More lore on fanciful "foreign" tornadoes (cross posted here from
wx-chase):
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A research meteorologist (I spoke with years ago) stated he had
witnessed 2 huge tornadoes in northern India. I understand it doesn't
take a big tornado to be a killer, but what was described to me sounded
like a basic wedge. Using rank speculation, I bet the manor in which
the Himalayas curve to the southeast could serve to channel the
mid-level jet over the region. Considering what I do know about the
monsoon flow over there it sounds like a good directional shear setup.
I've even heard discussion of a dryline....downslope from twice the
height of the Colorado Rockies...that might be a good dryline. Someday
I'll dig into it, but for now I have some new software to figure out.
Here is a section from the referenced articles; note the last
paragraph.
In the district of Tangail, there are better data that allow me to
define a more accurate track of tornadoes. The severe thunderstorm that
produced a tornado in Madarganj around 4:00 p.m. entered Gopalpur, the
northwestern part of the district of Tangail, around 4:30 p.m. It
changed its direction in Ghatail thana from SSE to SE. The ending point
of the tornado was Mirzapur at 6:00 p.m. There were four tornadoes
produced by the cell, and the total path length in the district of
Tangail was nearly 25 km. The maximum path width exceeded 1.5 km. The
moving speed was estimated around 40-45 km/h. The Meteorological
Department in Dhaka estimated the maximum wind speed of 320-450 km/h
based on the fact that a pump machine (600 kg) was thrown a distance of
56 meters. This indicates a tornado on the the F-scale of F3-F5. My
field survey in Mirikpur ranked the tornado as F-4, based on the facts
that healthy trees of 2-meter diameter and more than 20 meter height
were uprooted, a concrete school building collapsed, and many trees were
debarked.
According to a report of the Meteorological Department, the weather
condition of the day was, "In the morning of 13 May 1996, NE and
NWsection of the sky were cloudy. Light southerly wind was blowing.
After 12:00 p.m. wind suddenly became calm. Some people felt an
unbearable heat half an hour before tornado hit". I checked the radar
picture of the day of 13 May 1996 at the Meteorological Department.
There were no echoes in the tornado affected areas in the morning, but
suddenly two strong echoes appeared over the northern affected area and
over northeastern Bangladesh with almost same latitude around 3:00 p.m.
Both of the storms strengthened and moved southward. There was no front
in the synoptic weather charts in the area, so it can be said that those
thunderstorms were convectional. However, atmospheric conditions must
have been very unstable since softball-size hail was observed
immediately before the tornadoes hit the affected area. This implies the
existence of very cold air in the upper level, probably coming from
Tibet over the Himalaya Range. The light southerly wind could carry
moist air from the Bay of Bengal. The temperature is highest in the
pre-monsoon season in Bangladesh, and the maximum temperatures were over
35o C in the inland. Very dry (dew point < 4o C) and warm (temperature >
40o C) air existed in India. These are favorable conditions for
developing super-cell thunderstorms, which can spawn strong tornadoes.
However, I could not determine if a meso-cyclone existed or not.
Tornado frequency is unknown for Bangladesh. This research on tornado
occurrence per 10,000 square miles revealed that central Bangladesh has
very high values - as much as the Great Plains states in the United
States. During the period of 1990-1994, 44 tornadoes were reported
(8.8/year), and 25 of them (57%) occurred in April and May.
Gene Moore
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--
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Jesse Ferrell - Meteorologist - j{at}weatherwatchers.org
Central Atlantic Storm Investigators - www.weatherwatchers.org
"A tornado? Why wasn't it dissipated by the weather
modification net?" --Jean-Luc Picard || ICQ No. 136862 ||
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