No. IV-18.4 - (IMD), Pune

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2 1.3 In this report, we will deal with the weather over the south Peninsula during the "Northeast Monsoon" period (i.e.) October—December, illustrated with typical synoptic situations. 2. General Features 2.1 With the withdrawal of the southwest monsoon from northern and central India and the northern parts of Peninsula,between the second half of September and the first half of October, the pressure and upper wind circulation pattern:; over India rapidly change from the summer monsoon type and the winter monsoon type flow pattern makes its appearance. By October, a low pressure area establishes itself over the central and south Bay of Bengal, which shifts to south Bay in November and further southwards to the south of Lat. 5°N in December. The low is somewhat more marked over west central and southwest Bay, particularly' in October and November. In the Arabian Sea, though no low pressure area is seen during these months, an east-west oriented trough is noticed in nearly the corresponding latitudes as in the Bay. 2.2 The trough system from south Bay to south Arabian Sea with the embedded lows in it extends in the upper air also upto 700 mb; higher up in the middle and upper troposphere, easterlies prevail over south Peninsula which gradually veer to southerlies and then to southwesterlies as the season progresses and the sub-tropical ridge at these levels shifts southwards. The Tropical "Easterly Jet which is the main feature of the upper tropospheric circulation over the south Peninsula in the southwest monsoon season completely disintegrates with from the withdrawal of the southwest monsoon over the country. The wind field in the entire troposphere over the 6outh Peninsula is only light to moderate during this season. 2.3 The increase in rainfall activity along south Andhra—Tamil Nadu coasts which takes place sometime in first fornight of October has been generally understood as the "setting in of the northeast monsoon". However, there is, at
3 present, no well-defined criteria laid down for the withdrawal of the southwest monsoon from the south Peninsula and the ushering in of the northeast monsoon there. 3. Rainfall 3.1 The mean monthly rainfall, the mean number of rainy days etc. in the various meteorological sub-divisions in the south Peninsula during the period October--December, are given in Table I. ( See. also Fig. 3.1) 3.2 The Table shows that for the south Peninsula as a whole, October is the rainiest month. However, in Tamil Nadu, November is as much rainy as October. By December, the rainy season is practically over, when the rainfall becomes very small except in Tamil Nadu. The following are the details of rainfall distribution in the different sub—divisions:
Page 2 and 3: FORECASTING MANUAL REPORTS Ho. 1-1
Page 4 and 5: Contents: 1. Introduction 2. Genera
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 58 and 59:
54 i) During this period, the antic
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
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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
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FIG. 14.5 1200 GMT 6 NOV. 69 24 HR.
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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
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FIG. 16.2 UPPER WINDS OO GMT 7 OCT.
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FIG. 16.7 UPPER WINDS 00 GMT 10 OCT
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FIG. 16.10 TIME CROSS SECTION CHART
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FIG. 17-2 UPPER WINDS 6 D E C . 7 1
Page 117:
FIG. 17-6 UPPER WINDS OO GMT 8 DEC.
Page 121:
FIG. 18-3 UPPER WINDS OOGMT 25 OCT.
Page 124 and 125:
Page 126 and 127:
FIG.195 SPACE CROSS-SECTION 9 N0V.
Page 128 and 129:
Page 130 and 131:
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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