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

2. 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

3. Okay, go ahead…now’s your chance!

4. Welcome to Earth.

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

6. Earth Circulations & Jet Stream

7. Earth Circulations & Jet Stream

8. Earth Circulations & Jet Stream

9. 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

10. Jet Stream Winds

11. Atmospheric Pressure Systems

12. Atmospheric Pressure Systems

13. Atmospheric Pressure Systems
stable
pressure
system
unstable
pressure
system

14. Atmospheric Pressure Systems
clouds
form
clear
skies
stable
unstable

15. 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)

16. Frontal Systems & Cloud Formations

17. Frontal Systems & Cloud Formations

18. Frontal Systems & Cloud Formations

19. Frontal Systems & Cloud Formations

20. Frontal Systems & Cloud Formations

21. Frontal Systems & Cloud Formations

22. Frontal Systems & Cloud Formations

23. Snow Storms & Arctic Air Masses

24. 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.

25. Snow Storms & Arctic Air Masses

26. Snow Storms & Arctic Air Masses

27. High Winds in Wyoming

28. WIND: A love-hate relationship

29. 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

31. Wyoming Wind

32. Wyoming Wind

33. Wyoming Wind – Bernoulli’s Equation

34. Wyoming Wind – Hot Spots

35. 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

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

37. Precipitation Types & Understanding Radar

38. Fair Weather Thunderstorms & Supercells

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

40. 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

41. 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

42. 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)

43. How do Tornadoes Form?

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

45. Reading Maps & Finding Real-Time Weather Information

46. 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

47. Reading Surface Maps

48. A Little Bit About Numerical Weather Models

49. 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)

51. 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.

52. Road Weather Forecasting A different beast.

53. 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)

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