Local forecast by
"City, St" or zip code |
Search
by city or zip code. Press enter or select the go button to submit
request
|
|
You are at: SRH
Home » SHV Home »
Meteorological
Inquiries » Past Questions 5
ArkLaTex
Meteorological Inquiries |
If you ever
wondered why the sky was blue or any other weather phenomena, then we
invite you to submit
your questions.
Questions submitted will be answered and then selected ones will be posted
on this page.
We look forward to your questions!
| What
would be the ideal conditions for a very significant snow storm
in the 4 state area? |
The first ingredient
would be a large depth of cold air. Sometimes the
four state region receives sleet or freezing rain because the cold
air
is too shallow. However, if the vertical temperature profile of
the
atmosphere is below freezing, then the area is primed for snow if
precipitation falls. The only time we get cold enough for winter
precipitation is when we have an incursion or repeated incursions
of
Arctic air from Canada.
Once its cold enough, look for a storm system (low pressure)
to develop
south of the region (possibly in the northwestern part of the
Gulf) and
track northeast across and southern and eastern sections of Louisiana.
This track would help pull Gulf moisture into the region, but
keep the
area on the cold side of the storm.
Here is another way the area receives snowfall in winter. When
a cold
front moves into the Gulf of Mexico, sometimes the wind above
the
surface (a few thousand feet) begins to advect back northward
over the
colder air at the ground. The air is being lifted as it moves
over the
colder air at the ground, which produces the clouds and possibly
the
snow.
Bill Murrell
Meteorologist
|
| What
factors determine the type of wintry precipitation that falls?
Why does it sometimes snow, while other times it sleets, or there
is a mixture of both?
|
|
The type of wintry
precipitation we receive in the Arklatex depends on
the temperature profile in the lower to middle part of the atmosphere
(surface to near 10000 feet above ground level.) Snow usually
occurs
when the atmospheric temperature profile is completely below freezing.
While sleet usually forms when a shallow layer of warm air (above
freezing) is above a deep layer of cold air(below freezing) at
the
surface. Precipitation melts in the warm layer(snow) or remains
the
same(rain), but as it falls through the cold layer the liquid
freezes
before it reaches the surface...giving us sleet (small ice pellets).
View our web site on Winter Weather,
you will find more information on
winter precipitation. Also you may go directly to our site for
the
Winter Storm on December 25-26
2000. Here we have sample atmospheric
temperature profiles for sleet, snow, and freezing rain.
Bill Parker
Public Outreach Meteorologist
|
| What
happens to the dew point temperature of descending air and why?
|
|
As
air descends, it becomes warmer due to compressional heating,
but
the dew point remains the same as long as water vapor is neither
added
nor taken away from the air mass. Descending air can undergo an
internal temperature change but not an internal dew point change
under
these circumstances.
For example, at a top
of a mountain there is a parcel of air with a
fixed amount of water vapor. As the air parcel begins to descend
the
mountain, the volume of the air parcel contracts because of the
increased pressure of the atmosphere on the air parcel. The smaller
volume of the air parcel causes the internal pressure to increase
in
the air parcel, which in turn causes the temperature of the air
parcel
to warm. The water vapor or dew point will remain basically unchanged,
but because the air parcel has warmed the relative humidity will
be
lower.
Descending air warms
approximately 5.5 degrees Fahrenheit per 1000 feet.
If a parcel of air
had a temperature of 50 degrees Fahrenheit and a dew
point of 45 degrees and then descended 4000 feet, the air parcel
would
then have a temperature of 72 degrees with the dew point remaining
at
45 degrees. The relative humidity of the air parcel before it
descended was 83 percent, while after it descended 4000 feet it
was
only 38 percent. A good example of this would be the Chinook Winds
in
the Lee of the Rockies and the Santa Ana Winds of California.
Bill Murrell
Meteorologist |
| Is
there a special instrument to measure damage done by a tornado?
|
|
The
short answer is no. Any assessment or measurement
of the damage done by a tornado is done by on the spot storm surveys
preformed by experienced, trained meteorologists from the National
Weather Service after the tornado has passed.
The strong winds associated
with a tornado are responsible for the
damage done by a tornado and on a few occasions, Doppler radars
have
been able to measure the winds speeds in a tornado. The highest
speed
ever measured was 318 mph.
Lee Harrison
Meteorologist-in-Charge
|
| In
a Hurricane is the the low pressure air hot or cold? |
A hurricane is what
we refer to as a "warm core low", i.e., the
temperature increases as you move in towards the center of the
storm.
The greater the temperature differential between the edge of the
storm
and the core of the storm, the stronger the storm is.
Lee Harrison
Meteorologist-in-Charge |
|
www.weather.gov
