No. IV-18.4 - (IMD), Pune

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The percentage frequencies of occurrence of vigorous, active and normal monsoor
in the five sub—divisions associated with the above-mentioned synoptic situations
are given in Table IV.
TABLE IV
Percentage frequency of Vigorous, Active and Normal Monsoon days associated
with various synoptic situations
(Based on data of October to December 1967—71)
(a)Goastal Andhra Pradesh
Oct. Nov. Dec.
V A N V A N V A N*
1. Storms and depressions 33 25 20 100 100 22 75 — 17
2a.
Low pressure areas (including low
pressure waves) 50 12 23 — — 41 - - 33
b.Upper air cyclonic circulation or trough - 13 5 - - -
3. East—west oriented trough across
— 50 —
Peninsula, seasonal trough over
Bay well—marked, trough of low
pressure off Kerala coast 17 50 5.2 — — 37 - - 39
4. Other features --- - - - - 25 50 11
(b) Tamil Nadu
Oct. Nov. Dec.
V A N V A N V A N*
1. Storms and depressions 83 15 7 45 8 15 57 10 14
2a.Low pressure areas (including 17 53 39 55 67 31 43 50 42
low pressure waves) trough
b. Upper air cyclonic circulation or 0 5 5 — 10 —
3. East—west oriented trough across
Peninsula, seasonal trough over
Bay well-marked, trough of low
pressure off Kerala coast 0 27 49 — 25 54 — 30 37
4.
* V - Vigorous Monsoon; A - Active Monsoon; N - Normal Monsoon