Hailstorm lashes parts of Rajasthan, Madhya Pradesh and Uttar Pradesh

FROM THE NEWS EDITION: http://www.downtoearth.org.in/news/hailstorm-lashes-parts-of-rajasthan-madhya-pradesh-and-uttar-pradesh-51643 (DATED 29TH OCTOBER 2015)

Temperatures dip in a number of places, experts say occurrence good for Rabi crops

•  
•  
•  
•  

Hailstorm in Jhansi area of Uttar Pradesh. According to weather experts, hailstorm at this time of the year is not a normal phenomenon Credit: Ritesh Garg

An upper air circulation brought on by western disturbance caused hailstorm in parts of eastern Rajasthan, Madhya Pradesh and Uttar Pradesh on Wednesday.

Lightning due to severe weather claimed six lives in Mathura, Aligarh, Allahabad and left over a dozen injured.

As per initial reports, hailstorm was reported from Bharatpur, Alwar, Jaipur and Sikar in Rajasthan. Available Doppler radar images taken on Wednesday afternoon indicated more incidents of hailstorm in isolated areas of east and north-east Jaipur.

Following hailstorm, temperatures dipped in Jaipur. The pink city recorded 21.7 mm rainfall on Wednesday and the minimum temperature touched 12.6°Celsius, 4°Celsius below normal, on Thursday morning.

The Bundelkhand region of Madhya Pradesh was severely affected. Areas like Ashoknagar, Shivpuri, Khurai, Malthon, Damoh, Chattarpur, Dabra, Gwalior, Anchal Kheda, Sevda and Datia witnessed severe hailstorm on Wednesday. Coin-sized hails fell for a long time in many areas of the state. Here also, temperatures registered a dip.

Jhansi, Mathura, Aligarh and Baghpat districts in Uttar Pradesh witnessed hailstorm mostly on Wednesday afternoon. Heavy rainfall was reported from Jhansi, Lucknow, Kanpur, Farrukhabad and Banda. Strong winds uprooted several trees and electric poles as a result of which telecommunication and power supply were disrupted.

Jhansi's maximum temperature on Wednesday touched 22.1°Ceslius, registering a departure of -10°Celsius from normal.

Was the hailstorm normal?

According to weather experts, hailstorm at this time of the year is not a normal phenomenon. If one looks at the climatological table (1971-2000) of these places, the mean number of days with hailstorm in October is zero.

What is even more striking is that as per climatology, Jhansi never gets hailstorm (the mean number of days with hailstorm is zero for all months).

However, observations clearly suggest that hailstorms are becoming more and more frequent. Since 2011, parts of Rajasthan such as Sikar and nearby areas have been experiencing hailstorm practically every year in the January-April period, but perhaps it is for the first time that it occurred in October.

Some amount of rainfall will be beneficial for Rabi crops at this time. According to Bharatiya Kisan Union general secretary Anil Malik, hailstorm at this time of the year will prove to be beneficial for Rabi crops. "It would have proved disastrous if the hailstorm had occurred during February and March," he said.

N Chattopadhyay, deputy director general of meteorology (agricultural meteorology), India Meteorological Department, said as the Rabi sowing period is going on, Wednesday's rains in parts of Uttar Pradesh and Madhya Pradesh will be beneficial for agriculture. Such rain helps in increasing soil moisture which is very important for proper growth of crops.

However, strong winds and hailstorm have reportedly damaged standing crops and vegetables in Madhya Pradesh and Uttar Pradesh. Some areas in these two states have witnessed back to back hailstorms since the past few years. Several areas of Madhya Pradesh were badly beaten by hailstorm during March-April this year.

Crop damage is a bad news for drought-hit farmers. This year, the south-west monsoon brought scanty rainfall in eastern Madhya Pradesh and Uttar Pradesh. The eastern part of Madhya Pradesh received 29 per cent below normal rainfall this time, eastern Uttar Pradesh received 47 per cent below normal whereas western Uttar Pradesh received 43 per cent below normal rainfall.

Fewer Doppler radars

Doppler radars play a vital role in detecting lightning and hailstorm. Based on these detections, people can be warned well in advance about such occurrences. Hence, for an efficient forecasting, there must be a high coverage of these radars. United States has an extensive grid of about 155 Doppler radars as against just 16 in India.

Out of these 16, three (in Hyderabad, Lucknow and Nagpur) are non-functional at present. Big states such as Madhya Pradesh and Uttar Pradesh have just two radars in Bhopal and Lucknow respectively. These installed (S band) Doppler radars work best only within a radius of 250 km.

As Lucknow's radar was non functioning on Wednesday, most areas in Uttar Pradesh (where both hailstorm and lightning were reported) were out of coverage area. Even Bhopal's radar could not properly track hailstorm beyond its 250-km range. In north-central Madhya Pradesh, large areas were out of coverage because of their distance from Bhopal's radar.

Last year during February-March when severe hailstorms hit many parts of India, more than half of the Doppler radars in India were not working. Some of them were broken like Nagpur's radar and others were undergoing maintenance. Thus, India has a long and unfortunate history of "out of order" radars.

India is not a weather-ready nation. As per records, lightning strikes killed over 2,500 people in India in 2014 as compared to 26 in the US during the same period.

Possibility of severe thunderstorms in parts of India

FROM THE BLOG EDITION : http://www.downtoearth.org.in/blog/possibility-of-severe-thunderstorms-in-parts-of-india-51602 (27TH OCTOBER 2015)

Existing weather system can even cause hailstorms in eastern Rajasthan, northern Madhya Pradesh and parts of Uttar Pradesh

This past weekend, an upper air trough (western disturbance) significantly impacted North India, especially Jammu and Kashmir. As anticipated, maximum temperatures dipped by 12-15°C in most places in the state on Sunday, October 25, due to rain and snow. Jammu-Srinagar highway was closed to traffic due to frequent landslides. Rain caused water logging in Srinagar on Sunday. Thundershowers were also reported in Punjab and Haryana. 

This upper air trough is set to move southwards till central India during this week and set the stage for thunderstorms and rain in parts of eastern Rajasthan, Madhya Pradesh, north-western Chhattisgarh, Uttar Pradesh, Vidarbha, Bihar and Jharkhand till Friday, October 30. 

What does this atmospheric pattern mean? 

 

•  
•  
•  
•  

GIF showing the approach of 'western disturbance' (represented by the reddish patch) from Pakistan into north-central India between October 27 and 30, 2015 (Courtesy: COLA/IGES)

 

A section in my previous blog explains what upper air troughs are. Usually, such troughs don't dip as low as central India in October. The "unseasonal" rain India saw in February and March this year was also because these troughs were very intense and had dipped more than usual. Such troughs move from west to east and ahead of their arrival, they destabilise the troposphere (part of atmosphere where weather systems exist), creating conditions for thunderstorms. Under ideal conditions, these thunderstorms intensify into severe thunderstorms and are capable of producing heavy rain in a short time, strong lightning, hail and strong winds. 

Associated with such upper air troughs, which are typically observed at around 30,000 feet, are cyclonic circulations or low pressure regions with anticlockwise spin of air in the northern hemisphere, in the lower levels of troposphere (around 20,000 feet). These circulations typically develop because of upper air troughs and they move along with the troughs. The image above shows one such circulation coming from Pakistan to north-central India by October 30. This circulation will reach northern Madhya Pradesh by Wednesday, October 28, and travel south-east near Uttar Pradesh by Thursday, October 29.

What is expected from this setup? 

 

•  
•  
•  
•  

Area circled in grey has the highest chance of witnessing severe thunderstorms on October 28 and 29

 

Such troughs are known to bring a lot of cold air to the region where they are present from regions which are to their north. Cold air is dense and reduces the height of the freezing level in that region. In the troposphere, the temperature of air decreases with an increase in height. Freezing level is that level in the troposphere which has a temperature of 0°C. Above that level, the temperature of air is negative and towards the Earth's surface, the temperature of air is positive.

If this level is further away from the Earth's surface, hailstones get enough time to melt after they have precipitated from thunder clouds. The positive temperatures between this freezing level and surface of the Earth are responsible for this melting. If this level is nearer the ground, hailstones reach the ground without evaporating much and what we get is hail. 

On Wednesday, October 28, severe thunderstorms capable of producing rain and lightning can be expected in eastern Rajasthan (areas east of Jaipur, Sawaimadhopur), parts of Madhya Pradesh (particularly around Jhansi-Gwalior) and parts of Uttar Pradesh (areas west of Kanpur-Allahabad) adjoining northern Madhya Pradesh and Rajasthan. The freezing level in these areas has reduced below normal and owing to high instability, some  thunderstorms in these regions can even produce hail. 

On Thursday, October 29, the region of thunderstorms and rain will shift slightly eastwards. Eastern Madhya Pradesh, north-western Chhattisgarh, eastern Uttar Pradesh (around Allahabad), and parts of Bihar and Jharkhand will get rain. Some areas may also get hail. People living in these areas must remain alert. 

Climatologically speaking (based on 1971-2000 data), these areas had not seen a single day of hail. Hence, if the anticipated hail arrives, it will be considered a bit unusual. 

Update on low pressure systems

•  
•  
•  
•  

Approximate positions of low pressure systems (denoted by 'L') in the Arabian Sea and the Bay of Bengal according to a satellite image as of the afternoon on October 27 (Courtesy: India Meteorological Department)

According to IMD's update on Tuesday afternoon, the Arabian Sea low pressure has become a "well-marked low pressure" system. Data from the Thai Meteorological Department suggests that this system has a mean sea level pressure of 1006mb while the system in the Bay of Bengal has mean sea level pressure of 1008mb. But, as per present weather models, the low pressure in the Bay of Bengal isn't expected to intensify much due to unfavourable conditions. It will lead to the onset of northeast monsoon in parts of South India on October 28 and won't cause any threat to India. 

However, due to marginally favourable conditions, the Arabian Sea low pressure can intensify slightly as it moves towards Gulf of Aden. Present weather models don't expect this low pressure to track towards India and hence, it isn't expected to threaten India.

Rainfall, snow expected in northern India over weekend

From the blog edition: http://www.downtoearth.org.in/blog/rainfall-snow-expected-in-northern-india-over-weekend-51565

A variety of weather events will be witnessed in India in the coming week 

•  
•  
•  
•  

The satellite image taken on October 23 shows the position of the western disturbance (circled in red) and the low pressure system (denoted by L) in the Bay of Bengal Credit: IMD

A powerful upper air trough (popularly called western disturbance by the India Meteorological Department) is all set to hit northern India by this weekend.

As a result of it, the hilly areas of Jammu and Kashmir, Himachal Pradesh and Uttarakhand will receive snowfall from Saturday (October 24) till Wednesday (October 28). 

The maximum amount of rainfall (to be witnessed in the low-altitude areas of these three states) and snowfall will be witnessed from Saturday to Monday. During this period, landslides will be witnessed on the Jammu-Srinagar highway, which will likely to remain shut for a few days.

Temperatures in much of the Kashmir Valley (including Srinagar) are already above the freezing point. Hence, the expected rainfall may create water logging and flooding. Travellers should remain cautious.

Along with rainfall and snowfall, thundershowers are also expected in Punjab, Chandigarh, parts of Haryana, Delhi and the National Capital Region from Sunday to Tuesday.

Arrival of winter

Winter has gradually started arriving in the hilly areas of north India. From Saturday onwards, maximum temperatures will decrease by an average 2-3° Celsius in Jammu and Kashmir, Himachal Pradesh, Punjab, Haryana and Chandigarh due to rainfall.

Rainfall will bring about a temporary rise in the minimum temperatures till October 26, but after that, minimum temperatures will significantly fall in these areas bringing colder nights.

Already several places in northern India are experiencing chilly conditions. Leh in Jammu and Kashmir recorded a minimum temperature of -1.9°Celsius on Friday morning.

Other places such as Gulmarg (J&K) recorded a minimum temperature of -1.4°Celsius (3° Celsius below normal), Srinagar recorded 5.5° Celsius, Pahalgam and Keylong (Himachal Pradesh) recorded 0.6° Celsius and Manali stood at 4.6° Celsius.

Not to be outdone, the plains in north India have also started witnessing mild winter conditions. Places in Punjab and Haryana are witnessing minimum temperatures in the range of 14-17°Celsius. Even Safdarjung in Delhi recorded a minimum temperature of 17.3°C on Friday morning.

Southern story

However, south tells a different story. If one travels a bit southwards, a contrast in the weather will be observed.

•  
•  
•  
•  

The image shows maximum temperatures in several places across India on October 19, 2015. Red patches indicate maximum temperatures above 35°Celsius. Credit: RMC Delhi/IMD

The maximum temperatures in the past 15 days have been consistently in the range of 35-40°Celsius in states such as Maharashtra, parts of Karnataka, Telangana and Andhra Pradesh.

In western India, a few places in the Kutch area of Gujarat recorded maximum temperatures above 40°Celsius.

Mumbai is also "boiling" as was expected (read http://www.downtoearth.org.in/blog/tropical-depression-forms-in-the-arabian-sea-51447).

On October 16, a 43-year-old record was broken in Mumbai. The day was the hottest in October in Santa Cruz area. On this day, the maximum temperature stood at 38.6°Celsius, which was 5.2°C above normal. Earlier, 37.9°Celsius was recorded on October 23, 1972.

Generally, Mumbai is not known for so much heat, but the maximum temperatures have remained above 35°Celsius for several days. Places in Vidarbha are witnessing maximum temperatures in the range of 35-40°Celsius.

Such high temperatures are affecting Maharashtra's agriculture. The state's water stock is at its lowest in the past five years due to poor monsoon this year. 

Weather conditions will continue to stay hot in western and central India, as no significant change in weather conditions is anticipated in the remaining days of October.

The temperature contrast between north and south India is a typical feature the country witnesses every year in October after the south-west monsoon withdraws.

This year, the south-west monsoon withdrew from entire India on October 19, as per the IMD. Dry, northerly winds in north India are keeping the skies clear. This, in turn, is causing radiative cooling (a process in which heat from the Earth's surface is radiated back to the space). Central and western India witness high temperatures in October due to the prevalence of dry winds. The lack of any rain-bearing system during this period is also responsible for this situation. But, this time the duration of such high temperatures is more than normal.

Strong low-pressure system possible in the Bay of Bengal

At present, there are two low-pressure systems in the north Indian Ocean. One is in the Arabian Sea, off the shore of Lakshadweep and another is in the Bay of Bengal, off the shore of Sri Lanka.

Weather models suggest intensification of this system in the Bay of Bengal early next week. If we believe in the present forecast, the system will reach near the Tamil Nadu coast by Wednesday. It may bring heavy rainfall in the coastal areas of Tamil Nadu and Andhra Pradesh. With this, the much awaited north-east monsoon is anticipated to commence in southern India.

The southern peninsula (particularly the eastern coastal areas of South India) gets a large percentage of its annual rains because of the North-East Monsoon. Tamil Nadu is known to receive about 48 per cent of its annual rainfall between October and December, which is known as the North-East Monsoon period. There are several criteria for declaring the onset of the North-East Monsoon. IMD usually declares this around October 20, mainly after an increase in rainfall activity in the coastal areas of Tamil Nadu and Andhra Pradesh.

Also, we cannot rule out the possibility of the low pressure intensifying into a tropical depression or even a tropical storm. Hence, it will be monitored closely and an update will be given, if at all, it poses any significant risk for the south-east coastal areas of India.