Weather and Climate: Ch. 9 Flashcards
Boundary between 2 air masses
Front
In a front, one air mass is usually _________ and contains more __________
warmer; moisture
Warm air gliding up and over a cold air mass
Overrunning
Identification on maps:
- Sharp temperature change
- Shift in wind direction
- Sharp dew point change
Front with no movement
Stationary Front
Winds in a stationary front:
parallel but opposite direction, separating warm and cold air
In a cold front, ___ (dominate) replaces ___
cP; mT
Shape of a cold front
steep, nose shape
Cold fronts move ___% faster than warm fronts
50
Characteristics of a Cold Front Before Passage:
- Temp: Warm
- Humidity: High
- Winds: S to SW
- Pressure: Falls
- Line of thunderstorms in distance
Characteristics of a Cold Front After Passage:
- Temp: drops (cold)
- Cold air advection
- Humidity: drops
- Winds: Shift SW to NW
- Pressure: Rises and skies clear
If warm is relatively stable in a cold front what type of clouds?
Nimbostratus and Altostratus
If warm air is unstable in a cold front…
uplift is vigorous and towering Cumulonimbus form
What type of weather comes when warm air is unstable in a cold front?
strong gusty winds, hail, or tornadoes
No two cold fronts are exactly _______
alike
Some cold fronts pass with _____ in dew points, _____ wind shift
drop; slight
In a warm front, ___ (dominate) air overrides ___
mT; cP
In a warm front, _______ lifting produce clouds and precipitation
gradual
Characteristics of a Warm Front Before Passage:
- Clouds lower and thicken
- Winds: E or SE
- Temps: Cool
- Humidity: Moderate to high
- Pressure: Falls
- Precipitation: steady light to moderate - may exceed 24 hours
Winter precipitation in a warm front Before Passage:
snow –> sleet –> freezing rain –> rain
What clouds lower and thicken in a warm front Before Passage?
- Cirrus clouds (600 miles)
- Cirrostratus
- Altostratus
- Stratus
- Nimbostratus (180 miles)
Characteristics of a warm front after passage?
- Winds: S or SW
- Temps: Rise (warm) - Warm Sector
- Warm air advection
- Humidity: High
- Pressure: Rises
Rapidly moving cold front overtakes warm front
Occluded Fronts
Later stages of a storm’s life cycle
Occluded Front
Separates moist air from dry air
Dry Line
Dry Line has a role in ______ weather
severe
Synoptic-scale, low pressure system
Midlatitude Cyclone
Midlatitude cyclone has a diameter greater than ____ miles
600
Midlatitude cyclones travel _____ to _____
west to east
Midlatitude cyclones last few days to …
over a week
Development begins along polar front
Polar Front Theory
Separates cold polar air from warm air
Polar Front Theory
Development and strengthening of a storm system
Cyclogenesis
Where do Midlatitude Cyclones form?
downwind of mountains and along coastlines
All storms tend to converge toward the ___
NE
Forms near TX and OK panhandle
The Panhandle Hook
Panhandle Hook storms travel ___ and bend and travel sharply __________
NE; northward (WI)
Form near CO
Colorado Lows
Colorado Lows storms travel ___ and then ___
SE; NE
When are Colorado Lows most common?
fall, winter, and spring
East side of Canadian Rockies in winter
Alberta Clipper
Alberta Clipper brings a _____, ______ storm
cold, windy
Alberta Clipper storms dive ____ into ________ and across Great Lakes
SE into Dakotas
Travel from Mid-Atlantic coast to New England
Nor’easters
When are Nor’easters most frequent and violent
September-April
Storm that form in the south yield _____ precipitation
more
Forms that form in the south draw…
moisture-rich air from gulf
Undergoes explosive development
Cyclone Bomb
Cyclone bombs drop at least ___ mb in ___ hours
24; 24
Needed for cyclones and anticyclones to maintain or intensify
Convergence and Divergence
For a surface LOW to strengthen (deepen), surface LOW must be ______ of ______-level low
east (right); upper-level (trough)
For a surface LOW to strengthen (deepen), upper level Divergence of air must be ______ than surface Convergence of air
greater
For a surface HIGH to strengthen (build), upper level Convergence of air must exceed…
low-level Divergence of air
In Convergence and Divergence, movement controlled by ________ winds at _______ (500 mb) and travel faster in ________ months
steering; 18,000’; winter
Zone of overunning as mT overtakes cool air
N/NE Quadrant
E-NE winds are in what quadrant?
N/NE Quadrant
In what quadrant is it cloudy and precipitation is steady, substanital
N/NE Quadrant
“Winds out of ____, weather a beast” is a part of the ____ Quadrant
east; N/NE
What are the quadrants for cyclone weather?
- N/NE Quadrant
- SE Quadrant
- SW Quadrant
- NW Quadrant
Mildest air in warm sector of storm is ___ Quadrant
SE
In which quadrant do south winds advect mT air in northward from Gulf of Mexico?
SE Quadrant
In the SE Quadrant, skies ______ cloudy and dew points ______
partly; high
The Terrible Triangle is in __ Quadrant
SE
There is _______ weather possible in the Terrible Triangle
severe
Follows cold front to south in ___ Quadrant
SW
The SW Quadrant has a narrow band of…
cumuliform clouds, showers, and thunderstorms (squall line)
In the SW Quadrant, there are _____ skies behind ____ front
clear; cold
Head of comma is in the ___ Quadrant
NW
The storm is still ________ in the NW Quadrant
developing
What quadrant has the lowest air temps?
NW Quadrant
In the NW Quadrant, strong NW winds advect __ or __ southward
cP; A
Nimbostratus clouds bring rain or snow in the ___ Quadrant
NW
In a cyclone, coldest air is located to …
NW of low center
In a cyclone, warmest air is located to …
SE of low center
Chicago experiences WARM SIDE of storm on track __ of a cyclone
A
Chicago experiences COLD SIDE of storm on track __ of a cyclone
B
Center of low to your _____ on Track A
north
Track A is a mature storm system with passage of fronts:
- Ahead of warm front (#1)
- Warm front (#2)
- Cold front (#3)
- Behind cold front (#4)
Center of low _____ of you on Track B
south
Track B has no _______ passages
frontal
Track B brings ______ snow or rain (__ hours or more)
steady (12 hours or more)
The heaviest snowfall on Track B runs parallel about ____ miles to __ of storm track
150 miles; NW
Track B has gusty __-__ winds shift to __ and ___
E-NE; N and NW
Skies clear and temps fall on Track __
B
Anticyclones bring _____ skies and ______ conditions
clear; calm
Air modifies in Anticyclones:
- NW winds ahead
- South winds as it moves away
Record cold in winter and heat waves in summer
Anticyclones
Prevent usual west to east movement systems
Cutoff Systems
Cutoff Systems can persist for ____
weeks
Example of weather extreme in a cutoff system
droughts
850 mb chart (1 mile):
- conditions near surface
- warm and cold air (air mass locations)
700 mb chart (2 miles):
Steering winds for thunderstorms
500 mb chart (18,000’):
Forecast direction of Midlatitude cyclone
When was the “Storm of the Century”, most massive and disruptive MLC storm in US history
1993
Where was the “Storm of the Century”?
Eastern 1/3 of country
“Storm of the Century” produced greatest distribution of significant _____ in modern times
snow
