Advanced Shallow Weather and Orographic

Boundaries Thunderstorm Outflows Lake Breezes

Arc of blowing dust Reflectivity “thin lines” Gust Fronts Very shallow feature, emanate from a thunderstorm. Recall the depth-detection discussion.

Example of Boundary in Reflectivity -10 to 20 dBZ

Rapid Storm Evolution (Time lapse < 5 hours) Animation 120 km

Movie Loop Showing Cold Front, Gravity Wave and Dry Line Interactions International H 2 0 Water Vapor Project (IHOP) May 11, 2002

Gravity Waves International H 2 0 Water Vapor Project (IHOP) May 11, 2002

Drizzle

A Typical Z – R Beijing Summer

Reflectivity and Drizzle Beijing Summer

How to remember beamheight numbers? Aside

S = r θ 1 o = 180/pi = radians At r=100 km then s = 100 * S = 1.75km = beamwidth at 100km For flat Earth, for beam at 1 o elevation angle, height of beam centre ~= 1.75km H = sqrt ( r^2 + 2*Ke*ae*r + sin ( theta_e ) ) – ke * ae r s θ

Beam Height Diagram

What is the approximate Height / Width the Beam 0.5 o beamwidth1.0 o beamwidth Elevation Angle0.5 o 1.0 o 0.5 o 1.0 o Range 50 km 100 km Arc distance = r theta 1 deg = 180 / pi =

Forest Fires

Kelowna Forest Fires

Nocturnal bird migration looks like drizzle

Insect migration and Cb

Lake Breezes and Tornados Pat King and Dave Sills

Morning Mid Afternoon “Pure” LB example Enhance convergence Lake Breeze Boundaries Lake Huron Lake Ontario Lake St Clair Lake Erie

++++ = Pure lake breeze Moderate SW Flow Lake Breezes

Average of 6 VIS Images from UTC

Spring (15 Mar - 15 Jun) Tornado Touchdown Points Confirmed and probable only

Spring (15 Mar - 15 Jun) Tornado Touchdown Points … overlaid with boundaries from 31 July … tornadoes are suppressed in regions where Southwest winds are onshore... … and enhanced in regions where lake breeze boundaries often form. Forecasters use knowledge of lake breeze positions in their severe weather forecast for weak tornadoes

Lee Side Troughing On a very small terrain feature

Southern Ontario is relatively flat. Elevations rise from about 200m on Lake Huron to about 400m just south of Georgian Bay. Lake Huron Lake Ontario Lake Erie Georgian Bay Topography of Southern Ontario

Average of six GOES images over a 3-hour period Moderate WSW flow Dissipation of thin SC cloud in downslope flow SC cloud forming beneath an inversion at 1500 m above ground Dissipation of Clouds in a SW Flow

Topography of Southern Ontario Niagara Escarpment Average of six GOES images over a 3-hour period

20 February, NWA Conference - Louisville, KY Sam Lashley – National Weather Service Northern Indiana Jon Hitchcock – National Weather Service Buffalo, NY

Mountain Top Radars Show Rodger Brown Paper graphs

Negative Elevation Scans Show DEM and the one degree beam Show negative elevation angle Discuss caveats – need gc filtering Need 3dB filling Show

Scanning in Complex Terrain Valley Radars Show the v10 radar DEM and discuss with respect the weather NOT surveillance

Radar Detection Issues CAPPI (too high) 0 o PPI

Lake Breezes and Convection Initiation/Suppression Review the wilson boundary rules/Aurora did a poster on this Show Pat King Lake Breeze and Prevailing Wind Analysis Show Pat King Tornado climatology and Lake Breezes Show AF358 or another case

Lake Effect Snow Bands Show the EGPM lake effect snow bands Show single bands Show multiple bands Show the convergence in the middle of the band Talk about TREC tracking

Sea Spray

Orographic Effects Precipitation Enhancement – upslope condensation and development Precipitation Suppression –lee side troughing –Blocked flow –Radar Blockage – can not see Explanation – Impact of Froude Number