Moisture

1
Moisture

• Gulf of Mexico near surface moisture
• Gulf of California and Pacific Ocean mid to
  high level monsoon moisture

2
Lifting mechanisms
Cold Front cold air undercuts warm air Warm
Front warm air overruns cold air Stationary
Front a stalled front Dry Line dry air
undercuts moist air Low Pressure Areas draws
air in and lifts it Thunderstorm Outflow cold
air flowing out from a storm undercuts warm
air
Hills / Mountains
3
Upper Level Disturbance
Upper-level disturbance and jet streak draws air
skyward.
L
4
The ground heats the air
5
Buoyancy
The tendency or capacity to remain afloat in a
liquid or rise in the air. The upward force that
a fluid exerts on an object less dense than
itself.
6
Buoyancy
7
Buoyancy
8
Buoyancy
9
Buoyancy
10
Buoyancy
11
BuoyancyWhy storms DONT form on some warm and
humid days
In cloud temps
Environmental temps
12
BuoyancyWhy storms DONT form on some warm and
humid days
13
Buoyancy
20,000 ft 0F 15,000 ft 25F 10,000 ft
40F 5,000 ft 62F 0 ft 85F
9 27 45 63
A cloud formsso the parcel will cool more slowly
at a rate of 3.5F/1000 Feet.
At 3000 Feet Parcel Temp drops to 70F .
5F / 1000 Ft
14
Buoyancy
In cloud temps
Environmental temps
15
Overshooting tops
16
Buoyancyas buoyancy INCREASES,updraft strength
INCREASES
17
Weather Radar VIL
VIL Vertically Integrated Liquid. (KG/M2)
VIL
63
VIL is a measure of the updraft strength and a
good hail indicator.
18
Weather Radar VIL
VIL Vertically Integrated Liquid. (KG/M2)
VIL is a measure of the updraft strength and a
good hail indicator.
19
Mid- and Long-distance cloud features
Courtesy Evan Bookbinder
20
Thunderstorm Spectrum
Single Cell Cluster Squall Line Supercell
Short-Lived Severe Pulse Severe Rotating
Updraft
21
Pulse storms
- Weak winds aloft. - Very buoyant air can
result in strong, nearly vertical updrafts. - As
the downdraft overwhelms the updraft (falls
through the updraft), ONLY a short period of
rain, wind, and possible hail occurs.
22
Pulse stormupdraft sequence
Initial Later
Finally
Storm is initially dominated by the updraft, Then
after a short time...the downdraft overwhelms
(falls through) the updraft
23
Multicell cluster
24
Multicell line stormsSquall lines
25
Squall line shelf clouds
Shelf clouds occur on the edge of the updraft-
downdraft interface Shelf clouds slope down AWAY
from the rain When you see a shelf cloud, think
strong winds
26
Shelf cloud
Formed by 2 different air-masses interacting
Cool Outflow
27
Accessory Clouds

• Often turbulent with small scale twisting and
  curling motions in clouds.
• - Motion is neither organized nor persistent.
• - Scud clouds may form and dissipate rapidly.

28
Multicell Squall line Radar View
29
Bow Echoes / Squall Line
As winds aloft accelerate toward the ground the
squall line bows forward. A bow echo is a radar
signature strongly suggesting wind damage.
30
Macrobursts
31
Gustnadoes
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End of Part Two

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