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.

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

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

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

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

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

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

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

Introduction Scales - horizontal length vs. vertical length scale

Introduction Vertical structure of the atmosphere

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

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

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

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

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

overshooting Anvil

Overshooting Anvil

Stratiform cloud if any NO LFC LCL