1. Introduction 1. Why forecasting is important?
Safety, outdoor activity, work, agriculture, etc.
2. What specific factors, parameters, or variables
are important to a forecast?
Data communication (leading time)
(some need to send out in time, e.g., flash flood)
When, where, how severe, how much precipitation, how cold/hot, etc.

2. Introduction Problems of Forecasting ? 1. Numerical modeling
Model spatial resolutions limited to computer resources
Parameterizations limited to our understanding of weather
Boundary conditions of mesoscale models limited to available
global data (every 6h)
Initial conditions limited to observations.
2. Failure of communications

3. Introduction What can we do to improve forecasting?
Backup plan if communication fails
Improve numerical model
- improve our understanding of weather: better physics parameterization
- improve numerical schemes
Improve computational power
– higher resolution or more forecast members
Improve initial conditions, observations, and weather analysis.
Our focus in this class

4. Introduction Scales - time and space
Microscale – up to few km or tens km
Mesoscale – tens km to hundred or 1000 km
Macroscale – above 1000 km

5. Introduction Scales - time and space Microscale Supercell (~ 20 km)
Tornado (~ 100 m – 1km)
Supercell (~ 20 km)

6. Hurricane (multiscale)
Introduction
Scales - time and space
Mesoscale
Cold front (~100 km)
Hurricane (multiscale)

7. Rossby waves (~ several 1000 km)
Introduction
Scales - time and space
Macroscale
Cyclone (~ 1000 km)
Rossby waves (~ several 1000 km)

8. Introduction Weather system scales –
time scale vs. horizontal length scale

9. Introduction
Scales - horizontal length vs. vertical length scale

10. Introduction
Vertical structure of the atmosphere

11. Introduction Resolutions - time: How frequent? space: How fine/coarse?

12. Review of Skew-T Log-P diagram
Temperature
Potential
Temperature or
Dry adiabat
Moist adiabat q q
Water vapor
mixing ratio

13. Review of Skew-T Log-P diagram
Potential
Temperature or
Dry adiabat
Moist adiabat T =
Poisson equ
at 1000 mb

14. Review of Skew-T Log-P diagram
lifting condensation
level (LCL) Td T
T (skewed)

15. Level of Free Convection
overshooting
cirrus anvil
cumulonimbus EL
Equilibrium level p
CAPE
LFC
Level of Free Convection
LCL
Lifting Condensation Level
T (skewed)

16. overshooting
Anvil

17. Overshooting
Anvil

18. Stratiform cloud if any
NO LFC
LCL