Shaorong Liao // Julio Garcia

Notes for Meteorology 356

September 10, 2004

 

Readings:

Williams Up through Page 36; 63-71

 

Information covered:

 

-       Reviewed information on satellite imagery with emphasis on Infrared satellite (IR) images.

-       Covered information on severe thunderstorms and Hurricanes.

-       Discussed seasonal shift

-       Looked at surface weather maps. Determined dewpoint temperatures and relative humidity for various locations with the use of weather symbols.

 

 

Satellite images:

 

  1. IR satellites detect energy emitted by molecules from objects at different temperatures. White areas on IR images represent cold regions that are intimately related to cumulonimbus clouds (tall and thick clouds with temperatures ranging from -60C to -70C at their tops at an elevation of 60,000-70,000 ft) whereas black areas typically represent warm temperature sectors (16C) that are representative of fog (stratus) especially in the California coast.
  2. IR satellite images are useful tools to determine where severe weather is happening.

 

 

Severe thunderstorms:

 

  1. Severe thunderstorms must include:

     

Sustained surface winds in excess of 57 mph (50 knots) or more and hail 3/4Óin diameter.

                       

Precipitation is not included in the definition of severe thunderstorms because it is present in all thunderstorms.

 

  1. Hurricanes are associated with severe thunderstorms:

 

A.  They are strong tropical cyclones with sustained surface winds in excess of 74 mph.

B.  Fueled by warm temperatures and moisture

 

 

Seasonal Shift:

 

We looked at temperatures in Canada using weather maps and identified a cooling temperature pattern emerging during this time of the year.   This is significant important as this trend will affect our region in the near future. 

 

The concepts of equinox and solstice were discussed:

 

Equinox refers to the time at which the sun passes directly above the equator and we have equal hours of daylight and night. This happens on March 21st and September 21st.

 

Solstice is the time at which the sun is farthest north or south of the Equator. In the northern hemisphere, the summer solstice falls on 21 June and the winter solstice on 21 December.

 

Dewpoint and Relative Humidity:

 

Also discussed in early lectures, these two concepts help us analyze the amount of water vapor in the atmosphere.

 

Dewpoint Temperature refers to the temperature the air must be cooled down for water vapor to condense.

Relative Humidity is related to the difference between the Dewpoint temperature and actual temperature.  The smaller the difference between these two values, the greater the relative humidity.

Relative humidity is also defined as the ratio of the mixing ratio to the saturation mixing ratio.

Water vapor mostly comes from the oceans. During this time of the year, we find low values of Dewpoint temperatures along the pacific coast. In the East coast, however, Dewpoint temperatures reach 70~80F values which mean that more water vapor is present and thus the potential for severe weather.