vagaries© of the weather.blog written by rajesh kapadia.concentrating on meteorology of the Indian sub continent and extreme world weather since 55 years For Any Information taken from here, due credit must be given to Vagaries.
Wednesday, May 30, 2007
After a line of W.D.'s, Delhi this May (only May, summer not yet over) had absolutely normal temperatures. None of the extreme heat, except for only a couple of days early in the season when the mercury touched 43c, and thus maintaining a normal average. The minimum temperature in Delhi has been below normal and "comfortably ok".None of the 32-33c in the nights as yet. In fact there were a few days with the low around 20c, 19.6c to be exact. The overall average temperature for May this year was just normal, 0.14c below normal to be precise !The diagram for May gives a clear picture of the average and the maximum and minimum temperatures, and the departures from normal (red and blue colours indicative of the variation).
For information, in contrast, the highest ever recorded at Delhi (Safdarjung) was 47.2c on 29th. May 1944. While the lowest ever recorded in May was17.5 on 12th.May 1964, not too far from this year's minimum.
No surprise that Delhi had 74mm of rain in May, surpassed only once before in 2002, when 132 mm of rain was recorded. And the number of rain days this year was 10 in May, against a normal of 2/3 days. This diagram gives a clear picture of precipitation this year.
Monsoon Watch - 20
Carrying on from MW-19, the" sudden push" mentioned has pushed the monsoon into Karnatak, on the next day ,29th. But, as estimated, the gathering of the clouds in the Arabian Sea is not gaining enough monentum to keep up the pace of the last two days. Heating up in the plains of the sub continent is taking place, but slower than expected, and the "tail" of the W.D. hangs around in the form of an upper air trough. A mass of rain bearing clouds has developed over the Sindh coast very near to Karachi.
Thus for the monsoon clouds to get organised in the western arena it may take yet another 3 days.The winds are not strong enough and cannot gain strenght due to lack of temperature gradiant (low pressure not enough inland). The only positive factor for this today is the trough off the west coast of India.
These observations are best that I can infer from my experience, and I am no expert. The actual behaviour of nature will always puzzle the best of meteorologists and computer models and prove the weatherman right or wrong.
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Tuesday, May 29, 2007
Very cold weather in U.K. on 28/29th. May caught my attention. I feel that any extreme weather or records regarding the weather in any part of the world , must be put up on my blog.
Rain and strong winds ravaged southern England,St Catherine’s Point on the Isle of Wight was one of the wettest places in the UK, receiving an incredible 80mm, (just over 3 inches) of rain during the weekend.Temperatures struggled across many parts and were unseasonably cold. Highs ranged between 7 and 10 Celsius (45 – 50F). Normally temperatures would be nearer 17 or 18 Celsius (63 – 64F) at this time of year.A maximum temperature of 7C was recorded at Heathrow Airport and 8c at London Weather Centre making it the second coldest May day on record, according to the met office.The minimum was 4c at Heathrow on 29th.
One of the country’s biggest carnivals in Luton, which was expected to attract around 100,000 people was cancelled.At 1500GMT temperatures were below 8C over an area from Surrey to the E Midlands and the Thames Valley, making it feel unusually cold here as the rain continued to fall.
Fresh snow fell on some of the higher peaks in the Highlands. Rainfall totals in 24 hours ending 1800GMT included Weybourne 54mm, Liscombe 56mm, Wattisham 60mm, Benson 62mm, High Wycombe 64mm and St Catherine's Point 81 mm. Max. temperatures were Killowen 14.7C, Kenley 6.6C ,and minimum Cairngorm -2c.
The IMD has announced the advance of the South West Monsoon over Kerala on 28th. May.
Bang on target, as expected, after the moving away of the W.D., the south west winds regrouped fast, and even formed a low pressure off shore trough off the west coast of india,(as seen here on this IMD streamline map).
http://www.imd.gov.in/section/nhac/dynamic/hp925sa.htm( click and paste this if unable to direct click).
The "push effect" was fast, as I was only expecting the winds to pick up from today, and take a day or two, but it has actually pushed the monsoon current into the south west coast, where ,in Kerala, heavy rainfall ranging from 40- 120 mms was reported today.
Due to this sudden thrust, I think the actual winds from the south west may take 2 days more to again gain the required momentum to again push the monsoon northwards. The satellite image today shows clouds off the southern tip and Kerala, but more gathering of clouds are needed in the central Arabian Sea for a further movement north of the monsoon. Due to the low pressure trough persisting off the west coast, further thickening of heavy clouds in the central and eastern Arabian Sea will take place in a few days , and further northward movement of the monsoon may take 2/3 days time.
The highest temperature in the sub continent today was 44 degrees at Nagpur and Nawabshah. But with the moving away of the W.D. from the northern areas of the sub continent, the Sindh areas of Pakistan, and Rajasthan in India will see a sudden rise in day temperatures, maybe to around 46-47 in a day or two. Interestingly, stations in Saudi Arabia
Dhahran Airport recorded 47 ,Al Ahsa Airport and Dammam Airport recorded 46° today. This augments well for the monsoon, as the seasonal low of the monsoon has to spread upto the Arabian Peninsula by the time the monsoon starts in the sub continent.
Karachi, which had shot up to 42 degress 2 days ago, can expect a return to 35/36 degrees. As the Arabian sea breeze has now rearranged itself, the north wind from the interiors, having caused the sudden rise have abated.
Mumbai, is getting more humid and stuffy. The temperatures are now at present ranging from 35 in the day to only 29 as the minimum, with high humidity levels. But with the situation showing signs of the monsoon progressing soon, initial pre monsoon showers could be expected in Mumbai around 31 May.
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Saturday, May 26, 2007
As indicated in "MW"-17, the W.D. is today moving across Northern India and Pakistan. Rain has been reported from many places today in North India, and the temperatures were below normal all over the North (India and Pakistan). Now, this is in sharp contrast to the heat that was prevailing in late April and upto mid May. Different forecasts have been seen on the future behavior of this W.D.
IMD expects this W.D. to move away in two days, while some models expect the W.D. to hang around the region for a week more, that is till 2/3 June.
So long as this is in place, the SW Monsoon can not proceed northwards. Personally, looking at the situation, "push effect" from the Southern Hemisphere cross winds is likely to move the W.D. away in two days, and get the monsoon current back on stream from 28th.May. The anti clock-wise wind movement is flattening (luckily),and the streamline shows some re-grouping. The south West winds should pick up from early next week, and bring in the cloud formation of the monsoon again in the Arabian Sea and a low pressure to form off the west coast of India around 1 June. Hence, I expect the monsoon to be in Kerala by the 1/2 June.
The sea temperature of the Arabian Sea is also at 31, which is ok to form convective clouds, when the cross winds bring in the moisture.
A small strip of sea temperature off the Somali coast should be low, at 18-20 degrees about 10 days before the monsoon clouds arrive on the West coast of India. The stronger the temperature gradiant between the strip and the vast area of the Arabian Sea, stronger the impact on the monsoonal winds, forcing them towards the east. Today, the strip off the Somali coast is at around 25 degrees, and cooling every day.
Also, if the prevailing W.D. moves away in a day, the northern regions and areas of Sindh and central India can expect a sudden revival of the heat. This will help in the quick formation of the seasonal monsoon low in a week or so.
But the rain I mentioned in the last blog, coming up the west coast of India this weekend is not to be mistaken for the monsoon. These rains are due to the upper westerly trough of the W.D. and will move eastwards. The interior areas of Karnataka and TamilNadu are bound to get rains this week end as a result of this westerly trough moving eastwards. But these rains will dry up, as the real monsoon current closes in from behind, and this monsoon current will travel north.
Friday, May 25, 2007
A look at todays streamline of the Arabian Sea, shows a totally messed up view (check the IMD site). An anti clock-wise wind formation seems to be churning the sea, indicating, maybe the formation of a high pressure ! The winds along the west coast of India is North-South,and the wind discontinuaty off the Oman coast has produced cloud formations in the southern parts of Oman. A sharp contrast from the superb cross equatorial flow we saw 10 days back. And as a result, the massive cloud formation in the Arabian sea has all but vanished today.
Now, all this has resulted because of the W.D.'s ruling the northern parts of the sub continent for the past week. The result is normal to below normal temperatures all along central and northern India and Pakistan, and the forecast of another W.D. coming (IMD) is going to result in more lower than normal temperatures for a few more days. (In the extreme north, Pahalgam,Kashmir had a low of 3 on the 23rd.).
[Just compare the temperatures in Pakistan a year ago, on 27th. May 2006
ISLAMABAD 23.5 41.7 QUETTA 19.5 35.5 SIBBI 33.1 50.1 JACOBABAD 31.2 51.0 ROHRI 28.3 49.0 NAWBSHAH 27.5 47.2 HYDERABAD 27.0 42.5. KARACHI 26.2 35.0
Temperatures, hot enough to produce a sub continent low of 994 mb. This year the same low is stuck at 998 mb.]
A spell of rain and thundershowers is projected to move up the west coast of India upto Gujarat, this week end, as mentioned by Jim, in his latest blog. But this should not be mistaken for the arrival of the monsoon.
I think (and hope), that the monsoon regrouping of winds and clouds should restart from 28th. May, after the W.D. moves away. We can still hope to see the monsoon arriving around the normal date.
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Wednesday, May 23, 2007
Beaches in South East Asia reopened on Monday after giant waves triggered by intense winds thousands of kilometres away crashed ashore last week, reviving memories of the 2004 Indian Ocean tsunami. The waves, which were 7 metres (23 feet) high in some areas , struck large parts of Indonesia, the Maldives, Thailand and Western Australia. There was no official warning about the freakish waves that killed at least one person, damaged hundreds of homes and displaced thousands of people. Weather officials said the waves were the result of an accumulation of winds in one spot on the ocean, but were looking at why they were so intense. The phenomenon was likely caused by Kelvin waves, giant waves caused by a surge of irregular wind patterns in the Indian Ocean. It could have easily been predicted because such waves commonly occur around this time. "However, we didn't expect the waves to be of this size, that's why we need to analyse the other factors first before arriving at a conclusion." The European Space Agency said the huge waves were generated by intense storm winds in the Southern Ocean.
The line of a couple of W.D.'s has trimmed the heat in the subcontinent persistently since the last 5/6 days. Today the highest was 44°,(only), again in Machillipatnam and in Nawabshah. In a most of the places the days were normal to below normal.
IMD and international models forecast another two W.D.'s coming from Pakistan into N.India between the 22nd. and 27th. May. Even though these will be in the form of lows in the" upper atmosphere", they will bring rain and thunder showers to N.Pakistan and N.India, as a result keeping the temperatures around the normal levels through this week.
In fact, today, the smooth flow of the south westerlies from the Arabian Sea was broken due to the W.D. movement. A line discontinuaty in the winds has formed off the Oman coast in the Arabian Sea. The progress of the weak low, already formed off the Africa coast, will be stagneted and can strenghten only when the low aloft forms a trough from Pakistan southwards.(That is after the passing away of the W.D.).
Hence the week commencing 28th.May should see the monsoon winds in the Arabian Sea getting organised and re curving again towards the west coast of India.
Meanwhile the Bay branch of the monsoon has moved north, and should hit the hills of the north eastern region of India in two days, by the 24th. Normally, the monsoon hits Kerala and the North east region on the same date on 1st. June. But this year,the Bay monsoon current is early, an the monsoon could have kept its normal arrangement in the Arabian Sea branch too, but for the "out of place" W.D.'s.
As is said, man proposes, but God disposes !
Sunday, May 20, 2007
The W.D. in the northern region has been restricted a bit to the North, but not enough, as it has pushed off the heat wave. As the temperature map from IMD shows, the heat wave is now restricted to a small area in the east, and much of the subcontinent is normal, or even below normal.
The temperatures are fairly "moderate'' and the highest in the subcontinent today was Machhillipatnam(east India) at 45° and then Nawabshah and Jacobabad at 44°.
Now this has weakened the south westerly flow from the Arabian Sea temporarily, due to poor temperature gradiant, and as this streamline from IMD shows, the south westerly flow has somewhat bifurcated into two parts, that is weakened, from the western Arabian Sea area.
The cooling of the sea waters off the Somali coast has also slowed down to some extent, and as a result, the pushing of the mass of monsoon clouds towards the Indian shores has halted, as of today, near the 60°E line as seen in this satellite image from NCEP.Image also shows the weak clouding of the W.D.in the North.
But I think this may have only delayed the monsoon date by a few days (from 24th. May). As the W.D. weakens, the South West winds should regain strenght, and bring back the monsoon cloud mass towards Kerala, maybe a few days later towards the end of May. The COLA site at http://wxmaps.org/pix/prec6.html indicates a burst of monsoon over Kerala between 28th. May and 3rd. June.
Due to the reversal of the sea breeze,the temperatures in Chennai have been high at 42°, since the last few days.
Saturday, May 19, 2007
The flow in the Arabian Sea is getting stronger, and the cloud formation in the sea has started forming near the warm edge of the central Arabian sea. This indicates, and the sea temperatures also show, the required cooling of the waters off the Somali coast.This cooling pushes the massive cloud formation in the Arabian Sea eastwards. All ok till here.
But a slight let-up in the heat over the India Subcontinent is seen since a few days . About 45 °,mostly in the east.The culpritis and will be one or more Western Disturbances due in the next 4/5 days. Now W.D.'s are known to shield the northern movement of the monsoon, if they are large enough. So, lets only hope this line of a couple of W.D.'s coming do not upset the as yet smooth approach of the monsoon. We will have to wait and observe !Not too sure still !
Wednesday, May 16, 2007
The temperatures over a larger part of the sub continent are almost at normal levels since the last couple of days, with a few hot spots today like Jacobabad at 49°, Nawabshah and Sibi at 46° andHissar at 45°. The sea level pressure is falling over central India and adjoining Pakistan, and is now at 995mb.
Strong winds are now blowing south to north off the Somali coast, portending quick cloudiness in the Arabian Sea. The ECMWF has forecasted the formation of a low in the central Arabian Sea on the 22nd. of May. It also projects the same low becoming stronger (maybe a deep depression) by the 24th. and crossing the North Maharashtra coast on the 25th. But this needs daily watching, for even though the wind and sea temperatures support such a formation, the actuality may be different.
Sunday, May 13, 2007
Continuing from the last "MW", it seems the estimate that the monsoon will cover the Bay in 10 days time holds good. The depression in the Bay, has now become deep, and may even become a cyclone. It is heading north, and as per the forecast by ECMWF, the system will intensify into a cyclone and cross West Bengal coast by May 17th. The monsoon will be pulled with this system to the Bengal coast and the North East region.
Meanwhile the heat wave in the north has abated, and thanks to some duststorms and thundershowers, the temperatures have come to near normal levels. But mild heat wave conditions prevail in the Vidharbh region.The highest in India and Pakistan today was 45° at Nagpur and Nawabshah.
Still, the U.S. based COLA, indicates a "burst" of rains starting over Kerala around the 21/22 of May. The ECMWF predicts a low in the Arabian Sea around the 23rd. of May, thus on similar lines, predicting rains in Kerala from around the 24th. of May. Thus, early Monsoon, by a week, is estimated by international projections.
Even the current streamlines show strong south west winds, pulled by the deep depressoin in the Bay, at the Sri Lanka coast.
Tuesday, May 08, 2007
As indicated in "MW-11', the cross equirorial flow has developed well, and recurves across the Somali coast perfectly.This belt of strong southwesterly wind is known as the `Somali Jet`; it is an essential part of the whole SW Monsoon circulation.This map from the IMD shows the strong gush of south westerlies developing near the Andamans and the Sri Lanka coast.
Also the heat wave has now established a heat low in central India,and pressures of 999 mb. has developed around M.P. Thus the heat low over North India and the low over central India form a vertical trough.
Now, both the above situations are normally established around the 20th. of May. After this the vertical trough tilts a bit and becomes a little horizontal, creating "on set" conditions, and then becomes fully horizontal, with the east end in the Bay after the monsoon has set in.
The monsoon over south Andamans now, should also move north in a day or two, and cover the Bay area in another 10 days time before reaching the Bengal coast and North East area.
But this year, as yet, things are moving fast and if this rate of development continues, and if nothing changes the situation, the monsoon can strike Sri Lanka by 18th. and Kerala by the last week of May.
Mumbai can get pre monsoon showers in the last week of May, and regular monsoon rains by 1st. June. Till then, hot, humid days and nights !
It was my observation in "MW -10", that the trail of the last depression in the bay was pulling the south west winds into the Andaman area.Since yesterday, the South Andaman area is experiancing south west winds and rain. The cross equitorial winds have now 'gracefully ' recurved along the line of the equator into the south west direction, thus indicating that the ITCZ is now along the equator.
Thus, according to me, it can be said that the south west monsoon has set in over the South Andaman Sea, upto the 10° line.(The normal date for this region is 15th.May).
As Jim, international weather expert, states in his blog of Monday, 7th. May, quote,"While in South East Asia, I believe it is safe to say that the South West Monsoon has set in over most of Indochina and southern Myanmar."
The sub continent heating continues,with Jacobabad at 47.5°, and Bhawalnagar at 47.3°, and some places in India at 45° today. Unusual today was Karachi at 40°.
Sunday, May 06, 2007
As anticipated, the bay did host a low,wich became well marked on the 4th. On the 5th. it moved rapidly north, and crossed the coast of Myanmar as a depression. Now,the entire bay is warm enough to welcomethe monsoon current of the bay branch. It is around 31° - 32° all along from the Bengal coast to the Andamans,thus behind the last low, south westerlies are prevailing over the Andamans,and more rain is predicted there, as as per my observations, the cross equitorial winds are crossing the equator below the bay and aiming at the Andamans, thus assuring the monsoon there within a few days.
This is as far as the Bay branch is concerned. As regards the Arabian Sea branch (which hits the mainland), the cross equitorial winds are now only turning towards the Arabian Sea, and are gaining strenght near the Somali coast. Another 15 days from now and the winds should be strong enough to bring the monsoon clouds to kerala any time after 25th. May. This is possible,as the heat gradiant required to pull the winds is building up and will get stronger as the heat wave is forcasted from Monday onwards.The renewed heat may see temperatures as high as 48-49° in Pakistan,and 47° in Rajasthan and Vidharb region of Maharastra.
The north south trough prevails from central India to peninsula,and has created relief thunderstorms. But this was a temporary respite to some areas,larger parts of North,central and peninsula India are to experiance a fresh heat wave.
Wednesday, May 02, 2007
The bay temperature has now been steadily constant at 31-32°, and is sufficiently ready to host a low. Hence with the formation of an "UAC", it is expected that this"UAC" will descend to form the first "low" of the season in a day or two.This formation will surely be triggered by the "shoot-outs" from the ITCZ, which is at present located near the Malaysian area. If the "low" gains and attracts the heavy cloud formation around it, and the southwesterlies currently prevailing over the Malaysia area migrate northwest, it could herald the setting of the South West Monsoon in the South Andaman Sea around the 8th. of May.
The ITCZ movement northwards is to be followed for the mainland, as when it is near the Southern tip of India and SriLanka, the monsoon gets triggered on.But to reach this lattitude, at the present rate of developments, should be in around 25 days from now.
Meanwhile the heat wave over India/Pakistan continues, with Bhawalnagar(Pakistan) topping 47° , and Hissar and Akola at 46° yesterday. Today it was Jacobabad and Bhawalnagar(Pakistan) at 46° and Ganganagar (India) at 45° among the highest.
The low, has literally "whizzed" past,and thru the central regions, and by saturday night, is already over south Rajasthan/Gujarat...