Lamont Bain OWL Director of Operations. Thickness Thickness- distance between two pressure surfaces,...
-
Upload
doreen-mckinney -
Category
Documents
-
view
215 -
download
0
Transcript of Lamont Bain OWL Director of Operations. Thickness Thickness- distance between two pressure surfaces,...
Winter Weather Forecasting Primer
Lamont BainOWL Director of Operations
Thickness Thickness- distance between two pressure
surfaces, usually denoted in decameters. Derived using the hypsometric equation:
Knowing the thickness between two different pressure surfaces can give you an idea of the mean temperature in that layer.
Diagnose Warm Air Advection (WAA) and Cold Air Advection (CAA) at the surface using “the trapezoid” method and diagnose possible boundaries.
Suggested reading: www.theweatherprediction.com/winterwx/thicknesscriteria/
“Critical Thicknesses”
Diagnose WAA/CAA
weather.ou.edu/~metr4424
Thickness Sources•HOOT: 1000-500 mb thickness with 500mb heights and temperatures (expansion is anticipated)•Patrick Marsh’s Map: Page 1000-500mb thickness with MSLP •College of Dupage: Various Layers for Critical Thickness.
Forecast Soundings: A top-down approach Not just for thunderstorms!Guide for thermal structure and thus “p-
type.”Ice Nucleation and Snow GrowthFreezing Rain? Sleet? Snow? Just a cold rain?
Ice Crystals• For Snow to occur, ICE MUST BE PRESENT
IN CLOUD• Plains -9C suggests that IN have become
activated.• -15C ice is likely! • -12C to -16C layer is often refereed to as the
Dendridic Growth Zone or DGZ (per RAOBs) • How do I determine the temperature?
– RAOB or IR Satellite Imagery
Top-Down Method Is it cold enough to support ice crystals in clouds?Are UVVs and higher RH values (or other
moisture proxy) collocated within the Dendritic Growth Zone?
Negative Omega-Upward Vertical MotionPositive Omega-Downward Vertical Motion Is there any WAA/CAA in the column?Dry or Moist Advection at mid/upper levels?Evaporative Cooling/Melting?Will temperatures at the surface support liquid,
freezing, or frozen precipitation?
SPC Sounding
BUFKIT Forecast Sounding
BUFKIT Time Series Plot
January 28-29th 2010 Ice Storm Saturated mid/low levels of the troposphereSub Freezing Temperatures at the SFCWarm Air AloftConvection!?
12Z & 15Z OUN RAOBs
18Z & 21Z OUN RAOBs
0Z OUN RAOBs
Questions? Concerns? Comments?