Wednesday, May 14, 2014

Monsoon Watch -4 ....14th May 2014

Synoptic Situation
(1) Season's first well marked low pressure area formed over Comorin area and neighbourhood on 6th  

(2) Northwestern India and North-Central Pakistan  received precipitation due to consistent passage of systems in westerlies. 

(3) Pre-monsoon convective activity increased over central and peninsular India due to presence of wind discontinuity. 

(4) Heat wave conditions prevailed in some parts of west Rajastan during initial part of the week. But, subsided later. 

(5) MJO gained amplitude over the Atlantic & African regions and propagated eastwards approaching Indian Ocean. This is seen to be manifested in the form of a low pressure area over southwest Bay of Bengal. Also, the lower tropospheric wind anomalies  indicate stronger than normal easterlies over south Peninsular region which caused moisture incursion leads to increase in rainfall activity over peninsular and northeast India. 

1. Seasonal Low: Indicator: -ve
The NW plains heating picked up initially, and laxes again, as WDs starting streaming in.
Heat should  to pick up in the Rajasthan/Sindh regions soon,  so good chance for the seasonal low to form and establish itself, at least by the 20th. Today the pressure at MSL is 1004 mb, with the core at 1002 mb.
The Sub Continent hot spots have just about touched the 45/46c mark (it is already Late. Refer MW-1) and should head for the 50c mark by around 20th May.

2. ITCZ: Indicator: +ve
As it is by the 10th, that we should have the ITCZ nearing the Equator. Only then would the Bay branch of the SWM could commence in the Southern Bay by the 15th of May. But, it has crossed Equator and is around the 5N latitude.

3. Jet Streams: Indicator:-ve
These are streaming away in a Westerly direction above the 25N line. But the trough looping down is not a very healthy trend.They are just about getting Easterly around 10N. Needs a rapid change now.

4. Cross Equatorial Winds: -ve in Arabian Branch...+ve in Bay Branch
Somewhat getting  established in the Bay region. SW winds, with sufficient speed hitting the S.Myanmar coasts, covering the Bay Islands with 20-30 knts, and could herald the arrival of the SWM in a week's time there.
Arabian Sea winds are dis organised, and in fact winds are heading South in the Central Sea. Sufficient speed in getting the "Somali Current" established is still lacking. The SST off the Somali Coast is 22/24c, While the required SST in First week June is 17/18c. (Required to form masses of Monsoon clouds in the warm central Arabian Sea).

5. ENSO: The sea surface temperature anomaly across the NINO3.4 region (located in the central Pacific) has recently risen to +0.5 °C, warming by 0.1 °C from last week. El- Nino is firming up slowly. 
Since March, Nino 3.4 has warmed up by 0.3c (See Diagram). 

The Southern Oscillation Index (SOI) currently remains neutral. The latest approximate 30-day SOI value to 4 May 2014 is +5.2.

As indicated in earlier MWs, it is gradual in developing. We would expect full El-Nino conditions by August.

Complete on vagaries