The first cyclonic storm of the season, Extremely Severe Cyclonic Storm (ESCS “Fani” 26th April - 4th May, 2019) formed over the Bay of Bengal and crossed the Odisha coast close to Puri. Besides this ESCS, one short lived low pressure area formed on 30th May over southwest Arabian Sea off Somalia coast which dissipated on 31st May.
In India, Chronometric (C) and Fan (F) type radiosondes which were used in the fifties and sixties, were gradually replaced by Audio Modulated (AM) type sondes in the late sixties. The change of instruments apparently resulted in discontinuities in the time series of monthly means of contour heights and temperatures. This aspect has been examined in detail by studying the mean monthly values of contour heights and temperatures of six Indian radiosonde stations for five standard isobaric levels for four representative months of the year by using the data for 1he period 1951- 84. It has been shown by rigorous statistical tests that contour heights and temperatures fell substantially at stations that used C-type initially and that the fall was less substantial in those that used F-type first. The differences between the measurements by the various instruments have been shown to be independent of location and season. Thereupon the standard differences and their standard errors for contour heights and temperatures have been computed for all the five levels.
TIle'low frequency Iluctu atio ns in the troposphe ric wind field over India has been studied by spec tnuu~ na l l"i, tech nique. duri ng con trasting mon soons. namely, d rought and good monsoons ba sed on rainfall3cti\il)·. Si~ lliflc ant spectral peaks d urin g these years ha ve bee n iden tified.Zon al wind shea r in the lower tropospher ehan' also bern examin ed and the periodici ty in th e near 4()..day mode have bee n documented . Th e interannual, 'n.riill1i1ily of the mode and its potential as medium range predicti on tool has been examined in therrnpn perspect ive.
During 2019, in all 12 intense low pressure systems formed over the Indian Seas. These include; one Super cyclonic storm (KYARR), one extremely severe cyclonic storm (FANI), 4 very Severe Cyclonic Storms (VAYU, HIKAA, MAHA & BULBUL), 2 Cyclonic Storms (PABUK & PAWAN), 3 Deep Depressions and 1 Depression. Out of these 12 systems, 4 systems formed over the Bay of Bengal and 8 over the Arabian Sea. Arabian Sea remained exceptionally active in terms of cyclogenesis this year, especially in the post monsoon season. The season-wise distribution had been one cyclonic storm in winter, one in pre-monsoon season, 2 depressions and 2 very severe cyclonic storms during the monsoon season and 4 cyclonic storms and 3 depressions in Post monsoon season.
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