Metr 302.01 Class Notes

Nate Henke

Matt Brown

Writing Assignment #1:

-The average grade on the writing assignment is (As of 4/2) 88/100.

-A sheet is stapled to the back of the returned writing assignments that reiterates the assignment's grading criteria.

-2 people in the class received grades of 100/100 on the writing assignment.

NOVA 'Super Twister' episode:

A. Basic information:

-The Fujita Scale (Measures the intensity of tornadoes) is defined based on damage. So, to rate a tornado for research, it must inflict damage. (This fact is implied in the film during the segment that discusses Oklahoma City.)

-The tornado in the episode measured F5 on the Fujita Scale.

(Displayed 300 MPH winds.)

-A 'turtle' is a metal casing that contains a barometer. It is used to gauge air pressure at the center of a tornado.

(A barometer is a device used to measure air pressure.)

B. Inconsistencies in the episode:

-Lou Wicker's computer simulations attempt to show how tornadoes form. However, the computer simulations do not accurately depict how tornadoes are produced in nature. Wicker's technique for explaining tornado formation is considered a scientific 'blind alley'; it was abandoned 20 yr. ago.

-The video implies that a 12 minute warning is 'not good enough' a warning of an approaching tornado. Actually, 12 minutes is an excellent warning time.

Brazilian Hurricane:

A. Basic information:

-The Brazilian Hurricane discussed in class Mon. was proven to be a hurricane

(Possibly a Cat. 2 hurricane.) because it has a warm core.

-The storm's eye indicates that winds produced by the hurricane moved at speeds over 75 mph.

-The storm formed in the eastern Atlantic Ocean and moved due west.

-It is unknown why the Brazilian authorities denied it was a hurricane.

-Currently, there is controversy over whether or not the Brazilian authorities suppressed information supporting the assertion that the storm was a hurricane.

-U.S. hurricane meteorologists attempted to warn Brazil of the hurricane, but were stonewalled.

B. Visible Satellite Image of Brazilian Hurricane displays the following hurricane traits:

-Clockwise cloud motion.

-Spiral arms.

-Well defined eye.

C. Sea Surface Temperature Patterns for the day of the storm:

-Were measured in low 80's.

-If storm is moving to warmer ocean temperatures, it will intensify; this is the Southern Hemisphere version of the 'gyres'.

Homework Assignment #2:

-The colored bars on the storm tracks designate areas of different storm intensity.

How Nature Forms Low Pressure Areas:

A. Basic information:

-We approach the question of how nature forms low pressure areas by comparing a stack of bricks to a stack of 'atmospheric bricks' (Air parcels).

-Removing bricks from the top of the stack of 'atmospheric bricks', an action referred to as 'spreading apart' the atmospheric bricks, produces air pressure changes.

-Divergence: The motions that result in neighboring air parcels of a given level 'spreading apart'.

-Spreading apart of atmospheric bricks is theoretical example of divergence. It produces LOW PRESSURE AREAS.

-Convergence is the stacking (As opposed to removal of) of atmospheric bricks. It produces HIGH PRESSURE AREAS.

B. Rules governing How Nature Forms Low Pressure Areas:

-RULE: If you have unequal pressures in two areas, air blows from high to low pressure.

-Step 1: Divergence occurs in the upper atmosphere.

-Step 2: Air rushes upward to replace air moving outwards. (Because nature abhors vacuums.)

-(Steps 1 and 2 occur simultaneously.)

-Step 3: A LOW PRESSURE AREA forms at the surface.

-Step 4: Air rushes into the low-pressure area at the surface.

-Step 5: Friction slows this inrush of air so that the amount of air entering at the bottom does not balance the amount of air diverging at the top.

-RULE: Divergence aloft is associated w. surface low-pressure area development.

Bottom Line: Divergence is the main reason for surface pressure systems.

C: How does the Upper Tropospheric Divergence occur?

-Upper Tropospheric Divergence occurs in two main ways.

-Refer to the Warm Core Pressure Systems link.

Bottom Line: Review Thermal and Dynamic Pressure Systems.

D: Differential heating and cooling creates a low-pressure area at the ground. Its official name: THERMAL LOW. (A synonym for this is 'warm core'.

E: Convection is illustrated:

-Convection: Comes from English word, "To convey".

-Is important to: Meteorology, Geology, and Oceanography.

-Rising air motion produces clouds and precipitation.

-Sinking air motion does not produce clouds and precipitation.

F: Subsidence (Sinking air motion):

-Subsidence: Comes from English word, "To subside."

-Polar regions do not have much precipitation because they receive subsidence. (Remember that sinking motion does not produce PPT.)

The Point of this Class:

-To discuss SURFACE PRESSURE SYSTEMS.

Assignment:

-Review 'Main Reason for Development of Surface Pressure Systems' link.