Wednesday, April 29, 2009

Unbelievable heat wave map of today's maximum temperatures of the sub-continent. Wednessday 29th. April.

Tuesday, April 28, 2009

Heat Wave in the Sub-Continent:

A severe heat wave is now baking almost the entire region of the north/west/central and eastern parts of the sub continent.

Todays (Tuesday) exceptional highs: Nawabshah 48c, Jacobabad 47c (Pak), Nagpur, Jaisalmer and Akola 46c, several 45c and many at 44c. Map from IMD shows the areas of India with the highest temperatures of Tuesday.

Meanwhile, it has become blazing hot eastward into India, with Kolkota maintaining its readings today at 41c, highest for April in 60 years..

The other map of the anomoly shows the heat wave creeping down south. High anomolies of upto +8c above normal are seen (light green), extending right into central Indian regions.

Meteorological analysis and numerical weather prediction models indicated further rise by 2 to 4c in maximum temperatures over parts of Northwest, Central and adjoining East India during the next 4 days.
This is due to a huge seasonal anticyclone (high-pressure area with warm air) pushing west from the Middle East regions.
Vidarbha and adjoining Marathwada, with north interior Andhra Pradesh may witness some record heating during this phase. Chhattisgarh, Jharkhand and West Bengal, which may record unusually high temperatures.

The high pressure in the upper atmosphere approaching over western India , will have an eastward shift of high pressure aloft. This upper ridge will settle over the Subcontinent through most of the week.
This upper ridge will result in the Westerlies moving well northwards, resulting in a severe heat wave.

As per the IMD, by May 2, heat wave conditions would have fully evolved over parts of Northwest, Central and East India.

For the next 4 days,highs above the 45c mark will be reached daily in Rajasthan, Vidharbha, and areas of central and northern India.

Highest readings of 50 degrees C may be seen in Sindh.

Saturday, April 25, 2009

Monsoon Watch-6

For the last one week, the monsoon build-up has shown no progress. In fact, it may have reversed to some extent.

The reason: A passing W.D. causes some drop in temperatures in the Indian Sub-Continent. The IMD deviation map of the day temperatures on 25th. for India shows a region in the U.P. and Punjab region in the "below normal" colours. Otherwise too, the entire country is now in the "normal to +1c region". Indicates the complete abating of the heat wave of the last 15 days. Another important factor which has halted the monsoon development progess are the night temperatures going downwards The map of the minimum temperatures shows a vast area in central/western India in the "below normal" colours.

But this effect will reverse soon, and by early next week, heat wave , or above normal conditions will prevail over north-west India, and will susequently spread eastwards.

The seasonal monsoon low over the Thar desert, with its centre at Bikaner, has not yet formed. Normally, by this date, end April, we see a low of 1006 mb forming. But the prevailing pressure today over the concerned region is 1010 mb.

The "hesitation" in the sub-continent region, has prevented the winds in the southern continent from gaining speed, and slowed their preparedness to cross the equator. The ITCZ still hovers in the 10S line.

But, as the streamline map shows, northerly winds are down the Arabian Sea, and re-curving into southerly winds after going around the tip of India. This indicates the presence of a trough in the southern peninsula.

As a result, some rain in Kerala, southern T.N. and southern Karnatak can be expected during the next 2 days, and coastal Kerala may get a burst of heavy rain in next couple of days.

But, I am just elaborating the actual situation and observations of last week. The monsoon progress and development, can still catch with the time schedule with the right conditions next week, and monsoon can still be on time.

The NCDC also determined that March snow cover extent was near the 1967-2009 average in North America, but below average over Europe and Asia. The snow cover over Europe and Asia in March, is one of the parameters to forecast and calculate the quantum of monsoon rains in India.

An interesting fact On the Global scene.

Despite what seems to have been a winter that wouldn’t end across many parts of North America, March 2009 has turned out to be the 10th warmest March worldwide since records began in 1880. .
Land areas of the southern hemisphere experienced their fourth warmest March on record while the dry surfaces north of the equator experienced the 12th warmest March on record. See graphic illustration.

Arctic sea ice coverage was at its sixth lowest March extent since satellite records began in 1979, according to the National Snow and Ice Data Center.
Antarctic sea ice extent in March was at its fourth-greatest level of the 31-year observational record. Antarctic sea ice extent reached 15.8 percent above its 1979-2000 average.
Since 1979, Antarctic sea ice extent for March has increased at an average rate of 4.7 percent per decade.

Sunday, April 19, 2009

Monsoon Watch -5

The first "low" of the season, which formed last week in the Bay, intensified into a cyclone "Bijli". But, the cyclone was short lived, and after interacting with the ridge aloft, fizzled out over the Bangla Desh region within a day.

No harm done for the monsoon build up !

The streamline map indicates not much disruptions due to the cyclone. A few marked developments observed :

1. The south-easterlies from below the equator, required to hit the Indian coast as the South-West monsoon current, have picked up in the eastern -most segments of the bay. Though still initial, it shows good recurving to the south-west direction over the southern coast of Myanmar.

2. The Intertropical Convergence Zone (ITCZ), also known as the Intertropical Front, Monsoon trough, is a belt of low pressure girdling Earth at the equator. It is formed by the vertical ascent of warm, moist air from the latitudes north and south of the equator.The location of the ITCZ varies throughout the year and while it remains near the equator, the ITCZ over land ventures farther north or south than the ITCZ over the oceans due to the variation in land temperatures. The location of the ITCZ can vary as much as 40° to 45° of latitude north, as in the Indian monsoon season, or south of the equator, as in winter, based on the pattern .

The ICTZ is normally required to cross the equator (from the southern hemisphere), by around the 1oth. of May. From that date onwards, it moves northwards gradually, and the monsoon trough gets embedded in it. By the 15th. of May, the bay segment of the ICTZ nears the Andaman Islands, thereby starting the monsoon.

The streamline map shows the ICTZ today. At the extreme west, near 40 E, it is almost at the equator. There onwards, it slopes southwards almost to the Australian coast.

3. A line of dis-contiunity has re-appeared in the southern Indian peninsula. With this emerging again, a fresh flow of easterlies will re-enrich the southern areas with the much needed "pre monsoon" moisture in the atmosphere.

Good indications and positive parameters for the monsoon.

The other good sign is the heat wave in Rajasthan/Gujarat and Maharashtra. Though the seasonal low over the sindh/rajasthan region has not yet started forming, it can be expected to form around the normal time this year, i.e. by the 3/4 week of April.

Todays day temperatures are projected in the map. A 45c at Akola, surrounded by a number of cities recording between 42-44c.

See the map. The west coast seems to be in the midst of "winter" comparitively !!

The El-Nino phenomena is forecasted to be "neutral" throughout the June/July /Aug. period
Hence, the monsoon can be expected to be normal. As the ''neutrality" increases after June, the first month of the monsoon may experiance heavy rainfall.

Conclusion: Monsoon may arrive on time. Around 15th. May in the Andamans, 1st. June over Kerala, 8th. June over Maharashtra.

Weather Over the Garhwal/Kumaon Hills for the next 10 days.
A short spell of rain is expected over the hills and plains of Utteranchal on the 21st/22nd. Thereafter it will be mainly dry with no major system approaching till the 1st. of May. The period from 23rd. to 30th. will see a rise in day temperatures.

In the first week of May, we may see some thundershowers on a couple of days.

Wednesday, April 15, 2009

Monsoon Watch-4

The low/depression in the bay concentrated fast and now has attained the strength of a cyclone. Named "Bijli", the cyclone is today (wednessday evening), CENTRED AT , NEAR LAT. 15.00 N AND LONG. 86.50 E, ABOUT 470 KM SOUTHEAST OF VISAKHAPATNAM, 750 KM NORTHWEST OF PORT BLAIR .

The map from JTWC shows the projected path. As mentioned, the recurving is due to the W.D. now over the hilly regions of north India. Also, as the system lies close to an upper ridge, it can recurve as stated.

The days in the major part of north/central and western India and adjoining regions continue to be hot, and record "heat wave" temperatures in the northern states. Map shows a vast region of over 40c, with 44c, the highest Akola.

In fact, the storm moving away from the east coast of India, may be "good" in some ways. The "heating of the land mass" can continue uninteruppted now, and the seasonal low may form faster. And, the quick formation of the system in the bay, which ever direction it may move, is a necassary "pre monsoon " requirement for the formation of a subsequent trough.

The strong westerly upper winds at 200hpa, too have started moving northwards, though very gradually. Mild Easterly winds at 200hpa are observed at 8N, the tip of the Indian Peninsula.

The monsoon can be estimated to be at the Kerala coast as per the scheduled date.

Bangalore, now sweating in oprresive heat, can expect some welcome relief showers on the weekend. Bangalorians can expect a fall in day temperatures to the 32c levels from Monday

Weather for the Garhwal/Kumaon Hills:

The current W.D. is causing some rains in the hills of H.P. and Utteranchal. Generally, the Kumaon/Garhwal hills get some rain in this month (April) as W.D.s approach the region. After the month of April, when the temperatures start rising, rains will also occur in the hills of Utteranchal due to local convection. This phenomena becomes a little difficult to forecast, and can be done perfectly only by being actually present in the region and observing the clouds formation and wind direction. But overall, a safe forecast can be made for the hills of Utteranchal region 8to10 days in advance.

As on today, rain is epected in the Kumaon region only upto the 16th. A comparitively dry spell is pected upto the 25th. at least. a thundershower can be expected on a couple of days in the first week of May.

Updated forecast will be posted on this blog.

Monday, April 13, 2009

The days have really started heating up in the northern/central regions of the sub continent. In the map, (day temperatures of the 13th.),the spread of the 40c and above is distinct throughout the northern plains with 44c at Akola.

The estimated low pressure has formed over the southern areas of the bay.

But with a fairly "good" W.D. approaching, it may push the low, maybe after it develops into a depression, eastwards. It may miss the east coast of India. The low "aloft", (W.D.) may deflect its movement towards the north Myanmar coast.

Just a note on these developments.

Sunday, April 12, 2009

Monsoon Watch-3

Cooling was limited and short-lived over northern/central India on Wednesday and Thursday. Already, as of Saturday and Sunday, it has heated markedly over Maharashtra, both inland and at coastal. At Mumbai, strong sunshine made the mercury touch nearly 40 degrees C. The high was 39.7, and 39 on Friday and Sunday.

Well, in the interior,Akola registered 43c on Sunday. Surat, heated to 42c .Normal heat in Surat would be about 37 c.

It is going to get hotter over the Subcontinent, as a whole, and it will stay that way through at least the middle of next week. Owing to the strong winds from the north/west over the region, as seen in the streamline, and a high pressure aloft at 500hpa, holding on over the Subcontinent through the coming week. This will create a heat wave and,. I estimatefor 42- 45c range heat away from the coast, that is inland over north-west, central and Maharashtra regions.

All this augments well for the pre monsoon developments, estimated to start by the end of next week. That is the starting of the seasonal low. At present the pressure in the required region, Rajashtan and adjoining regions is at 1006 mb.

The streamline map indicates that the southern hemisphere winds are taking a little longer to get organised for the "monsoon assault".

Again a reminder, One heat wave does not prove or disprove climate change.
"Often the public blurs the distinction between the two," says the Environment Canada spokeman."But they're very different and at times it's frustrating."
When meterologists use the term "climate," they're referring to long-term averages of weather patterns, measured not in years but decades.
What's less clear is the correlation between climate change and extreme weather patterns.

My attempt illustrates the difference is to show that, no, you cannot "term" a record-breaking cold snap last winter or heat wave this summer into a climate change-related discussion. Climate models are measured in larger scales than one day, or even one season.

A low pressure area has started building up around Sri Lanka. This will keep almost most of southern India away from the the worst of the heat, at least for the next two to three days. And there will be showers and thunderstorms in Karnataka, with isolated spots getting upto 5-7cms of rain in T.N.

Also, it would be the perfect pre monsoon condition, if as forecasted, the Bay of Bengal could give rise to depression or cyclone, within the next several days. I would be cautious in forecasting a cyclone as yet. But , vis-a-vis the weather, one can never say !

Monday, April 06, 2009

Monsoon Watch-2

Central regions of India, as seen in the map, continues to heat up, with above normal day temperatures continuing to hold sway. Highs of 42c are seen in the Nagpur/Akola areas, and the outer region of 38c to 40 c is getting enlerged to cover a larger area. Across the international border, days have started touching the 42c mark, and this could herald the formation of the seasonal low in the area (mentioned in the previous blog), by the middle of this month. Thus, a requisite pre monsoon requirment could well start on schedule. As on today, though, the pressure in the region is hovering around 1008 mb. with a cordened area of 1006mb.

Streamline map shows the line of wind dis-continuity gaining prominence. Again, a good indication of a formation of a trough, required for the larger monsoon trough to get embedded into.

The sst around the Indian peninsula is also above normal. Hence, the "pre requirments" for the set up of the month of April is on stream and on schedule.

Now, shifting down south into the southern hemisphere, a "high" is required in the South Indian Ocean, which will act as a "power house" of the Indian Monsoon. From this "high'', south-east trade winds will get generated, and cross the equator to become the south-west, and rush towards the west coast of India.

For the ''high" to form, the south Indian Ocean has to now cool down, after a long summer season. The sst map show the sea temperatures in the region as just about "below normal''. And, as a result, the formation of cyclones in the southern hemisphere has now ceased. If the trend continues, a preliminary "high" can form in the next 10 days.

Cooling of the seas down, in the next 15 days, also will give the required northward momentum to the ICTZ.

All parameters on schedule as of now, I see no reason for a delayed south-west monsoon.

Meanwhile, I would like to elaborate and mention the abnormal heat Banglore is facing. After a few days of 35c, which is also hot for the place, the city today(Monday) touched 37c! Thats 4c above the normal. The temperature map above shows the" 37c line" coming right down towards Banglore. Now, thats just a degree away from the all time April high of 38.3c, way back in 1931.The highest ever to be recorded in Banglore was the 38.9c , also in 1931, on May22nd.

Please do not mention "global warming" in Banglore. In 1931 too, it was 38.9c !

A diagram illustration of the last 30 days, of this year, in Banglore, shows how the city has heated up in the period . The "red" areas (hot! above normal), are popping up throughout, but is constant after the 26th. of March.

I do not see any big relief for the city till Friday, 10th. Temperatures may drop after that, and , as a trough develops in the southern peninsula, showers could be expected in Banglore only on Sunday/Monday.

Thursday, April 02, 2009

Monsoon Watch:-1
The hottest spots in Asia today were Surat and Akola at 43c, Nagpur and Baroda at 42c and Aurangabad at 40c ( several stations recorded 40c in India though).

Now, all this, and the heat wave in Mumbai yesterday, when the mercury touched an unbelieveable 41.6c at Santa Cruz, (+8c), is due to the W.D. This is passing in the form of a low "aloft". Creating strong, warm northerlies to flow southwards, this system , and the other one due by the 4th. , may maintain the above normal heat wave in central India for another couple of days. The image of todays maximum temperature shows the patch of land heating up abnormally in the central regions.

Now, this should be a plus point in the formation, or a quicker formation of one of the pre monsoon weather requirments, the seasonal low , required start taking shape for the monsoon by the second week of April. The seasonal low, over the Arabia thru India stretch ,normally starts forming in the Barmer and adjoining regions in the second week of April. As yet, the MSL is around 1010mb in the region. (The ultimate low, in June when ready, should be 994mb.)

The current heatwave can facilitate a quicker formation the low. In fact, a line of dis-continuity in southern Maharashtra now existing should make it happen early.

The other factor for the monsoon, the sea temperatures, are as yet favourable for this time of the year. The 2 images shown of 2008 and 2009, the current year show waters on both sides of the Indian peninsula above normally heated, as compared to last year, when the Arabian Sea was still to heat up.

Another pre monsoon seasonal normal requirment is the creation of a low in the Bay by the second week of April. This is necassary to trigger off the flow and formation of lows from the bay.

In fact, as a result of the sea temperatures anomolly mentioned above, a few international forecast models show the brewing up of a low from the bay in the 2nd. week of April.

All this is favourable as yet for a timely monsoon.