The Hindu Business Line : Monsoon onset delayed, cyclone watch reset

Thiruvananthapuram, May 29 The southwest monsoon has missed the nine-day median of May 29 for onset fixed by India Meteorological Department (IMD) even as the cyclone watch in the Arabian Sea came unstuck for a third successive time over the past week or so.

But the buzz from the waxing and waning monsoon current continues to engage forecasters elsewhere — the latest is the Global Forecast System (GFS), the numerical weather prediction model run by the US National Oceanographic and Atmospheric Administration.

The GFS sees scope for ‘cyclogenesis’ around the middle of the next week, with the system forecast to make a landfall over southeastern Arabia. The Roundy-Albany forecast model has persisted with its outlook for a land-falling cyclone around June 10. But these would bear some watching, judging from the ‘conversion’ record of model runs.

The Marine Meteorology Division of the US Naval Research Laboratory (NRL), Monterey, has put the mass of clouds now located over the west-central Arabian Sea for signs of intensification. NRL assigned the moniker, ‘98A Invest’ (‘A’ for Arabian Sea) to the system, which featured wind speeds of 15 knots (28 km/hr).

Pattern upset

The onset over Kerala has been delayed due to a combination of factors with one-to-one cause-effect relationships. For one, the dry northwesterlies have continued to foray into southern latitudes, upsetting the pattern of the upper-level easterly flows into the peninsula.

For another, the cloud formation to the west of Maldives, which was expected to drive the first few spells of rain into Kerala, has since drifted further away. This has in turn upset the flows off Somalia, although the cross-equatorial flows continue to be strong in the region.

POOR BUILD-UP

The relative humidity in Thiruvananthapuram hovered around the 50 per cent mark through Thursday, reflecting the poor build-up to the monsoon. It was demonstrably better along coastal Karnataka, especially Mangalore, which recorded between 70 to 80 per cent. This region experienced brief spells of showers on Thursday.

Model runs now suggest that the southwesterly flows across the Arabian Sea would start peaking from June 2, likely precipitating in the monsoon onset over Kerala. Upper level easterlies too are shown cruising along or even above the Chennai latitude around that time, thus setting up a strong east-west shear zone of monsoon turbulence.

IMD update

An IMD update on Thursday said that the offshore trough continued to exist along the Karnataka-Kerala coast. An east-west shear zone ran across the fringes of the south peninsula.

Related Stories:
Cyclone watch on as parent ‘low’ forms
‘Classic monsoon onset’ not seen until June

More Stories on : Climate & Weather | Climate & Weather

Article E-Mail :: Comment :: Syndication :: Printer Friendly Page