2/21/98 Chase Summary by David Shohami


From: David Shohami (davidsh@mail.geocities.com):
Hi, this is my chase report of a tornado that developed in Israel.
Although it isn't as strong as those in the US... but it was still an
exciting and interesting chase, in a day when the chances for severe
weather were none.


The February 21, 1998 Shoeva, Israel, Tornado Chase Report


    On February 21 a quite rare event took place near Shoeva in the
western Judean Mountains, 20 kilometers west of
Jerusalem. A single thunderstorm produced a tornado, when the chances of
severe storms were very low. In fact, the tornado
producing storm was the only storm, that developed that day in Israel.

    A large area of low pressure came down from Russia towards Turkey on
Wednesday, February 18. The warm front pulled
a Red Sea Trough towards the Middle East, which connected to the low,
now in north-eastern Syria, on Thursday February
19. That caused the formation of scattered storms in Israel, and the
forecast was for more storm development until Friday. But
on Friday the low pressure became weaker, and the Red Sea Trough
retreated southwards. The chances for severe weather,
or any weather at all, were becoming very slim. On Saturday, February 21
the small low pressure was still around, now in
eastern Jordan. It was still connected to the Red Sea Trough, but the
conditions were not quite right for classic severe storm
development in Israel. The forecast said nothing about any chances for
severe weather, but I still had my hopes up. A Red Sea
Trough is very hard to forecast, and on more that one occasion in the
past the forecast was completely wrong...

    Already in the early morning of Saturday, February 21 I saw towering
cumulus developing in western Jerusalem. Jerusalem
itself was clear, so I figured the best place to be was west of
Jerusalem. In 11:30 AM I went to Har-Adar, one of the highest
mountains in the area, and saw towers forming above the area where the
Judean Mountains were starting to rise from the plains
of central Israel, while the other areas were completely clear. By 13:30
PM the sky was cloudy. I drove to the western-most
edge of the Judean Mountains, near the small town of Shoeva, 20
kilometers west of Jerusalem. From there I had a good view
of the plains and the Mediterranean coast, where I saw that the weather
was sunny. In 15:00 PM an area in the clouds above
me became darker, and large rain drops began falling. I noticed a wall
cloud about 50 meters to the north, where the severe
thunderstorm had developed unnoticed among the other clouds. I couldn't
see the storm structure because of the clouds, but
the wall cloud and updraft base were ominous enough for me. 2 minutes
later a downburst of marble-size hail started, which
lasted for about 35 minutes. I couldn't see the wall cloud, and at that
moment I thought that this will be everything this small
storm had to offer. I got into my car and started to drive away from the
storm to avoid the hail, when I took a quick glance
above me, just to make sure I wasn't missing something. And what I saw
took me completely by surprise - A rapidly rotating
funnel just 40 meters away, 1/4 of the way to the ground! I never
thought I'd see a tornado when I woke up that morning... I
quickly took the video camera and started filming the funnel, which was
getting wider, but not lower. The hail completely
stopped, and everything was quiet, except the wind... I took some
photographs too, and I noticed that the cloud around the
funnel started rotating. Suddenly the funnel started to lower, and
rotation increased. A tornado formed, but it began to retreat
about a minute later. 4 minutes later the tornado roped and almost
completely disappeared. Another funnel became visible
again 2 minutes later, but it lasted for about 3 minutes. There was
still cloud rotation afterwards, but then it stopped too, and
hail began falling again. The entire tornadic event was about 20
minutes. 10 minutes later another wall cloud formed but soon
disappeared. I stayed in the area for about an hour just to make sure
nothing else is going to develop, and I drove home, very
happy after a surprisingly successful chase.

    The possible answer to the question why a severe storm developed
near Shoeva in the Judean Mountains, was the wind
direction. The trough was east of Israel, so the winds were coming from
the WNW. Humidity entered Israel from the
Mediterranean Sea, and as it hit the mountains of central Israel clouds
developed, and because of the presence of the Red Sea
Trough (even though it was week) the atmosphere was conditionally
unstable. The clouds continued to develop, while the rest
of Israel remained completely sunny. A cold low pressure in high
altitude was probably the cause of the severe nature of the
storm, but that's still not an explanation for the development of a
tornadic storm. During the next days I will collect as much data as
possible from the Meteorological Service of Israel and try to
understand the exact cause of this rare and fantastic event.

David Shohami, 1998
comments and questions, please e-mail to: davidsh@mail.geocities.com
for pictures and information on the weather of Israel:
www.geocities.com/CapeCanaveral/Hangar/1911/index.html


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