A comparison with previous
years shows the difference this year. In 2010, the first 45c was touched on
10th. April, and on the same day Nagpur was 44c, Delhi 42.8c. Soon on 15 th April
2010, Nawabshah (Pakistan) soared to
47c, Simla to 28.2c on 16th, Ganganagar,
Akola and Hissar to to 46c.
But, 2011 was similar to
this year. This year also, we are yet to reach 45c anywhere in the
Sub-Continent, as was in 2011. Into the 3rd. week of April now, and the heat
wave is missing.
As on 17th. April, the
lowest pressure, in the Thar Desert region is at 1002 mb. (though last year was
1006 mb, 2010 was at 1002 mb this time) and this "low" region is restricted to a small area. As mentioned,
it normally should reach a low nadir of 994 mb in June, and with 1008mb in the
South Arabian Sea, a perfect gradient is created to attract the south -west
winds towards the coast.
The quick formation of an
optimum Seasonal Low due to persistent A-2 (mentioned in the Vagaries' weekly
forecast), and absence of heat wave in Central and Northern regions of the
Sub-Continent, continues to be un-favourable.
2. The ENSO is neutral in
the Pacific Ocean, with a further warming of the SST in the past 2 weeks. On an
average, it is warmer by about 0.1c over the last 15 days.
The SOI is at its lowest
level since early 2010, but remains within values indicative of neutral ENSO
conditions. The latest (8 April) 30-day SOI value is −3.8, while end of March
was +2.8.
3. Last week, the Cross
Equatorial Winds,( Monsoon winds), which originate from the Southern Indian
Ocean as SE winds, and cross the equator to become south -west, were weak, and
not developed.
Let me explain, that the
winds before crossing the equator break into 2 branches. 1) gushing into the
Arabian Sea, and 2) moving into the Bay of Bengal.
Today, we find, the winds
south of the equator better organised for the Bay branch, in the region south
of the Andaman Sea. SW Currents are seen off the Sunmatra coast. And that is
exactly where the start should be for the SWM to arrive at the Andamans.
The Arabian Sea branch is
still struggling to get organised. Here, wind speed off the Kenyan coast has
maintained the SE flow. But should re-organise fast.
The Mascarene high pressure
zones in the South Indian Ocean, at 1030 mb, between Madagascar and Australia,
have been observed, and the "Power House" of the Monsoon winds is
slightly behind schedule, for this time of the season.
I have put up the SST of
this year and of last year as on date. Comparison shows it is slightly "un-favourable" around the equator, where the winds turn for the
Arabian Sea.
But the pre Monsoon Low in
the Bay is still elusive. As discussed, we should normally see a low sometime
after the 15th. of April. But as on today, a high pressure region prevails over
the Bay.
5. To bring the existing SE
winds above the equator, the ITCZ should move northwards. Around 1st. of May,
this should cross the equator. The ITCZ,
is in its "normal"
position, as of now, at 5S.
So, overall, we can summarise
as:
Parameter:1): -ve. 2):
Normal. 3) Normal 4) -ve. 5) Normal.
Most parameters are
"Normal" as of today. In today's situation, Monsoon arrival in Kerala
could be on normal dates in Kerala and the Bay Islands, and the NE states.
But, situations can change
fast, and by the time we discuss the next MW, some factors can suddenly become
+ve or -ve. So, MW discusses and follows the developments as they emerge, and
discuss the parameters as is where are.
No model can commit from
today when the Monsoon can arrive. Things get clearer by last week of April.
Vagaries' (in MW) normally remains true to estimates around early May.
No comments:
Post a Comment