WEATHER CORNER

BY JAN NULL
Special to the Mercury News

Q. The high temperatures reported for San Jose for those three hot days last month seemed incorrect and quite different from those I hear on the radio. Since the readings are for 24 hours and taken in the late afternoon, could they be reporting the previous day's reading? Besides that, it seems like the temperature reported at San Jose Airport is too high regardless of the timing issue.
Mike Voss - San Jose 

A. Your supposition that they are ``left over'' from the previous day is probably correct. This happens when the previous day's high falls late in the afternoon and the thermometer is not reset the next morning. This, however, is only part of what seems to be a multifaceted problem with
temperatures in San Jose.

One point of confusion is that the ``official'' downtown San Jose daily high and low readings are taken at the Civic Center near North First and Hedding streets, while the hourly readings that you hear on the radio or on television are from San Jose International Airport. I agree with your
observation (and that of many others in the last five years) that airport readings seem too warm because the airport is closer to the bay.

A final complication is that some radio and television stations have their own temperature sources.

Q. I have been recording high and low temperatures in the Barron Park area of Palo Alto since 1989. My records show that the average high in July was 5.4 degrees below the average for the years 1989 through 1999.  Is the weather in San Jose so different?  Thomas Gale Moore,
Hoover Institution, Stanford

A.  You're referring to the fact that two weeks ago I indicated July temperatures in San Jose were 1.8 degrees below the normal 82-degree highs for the month. Given the strong push of cool marine air we get, I would expect greater differences up the Peninsula -- and a drop of 5.4 degrees for Palo Alto does not seem unusual. Another consideration is the normal I used was
based on a 50-year average and yours was 10 years. 

This is another great example of the significant differences in Bay Area microclimates.

Q.  The National Weather Service issues flash flood, tornado, severe thunderstorm, tropical storm and hurricane watches and warnings. But it does not issue lightning watches and warnings, despite statistics showing lightning kills more people in this country per year than hurricanes and tornadoes. Why won't the NWS include watches and warnings for lightning? Paul Locher - Santa Clara 

A. I think most people know that thunderstorms produce lightning and that lightning can be deadly. Plus, there are thousands of thunderstorms each year, and fatalities are quite low. To issue some kind of warning for every storm would probably inundate the public and the media, quickly
reducing its intended impact.

There are an average of 81 lightning deaths in the United States per year, compared with 69 from tornadoes and 24 from hurricanes. The United States' two biggest weather killers are floods (140 deaths) and extreme heat (131).

For excellent information about lightning and lightning safety, call up www.nws.noaa.gov/er/mhx/lightnt.htm .

Jan Null, founder of Golden Gate Weather Services, is a retired lead forecaster with the National Weather Service. Send questions to Weather Corner, San Jose Mercury News, 750 Ridder Park Drive, San Jose, Calif. 95190. You also can telephone and fax them at (510) 657-2246 or e-mail them weathercorner@ggweather.com.