1.

Precipitation:

(I)

Types:

(a) Rain:

Steady precipitation. Normally falls from layer clouds.

(b) Showers:

Relatively short-lived, usually 15-20 minutes but may last an hour. Often, but not always, separated by partly cloudy to clear skies. Unlike rain, showers usually begin and end suddenly.

(c) Thundery showers:

Showers from one or more convective clouds in which electrical discharge can be seen and heard as thunder by a person on the ground. Thunderstorms produce one or more of the following:
(1) Strong wind gusts at the ground
(2) Water spouts
(3) Heavy rain likely to cause flash floods or floods

(II)

Duration:

(a) Occasional:

Situations where showers/rain occur(s) in spells which are separated by half hour to a few hours. The situation usually persists for 6 hours or more.

(b) Frequent:

Similar to occasional showers but spells are of higher frequency. Seldom used because prolonged periods of bad weather tend to be more 'rain'-type than 'shower'-type.

(c) Intermittent:

Similar to occasional rain but of higher frequency.

(d) Continuous:

Rain without any break or with breaks each lasting less than 10 minutes.

(III)

Intensity:

(a) Slight or light rain/showers:

Individual drops easily identified, puddles form slowly, small streams may flow in gutters, no or slow accumulation.

(b) Moderate Rain/Showers:

Rapidly forming puddles, down pipes flowing freely, some spray visible over hard surfaces.

(c) Heavy Rain/ Showers:

Falls in sheets, misty spray over hard surfaces, may cause roaring noise on roof.

(IV)

Distribution:

(a) One or two areas* (e.g. northern & central)

Less than 25% of Singapore affected by rain or showers or thunderstorms.

(b) Three areas:

Between 25% and 50% of Singapore affected by rain or showers or thunderstorms.

(c) Most/many areas:

Between 50% and 75% of Singapore affected by rain or showers or thunderstorms.

(d) Widespread:

More than 75% of Singapore affected by rain or showers or thunderstorms.

2.

Time Description:

(a) Early hours:

MN to 4am

(b) Pre-dawn:

4am - 6am

(c) Dawn:

6am - 7am

(d) Early morning:

6am - 9am

(e) Mid-morning:

8am - 10am

(f) Morning:

6am - MD

(g) Late morning:

9am - MD

(h) Early afternoon:

MD - 3pm

(i) Mid-afternoon:

2pm - 4pm

(j) Late afternoon:

3pm - 6pm

(k) Afternoon:

MD - 6pm

(l) Early evening:

6pm - 8pm

(m) Evening:

6pm - 9pm

(n) Night:

6pm - MN

3.

Sky condition/coverage:

(a) Overcast:

100% of the sky covered, giving dull, grey conditions

(b) Cloudy:

More than 75% but less than 100% of the sky covered

(c) Partly cloudy:

25% to 75% of the sky covered

(d) Fair:

Less than 25% of the sky covered and no precipitation and no extreme weather

4.

Definitions and other weather terms used:

(a) Fair:

No rain/showers or precipitation expected.

((b) Fair except for ...:

Describes mostly fair weather. Showers/rain (specified explicitly) in a few areas may still be expected.