Sunday, June 22, 2008

The last 7/8 days has seen the monsoon trough lying north of its normal position. It has been almost hugging the foothills of the himalayas, and on 2 occasions during last week, had mid level lows embedded in it. The western end of the trough has been fixed in the north Pakistan hills and running through Punjab,U.P. and down the states of Jharkhand and Bihar into the northern bay.
The result:During the week, excessive rains in the Jharkhand,Orissa and Bihar regions. Good rains in the northern states and Rajasthan and M.P. and north Pakistan regions. But, comparitively dry in the areas south of M.P. Deficiency has started to show in Marathwada,south Gujarat,north Karnataka and Kerala.
The wet spell in the excessive regions has lessened and the region is recovering from the flooding.
But the regions of Gujarat, Maharashtra, Karnataka,Kerala and A.P. are in dire need of the rains now. In fact, barring the coastal areas, the interiors of the west coast states have not yet had a decent rain shower. ( take for instanceAurangabad, has had only 18 mms).In Mumbai, though the total rain is 635mm, above normal almost double, it has had only" 8rainy days" out of the 22 days of June.
The situation as on Sunday night is that the monsoon trough is still in the "more than normal" north position. The embedded lows are weak, and thus the rains in the trough areas will also lessen in the next 2 days. But with this trough anchored there, it is not going to help the western and southern states.
What is needed now is a low in the bay to bring the trough to the central India regions, and bring back the precipitations southward. With a low in the bay, the monsoon trough comes back to its "natural" position.
IMD, and some other models have forecasted the formation of a low in the bay around the 25th./26th. Another low in the upper atmosphere is forecasted by some models in the north Arabian Sea, off the Gujarat coast. If this Arabian Sea low in the 500mb. level does form, it will be a boon for Gujarat and coastal/northern Maharashtra.
But events and dates are forecasts by some models, and some models make no mention of either low.
Eventually we will have to wait and see the reality.
I personally see the bay low forming around Thursday, and bringing rains to east A.P. first, then interoirs of A.P.,Maharashtra by Friday. Konkan and west coast may get increased rains from Thursday as a result of the low forming. Gujarat may have to wait to see the direction of the bay low, or the formation of the mid level low near its coast.
Coastal regions of Sindh,Pakistan can get its monsoon rains on the formation of the Arabian Sea nmid level low. Otherwise it will have to monitor the movement of a low in the bay.

1 comment:

shiraz satarawala said...

Dear Rajesh
Except for a sharp shower here this evening, the lull in the monsoon continues.
Regards, Shiraz
Mahabaleshwar, Maharashtra, India

Posted Wednesday evening : BB 8 tracks over M. P. Bringing good rainfall.  East MP 5-16 vms, West M. P up to 12 cms and a good 4-16 cms ...