Anthony's Weather
FAQ's
Anthony's Weather
FAQ's
Questions.....I get questions, here are some that I get many times.
This is one of those cases where another station is using marketing hype to make you think something is bigger than it really is. It's sort of like telling a "fish story".
While some stations in the Midwest may buy their own special Doppler Radar for use on air, and in some cases they can do a better job than the taxpayer funded national network of NEXRAD Doppler radars, that isn't the case here. All of the TV stations in Chico and Redding use the same source of radar information, the National Weather Service NEXRAD doppler radars located at Beale Air Force Base KBAB, the NWS Sacramento Radar KSAC, the NWS Radar in Reno KRNO. and the NWS Radar in Eureka, KEKA See related FAQ What is NEXRAD Doppler?
We sometime use the individual site
displays, like at left, but more
often we use the Composite
Radar Display, which is a computer generated mosaic that combines the
pictures of all the radars in the area. Here's an example
for Northern California. All the TV stations in the Chico-Redding
area, including KHSL-TV, use the same NEXRAD radar data, funded by you the
taxpayer. It all comes down a satellite or internet feed to each TV station. Its
just presented differently on each station.
So whatever they want to call it, MegaDoppler, or Multi-Doppler, or "Super Dooper Swooper Doppler" its all from the same source here in the North Valley, the National Weather Service The difference is that at KHSL-TV 12, we simply call it "Doppler Radar" and leave it at that. Why call it something to make it look like "ours" when its really "yours", the taxpayer?
NEXRAD is an abbreviation that stands for: NEXt generation of weather RADars.
The project was conceived from research on Doppler Radar at the National Severe Storms Laboratory in Norman OK during the late 70's and 80's. I was part of the cooperative research then when I was a research assistant at Purdue University. It was learned that Doppler radar, which is capable of detecting MOTION in clouds in addition to reflection of radar echoes from rain droplets and snow, could also spot certain types of storm "signatures" in the motions. Certain types of signatures could indicate the possibility of a tornado formation as much as 30 minutes in advance of a touchdown!. Congress commissioned the NWS and FAA to build these new radars into a national network. The radar is officially known as the WSR-88D (Weather Search Radar- model 88D) It replaces several older models, including the WSR-3, the WSR-57, and the WSR-74. All of which I've worked on, and all of which had only limited ability to see details in storms.
The biggest improvement in the NEXRAD system over the older radars is that it combines computer image processing with a very sensitive Doppler signal differentiator. The result is that the WSR-88D can create graphical interpretations of storms "on the fly" and track the motions of storm cells using its computer database of signal returns. It can even predict the path of storms!
The UNISYS
corporation implemented the new NEXRAD network. In February 1996, I received
certification from Unisys on using the NIDS imagery produced by NEXRAD.
The University of Illinois has a good tutorial on NEXRAD Doppler radar.
Click here
to see it.
MIT also has a weather
radar lab with lots of info.
Doppler Radar Reflectivity Scale
All NEXRAD Doppler radars send microwave radiation as fast energy pulses into the air several times a second. The microwave pulses spread out at the speed of light into the atmosphere. When the pulse strikes something in the air, like a raindrop, a snowflake, dust particle or a mountain range, some of the microwave signal is reflected back to the radar. This is called an echo.
You can experience this yourself by standing on a rim of a canyon and shouting across the valley. The sound of your voice reflecting back is the echo, just like a radar "hears" its microwave pulse being reflected back.
NEXRAD measures the amount of the echo received back at the radar. It also measures the amount of time it takes for the signal to bounce back, this is used to determine the RANGE i.e. the distance away. Like sound, the strength of the echo is measured in units of decibels (DBZ). A higher decibels value indicates a larger object.
In thunderstorms, large raindrops and hail produce high
DBZ values, like usually over 60 DBZ. Usually decibel values greater than 15-20DBZ indicate areas where
very light rain or snow is reaching the ground. Often in the winter, you'll see
lots of "blue tones" in the radar picture used on KHSL. This is
usually light rain or snow. In the spring and summer, the blue tones are often
replaced by the stronger reflections from thunderstorm cells, giving greens,
yellows, and reds.
The
NEXRAD Doppler radar can run in two different setup modes, clear air, or precipitation.
The picture at the left shows the NEXRAD Doppler image in "clear air mode". Notice the brown and bluish specks near the center of the picture. This is often called "ground clutter".
When the NEXRAD operator sees that there is no precipitation inside the radar's maximum range (about 140 miles), the radar system can be switched into "clear air" mode. When running in "clear air" mode the sensitivity of the NEXRAD radar is tremendous..
Click for a larger picture
Ground clutter comes from echoes generated by terrain, bugs, dust, fog, smoke,
swarms of birds, even swarms of bees!
The NEXRAD can detect echoes from objects so small they shown as negative
numbers (such as -10 DBZ). This is often the source of the "ground
clutter" even if its not false reflections from local terrain. In most
cases when we show the NEXRAD picture on TV, we remove the ground clutter so as
to not confuse you. Often we don't show it at all when the weather is clear,
since there's nothing to show.
You can thank the British for this one...
GMT, or Greenwich Mean Time, is the time zone that spans the prime meridian, which just happens to pass thought the very center of the dome of the Royal Observatory at Greenwich, England. The became the "base" time for the world because of the British Navy, which had a need for accurate navigation charts to sail the seas. To create these charts, they needed astronomy, and accurate clock. A location of a ship at sea could be determined by an astronomical measurement through a sextant, and an accurate time reading from the ships chronometer. The navigator would then refer to a book of tables published by the Royal Observatory, and figure out his position. Since the British ruled the seas, they got to set the time "starting point" on which the tables were based (a predecessor to our modern time zones, but that's another story).
It became known as Greenwich Mean Time
or GMT for short. Due to the location of the observatory.
GMT is the time standard
used in all global meteorology (since the world is one weather system, we had to
pick a base time, just like the Navy). You might also see GMT listed
as Z, Zulu time, or UTC, short for Universal Coordinated
Time.
To obtain U.S. civil time from UTC, GMT or Zulu Time, use
the following table.
Or use the TIMEZONE
CONVERTER
| To obtain | Atlantic Daylight Time | subtract 3 hours from UTC |
| Atlantic Standard Time | subtract 4 hours from UTC | |
| Eastern Daylight Time | subtract 4 hours from UTC | |
| Eastern Standard Time | subtract 5 hours from UTC | |
| Central Daylight Time | subtract 5 hours from UTC | |
| Central Standard Time | subtract 6 hours from UTC | |
| Mountain Daylight Time | subtract 6 hours from UTC | |
| Mountain Standard Time | subtract 7 hours from UTC | |
| Pacific Daylight Time | subtract 7 hours from UTC | |
| Pacific Standard Time | subtract 8 hours from UTC | |
| Alaska Daylight Time | subtract 8 hours from UTC | |
| Alaska Standard Time | subtract 9 hours from UTC | |
| Hawaii-Aleutian Daylight Time | subtract 9 hours from UTC | |
| Hawaii-Aleutian Standard Time | subtract 10 hours from UTC | |
| Samoa Standard Time | subtract 11 hours from UTC |
Thus, 11:00 UTC is the same as 5:00 CST. When converting zone time to or from UTC, dates must be properly taken into account. For example, 10 March at 02:00 UTC is the same as 9 March at 21:00 EST. The table can also be used to determine the difference between the time observed in any two zones. For example, the table shows that Eastern Standard Time is three hours "ahead" of Pacific Standard Time.
The US Naval Observatory in Washington DC has everything you ever wanted to know about time, sunrises, moon phases, etc.
The National Weather Service provides almost all of the data on these pages in one way or another. Lately, since Jan 1st, they've been REALLY falling down on the job, mainly on the internet. Its all part of their technology restructuring, mandated by congress. The "faster, better, cheaper" mindset. So, if the forecast is old, links to weather service data stop working, etc. please don't blame me or KHSL-TV, write your congressman or senator and ask that the NWS get better funding. After all, its the one free government service that is used by everyone, every day, and congress just loves to squeeze it for other more important "pork barrel" projects.
In the meantime, we'll do what we can to stay on top of things and to provide alternates.
I get this question about 2-3 times a week. The simple answer is, we can't fit them all on and still have the map readable on TV. KHSL-TV covers a geographic area about the size of the state of Ohio (see our coverage map). There are over a hundred small towns in this coverage area. It is impossible to put them all on, so I have to make choices based on population size and something I call the "destination factor" i.e. do people drive through there a lot or visit there (like Chester for example). Another factor is weather data, if none is available for a town, I can't report on it. Please, don't send me email on this, I can't make changes to the map no matter how much you lobby for your town...I'm sorry, that's the way it must be.
We aren't trying to ignore your town, but we can only do so much in a three minute weather show.
There are several ways:
There are several reasons:
The main reason is cheap home thermometers that are improperly mounted or improperly
sheltered from stray infra-red radiation. Often, people mount thermometers to the side of
their home, or have them in direct sun, or have them near an asphalt or concrete driveway
which reflects infra-red heat. All of these factors can cause a cheap home thermometer
(like you buy at Wal-Mart) to read as much as 10 degrees high! When I
take the temperature at KHSL-TV, the digital weather station I use has a radiation shield.
(See below)
Infra-red Radiation shield used at KHSL-TV
It is used to prevent sunlight, infra-red, or other factors from biasing the temperature reading. That's why you sometime see these little "white chicken coops" called Stevenson Screens at National Weather Service and CDF offices where there are outside weather stations. In 1990 during a heat wave, I did an extended weather report asking people to call in their home temperatures from around town in Chico and in Redding. When I presented them on the air, we had differences as much as thirteen degrees from one end of town to the other! So you can see what I mean.
Another reason is local terrain and local vegetation. If you live an area where there is a lot of asphalt, concrete, buildings, or roads, and very little vegetation or trees, you will likely have much higher daytime temperatures, especially in the summer. Also, the terrain and elevation can affect temperature significantly, even over a short distance.
As for rain, it is highly variable by nature. Thunderstorms especially so. They can often leave an inch of rain in an area just a mile or so wide, and leave none on either side! In winter, the biggest reason is terrain and elevation. Paradise and Magalia are the worst problem cities for this. The variance in elevations in town can cause temperatures and rainfall to be far different over even a mile! Another problem is placement of some of the cheap rain gages you can buy at the five and dime....I've seen some people put them in their backyard where their tree branches drip into them! Is it any wonder I get calls telling me I'm all wet in my rainfall totals?
The bottom line: No matter what is reported, there will always be a different temperature or rainfall somewhere in your town, or at your own home. Just use what we report as a guide, knowing that what we report at Channel 12 was measured using accurate and properly placed and shielded weather instruments
There are several reasons:
Answer: Yes or No...depending on the weather!
Please folks, if you meet me in public, just say "hello". I figure I've been asked this question 1,237,486 times during my career, so its time for a new question. How about- "how's the weather Anthony"?
