ATM OCN (Meteorology) 100 - Lecture 3

MIDLATITUDE WEATHER SYSTEMS
PART II: THE EXTRATROPICAL CYCLONE

Lecture 3: Fall 1997

Lectures #27 & 28 Scheduled for:

5 NOV 1997 (W) and 7 NOV 1997 (F)

Recommended Readings from Moran and Morgan (1997):

pages 261-272; 272-276; 391-394.

Objectives:

• To identify regions of cyclogenesis.
• To identify the relative size and characteristics of an extratropical cyclone.
• To describe briefly the contribution made to meteorology by J. Bjerknes and his associates in the Norwegian School with the polar front cyclone model.
• To locate and describe the general cloud and precipitation pattern associated with a model extratropical cyclone.
• To describe the temperature-field distribution in a model extratropical cyclone.
• To locate and discuss the wind field surrounding a model extratropical cyclone.
• To locate the regions of greatest pressure change with respect to time in a migratory extratropical cyclone.
• To outline the sequence of stages in the life cycle of a migrating midlatitude wave cyclone.
• To distinguish between warm frontal weather and cold frontal weather and their associated weather sequences during frontal passage.
• To locate the position and forecast the movement of an extratropical storm by interpreting the sequence of wind direction, pressure change, temperature change and cloud/precipitation type at a station.
• To describe the weather sequences (i.e., changes in wind direction, pressure tendency, cloud type and coverage, precipitation and temperature) when the center of a wave cyclone passes to the north of an observer.
• To define forecasting terms used to describe winter storms.

Outline:

A. INTRODUCTION

• Practical Problems
• Historical Perspective

B. THE NORWEGIAN or POLAR FRONT (WAVE CYCLONE) MODEL

• Designation of Extratropical Cyclones
• Distinguishing Features of a Mature Polar Front Cyclone

C. OBSERVED WEATHER FEATURES SURROUNDING THE CYCLONE

• Fronts
• Pressure Fields & Pressure Tendency Fields
• Wind Fields
• Temperature Fields
• Cloud Fields
• Precipitation & Other Significant "Weather" Events

D. LIFE CYCLE OF AN EXTRATROPICAL WAVE CYCLONE -
THE OCCLUSION PROCESS

• Storm Formation (or cyclogenesis)
• Early Developing Stage
• Mature Stage
• Occluding Stage
• Occluded Stage

E. OTHER FEATURES OF THE POLAR FRONT CYCLONE MODEL

• Cyclone Families
• Energetics of Cyclogenesis - The Driving Force
• Limitations and Complications of the Polar Front Model

F. MOVEMENTS OF EXTRATROPICAL WAVE CYCLONES

• General Movements
• Principal Cyclone Tracks over North America
• Time Sequences of Weather Events - Single Point Forecasting

G. WINTER STORMS

• Definitions
• Winter Weather Conditions
• Public Information Dissemination and Public Safety Precautions

Links to Other References:

• For Educational Resources
  • Winter Storm lesson in the The Severe Weather Information Kit (SWIK) from Univ. of Nebraska at Lincoln.

Last revision 30 November 1997

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