IntroductionBasic dynamics

Anatomy of a stormForecasts

The Jet Stream, high and low pressure systemsand fronts; Understanding the weather

Joe LaCasceDept. of Geosciences

January 25, 2010

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Table of contents

1 Introduction

2 Basic dynamicsGeostrophic balanceHydrostatic balanceThermal wind balanceThe Jet Stream

3 Anatomy of a stormStorm formationFronts

4 Forecasts

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Hurricane

Figure: Hurricane Ivan, Sept. 2004

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Polar low

Figure: A polar low over the Barents Sea, 27 Feb., 1987

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Hurricane

Figure: Hurricane Katrina, Aug. 2005

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Flooding

Figure: Coastal flooding, England

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Snow

Figure: Chicago, 2009

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

8 Jan., 2010; www.yr.no

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

8 Jan., 2010; www.yr.no

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Geostrophic balanceHydrostatic balanceThermal wind balanceThe Jet Stream

Dynamics

Basic balances:

Geostrophic balance

Hydrostatic balance

Thermal wind balance

Phenomena:

Pressure systems

Jet Stream

Fronts and precipitation

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Geostrophic balanceHydrostatic balanceThermal wind balanceThe Jet Stream

Rotation

veltotal = velperson + velrotation

so:velperson = veltotal − velrotation

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Geostrophic balanceHydrostatic balanceThermal wind balanceThe Jet Stream

Deflection

Figure: Deflection to the right in the Northern Hemisphere

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Geostrophic balanceHydrostatic balanceThermal wind balanceThe Jet Stream

Low pressure without rotation

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Geostrophic balanceHydrostatic balanceThermal wind balanceThe Jet Stream

Low pressure with rotation

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Geostrophic balanceHydrostatic balanceThermal wind balanceThe Jet Stream

High pressure with rotation

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Geostrophic balanceHydrostatic balanceThermal wind balanceThe Jet Stream

Geostrophic balance

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Geostrophic balanceHydrostatic balanceThermal wind balanceThe Jet Stream

Hurricane

Figure: Hurricane Ivan

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Geostrophic balanceHydrostatic balanceThermal wind balanceThe Jet Stream

Hydrostatic balance

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Geostrophic balanceHydrostatic balanceThermal wind balanceThe Jet Stream

Thermal wind

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Geostrophic balanceHydrostatic balanceThermal wind balanceThe Jet Stream

Jet stream

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Geostrophic balanceHydrostatic balanceThermal wind balanceThe Jet Stream

Jet stream

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Geostrophic balanceHydrostatic balanceThermal wind balanceThe Jet Stream

Jet stream

Figure: Wallace and Hobbs, 2006

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Geostrophic balanceHydrostatic balanceThermal wind balanceThe Jet Stream

Instability and turbulence

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Storm formationFronts

Jet stream

Figure: Wallace and Hobbs, 2006

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Storm formationFronts

Storm formation

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Storm formationFronts

Storm formation

Figure: Wallace and Hobbs, 2006

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Storm formationFronts

Fronts

Warm/cold fronts

Vertical motion

→ precipitation

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

Storm formationFronts

Squall

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

8 Jan., 2010; www.yr.no

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

8 Jan., 2010; UK Met Office

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

9 Jan., 2010; UK Met Office

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather

IntroductionBasic dynamics

Anatomy of a stormForecasts

25 Jan., 2010; UK Met Office

Joe LaCasce Dept. of Geosciences The Jet Stream, high and low pressure systems and fronts; Understanding the weather