Friday, April 16, 2010

Monsoon Watch - 2

The Monsoon Rains performance this year is very very critical for India. Its economic growth hangs on the agriculture output this Kharif Season, and the water table needs a boost after the extermely poor Monsoon last year. (Mumbai has very limited water reseves now). IMD has optimistically stated that " 2 sucessive Monsoon failures are very rare."
Lets really hope so.

1. 4. El-Nino factor, is fast turning +ve,change from last week :
Nino 3 +0.8 +1.0 0.2°C warmer
Nino 3.4 +1.0 +0.8 0.2°C cooler
Nino 4 +1.0 +0.9 0.1°C cooler
Sea surface temperatures in the tropical Pacific have continued to cool over the past week, though still above El Niño thresholds. Temperatures in all the main ENSO monitoring areas are now less than 1°C above normal, a situation which last occurred in late September 2009.
The decline in the current El Niño event is consistent with which suggest Pacific Ocean temperatures will cool steadily over the coming months, and climate model predictions suggest returning to neutral levels by summer 2010.
The SOI also became positive on 8th April, first time after Sept last year. The latest Soi reading is a healthy +3. A +ve SOI means weakening of the EL-Nino. Lastyear we had a _ve SOI from June thru December.

2. The only +ve factor from the previous MW discussion, the quick formation of the Seasonal Low due to the intwnse heat wave in Central and Northern regions of the Sub-Continent, continues to be favourable. Into the 3rd. week of April now, the heat is relentless. Highs of 46.4c (Ganganagar) today (16th.April), and 46c in Akola and Hissar, has mercilessly baked the North/Central and Eastern region, and Vidharbh, in Central India was scorching at over 45c, at Chandrapur and Nagpur. Across the border, Nawabshah overtakes at 47c on Wednessday last week.
Augurs well for the formation of the Monsoon Low, and creation of the gradiant required to pull the monsoon winds into the scorched landmass. As on today, the lowest pressure, in the Thar Desert region is at 1002 mb. and this "low" tends to extend into the Indian heartland. As mentioned, it reaches a low nadir of 994 mb in June, and with 1008mb in the Soutrh Arabian Sea, a perfect gradiant is created to attract the south -west winds.

3. But, last week , the Monsoon winds, which originate from the Southern Indian ocean, cross the equator to become south -west , were still weak, and not developed . Now, we find, the South-east winds (below the equator they are SE), have organised themselves in the region south of the Andaman Sea. Currents are seen off the Sunmatra coast. And that is exactly where the start should be. Also, strong SE winds are seen along the Kenyan Coast.
The 3 high pressure zones in the South Indian Ocean, between Madagascar and Australia, have been observed, and the "Power House" of the Monsoon winds is on stream. Almost on time, as per schedule.

4. Another factor, which helps the winds gain strenght, and bring more moisture into the Indian landmass, is the sea temperatures on both sides of the Peninsuala. Optimum (warm) temperatures will hasten and create more clouds, and help in faster forming of the lows from the Bay. This parameter, is almost "normal" and favourable as on date. And I have put up the SST of last year on date to compare the and show the better position this year.
But the pre Monsoon Low in the Bay is still elusive. As discussed, we should see a low sometime after the 15th. of April. But as on today , a high pressure region prevails over the Bay.

5. The ITCZ, is in its "normal" position. Its movement northwards, to bring the existing SE winds above the equator should be observed around 1st. of May. At least not till cyclones are active in the Southern Hemisphere.

6. The 200hpa Jet Streams, required to be Easterlies during the Monsoon are not yet organised. Starting their Northward movement from 8N, they should be moving "up North" by the end of April, to facillitate the lower Monsoon winds.
Summary: 1.Getting +ve. 2. +ve. 3.Getting +ve. 4.Normal. 5.Normal.
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