer of BKN or OVC extent, changes to or passes 30, 60, 150 or 300 m (100, 200, 500 or 1 000 ft) AND 450 m (1 500 ft), where significant numbers of flights are operated in accordance with the visual flight rules VERTICAL VISIBILITY CRITERIA Where the sky is obscured and the vertical visibility changes to or passes through 30, 60, 150 or 300m (100, 200, 500 or 1 000ft).

Cloud height along with Cloud cover of BKN or OVC 1500ft 1500ft Cloud height lifting or improving AND changes to or passing through Cloud height lowering or deteriorating AND passing through 1000ft 1000ft 500ft 500ft 200ft 200ft 100ft 100ft Earth’s surface

PRESENT WEATHER CRITERIA ... ... the following significant weather begins or changes or ends in intensity TS (with or without precipitation), freezing precipitation Freezing precipitation FZFG Mod or heavy precipitation (including showers thereof) DRDU, DRSA, DRSN BLDU, BLSA, BLSN DS, SS and including snowstorm SQ FC (tornado or waterspout) …………begins or ends or changes in intensity

Present weather – (the start or cessation of) marked by the advance of a “wall of dust” up to 3000m high including showers with or without precipitation Moderate Heavy precipitation FC TS course sand particles up to a max of 20–30m a sudden increase in wind speed of at least 16 kts with a new speed of at least 22 kts and lasting for at least 1 minute raised by the wind to more than 2m agl BLDU BLSA BLSN raised by the wind to less than 2m agl SQ DS SS FZRA FZFG DRDU DRSA DRSN Surface temperature must be < 0 °C for precipitation or fog to freeze on contact with the surface.

SURFACE TEMPERATURE CRITERIA When an increase in air temperature of ≥ 2°C from that given in its latest report occurs. TEMP An increase of ≥ 2°C at any given point in time