Mega hail in India and Bangladesh

MJ Poore

MJ Poore

EF2
Joined
Sep 28, 2006
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Location
Johannesburg, S Africa
I was reading about a number of incidents in India and Bangladesh in which pineapple (!) sized hail fell from the sky. Needless to say the death toll in every case was quite severe from these massive hail stones. Entire villages being destoyed, hundreds dead. I also saw that program on National Geographic's Riddles of the Dead in which some 300 bodies were found entombed in a glacier in the Himalaya's, all of them had died from head wounds and fractures to their skulls. Scientists worked out that the bodies were once a party of pilgrims some 300 years ago who got caught out in a freak hail storm that dropped 1kg stones on them, and they had no where to hide.

I'd like to start a discussion about mega hail, can anyone tell me why India and Bangladesh get this lethal pineapple sized stuff. Is there anywhere else that gets this extreme hail? And can it be predicted?
 
there are others well more qualified then me, and im sure they can provide you with a better set of answers...

i dont think that kind of hail is exclusive to india or bengladesh or anywhere...if you have extremely high-instability values inside of freezing cold (-30c) temps, you can get large hail stones...

maybe the topography has something to do with it...the himalayans are over there...

i doubt it, but i guess i would leave it like that...the conditions were there for giant hail, and hailstones formed...whether its aurora, NE or dante, SD or bengladesh...

also, im sure you already know that the reasons for such death tolls is that the structures there are probably alot weaker...small farming villages with no warning...people could just be out in a rice patty seeing a bad storm coming in...only to get wailed on by lethal hailstones...a straw house would be no match for such a storm...
 
I think that first factor would be that most of such news are exaggerating. NO official measurements of hailstones were taken there, so I seriously doubt that 1kg chunks of hail would be that common there.
But to speak of Banladesh, I have seen a Skew-t from there which showed more than 7000 j/kg of CAPE and good wind shear. Himalayas actually divert the mid-level wind flow to the north and south, so that India and Bangladesh are in much better wind profile regions than is common in tropics. Such instability released in nicely organized storm could probably result in the record-breaking hailstones.
 
The world record for largest hailstone was reported in Bangladesh:

Hailstones weighing 2.2 lb (880 g) fell on the Gopalganj district of Bangladesh killing 92. Here is a weather chart in English units for around the time of the event I suppose:

http://bangladeshtornadoes.org/surface/04148609zsf1.gif

As you can see, it was rather juicy, particularly north of the boundary (93/82). Such values are not unheard of in the Midwest during the late summer, but you won't see those kind of values ahead of a dryline very often. I can imagine the CAPE was probably rather large, as mentioned above there are similarities between the geography there and that in the central US that favors development of volatile instability from time to time.
 
Generally here when the temperature gets above 95 degrees we see reductions in the dew point thus impacting (below) cloud base RH values. Kansas is just too far from the moisture to maintain that high of a moisture value. This heated mixing in turn raises the cloud base height and increases the outflow RFD etc. If for example we could get the best possible dryline coming out of TCC against the highest moist inflow from HOU then we might come close. Other than that fantasy scenario the only other area known for super high Td's in eastern Iowa into SE SD from extreme evaporation in the late summer months. Still, those Td approcing 80F do not have 100F temperatures. Their drylines are off the super high elevations vs the moist axis from the nearby Indian Ocean. These factors make for thermodynamic conditions we cannot equal here in the US, at least from some of the big day soundings I've seen. I would imagine that region of the world is capable of not only the largest hail, but probably the biggest tornadoes. That said, tornado EF ratings will likely be low due to poor construction of structures outside the major urban areas.
 
Gene Moore said:
I would imagine that region (E India/Bangladesh) of the world is capable of not only the largest hail, but probably the biggest tornadoes. That said, tornado EF ratings will likely be low due to poor construction of structures outside the major urban areas.
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I'm not convinced that they get that many large and/or violent tornadoes. At lease not as many as the US or southern Brazil/Argentina. Eastern India/Bangladesh has some of the highest population density in the world with a population that is very poor living in shacks for the most part. Weak tornadoes can cause more fatalities than we normally get from violent tornadoes in the US. If large violent tornadoes are common there then I would expect to see death totals in the thousands on a regular basis. Of course they do get some violent tornadoes and we have see 1000s of people killed but it isn't that common.
 
scott r currens said:
I'm not convinced that they get that many large and/or violent tornadoes. At lease not as many as the US or southern Brazil/Argentina. Eastern India/Bangladesh has some of the highest population density in the world with a population that is very poor living in shacks for the most part. Weak tornadoes can cause more fatalities than we normally get from violent tornadoes in the US. If large violent tornadoes are common there then I would expect to see death totals in the thousands on a regular basis. Of course they do get some violent tornadoes and we have see 1000s of people killed but it isn't that common.
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Actually I have seen very high death tolls in India/Bangladesh, although there is often flooding associated with the coastal systems.
USA Today source: "Every year, storms batter Bangladesh, a country of 150 million, often killing large numbers of people. The most deadly recent storm was a tornado that leveled 80 villages in northern Bangladesh in 1996, killing 621 people."
 Tornado project online: April 26, 1989 - What may have been the world's deadliest tornado took place on this day. As many as 1300 people were initially reported killed and 12,000 injured as a tornado cut a long track, up to a mile wide, about 50 miles northwest and north of Dhaka, striking 5 districts. The towns of Saturia and Manikgank sadar were leveled and about 80,000 people were made homeless. There were at least 600 deaths in the tornado, along with 992 dead on April 14, 1969, 500 dead on April 1, 1977, and 800 dead on May 26, 1989.

I didn't have to dig very long to find big death toll events. Consider the worst ever tornado in the US was the Tri-State with 625 dead. Other than that most death tolls are in the couple hundred range and that was generally confined to years before warnings. As for the population issue, I agree to a point, but much of that population is concentrated in the north and along the coast. There is a large area of desolated jungle where the population density is lower. Here is a link to the demographics and density.

http://en.wikipedia.org/wiki/Image:India_population_density_map_en.svg

As for the total number of tornadoes, I agree, probably not as many as the US, but they don't have the ability to report the smaller events in the rural areas. Seems most of their tornadoes are in a narrow swath. Here in the US, depending on the time of the year anywhere east of the Rockies is tornado prone with many of the worst events east of the Mississippi. Regardless, just looking at the explosive soundings that region of the world is capable for being a hotbed for big tornadoes.
 
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Gene Moore said:
As for the population issue, I agree to a point, but much of that population is concentrated in the north and along the coast. There is a large area of desolated jungle where the population density is lower. Here is a link to the demographics and density.

http://en.wikipedia.org/wiki/Image:India_population_density_map_en.svg
Click to expand...

Gene,
I think we agree for the most part on the occurrence and frequency of tornadoes in Bangladesh. Although I disagree with regards to the population density. If we only look at the rural most 1/3 of Bangladesh they still have a population density in the 100 to 250/km². By comparison Kansas and Oklahoma have population densities of 13 and 30/km². The rural most 1/3 of Kansas and Oklahoma have a population density of 1 to 6/km². I just think that the number of injuries and deaths from tornadoes in Bangladesh can be misleading. I can't even imagine the suffering that goes on in that part of the world.
 
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scott r currens said:
Gene,
I just think that the number of injuries and deaths from tornadoes in Bangladesh can be misleading. I can't even imagine the suffering that goes on in that part of the world.
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One of the high death events I found in my search was rated with winds at 125MPH....so that justifies your thesis on this...at least with that data point. And I agree there are likely more. Still, it only makes the case that weaker tornadoes can and do cause fatalities.

For now I'm going to stubbornly stick with my assertion that the area does produce violent tornadoes using the sounding data as justification. There is just too much research supporting big CAPE + big shear = big tube. Perhaps these situations don't set up that much, but we seldom get soundings that outrageous here in the the US.
 
In answer to the question, it is likely that it is the release of potential instability that causes such massive hail across parts of Bangladesh. It is normally a Springtime phenomena, these storms breaking out a couple of months ahead of the Monsoon. The site http://bangladeshtornadoes.org/surface/04148609zsf1.gif gives several clues.

1, The trough moving northwards across Bangladesh

2, High humidity in the lower layers of the troposphere. This is a combination of dampness moving northwards off the Bay of Bengal and the high elevation of the sun evaporating water off the Ganges, Brahmaputra delta. 93/82 (34/28) is certainly juicy, but humidities get higher than that. Dewpoints in excess of 90 (32) are sometimes recorded in May.

3, The dry-line bisecting the trough. This will be the area where the greatest release of potential instability will occur, where dry air over-runs moist.

4, Generally sunny skies at this time of year, pre monsoon allow for maximum solar input on any given day.

5, If the flow at 600mb is west or northwesterly, very dry air from the elevated Himalayas or the Tibetan Plateau will be drawn over the moist air lower down. This dry air will generally have a profile close to DALR over many thousands of feet, thus the teph profile will exhibit huge CAPE. The highest CAPE I have seen on a teph came from Bangladesh at 9200 J/kg-1. The ascent will show a profile close to SALR in the lowest layers with DALR above.

6, The jet stream across the southern Himalayas is frequently strong in April as the Indian subcontinent is warming up, whilst much of Asia north of the Himalayas is still cold. This will allow efficient exhausting of air out of the tops of developing Cb via the anvil.

All the parameters listed above occurring at the same time will bring the potential for some significantly giant hail. Using Fawbush and Miller technique for determining wind gust strength would suggest that given an ascent with CAPE values greater than 6000J/kg, then severe straight line winds will also accompany these storms with gusts well over 100mph (160kmph).

N.
 
Your explanation of mega hail here and its uniqueness sounds very good Nigel. Massive dewpoints combined with the intense mid level dry punch from the Himalaya's would be the secret sauce that makes it all happen? Could it theoretically happen anywhere else, like the US midwest?

On the subject of tornadoes in Bangladesh, it seems the LP's and associated surface winds I've seen plotted in East India and Bangladesh are not as extreme as they are in the US midwest, which would suggest the tornadoes could not be as strong there?
 
This can happen anywhere in the world during hot weather, where an elevated, dry, hot layer of air over-rides a layer of very warm, but very moist air. It is this set-up that produces the 'cap', this preventing the release of the moist lower level air into the dry air above, until, either insolation provides enough energy for the moist air to round the cap, or for precipitation from falling upper cloud such as castellanus eroding the cap by cooling and moistening the hot, dry layer.

The midwest of the USA is the best known for this phenomena, hot dry air riding off the Mexican Plateau and southern Rockies over-riding warm moist air extruding northwards from the Gulf of Mexico.

Much of Europe also experiences this phenomena, where hot dry air blows off the Spanish Plateau over-riding warm, moist air blowing in off the Med. However, in general the European phenomena is weaker than that of the US, although one storm I witnessed the aftermath of in the UK produced 7cm hail on the 26th May 1985 to the southeast of Great Dunmow, northeast of London. Stones in excess of 10cm have been reported from parts of France and Germany.

Other areas include the Argentine and southern Brazillian Pampas where dry air flows off the Rockies over-riding moist air extruding southwards from the Amazon, and parts of southwestern Asia bordering the Black and Caspian Sea.

N.
 
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