Notes for Meteorology 356

September 2, 2005

Written by Heather Williamson and Ramzy Ayyad

 

Assignments:

Some of the books are now available in the reserved book section of the library for 2-hour checkout.  No new reading assigned

 

Housekeeping:

Received Current Weather Conditions handout (Weather Map Symbols link on website)

Received Meteogram handout (Mobile Meteogram link on website)

 

Hurricane Katrina

A late 1990’s article from Scientific America: brief summary by Prof. Monteverde.  The article forecasted that a major hurricane hitting New Orleans was imminent, and that New Orleans is essentially a sitting duck due to is location and elevation.  The article forecasted 20 feet of water cover; and the economic suffering in the hurricanes wake effecting seafood, gasoline/oil, and more.

 

Weather Map Review (using Katrina)

Net Gram / Meteogram  (Mobile Meteogram link found on website)

24-Hour time span weather map displaying hourly weather observations over a 24-hour time span for a specific weather station. The map is from the Mobile weather observation station.

§       0500Z 8/29/05 through 0500Z 8/30/05:  10pm 8/28/05 – 10pm 8/29/05 PDT

§       Instead of a weather observation for a specific time; the chart follows a 24-hour interval; tracking the hourly observations.

§       We are responsible to know:  the date and time of the given map (in our appropriate time zone); the wind speed and direction at the weather station; the current temperature; and present weather symbol.

§       Learned the current weather hurricane symbol refer to the link and/or handout for all symbols

§       We found the following information from the map:

§       0700Z on 8/29/05, the wind direction was NE with a sustained speed of 20

§       1400Z on 8/29/05, the wind direction was ESE with sustained speed of 40

§       WGST on the map shows the gust wind speed at each interval

Š      The gust wind speed at 1400Z were 60

§       The map showed that Mobile did not experience the strongest winds of Katrina.  They missed the stronger winds because they were slightly east

§       We observed the symbol for wind speed of 50 (the flag), which is rare

§       Over the 24 intervals we observed the counter-clockwise shifting of the wind direction – like a running story of the storm.  We also observed the differences in wind speed, and current weather.

§       Temperature:  The top graph tracks the temperature over the time period with two lines.  The top line reflects the current temperature, and the bottom line reflects the dew point. 

§       We observed that it was warm throughout the 24-hours, from the upper 70’s to low 80’s, which is a tropical storm characteristic.

§       WX on the map is the present weather plot for the intervals – again refer to the link for a description of all the present weather symbols.

§       Prec:  the precipitation over each six hour period.  Instead of on the hour, the precipitation amount is tracked over six hours.  Adding up the four observations yields the total precipitation for the 24-hour period.  On this map, the total precipitation was around 4 inches.

§       The smallest unit reported on a map is 1/100 of an inch, or .01 inches.

§       On the same 24-hour time span, New Orleans received 16 inches of precipitation – which is roughly the rainfall in Los Angeles in one year.

 

As forecasted, the most damage from Katrina was caused by the storm surge.

§       Had there been more rain, much more damage from flooding would have occurred. 

§       Typically a hurricane has uniform rainfall in all directions (the same amount falls in the north, south, east and west of the storm).  However, the rainfall was slightly less severe due to dry air that prevented heavy rain.

 

Hurricane Strikes Graph (Hurricane Strikes link found on website)

§       In this class it will be important to study some weather statistics.  We will do this to learn what allows for the definition of “remarkable” for a storm or weather event. 

§       The graph tracks two things:

(i)    Blue Line:  total number of Atlantic formed hurricanes hitting the United States from 1851 to present – shown by decade

(ii)  Red Line:  number of those hurricanes from the Atlantic that were severe

§       The graph shows the natural cycle of Atlantic hurricanes for the last 150 years

§       Although the graph does not support this, Prof. Monteverde predicts (his own opinion), that more strong hurricanes like Katrina are likely to occur in the future (our life time and our children’s).

§       We have to be careful using weather statistics, because of their ability to be manipulated to support one specific opinion.

 

Effects from Katrina

A number of Universities in Louisiana are affected by Katrina.  The University of New Orleans is closed for at least this semester, and possibly more in the future, which has a direct effect on students.  Several university systems, including the Cal State University system (including SFSU), have offered to house and educate any of the effected students. 

 

There is also an interesting human-interest account of the hurricane that can be viewed on the University of Tulane website.  It is a worthwhile read for those interested in checking out the website. 

 

Satellite Images

We looked at detailed satellite imagery of California fog.  The link to the image is on the class website (NOAA link).

The satellite maps are used by meteorologists to observe among other things, clouds and fog.

Resolution abbreviated “res” on the map yielding 1 km (½ mile) is very detailed.

 

Geography of California

Meteorologist have a systematic way of deciding North, Central, and Southern California, which varies slightly from common thought. Northern California is the mid point of the Golden Gate Bridge to the mid point of the Carqiunez Bridge (Vallejo).  Southern California starts at Point Conception, Ca. Central California would be considered San Francisco.

 

Topography and California Weather

(Image of California topography: Annotated Topography of California link on website)

 

Mountain range information is important in meteorology because the mountain ranges affect wind direction.  In other words, they “channel” wind around them, which affects variation in rainfall for southern and northern California. In Northern California and the Bay Area the Sierra Nevada, the Cascade mountain range,  Mount Lassen , and Mount Shasta (active volcano), trend northwest to southeast. This group of ranges is referred to as the “coast and coastal ranges.” In Southern California, the Transverse ranges trend differently and are located behind Los Angeles and two major mountains there are The San Gabriel and the San Bernardino ranges.  They, unlike northern California ranges, trend west to east.

 

Fog in California

The topography of California also affects fog. Where there are fewer mountains there is more fog because the mountains block the fog from moving inland.  This observation can be easily studied from the high-resolution satellite image provided on the class website.

 

Important Geographic Place Names:

Should be able to locate these places on a map of California: Eureka, San Diego, San Francisco, and Santa Maria.

 

Conceptual Temperature and Condensation Information

Gas molecules, if forced to together, form a liquid.  Water vapor molecules, which are gaseous, do this naturally in our atmosphere.  This molecular behavior is known as condensation.  Also high humidity means there is a high amount of water molecules in the air.

 

Definition

Condensation- The connection of certain objects to form a liquid