1 / 16

Winter Weather Forecasting Primer

Winter Weather Forecasting Primer. Lamont Bain OWL Director of Operations. Thickness. Thickness- distance between two pressure surfaces, usually denoted in decameters. Derived using the hypsometric equation:

daphne-riley
Download Presentation

Winter Weather Forecasting Primer

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Winter Weather Forecasting Primer Lamont Bain OWL Director of Operations

  2. 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/

  3. “Critical Thicknesses”

  4. Diagnose WAA/CAA weather.ou.edu/~metr4424

  5. 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.

  6. Forecast Soundings: A top-down approach • Not just for thunderstorms! • Guide for thermal structure and thus “p-type.” • Ice Nucleation and Snow Growth • Freezing Rain? Sleet? Snow? Just a cold rain?

  7. 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

  8. 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 Motion • Positive 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?

  9. SPC Sounding

  10. BUFKIT Forecast Sounding

  11. BUFKIT Time Series Plot

  12. January 28-29th 2010 Ice Storm • Saturated mid/low levels of the troposphere • Sub Freezing Temperatures at the SFC • Warm Air Aloft • Convection!?

  13. 12Z & 15Z OUN RAOBs

  14. 18Z & 21Z OUN RAOBs

  15. 0Z OUN RAOBs

  16. Questions? Concerns? Comments?

More Related