Sunday, August 08, 2010

Leh Cloudburst: How much it had rained ??

Source - Wall Street Journal, Hindu Business Line, Wikipedia

Sudden overnight rains caused flash floods in the town of Leh, the administrative center of the mountainous northern Ladakh region that borders China and Pakistan, killing more than 100 people and leaving hundreds injured, AP reported Friday. Many news reports described the downpour as a “cloudburst,” which the Indian Meteorological Department described Friday evening as a “disastrous weather event” in which “rate of rainfall may be of the order of 100mm [millimeters] per hour.”

Reports are that Leh received 48.6 mm rain in 60 seconds. In a special bulletin, the IMD said on Saturday that the high-impact event was so localised that that a nearby meteorological observatory of Indian Air Force (IAF) reported only 12.8 mm of rainfall during the 24 hours ending 5.30 a.m. on Friday. There is no official rainfall figure for the “fatal hours” available since it did not have an observatory in the region.

Comparing the Leh event with the year 2005 drencher over Mumbai, the latter was with two thunderstorms that poured 94 cm of rain in a radius of about 10 km around Mumbai together lasting about 18 hours on July 26 that year. In contrast, Colaba at the southern tip of Mumbai city had only 7 cm of rain during the same period. This is the nature of thunderstorms whose size and scale are small compared to low pressure vortices.

Based on the comparison the true rainfall figure in the affected area in Leh may never be known.
Many buildings crumbled after sudden rains and flash floods in Ladakh.

Rainfall is very, very scarce in the Ladakh region—it’s a dry, high-altitude region—so when it does happen it causes havoc because the houses and towns aren’t designed to deal with it. We were curious to find out exactly how much it had rained in millimeters, and whether this was typical for this time of year (it is monsoon season in India from June through September) and none of the day news stories carried the amount of rainfall.

A meteorologist at the Srinagar office of Indian Meteorological Department, G. R. Rathore, explained that the Srinagar office collected rainfall data for Leh from 1941 to 1981 (he put average annual rainfall for the period at just under 11 centimeters) and then stopped.

From 1981 on Mr. Rathore said that the IMD hasn’t had its own observatories in Ladakh and added that the Indian Air Force runs the three observatories there now. The armed forces have a strong presence in this region, which is part of India’s Kashmir state, because of its location bordering Pakistan and China. The IMD hopes to install one manned rain observatory in Leh by next summer and add several observatories across Ladakh as well, Mr. Rathore said.

According to him, the cloudburst lasted from 1:20 a.m. to 2:20 a.m. on Friday morning but he didn’t have data on how much rain had fallen in that hour because lines between Srinagar and Leh were down. He referred us to the weather section of the Indian Air Force in Srinagar for more information on the cloudburst. But at the Air Force, a senior official said that they weren’t supposed to disclose this information and referred us back to the civilian meteorological authorities. Getting this basic piece of data was starting to feel like a piece of classified information.The average for the whole month of august is 15.4 mm and the highest ever recorded in a 24-hour period is 51.3 mm, in August 1933.

Major Cloudburst Tragedies in India

  • August 31st, 1960 – 50mm of rain in 3hrs in Mandi and Suketi valley, Himachal Pradesh led to 103 deaths.
  • July, 1970 — Cloudburst in the upper catchment area led to a 15 metre rise in Alaknanda river. Entire river basin, from Hanumanchatti near Badrinath to Haridwar, affected; An entire village was swept away.
  • On August 15th 1997, 115 people were killed when a cloud burst came bustling and trail of death are all that is left behind in Chirgaon in Shimla district, Himachal Pradesh.
  • On August 17th, 1998 — A massive landslide following heavy rain and a cloudburst at Malpa village in Kali valley of Kumaon killed 250 people including 60 Kailash Mansarovar pilgrims. Among the dead was Odissi dancer Protima Bedi.
  • On July 16th 2003, About 40 persons were killed in flash floods caused by a cloudburst at Shilagarh in Gursa area of Kullu, Himachal Pradesh.
  • July 6th 2004, At least 17 people were killed and 28 injured when three vehicles were swept into Alaknanda river by heavy landslides triggered by a cloudburst that left nearly 5,000 pilgrims stranded near Badrinath shrine area in Uttaranchal's Chamoli district.
  • On August 16th 2007, 52 people were confirmed dead when a severe cloud burst occurred in in Bhavi village in Ghanvi, Himachal Pradesh.
  • On August 7th 2009, 38 people were killed in a landslide resulting from a cloudburst in Nachni area near Munshiyari in Pithoragatrh district of Uttarakhand.
  • On August 6th 2010, in Leh, a series of cloudbursts left 130 persons dead and over 600 injured in the frontier Leh town of Ladakh region in Jammu and Kashmir.

Record Cloudbursts

Duration Rainfall Location Date
1 minute 1.5 inches (38.10 mm) Barot, Himachal Pradesh, India 26 November, 1970
5 minutes 2.43 inches (61.72 mm) Port Bells, Panama 29 November, 1911
15 minutes 7.8 inches (198.12 mm) Plumb Point, Jamaica 12 May, 1916
20 minutes 8.1 inches (205.74 mm) Curtea-de-Arges, Romania 7 July, 1947
40 minutes 9.25 inches (234.95 mm) Guinea, Virginia, USA 24 August, 1906