Thursday, May 26, 2011


Monsoon Advances into Maldives Region and Sri Lankan Western and Southern Areas, and Central Andamans.

The Southern and Central Andamans are receiving sporadic rains for the last 3 days. Port Blair has measured 71 mms, 57 mms rainfall for the last 2 days, i.e. 25th/26th May. Port Blair got 114 mms in the 24 hrs ended 5.30 pm on Thursday.

As on 26th May, Vagaries advances the SWM as a weak current into the regions of Maldives, Sri Lanka and up to Central Andamans.

Heavy rains lashed Colombo on Thursday morning.

Vagaries is following and adopting the norms set by IMD for Monsoon Advance. All monsoon advances announced by Vagaries is as per the norms followed by IMD, but are strictly the veiws of the blogger, and for further commercial uses IMD may be referred to.

Giving below the IMD norms for SWM advance for readers' fast and ready reference.

MONSOON ONSET NORMS OVER KERALA:

The guidelines are followed for declaring the onset of monsoon over Kerala.

1. RAINFALL

CRITERIA:- If after 10th May, 60% of the available 14 stations enlisted, viz. Minicoy, Amini, Thiruvananthapuram, Punalur, Kollam, Allapuzha, Kottayam, Kochi, Thrissur, Kozhikode, Thalassery, Kannur, Kasargode and Mangalore report rainfall of 2.5 mm or more for two consecutive days, the onset over Kerala be declared on the 2nd day, provided the following criteria are also in concurrence.

2. WIND FIELD

CRITERIA:- Depth of westerlies should be maintained upto 600 hPa, in the box equator to Lat. 10ºN and Long. 55 ºE to 80ºE. The zonal wind speed over the area bounded by Lat. 5-10ºN, Long. 70-80ºE should be of the order of 15 ? 20 Kts. at 925 hPa. The source of data can be RSMC wind analysis/satellite derived winds.

3. OUTGOING LONGWAVE RADIATION (OLR)

CRITERIA:- INSAT derived OLR value should be below 200 wm-2 in the box confined by Lat. 5-10ºN and Long. 70- 75ºE.

Northern Limit of Monsoon (NLM)

Southwest monsoon normally sets in over Kerala around 1st June. It advances northwards, usually in surges, and covers the entire country around 15th July. The NLM is the northern most limit of monsoon upto which it has advanced on any given day.


4 comments:

Anonymous said...

What do you mean by westerlies? this word often troubles me please explain this word in as easy language as possible

Anonymous said...

Cyclone Keila also threatens Karachi and Pak coast...but forecasts are changing every day..FROM PWP

NT said...

The GFS model shows precipitation for Mumbai this Saturday night / Sunday morning. Forecast meteograms for Mumbai show a potential of around 8-10 mm rains. Also, the models for next week show a lot of rains creeping up to Mumbai in the coming week - it almost looks like Monsoon is coming up - which should not be the case as it is still 3 weeks away atleast from Mumbai. Is this due to the system forming in Arabian Sea?

rajesh said...

@anonymous. Westerlies means west winds.
@PWP: put up my views on vagaries just now.
@NT.monsoon in Mumbai is NOT 3 weeks away. I doubt any rains this weekend in Mumbai.And, pre monsoon rains should be around 2/3rd