No. IV-18.4 - (IMD), Pune

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54 i) During this period, the anticyclonic circulation over the central parts of the country was well—marked as an anticyclonic cell moved progressively eastwards from northwest Arabian Sea to west Madhya Pradesh in the lower troposphere. There was also a well—marked low pressure area in the southwest Bay of Bengal. Under the influence of these two systems, the wind flow over the Peninsula became more or less northerly in the middle troposphere. This feature was most pronounced on the 9th. ii) Minimum and dew point temperatures fell and were below normal over the Peninsula on the 10th. iii) During such occasions, early morning ground frost is a phenomenon in the highlands (like the Nilgiris), against which warnings are required to be issued. iv) This pattern again underwent changes as the low pressure area moved close to Tamil Nadu - Sri Lanka coasts and moist easterlies replaced the dry northerlies. v) Although the low pressure areas were present in the southwest Bay of Bengal and the Laccadives, there was no east—west trough across the south Peninsula, connecting the two systems. The absence of this trough appears to be the main reason for the pronounced dry weather over the south Peninsula. vi) Though the weather was dry and there was little or no clouding over the Peninsula, satellite pictures indicated considerable amount of cloudiness in the southwest and west central Bay of Bengal, which progressively travelled towards the south Peninsula along with the low pressure area and revived the monsoon there. ACKNOWLEDGMENT The authors wish to record their gratitude and thanks to Dr. P.K. Das, Deputy Director General of Observatories (Forecasting)', for going through the article and giving many helpful suggestions.
55 APPENDIX Specifications for the strength of Monsoon over land areas (Taken from DDGF's Forecasting Circular 1 of 1973) Descriptive term Weak monsoon <strong>No</strong>rmal monsoon Active/strong monsoon Vigorous monsoon Specifications Rainfall loss than half the normal. Rainfall half to less than times the normal, (mention of 'normal' monsoon may not be necessary in general) i) Rainfall to 4 times the normal ii) The rainfall in at least two stations should be 5 cm, if that sub—division is along west coast and 3 cm, if it is elsewhere. iii) Rainfall in that sub-division should be fairly widespread or widespread. i) Rainfall more than 4 times the normal. 1. While describing the activity of the monsoon, ii) The rainfall in at least two stations should be 8 cm if the sub—division is along the west coast and 5 cm if it is elsewhere. iii) Rainfall in that sub-division should be fairly widespread or widespread. i) The normals of stations, wherever available should be used, ii) Till normals for all the stations are available the following procedure should be adopted: Number of stations in a sub-division with normals <strong>No</strong>rmal for these stations Average normal for the sub—division Total number of stations reporting rainfall Actual total rainfall reported by these stations Therefore, the average rainfall for the sub-division a b b/a c d d/c Compare d/c with b/a and describe the activity of the monsoon accordingly, other conditions being fulfilled. 2. i) In the sub-divisions, where the percentage of hill stations is high, the hill stations must be also taken into account for describing the activity of the monsoon. In other sub-divisions, the hill stations will be excluded. ii) The monsoon activity will be described in all the sub-divisions of northeast India as is done for sub-divisions of other regions. iii) The monsoon activity need not be described over the Bay Islands and the Arabian Sea Islands.
Page 2 and 3:
FORECASTING MANUAL REPORTS Ho. 1-1
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Contents: 1. Introduction 2. Genera
Page 6 and 7:
2 1.3 In this report, we will deal
Page 8 and 9: 4 TABLE - I Mean Monthly, seasonal
Page 10 and 11: 6 iv)South Interior Mysore:— For
Page 12 and 13: 8 TABLE - II Division *Large excess
Page 14 and 15: 10 tions between 0300 and 0900 IST.
Page 16 and 17: temporarily shift north and come ov
Page 18 and 19: 14 Coastal Andhra Pradesh. 9.4 In a
Page 20 and 21: 16 The percentage frequencies of oc
Page 22 and 23: 11.2 Some details of the rainfall c
Page 24 and 25: ii) Depression and storms affect th
Page 26 and 27: 22 the incidence of storms in this
Page 28 and 29: 24 iv) Phenomenally heavy rains may
Page 30 and 31: 26 change chart or as a region of n
Page 32 and 33: 28 tilt usually towards a direction
Page 34 and 35: 30 rainfall is mostly along and to
Page 36 and 37: 32 south Peninsula. Rainfall was ge
Page 38 and 39: 34 even after the storm had moved i
Page 40 and 41: south Orissa coasts where speeds re
Page 42 and 43: 38 useful indications to prognostic
Page 44 and 45: 40 15.5 The main features in this s
Page 46 and 47: 42 Port Blair and also in the press
Page 48 and 49: 44 marked in the moisture field. Th
Page 50 and 51: 46 cloud configuration in the APT p
Page 52 and 53: 48 though it was still widespread (
Page 54 and 55: 50 area) than in the surface isobar
Page 56 and 57: 52 between the moist easterlies and
Page 60 and 61: 56 REFERENCES AND SELECTED BIBLIOGR
Page 62 and 63: 58 35. Raghavondra, V.K. and Rao, K
Page 64 and 65: 6"€. Venkiteshwaran, S.P. 1933: T
Page 66 and 67: FIG. 3.1 MEAN RAINFALL (Cm)
Page 68 and 69: FIG. 9.1 VERTICAL PROFILE OF MONTHL
Page 70 and 71: Fig. 10.2 Mean Tephigrams of Madras
Page 72 and 73: FIG. Il.l RAINFALL FOR 24 HRS. ENDI
Page 74 and 75: FIG. 12.1 TYPICAL DAY'S ISOHYETAL C
Page 77: FIG 13.2 UPPER WINDS 00 GMT 2 NOV.
Page 81: FIG. 13.6 UPPER WINDS 00 GMT 4 NOV.
Page 85: FIG. 14-2 UPPER WINDS 0 0 GMT 5 NOV
Page 88: FIG. 14.5 1200 GMT 6 NOV. 69 24 HR.
Page 92: FIG. 14.10 UPPER WINDS 00 GMT 8 NOV
Page 96: F1G.15. 4 UPPER WINDS 00 G M T 11 N
Page 99 and 100: FIG. 15.7 SYNOPTIC CHARTS 0300 GMT
Page 102: FIG. 16.2 UPPER WINDS OO GMT 7 OCT.
Page 107: FIG. 16.7 UPPER WINDS 00 GMT 10 OCT
Page 110 and 111:
FIG. 16.10 TIME CROSS SECTION CHART
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FIG. 17-2 UPPER WINDS 6 D E C . 7 1
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FIG. 17-6 UPPER WINDS OO GMT 8 DEC.
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FIG. 18-3 UPPER WINDS OOGMT 25 OCT.
Page 124 and 125:
FIG. 19.3 SYNOPTIC CHARTS 0300 GMT
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FIG.195 SPACE CROSS-SECTION 9 N0V.
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FIG. 19.7 SYNOPTIC CHARTS 0300 GMT
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FIG. 19.9 TEPHIGRAM OF BANGALORE &
Page 132:
No. IV-13 Rainfall of India - P. Ja
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No. IV-18.4 - (IMD), Pune

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