Subsequent to writing the MW-2, we are keeping a careful watch on the El-Nino developments. the Sub Surface Sea temperatures in the Nino 3.4 and other regions have been constantly warming up since end February. The next logical sequence is the warm waters rising to surface, heat up the Sea surface temperatures, and then effect the trade winds. But, against much over reaction on the El Nino, we see the warming taking its own time. Does not seem to be happening at a faster rate or in a hurried manner.
The last 2 weeks heating ( Nino 3.4) shows a very nominal warming up, of 0.3c. The meteorological point to be noted here: The anomaly in February was below normal, while now with a rise, the anomaly is near average. Nino 1+2 has actually declined by 0.7c !
The most recent ONI value is -0.7c...(El Nino is characterised by ONI values of 0.5 or above, La Nina is characterised by -0.5 or below).
So the ENSO conditions are still Neutral.
May happen that an eventual El Nino, though unavoidable, may actually form full fledged ( around August) after the main months of our South West Monsoon have been done with. South West Monsoon may get sluggish ( In Peninsula) after July, around August and September.
Indicator: -ve, as El Nino chances possible in Latter Months of Monsoon.
2. Sub-Continent Seasonal Low:
With every passing WD, (A-5 just moved away), the seasonal Low gets a set back. But, things are taking shape slowly.
Seasonal Low has shown signs of forming, core pressure at 1004/1006 mb...
The sesonal low in the Thar region is now weak.The pressure around the Thar desert region is now 1004mb (994mb required by June begining). Proper central core is forming now. And ,as per the required scheduled development, a proper gradient should be in the making.
Days temperatures have "performed miserably" in the MW-1/MW-2 inter period ! Below normal temperatures by as much as 13c had been recorded.
The highest on date in the Sindh areas is 45c. In India, it has reached 44c in AP.
Again, snow and rains in the Northern hills.
As a result, and expectedly, the day temperatures fell, and the seasonal low was almost wiped out.
An exception this year is the Vidharbha region. Even without the normally exceptionally heavy rains, the temperatures are just about managing 42/43c (till 27th April), and in some cities just hovering around the low 40s. Normally Vidarbha is a hotbed ! 45-47c is a "kid's playground" for the region.
In 2011, the minimum temperatures in the region were higher comparitively at this time. Minimum temperature touched 30c for the first time in 2011on 29th April at Kota (Rajasthan).
In 2010, 30c as minimum was recorded on 17th April.
And contrast this with the night temperatures today.
The max and min temperatures have to rise now in Sindh, Balochistan and North India. Trends of rising temperatures will be seen again in Vidharbh, Gujarat and adjoining regions of Sindh across the border.The entire plains of the Sub Continent and Interior Peninsula is set for a heat wave in the week beginning 28th April.
True, the entire sub-continent region has to suffer a heat wave, but the gains are much more.
The line of dis-continuity, currently "mis behaving" due to WDs and upper troughs, should shift back to its normal postion, in the centre of the Southern Peninsula region.
Out breaks of pre- monsoon thunder showers are expected normally in the southern states and South Maharashtra. Though the showers in the South are heavy. We need the thundershowers to commence and precipitate in Maharashtra and Interior Karnataka, indicating a proper flow of moisture into the peninsula region.
A LWD in the central peninsula region "looks after" the moisture content in the interior areas, and prepares the atmosphere with the humidity required fro a proper and good rainfall in the Lee ward regions.
3. Bay Low:
Continuing from MW-2, "Bay of Bengal" low pressure parameter is a worrying factor. Normally, the Bay should host a pre-Monsoon low anytime after 15th.April. Like I mentioned in the previous MW, in 2011 we had a cyclone in the Bay by the third week, and in 2009 a cyclone crossed the Bay on 12th April.2012 hosted a low around 25th April (BB-1).
As on today, this region still maintains a luke warm response to the formation of a quick low. The pressure is anything but low, and the winds indicate a weak "high" trying to stabilise itself.
What is needed now is a pulse from the Far East, to start with, and break up the existing high pressure area.
MJO has entered a weak phase in the Bay region. Fortunately, the MJO turns "Neutral" to slightly positive in the Maldives and Comorin areas after 30th April. This will bring a short spell of heavy rains in the region, giving a "false alarm" of the SW Monsoon, as, with the MJO, the rain patch will move East wards, and this will send favourable indications for the Bay. MJO can then get positive in Bay around 10th May...seems suitable for the Monsoon there !
The shading indicates outgoing longwave radiation (OLR; W/m²).
Only +ve sign of a quick formation is that the SST is conducive. Map shows around 31c near the Andaman Islands. Good temperature for quick low formation.
4. Cross Equatorial Winds :
The Southern high pressure region, the Power House of our Summer Monsoon, is strengthening down in the Southern Hemisphere, stretching off the Madagascar Island to the mid South Indian ocean.
The Mascrene Highs have, i would say gained to some extent... at 1033mb and 1022 mb.
The cross equatorial wind flow, has just about picked up in the Western sector Southern Hemisphere. Winds, have not yet achieved the required speeds, but just hitting the East African coast.
To get a defined Somali Current, we need a proper e-curving Northwards of the winds, on the Kenyan coast.
However, The region below the equator in the Bay sector is almost in the same situation as MW-2. In the Bay Branch, due to the prevailing High, West winds from the cross flow are tending to push Eastwards into the South of the Bay in the 95E-100E region. With no Low in the Southern Hemisphere region, the ICTZ has good scope for normal movement.
Remember, the normal date for SWM to hit the South Andaman Sea is 15th. May.
Amidst this, no cyclones are likely to form off Australia this season. If no further low pressure forms there till end of April, the ITCZ can start moving North. Currently it is at 7S. It needs to cross the Equator by 10 th May.As the ITCZ tracks north, associated MJO waves can "ride" alongwith. Meaning, after the shift, more MJO waves in the Northern Hemosphere (read Bay regions).
And with low pressure and ITCZ moving North, the High in the Southern Indian Ocean has a fair chance of getting stronger and anchoring well.
The 200 hpa Jet Streams:
The 200 Jet Streams too, show some awkward anomaly, in the last week. But seems to be getting rectified this week.
During the week, its core was located around Lat. 27°N with the wind speed varying between 84-103 kts around 200 hPa. The highest wind speed of 103 kts was recorded over Patna at 204 hPa. The Easterly core development is still weak.
Indicators: 1) ENSO -ve 2) Seasonal Low +ve 3) Bay Low -ve 4) Cross equatrial Winds Neutral. 5) UTH trough favourably forming around the Equator in the 80E -100E area.
Normally I would put up the estimated Dates of Monsoon arrival in this MW, but, seeing the changing scenario, would like to wait for a few days. Will put up an additional (brief) MW -4 on 1st May, with the Dates of expected arrival of Monsoon.
Then, next MW onwards, we go into analysing the quantum of rainfall expected, in the subsequent MW-5 (which as usual will be in 2 parts), and will be ready for publication on 2nd May.
These reports are my personal views, study and observations. Estimates and forecasts are also my own calculations and views, and may/may not tally with any other estimates. This may not be used for commercial purposes. The authour is not responsible for any commercial loss from this article, or this series of articles.