Lesson 401 Cyclonic Development Flashcards
List the the three factors that affect the central value of a low pressure system.
TDD
Topography
Diurnal pressure changes
Diabatic influences
List the six factors which contribute to divergence and convergence in devolving low pressure systems:
HHSSLH
Horizontal thermal advection Horizontal vorticity advection Surface vorticity Sensible heat transfer Latent heat transfer Heat transfer by vertical motion
A baroclinic zone in the atmosphere is when there is a:
Horizontal temperature gradient on the isobaric surface.
When an atmosphere is said to be baroclinic there can be changes in temperature, divergence, and convergence due to _________ ________ all resulting in ________ motion.
Thermal advection
Vertical
The atmosphere is said to be barotropic when there is no …
Variation in its temperature along an isobaric surface (at a given pressure level)
A barotropic atmosphere is thus characterized by the _________ of a temperature gradient on an isobaric surface.
Absence
The ________ the thermal contrast, the _________ the baroclinic zone.
Larger
Stronger
List the five stages in the life cycle of a baroclinic depression.
FDMOD
Formation Development Maturity Occlusion Dissipation
List the five methods that can be used to indicate the motion of a low pressure system.
HI5IB
History Isallobaric pattern 500 hPa flow Isobaric pattern Baroclinic zone
List the four thermodynamic factors favourable for the development of summer severe weather.
WCAD
Warming in the low levels
Cooling at upper levels
Adding moisture in the low levels
Drying at upper levels
List the three dynamic factors favourable for the development of summer severe weather
LUV
Low level convergence
Upper divergence
Vertical wind shear
List the characteristics of a tornado
Mesocyclone Very intense wind vortex Small diameter Extends from cumulonimbus Irregular track Duration Accompanied by other thunderstorm phenomena *waterspout over water
List the five stability indices commonly used in Canada
LSTGS
Lifted index (LI) Showalter index (SI) Total-totals index (TT) George index (K) Sly index
Examples of severe winter weather for which weather warnings are issued are:
Blizzards,cold wave, heavy snowfall, freezing rain, strong wind, heavy blowing snow, freezing spray, wind chill, heavy rain, snow squalls.
A blizzard is officially defined as a storm with:
Visibility less than 1 km in snow and/or blowing snow
Wind > 40 km/h
Temperature < -10 C
The above must persist for 6 hours or more.
Heavy snow is defined as _____ cm or more accumulation in _____ hours (or less) from a particular system.
15
24
What are the five characteristics associated with snow squalls
SNSDI
Shallow systems (tops generally less than 10,000') Narrow band of precipitation Snowfall can be heavy Duration - several hours to days Inland penetration up to 200 km
List the winter low pressure systems
Pacific lows, Alberta, Nebraska, Colorado, Great Lake lows, Atlantic lows, Newfoundland lows, Davis strait lows.
Colorado lows experience ________ to _________ snowfalls. Lows which track further south often bring ________ ________.
Moderate to heavy
Freezing rain
Snowfalls associated with Alberta lows rarely exceed _____ cm.
15
Atlantic lows are often accompanied by _________ precipitation of all types. They produce _______ snowfalls in Labrador and Northern Quebec.
Abundant
Heavy
List the three factors necessary for the formation of winter convective clouds (streamers):
LUL
Long fetch (150 km or more)
Unstable temperature profile (difference of 13 C or greater between lake temp. and 850 hPa level.)
Little wind shear (30 deg. or less below 3 km)
To diagnose instability, look for:
PPI
Pools or troughs of cold air aloft (700 hPa chart)
Pools or ridges of warm air in low levels
Indications of lapse rates higher than saturated adiabatic lapse rates
List the six stages of a baroclinic depression
Wave stage Developing comma Mature comma Occluding system Occluded system Dissipation
