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Control of Industrial Major Accident Hazards (CIMAH) Report Page 28
Ranhill SAJ Sdn. Bhd. Revision 01
Part D: Information on the Potential Major Accident Date Aug 2019

Daytime insolation Night-time conditions

Thin overcast
Surface wind Strong Moderate Slight or > 4/8 low <= 4/8 cloudiness
speed (m/s)
cloud
< 2 A A - B B E F

2 - 3 A - B B C E F
3 - 5 B B - C C D E

5 - 6 C C - D D D D
> 6 C D D D D

Source: Pasquill, 1961.

A: Extremely unstable conditions
B: Moderately unstable conditions
C: Slightly unstable conditions
D: Neutral conditions
E: Slightly stable conditions
F: Moderately stable conditions

D.4.4 Weather Profile

The meteorological data is obtained from the nearest meteorological monitoring
station in Malacca International Airport.

Atmospheric stability data is not available from the weather station and thus is
estimated using the Pasquill stability classes.

The following Table D.4.4 provides the percentage of the weather class and stability.
This data is applied for the dispersion calculation in consequence analysis.

Weather Category
(Wind Speed & Stability) Probability of Occurrence
< 2 m/s, F 48.6%

2-4 m/s, B 41.2%

4-6 m/s, D 8.6%

6-8 m/s, D 1.0%

8-10 m/s, D 0.3%

10-12 m/s, D 0.2%

12+ m/s, D 0.1%

Table D.4.4: Weather Class and Stability