Who Cares About the Weather? Julie Gondzar DayWeather, Inc. Cheyenne, Wyoming

What will be covered? Earth’s Circulations and the Jet Stream Atmospheric Pressure Systems Understanding Frontal Systems and Cloud Formations Snow Storms & Arctic Air Masses Wyoming Wind Precipitation and Radar Thunderstorms and Supercells Reading Maps and Finding Real-Time Weather Information A Little About Weather Models Road Weather Forecasting WYDOT and National Weather Service Forecasts

Okay, go ahead…now’s your chance!

Welcome to Earth.

What is Weather? Answer: Physics + Math Ideal Gas Law 1st Law of Thermodynamics Newton’s Second Law of Motion Hydrostatic Law Conservation of Mass

Earth Circulations & Jet Stream

Earth Circulations & Jet Stream

Earth Circulations & Jet Stream

The Jet Stream Over Wyoming Summer Season Polar jet stream stays to the north Subtropical jet stream is more active (monsoon) Winter Season Polar jet stream more active over Wyoming Subtropical jet stream stays to the south Sometimes responsible for high wind events

Jet Stream Winds

Atmospheric Pressure Systems

Atmospheric Pressure Systems

Atmospheric Pressure Systems stable pressure system unstable pressure system

Atmospheric Pressure Systems clouds form clear skies stable unstable

Atmospheric Pressure Systems Not all high/low pressure systems are alike Depends on their structure and origination Cold core and warm core systems Example: High pressure in summer (warm, carries moisture) High pressure in winter (bitter cold, dry)

Frontal Systems & Cloud Formations

Frontal Systems & Cloud Formations

Frontal Systems & Cloud Formations

Frontal Systems & Cloud Formations

Frontal Systems & Cloud Formations

Frontal Systems & Cloud Formations

Frontal Systems & Cloud Formations

Snow Storms & Arctic Air Masses

Snow Storms & Arctic Air Masses In Wyoming, arctic air comes from two places: Northern Canada Siberia Often times, sea surface temperatures forewarn us of an arctic outbreak in Wyoming.

Snow Storms & Arctic Air Masses

Snow Storms & Arctic Air Masses

High Winds in Wyoming

WIND: A love-hate relationship

Wyoming Wind Strongest Winds: October – March Reason: Strong jet stream winds mix to surface Cold front moving through (pressure gradient) Chinook winds Gap winds (Bernoulli Effect) Strong gusts from thunderstorms

Wyoming Wind

Wyoming Wind

Wyoming Wind – Bernoulli’s Equation

Wyoming Wind – Hot Spots

Wyoming Wind Problems: Wind damage is very different than other states High sustained winds  truck blow-overs Increased slick roads Blowing snow  low visibility & slick roads Drifting snow on roads Decreases temperature of road surface Quite often leads to road closures

Wyoming Wind – Not Completely Bad! Strong winds CAN keep us warm in the winter Let me introduce…. The Chinook Wind Mountains High Plains

Precipitation Types & Understanding Radar

Fair Weather Thunderstorms & Supercells

Wyoming Thunderstorms Two Types Fair weather thunderstorms (non-severe) Supercell thunderstorms (severe) Distinguishing Factors Size of hail Rotation

Fair Weather Thunderstorms No rotation Need warm air, moisture Air lifts, forms cloud and grows larger Cold air aloft increases this Strong & gusty winds Heavy rain Small to moderate size hail

Supercells (Severe Thunderstorms) Rotating thunderstorm (mesocyclone) Need warm air, moisture, wind shear and trigger (front) Air lifts, cloud grows rapidly Cold air aloft increases this Strong or damaging winds Heavy rain Moderate to large size hail Possible tornado development

Tornados not a guarantee! Severe thunderstorms do not always produce a tornado Large hail (low visibility, ice on road) Heavy rain (low visibility, standing water on roads) Flash flooding (rising water, bridge damage) Damaging winds (trees or signs down)

How do Tornadoes Form?

Identifying Severe Thunderstorms On radar: look for “hook-echo”

Reading Maps & Finding Real-Time Weather Information

1 millibar (mb) = 1 hPa (hectopascal) Reading Maps 1 millibar (mb) = 1 hPa (hectopascal) Jet stream map – 300 mb (~30,000 ft) Pressure systems & frontal motion – 500 mb (~18,000 ft) Strong winds, moisture & snow temp – 700mb (~10,000 ft) Surface pressure & temperature – 850 mb (~5,000 ft) NCAR Real-Time Weather MesoWest Weather Data

Reading Surface Maps

A Little Bit About Numerical Weather Models

Numerical Weather Models Global Forecast System (GFS) North American Model (NAM) Weather Research and Forecasting Model (WRF) Rapid Update Cycle (RUC) Canadian Regional and Global Models European Center for Medium Range Weather Forecasting (ECMWF) Japanese Meteorological Agency (JMA)

A weather model is only as good as the data given to it. Where models struggle. Geography and terrain are very difficult for models to see Placement and track of weather systems over time Timing of weather system Typically struggle as the start of season-changes (winter/spring) A weather model is only as good as the data given to it.

Road Weather Forecasting A different beast.

Road Weather Forecasting First: Nail down atmospheric forecast for period Determine surface type and condition Important factors: Sky coverage (sunshine or clouds?) Wind speed and direction (warming/cooling surface) Sun angle (time of day for start of cooling) Rate of temperature decrease Type of precipitation Assume worst case scenario (no plows/treatment)

Road Temperature Model? Working on developing an in-house road temperature model called, METRo Using numerical weather model data Using real-time RWIS data