Horizontal Vorticity and Convection Flashcards
What are the three terms of the vertical vorticity equation?
1) advection
2) tilting
3) stretching
____ horizontal vorticity is generated at the leading edge of the cold pool, causing the cold pool to ___ along the surface
negative | causing cold pool to move (or spread) along the sfc
There is ___ pressure underneath cold air, which causes the cold air to accelerate _____
higher pressure | accelerate outward
The ambient air flows ___ the cold pool from the east, and is lifted at the ___ edge of the cold pool
flows toward the cold pool | lifted at the leading edge
In the absence of any other sources of horizontal vorticity, the lifted air is then guided ___ by the cold pool general circulation
guided rearward
In the absence of any generated ____ buoyancy produced by lifting (i.e. if the ambient air does not reach its LFC), the ambient air will not travel any farther above the cold air
positive buoyancy
When a cold pool has vertical wind shear, a positive environmental vorticity couples with negative vorticity at the edge of the gust front to develop an ____ ____
updraft jet
When the vertical wind shear vector points to the east, it signifies ____ horizontal vorticity
positive horizontal vorticity
If the magnitude of the positive horizontal vorticity associated with the ambient shear is the same as the magnitude of the negative horiz vorticity produced along the leading edge of cold air, then the air approaching the cold pool will tend to rise as a ____ ____ ___
vertically-oriented jet (updraft jet)
This produces ____ lifting at the leading edge of the cold air than from the case of no ambient vertical wind shear
deeper lifting
When the cold pool interacts with vertical wind shear, the ambient air has a much greater chance of being lifted to its ____
LFC
Evenly matched, but opposite horiz vorticity in the vorticity dipoles maintains ___ ____
deep updraft
The triggering of convective cells is favored along the ____ portion of a spreading cold pool
downshear
The strongest, most-lived convective systems will be produced when there is a strong ___ ___ ___ to balance the cold pool generated circulation
LL vertical wind shear
____ shear is important in how a storm’s updraft may evolve
environmental shear
How can you evaluate environmental wind shear?
plotting a hodograph
hodographs depict the _____ ____ of the horiz wind
vertical distribution
with hodographs, points are plotted as a function of ___ ____ and ____
wind direction and speed
with hodographs, each point represents the ____ wind at a specified elevation
horizontal wind
with a hodograph, wind vectors for each level are produced by connecting the hodograph’s ____ origin point with the ____ point
central origin with the plotted point
with hodographs, ____ shear vectors are produced by connecting two sequential points
layer shear vectors
The ___ ___ is the leading edge of the rain-cooled air in the planetary boundary layer
gust front
The gust front forms along ___ ___ of mesoscale domes of rain-cooled air that result from the amalgamation of ____-____ downdrafts from individual thunderstorm cells
leading edges | evaporatively-cooled
thunderstorm cold pools are associated with ___-___ and may actually be crudely analyzed on a synoptic surface chart
meso-highs (i.e. bubble highs)
The gust front is a ____ discontinuity
density
___, ___ surface air flows outward from the meso-high
cooler, denser
High theta-e air is uplifted ___ the outward-flowing cold pool
above
New convection may form in association with this uplift if the lifted parcels can reach their ____
LFC (level of free convection)
____ ____ ___ can play a major role in determining how high a parcel may be lifted prior to reaching its LFC
environmental wind shear
gust front passage is characterized by what 5 things?
1) wind shift and abrupt increase in wind speed
2) abrupt temperature drop (most of the time)
3) sharp pressure rise
4) arc cloud (if BL is moist)
5) strong VWS
A gust front is a ____ feature
mesoscale
The ___ ___ ___ represents the gust front
low cloud line
air lifted upward by the gust front produces a ___ ___
shelf cloud
What three physical mechanisms control storm structure?
1) buoyancy processes
2) gust front processes
3) dynamic proceses
What are two examples of buoyancy processes?
1) lapse rate (CAPE)
2) moisture stratification
Environmental VWS affects the ability of the gust front to trigger new ___ ____
convective elements
environmental VWS affects the ability of the updraft to interact with this environmental shear to produce enhanced, ___-___ storm structure
quasi-steady
for the storm, shear is relative to the ____ of the storm
motion
a storm travelling at the speed of the mean vector wind (MVW) automatically develops an enhanced ____ _____ into its updraft
inflow of BL air
the LL air has a strong component of ___ ___ toward the approaching storm
low-level
the magnitude of the inflow can be properly matched to the magnitude of the ____ updraft
buoyant updraft
in the absence of suitable shear, the inflow will be _____ to sustain the vigorous updraft that might result from large thermal instability
insufficient
what are 2 examples of gust front processes?
1) strength of cold pool
2) strength of LL VWS
What are 2 examples of dynamic processes?
1) strength of 4-6 km AGL VWS
2) development of rotational (helical) updrafts and associated favorable vertical pressure gradients on the updraft flank
With an ordinary cell, ____ more important in maintaining updraft than ___ processes
buoyancy | dynamic
with supercells, ____ processes are more important than ____ in maintaining updraft
dynamic | buoyancy
vertical wind shear produces ____ ___ ___
horizontal vorticity tubes
horizontal vorticity tubes are incorporated into a ____ ____ and tilt ____
thunderstorm updraft | tilt vertically
the updraft begins to rotate in the same sense as the ____ ____ (cyclonic or anticyclonic)
vertical vorticity
updraft intensity is _____ within rotating cores
maximized
precipitation loading in updraft weakness between rotating cores produces a ____
downdraft
a downdraft separates the ____ updraft from the ___ updraft
cyclonic | anticyclonic
____ ____ occurs as each updraft sustains a separate storm cell
storm splitting
what is the first stage of storm splitting?
cyclonic and anticyclonic updrafts
what is the second stage of storm splitting?
the initial storm now splits into two
a rotating updraft can cause the storms motion to significantly deviate from the ___ ___ ___
mean vector wind (MVW)
with a cyclonically-rotating updraft, the Bernoulli effects produce ___ pressure on the ___ side of the cyclonic updraft in the mid-troposphere
low (high) | right (left)
with a cyclonically-rotating updraft, cyclonic storms move to the ____ of the MVW
right
with a cyclonically-rotating updraft, ___ supercells are favored within veering vertical wind profiles
SR supercells
cyclonically-rotating storms develop a ____ motion (right-mover) relative to MVW
rightward motion
with a anti-cyclonically-rotating updraft, the Bernoulli effects produce ____ pressure on the ____ side of the anticyclonic updraft in the mid-troposphere
low (high) | left (right)
with a anti-cyclonically-rotating updraft, anticyclonic storm moves to the ___ of the MVW (SL supercell)
left
with a no-shear ordinary cell, the gust front rapidly ____ the storm
outruns
with a no-shear ordinary cell, the storm is left totally _____ over BL cold pool
entrenched
with a moderate-shear multicell, the storm will move downshear at roughly the same speed as the _____ between the sfc and 6 km altitude AGL
MVW
with a moderate-shear multicell, new cell growth is enhanced along the ____ portion of the gust front
downshear
new cell growth along the downshear portion of the gust front ____ relative flow into the newly-developed cells
increases
new cell growth along the downshear portion of the GF ____ the length of time cells stay in the vicinity of strong LL convergence zone and associated lifting near GF
increases
for strong-shear supercells, rotation develops on the ___ ___ ___ ____ due to vertical tilting of pre-existing horizontal vorticity within the sheared flow
flank of the updraft
for strong-shear supercells, if the VWS extends through the middle-levels of the storm, the rotation dynamically induces a ____ pressure anomaly in the middle troposphere
negative (low) pressure
What does NPA stand for?
Negative pressure anomaly
the NPA produces a strong _______ pressure gradient which accelerates BL air violently upward
non-hydrostatic
rotating updrafts associated with mid-level NPA’s are _____ and remain ____ after the storm moves into a more stable environment
long-lived | remain vigorous
rotation also causes storm motion to deviate from the ____
MVW
_____ shear favors storm splitting as NPA
unidirectional shear
____ shear forms at mid-levels within rotating updrafts on both right (cyclonic) and left (anticyclonic) side of original storm
unidirectional shear
____ shear has split cells that are nearly identical rotate in opposite directions
unidirectional shear
____ shear has a climatologically favored veering shear pattern
curved shear
___ shear has strongly veering winds that favor strongly right-moving cells with cyclonic rotation.
curved shear
With curved shear, left moving anticyclonic cells are ____ _____
not favored
