A strong western disturbance over
the western Himalayan region caused cloudiness over northwest and adjoining
central India. If snowfall played truant in Himachal Pradesh on Christmas and
New Year's Eve, then it made up for the lapse with a vengeance. Snow walloped
Shimla, Kufri , Narkanda , Chail , Manali , Chamba and Dalhousie.
In fact the entire tribal belt of
Kinnaur, Lahaul and Spiti, Kullu and Chamba districts witnessed heavy snowfall.
Shahpur and parts of Hamirpur among other places also experienced snowfall and
sleet after a gap of more than three decades. And it's snowing in 'Queen of
Hills' Shimla as well. This after 8 years! The minimum temperature recorded
in the hill station fell to minus 0.8 degree C.
Dharamsala received snow after a
gap of 35 long years. Located at a height of only 1,350 metre and the abode of
Tibetan Buddhist spiritual leader the Dalai Lama, Dharamsala was totally covered
in white, making the town more picturesque. In fact the snowfall was unusually
heavy with McLeodganj, its tiny hamlet, known for its strong British heritage,
receiving some of the heaviest snowfall on record.
Even Nurpur experienced snow.
This after 45 years. But what really took weather forecasters by surprise was
heavy snow lower down in Kangra town. This was after a gap of a whopping 67
years! The peculiarity of Kangra, Nupur and Dharmasala are that these are
foothills where snowfall is not normally expected because of their low
elevation. But Himachal Pradesh is not complaining. Good amount of snowfall has
not only rejuvenated its glaciers, but also proved beneficial for its tourism
industry, with scores of tourists making a beeline to the hill state. Hotel
accommodation and flights are reportedly fully booked.
It gets even better. Probably for
the first time in the recorded history of Punjab, several villages of Pathankot
and Hoshiarpur districts experienced snowfall on Saturday morning. The two
districts normally experience maximum temperature of up to 45 degrees Celsius in
summer. The Met office however dismissed the event as a 'freak'
happening due to change in wind directions.
Last Friday, parts of New Delhi
and Amritsar woke up to be greeted by a hailstorm. It is not that hailstorms
are a rarity in these parts of the country. It usually takes place during the
transition period where winter gives way to spring. This is when temperature
rises initially in the southern parts of India, giving rise to thunderstorms and
squally weather, including hailstorms in Northern India. The problem is that we
are not in this transition period and in fact only now entering into the peak
winter season.
So
what could have triggered the hailstorms? My friend, Rajesh Kapadia who
administers the blog Vagaries of the Weather explain that conditions for snow are a) surface
temperatures are below freezing upto 2 deg C b) atmospheric temperatures are
below freezing c) air contains a minimum moisture level. Atmospheric
temperatures were below freezing but conditions of surface temperature and
minimum moisture levels for snowfall were not meet to create snow and so the
western disturbance impact on New Delhi and Amritsar probably took the shape of
hailstorms. This of course remains a logical conjecture.
Meanwhile, more than 3 feet snow
received over the past two days closed down Kashmir's main highway, stranding
hundreds of travellers. The snowfall on either side of the Jawahar tunnel,
blocked the only road link, connecting Kashmir to rest of the country, and
traffic has been suspended. Trucks carrying supplies to Kashmir haven't moved a
bit in the past three days because the Jammu-Srinagar highway that connects the
Valley with the rest of India is closed due to heavy snowfall and
landslides.
The heavy snowfall also knocked
out power and telephone lines after the 220 KV-Kishanpur-Pampore and 400 KV
Kishanpur-Wagoora transmission lines snapped on other side of Jawhar Tunnel due
to snowfall. Against the required 950 MW of electric power being supplied to
the valley, the availability this time is pegged at 120-150 MW. Among the
available power, 40-50 MW is being supplied to consumers while rest is being
used for running essential services. The plight of residents made worse as
J&K is already facing shortage of fuel- LPG and kerosene- for cooking and
heating purposes.
Temperatures at Srinagar
plummeted to minus 5.5 degree C, the coldest night in the city this winter. Due
to the extreme cold, water taps in most areas of Srinagar were frozen in the
morning. Picturesque tourist spot Gulmarg recorded a low of minus 16.5 degree
C. Qazigund’s low dipped to minus 8.4 degree C followed by Kokernag (minus 6.3
degree C), Pahalgam (minus six degree C) and Kupwara (minus 5.6 degree
C).
The Dal Lake was frozen at many
places too. Kulgam town in south Kashmir received 2 feet of snow while Srinagar,
around 5 inches of snowfall since last evening. High-altitude areas including
the ski resort of Kupwara district which recorded night temperature of minus 0.3
degrees Celsius, had 14.4mm of fresh snow till early morning.
Pahalgam, received fresh snow of
8cms during the time while the world famous hill resort in south Kashmir,
recorded a low of minus 1.8 degree C. Kargil district in Ladakh witnessed the
first heavy snowfall of the season with Kargil town recording 2 inches of snow
while Drass had about 3.5 inches on the ground this morning. Taisuru and Rangdum
also recorded 2 inches snowfall. In Leh, temperatures plunged to minus 18.8 deg
C.
India
is experiencing a harsh winter characteristic of a La Niña winter. So how does
rest of the world shape up this winter?
GLOBAL
WINTER
Let’s look at the latest
satellite temperature imagery for today.
From these temperature maps it is
evident that most of the extreme cold is confined to Canada, Russia and Northern
China. Winter by and large had been mild in most other areas within the
Northern Hemisphere. So mild that huge swathes of Northern India are currently
colder or at comparable temperature to much of Western Europe.
The table
illustrates that El Niño-Southern Oscillation (ENSO) by itself is not sufficient
conditions to determine the character of winters within the Northern Hemisphere.
More important is the Arctic Oscillation (AO) Index. The erratic
AO can generate strong shifts in the climate patterns that could overwhelm or
amplify La Niña's or El Niño’s typical impacts.
Technically, the Arctic
Oscillation is a measure of atmospheric pressure variations at sea level north
of 20N latitude. Whenever an Arctic high or low develops, it affects weather
thousands of miles away.
Last year the so-called
"Arctic fence" that keeps cold air penned up in the north broke down,
allowing frigid air to spill south. So far that's not happening this winter
which should explain the mild winter at the mid latitudes. However, the AO is a
fickle—not seasonal—phenomenon and can switch erratically between the two
modes.
As seen in the NOAA graph, the AO
has been in its positive phase for the last 4 months, being particularly very
strong all through December and first week January this year. The exception was
a couple of days around the middle of October and before Christmas when it
briefly flipped to its weakly negative mode. But each time it showed a strong
streak of resilience - rebounding quickly to its strongly positive mode
again.
But yesterday, it flipped back to
its weakly negative mode again as that Northern India and Pakistan received a
snow packing wallop. At the same time, in Europe, Austria found itself buried
under 4 feet of snow, creating chaos and disruption of traffic and power supply.
Snowfall trapped some 15,000 tourists at ski resorts on the Arlberg Mountain on
Friday, and while some roads are open there, others remain closed. High winds
are also whipping the nation, and closed an important rail line. Most snow has
fallen in the western states of Tyrol and Vorarlberg. 52 people were rescued by
an army helicopter there. An important rail line that connects Vienna and
Innsbruck with western Austria and Switzerland was to be closed until Sunday.
Two rail lines that connect western Austria with Germany were also
closed.
These two events may look
unconnected but they need not. They occurred the same time as the AO flipped to
it weakly negative mode. But the moot question is whether a negative AO is just
a blip or something longer in duration?
So what do weather ensemble
models indicate? As seen in the above graph, some show the AO index rebounding
and going positive while others (the majority) have it trending negative and
ending below zero.
Two
weathermen think on similar lines. On Twitter, former Accuweather and now with
WeatherBell, legendary weatherman Joe Bastardi observed: “10mb [stratospheric] warming on European [model] over
the pole by 360 hrs reaches 50C!!!! This is a huge event and will have
[northern] hemisphere cold implications…By that I mean, something major is about
to happen.”
Henry
Margusity Accuweather also anticipating a major change similarly
observed: “This is such an amazing weather
pattern evolving. I told all the [meteorologists] that we have a lot of winter
ahead of us.”
It
was left to Dave Tolleris of Wxrisk to make a more nuanced statement about a
possible pattern change. He stated: “All this being said
this does NOT mean the winter of 2011-12 is about to turn nasty for everyone and
or the Northeast is going to see big snows or noreasters. …It might turn that
way but we don’t know that yet. But the old winter pattern of 2011-12 that has
featured sustained warm/ mild dry pattern is going to end soon. And whatever the
new pattern … won’t be the same as what the last 45-60 days have
been.”
“Much of the excitement by Bastardi
and Margusity probably stems from a strong stratospheric warming event that is
now showing up on the model guidance and how it might lead to more blocking and
a negative Arctic Oscillation (AO). Remember, a negative AO means a cold and
sometimes snowy weather pattern over the eastern U.S...
The pattern change
ideas stem from research by Baldwin and Dunkerton published in a 2001 “Science” article
which documents how there is coupling between the
stratosphere and troposphere and that sudden stratospheric warming events can
have an impact on the AO (by helping modulate the strength of the polar vortex),
flipping it negative...
That research notes that once the warming
propagates down sufficiently to produce a weather pattern favouring a negative
AO (lots of high latitude blocking), the pattern tends to last for about two
months. That probably explains why some forecasters think that if the AO goes
negative it might stay that way through much of the remainder or the
winter....
The potent polar
vortex event and positive AO that has been going on for over two months already
appears to be on the wane with or without help from the stratosphere. This
strong vortex event has lasted longer than most such events so the forecasts of
it weakening may have some merit.”
What
all this means is that a big pattern change in winter outlook is due in the
next 7-14 days and the odds favour a strong negative AO. If Europeans and
Northern Americans have put away their woollies and not stocked up on their
heating oil, then it is time they did so in a hurry as a harsh winter is
speeding their way and when it does will probably not go away for the next 2-3
months.
In India, if you thought that
winter would have peaked by month end, you could be likely to be wrong.
Instead, the cold wave could turn even harsher. Much of the cold wave and snow
in the country is linked to what called western disturbance (WD), which is a
term used in India, Pakistan, Bangladesh and Nepal to describe an extra-tropical
storm, originating in the Mediterranean that brings sudden winter rain and snow
to the northwestern parts of the Indian subcontinent.
This is a non-monsoonal
precipitation pattern driven by the Westerlies. The moisture in these storms
usually originates over the Mediterranean Sea and the Atlantic Ocean.
Extra-tropical storms are a global, rather than a localized, phenomena with
moisture usually carried in the upper atmosphere (unlike tropical storms where
it is carried in the lower atmosphere). Once their passage is hindered by the
Himalayas, they are unable to proceed further, and they release significant
precipitation over the southern Himalayas. In winter it brings snow and sleet.
As a strong negative AO brings
cooling to the Mediterranean Sea and the Atlantic Ocean, this in turn creates
stronger WDs that in turn create higher likelihood of snow, sleet and plunging
temperatures.
Then again, the
AO is so unpredictable and could prove everyone wrong.
taken from http://devconsultancygroup.blogspot.com
