Monday, August 01, 2011



The probable weather scenario for the first fortnight of August.

Neutral ENSO conditions continue to prevail in the Pacific Ocean. Since mid-July most indicators of ENSO have remained close to normal. There are currently no precursors present for a La Niña or El Niño event to develop, and neutral conditions likely to persist through October 2011.


On a study of the MJO forecasts, it would be natural to decipher a lean, or supressed phase of the MJO for the sub-continent region. Studies show a weak MJO from (around) 5th August, lasting till around 20th August.

In a weak MJO period (lower above), expecting a system from our seas would be futile, and rare.

The current UAC over Gujarat, long having outlived its capacity, will show signs of waning from the 3rd/4th.

The current Bay UAC will have to decide its course of progress in the next few days. If it moves in by Tuesday/Wednesday, some heavy rainfall is possible for a day (as the UAC is not well established) in Vidarbh and adjoining South-east M.P.

But, as discussed many a times previously, in such a lean MJO phase, the monsoon axis could possibly move north of its normal position.

This could lead to good rains in the U.P. Gangatic plains, Bihar and in Nepal. Heavy rains in central Nepal and Bihar could be possible in the first half of August.

W.Ds are not really effected as such by a weak MJO, and if any W.D. inter-acts ( in the first half of August) with the north bound axis, heavy rains could be a possibility in Kashmir/H.P. Utterakhand and Northern Pakistan.

Rainfall in the central peninsula states (M.P./Gujarat/interior Mah/interior Karnataka) could get weaker, and the west coast rainfall would taper down considerably. South Interior peninsula not expected to revive meaningfully till mid-August.

Southern Pakistan rainfall can get scanty, as it would be bereft of any rain bearing systems, or trough precipitations.

Come Monday, 1st day of August, and the rains slowed down in Mumbai. Cloudy with a few showers, Monday saw 12 mms at Colaba and 5 mms at S'Cruz rain in the day, and the trend will continue into Tuesday/Wednesday. Rain amounting to around 15-20 mms/day.

Its just about possible, that there could be an nominal increase in rains on Thursday night. Say to around 30-35 mms.(Tentative).

Today, to give a forecast Friday onwards, i say a notable decrease in precipitation. Shall observe and review in a few days.

Pune, cloudy with no substantial increase in rains next few days till Thursday.

In Mumbai, July measured an average rainfall of 1285 mms between the 2 stations.Vagaries had estimated 800 mms.

Thanks for your views and analysis NT. Normal seasonal rainfall for Colaba has been reduced to 1920 mms From 2146 mms, and S'Cruz normal is 2422mms (2460 mms). July normal is 460 mms at Colaba and 553 mms for S'Cruz.

Looking at the above scenario, for Mumbai, I would expect rainfall to get a bit substantial in the 2nd fortnight of August. I could go wrong, but on the above 50-50 basis for the 2 halves of the month, I would estimate around 575-600 mms average between the 2 stations.


10 comments:

Anonymous said...

Sir pl answer my query it is eastern part of ni karnataka is getting heavy rains but nt westrn part y is t so, i askd abt dharwad in earlier cmt pl tel me wat amt of rain it receivd ths season and wat wil b d forecast

Saurabh said...

Amount of rain for any district can be seen at

http://www.imd.gov.in/section/hydro/dynamic/rfmaps/districtwise.htm

Click on Karnataka tab at the bottom to see rainfall for Karnataka districts

Saurabh said...

Sorry the URL is

http://www.imd.gov.in/section/hydro/dynamic/rfmaps/districtwise.htm

Saurabh said...

URL is getting cut

Anyways append districtwise.htm at the end of http://www.imd.gov.in/section/hydro/dynamic/rfmaps/

sset said...

Hi Rajesh,

What is the prediction for south interior peninsula?

Cauvery no rain - TN - Karnataka to heat up?

Regarding NE monsoon - will it happen or as usual shy away?

rajesh said...

anonymous:Seems N.I.Karnataka will have a lean patch now, as per my view. Till today, Dharwad town has received 327 mms this season, which is just a little above normal, by 19 mms. and the highest rainfall in the region. The lowest is at Gadag, 157 mms, just normal.
sset:Rains for interior Karnataka will be status quo till mid august at least. But why heat up ? Too early to say abt NE monsoon. Conditions on SWM withdrawing should be studied.

sset said...

thanks rajesh.

Your Mumbai estimate 575-600mm - is it for entire august or first half?

Anyway pattern of rain amount remains same as last year 2010.

But we badly require break from rain - need sunshine.

As per Pradeep stats - Konkan Goa comes in 11 of top 20 hits. Seems Karanataka/Kerala are loosing. We observe all lows from Bay move north none to south same with Arabian sea. Why is it so?

rajesh said...

sset: First half of Aug, may not precipitate so much rain if MJO weakens (possible). Estimate is for Aug.
generally the track of a bay system depends on the then position of the monsoon axis. Normally a trough or the axis acts as a corridor for a system.
Interior karnataka is not very slow this year..with only 3 districts actually in the -ve. Hassan @-36, ramanagara @-14 and Bangalore just -3.

emkay said...

IMD 2nd half forecast shows dim possibilities. Monsoon will be below normal.

rajesh said...

emkay: I feel August would be almost normal..throughout..Doubts abt Sept, as my assumption is that SWM will start its withdrawal from W.Rajasthan in first week of September.