exam 4 Flashcards
air masses are characterized by
homogeneous physical properties
-temperature & humidity
A or cA
continental arctic
cP
continental polar
mP
maritime polar
mT
maritime tropical
cT
continental tropical
what air mass is best described by the following:
canada, not as cold as arctic, lake erie modifies temperature upward
continental polar (cP)
what air mass is best described by the following:
gulf of mexico, austin, houston, new orleans, ingredient in thunderstorms
maritime tropical (mT)
what air mass is best described by the following:
think arctic circle, barrow, alaska, only reached austin a couple of times
continental arctic (A or cA)
c =
land
m =
water
T =
warm
P =
cool
A =
very cool
what air mass is best described by the following:
northern desert in mexico, part of new mexico, and arizona; hot and dry
continental tropical (cT)
dry air has a (higher/lower) molecular weight
higher
fronts are found
in troughs of low pressure
**surface convergence and upper level divergence
what is cyclogenesis
low pressure developing at the surface
what causes cyclogenesis
increased surface convergence and upper level divergence (low pressure)
what is a front
a boundary between air mass
frontolysis
a weakened or dying front
frontogenesis
the birth or growth of a new front
overrunning
when less dense air mass runs up over a heavier air mass (frizzing drizzle, lots of clouds)
cold front
4 - 5 mph
- when cold air ACTIVELY advances into a region formerly occupied by warmer air
- steeper slope
- the most dynamic weather comes from the cold frontal lift
a cold front is shown by the color _____ and a line of ________ pointing in the direction that ________________
blue ; triangles ; the front is moving
warm front
- when the surface position of a front moves such that warmer air occupies territory formerly occupied by colder air
- more gentle slope
a warm front is shown by the color _____ and a line of _________pointing in the way that ____________
red ; semicircles ; the front will move
stationary front
- when little forward movement of either air mass, usually upper level winds are parallel to the surface frontal boundary
- causes the floods in TX
a stationary front is shown by a line of ___________
ALTERNATING triangles and semicircles
occluded front
- when a cold front overtakes a warm front in the vicinity of a surface low
- more common over northern US
an occluded front is shown by a line of _____________
triangles and semicircles
all on one side of the line, unlike stationary fronts where the triangles and semicircles are alternating
what do dry lines do
separate two air masses - boundary between cT (hot, dry air) and mT (warm, moist air)
true/false: dry lines are a type of front
FALSE ; dry lines are not technically a front
the molecular weight of cT air is __________(heavier/lighter) than that of the mT air…..what does this mean?
heavier ; when it charges east a dry line lift occurs which can cause thunderstorms
define weather forecasting
predicting how the state of the atmosphere will change with time
what resources do we use to “piece together the puzzle” of weather forecasting?
- satellite
- doppler radar
- rawinsondes
- aircraft data
- lightning data
- buoy data
- weather charts/maps
- numerical weather predictions/comp model
- citizen weather observations
- surface aviation weather observations
- storm spotters/chasers
- looking outside
what air mass is best described by the following:
northern pacific/atlantic, foggy, rainy, chilly
*think Seattle
maritime polar (mP)
remember that air masses ________ as they move
modify
**meaning they can start off as one type (ex: cT) and modify into another as it travels (ex: mT)
severe weather and thunderstorms are associated most with which type of front
cold front
**need dynamic lift
define overrunning
less dense air spreading over/occupying more dense air
how does warmer air remover colder air
from the top…“eating” its way down
what type of front are floods associated with
stationary front
what type of front are clouds and fog associated with
occluded front
to be able to forecast the weather, what must be known
the current weather information over a large area
ASOS/AWOS cannot observe
- hail
- tornadoes
- sleet
- snow depth
what is one of the most reflective hydrometers
wet hail
humans augment what weather observations
- hail
- tornadoes
- sleet
- snow depth
what is the cone of silence
a single sight radar ; when a storm is near or over the radar site, data is unavailable and shows up as this black hole
***NOT SURE ABOUT THIS
what color representations on a radar are more reflective/less reflective
less reflective = green
more reflective = red
ASOS/AWOS can observe
- temperature
- pressure
- speed
how often are rawinsondes released
twice a day at hundred of locations worldwide ( 6-7 am & 6-7pm CST)
what do rawinsondes measure with ascension
- temperature
- humidity
- atmospheric pressure
- wind speed/direction
what is the average flight of a rawinsonde
60 - 90 minutes
how high do rawinsondes travel
as high as 100,00 ft (15 - 20 miles)
what are METARS
coded aviation (surface) weather observations that are transmitted globally >hourly ; it is a description of the meteorological elements observed at an airport at a specific time
what does WMO stand for
World Meteorological Organization
*it is a UN specialized agency
what is the WMO responsible for
the international exchanges of weather data and certifying that the observation process DOES NOT vary between nation since all weather observations must be comparable
where do people get their weather forecasts
- radio
- tv
- internet
- newspapers
- AMS/NWA
what does it take to be a part of AMS
AMS certified broadcast meteorologist have to pass a test ; joining the AMS/NWA is voluntary because we do not/rarely license meteorologists in the US
who issues weather watches/advisories/warnings
the National Weather Service (government)
**this is the SOLE source to issue these
which is described below: watch, advisory, or warning?
type of weather specified is imminent or is occurring and is a public inconvenience (smaller to larger geographic area)
advisory
which is described below: watch, advisory, or warning?
type of weather specified is imminent or is occurring and is an immediate threat to life and/or property (generally smaller geographic area)
warning
which is described below: watch, advisory, or warning?
atmospheric conditions are favorable for the type of weather specified (generally larger geographic area)
watch
time span of weather watches
longer time span: 4 - 6 hours up to 24 - 48 hours
time span of weather advisory
6 - 24 hours
time span of weather warning
.5 - 1 hour
what are the different methods of forecasting
- persistence forecasting
- steady state/trend forecasting
- analogue method forecasting
- ensemble forecasting
- climatological forecasting
- “gut” forecasting
what type of forecasting method is best described by the following:
looking at similar systems from the past
analogue method forecasting
what type of forecasting method is best described by the following:
looking at movement of system
steady state/trend forecasting
what type of forecasting method is best described by the following:
tied to numerical weather prediction; several members are run to collect data and test accuracy of model
ensemble forecasting
what type of forecasting method is best described by the following:
basing forecast on climate/previous trends of that location and season
climatological forecasting
what type of forecasting method is best described by the following:
most valuable in short term, use when pattern is stable
persistence forecasting
what type of forecasting method is best described by the following:
go with and make decisions based on your experience/instinct
“gut” forecasting
weather forecasting is a ___________ science
non-perfect
what method of weather forecasting should be used
all of them! don’t just look at one, use a combination
what does NWP stand for
Numerical Weather Prediction
what is NWP
computer atmospheric models made through programs
how often are NWP models run
1-4 times/day
what are some problems with the NWP system
- if bad data in, then bad data out
- model make certain assumptions therefore have certain biases
- data sparse areas of the world
- cannot adequately interpret many of the factors that influence surface weather
- small disturbances/errors tend to be amplified with time
what does POP forecasting stand for
probability of precipitation
true/false: POP forecasting is very misunderstood
true
how do we arrive at forecast POP
(forecaster certainty) x (areal coverage expected)
EX: 50% x 20% = 1000 or 10% POP
**it means there’s a 10% chance that it will rain AT A GIVEN LOCATION
it does not mean that it will be raining 10% of the time or 10% of the area
what is the short term forecast accuracy
80-90% (today/tonight)
what is the medium term forecast accuracy
over 80% (2-3 days out)
what is the monthly or seasonal outlook accuracy
much lower (30-90 days out)
what is the longer range forecast accuracy
70% (4-8 days out)
what percent of thunderstorms worldwide are classified as severe
less than 5%
true/false: straight line winds can cause more damage than tornadoes
true ; straight line winds diverge whereas the winds of tornadoes converge
what are the basic requirements for a thunderstorm
- lift
- instability
- moisture
how long to most thunderstorms last
about an hour
how are thunderstorms brought to an end
the down draft (cold, more dense air) cuts off the updraft and the storm commits atmospheric “suicide”
true/false: severe thunderstorms do not last as long as air mass thunderstorms
false ; severe thunderstorms are longer lasting because of an established/well developed wind structure (2 hours longer)
where do most severe thunderstorms occur
middle latitudes along cold fronts/dry lines
**cP/mP/mT/cT boundaries
what are the criteria for a US severe thunderstorm
- presence of a tornado
- 1 inch or larger diameter hail (@ surface)
- convective wind gusts of 50 knots/58mph
**this is an AND/OR list; only one criteria must be met for it to be considered severe
true/false: the presence of an initial tropospheric temperature inversion contributes to thunderstorm development
true
define squall lines
a line of thunderstorms
what is something you should always remember to look for in a squall line
always watch for the storm at the end of the line
what determines the severity of the individual thunderstorms in a squall line
the density of the storms along the line
define super cells
long lasting thunderstorms that develop a strong, internal wind structure and that control their atmospheric environment
true/false: super cells are always severe
true
define mesocyclones
a rotating updraft, usually 3 - 7 miles, within an intense cumulonimbus cloud/severe thunderstorm
what percent of mesocyclones produce tornadoes
less than 20%
what is a mesoscale convective complex/system
a number of individual thunderstorms that grow in size and arrange and organize into a long lasting convective complex
where are mesoscale convective systems commonly found
USA plains and into Mississippi Valley
how much larger can mesoscale convective systems be than average air mass thunderstorms
as much as 1000x
what does derecho mean
“straight ahead” or “direct”
what is a derecho
a widespread and usually fast moving convective wind storm
how severe is the reach and damage of a derecho
can produce damaging wind over areas hundreds of miles long and more than 100 miles across
true/false: thunderstorms are bad for the environment
false; thunderstorms are good for the environment because they help keep the Earth in electrical balance; they also serve as a great way for the atmosphere to release energy
what are the 4 different types of thunderstorms
- single cells
- multicell clusters
- multicell lines
- supercells
what are the stages of thunderstorm developement
- cumulus (updrafts dominate)
- mature (updrafts/downdrafts coexist)
- dissipating (downdrafts dominate)
lightning won’t develop until _____________ develop
downdrafts
at any given moment, how many individual thunderstorms are in progress worldwide
2000
of the 2000 individual thunderstorms in progress worldwide, what percent are severe or non-severe
over 95% non-severe ; less than 5% severe
what are the differences in hail size between severe and non severe thunderstorms
non-severe : hail less than 1” in diameter
severe: hail equal or greater than 1”
what are the differences in formation location between severe and non-severe thunderstorms
non-severe : found WITHIN mT airmass
severe : found ON boundaries of mT airmass
hail size (and thunderstorm severity) is entirely dependent on _____________
thunderstorm updraft and downdraft speed
largest hail often falls ________ (NW, NE, SW, SE) of tornadoes
NE
what is the number one weather killer in the US
summer heat
true/false: flash floods are one of the top weather killers in the US
true ; general public does not understand the power of moving water
**south central texas is considered the flash flood capital of the US
what are straight line thunderstorm winds
strong downdraft winds from thunderstorms with a divergent wind pattern
**referred to in general as downbursts
where are GOES satellites east and west located
GOES west is at 135 W longitude
GOES east is at 75 W longitude
what are the three different satellite image types
visible, infrared, and water vapor
what does the visible satellite image type display
shows what the sun light up, cannot see at night
what does the infrared satellite image type display
hotter colors denote colder cloudtops, 24 hrs a day
what does the water vapor satellite image type display
mid and upper level atmospheric moisture
reflectivity vs. velocity data
reflectivity will show levels of precipitation
velocity will show where it’s moving
what is clear air mode
when there is high certainty of no precipitation, satellites can enter this mode and not do as much work
what is dual pol
horizontal and vertical measurements/waves, this crossection allows us to capture both size and shape of hydrometers
ASOS stands for
automated surface observing system
AWOS stands for
automated weather observing system
an example of an airport that uses human augmentation
austin bergstrom
an example of an airport that does not use human augmentation
camp mabry
what are the most common lightning types
cloud to cloud & intracloud
a bolt of lightning is about the diameter of…
a pencil
within the lightning bolt, it is about ___ times the temperature of _______________
5 times the temperature of the outer surface of the sun
what about tornadoes kills most people
the flying debris
