Thermometer accuracy

Lee Poulsen
Wed, 16 Jan 2013 18:12:44 PST
You should test out the accuracy of the precise location prediction, especially on the coldest nights of the winter (and hottest days of the summer). NOAA uses some kind of algorithm to produce these very precise location-dependent predictions but their measurement locations that were used in the making of the algorithms (probably along with altitude data) are much coarser. I.e., there are not that many weather measuring locations and they're relatively much more spread out than what these predictions might cause you to believe. I checked a string of them all along the foothills of the San Gabriel mountain range along the route a co-worker of mine drives in to work early each morning, especially the night before last when we had our coldest morning. Then he noted the outside temperature his car measured as he drove in to work. His numbers corresponded much better with what I have been told over the years are the microclimates along that route than did the NOAA predictions. The lows he measured varied between 29°F and 37°F over altitudes that varied between about 800 and 1400 feet above sea level. However, some of the warmest spots along the route were at the higher altitudes; the entire route has shallow slopes along the foothills with no basin-like areas that might capture and hold a pool of colder air. NOAA predicted temperatures from 30° to 33° along that same route. I bet their algorithms work much better in places such as the eastern 2/3 of Texas where there is almost no variable topography other than the smooth and very gradual descent towards sea level.

Also keep in mind that the current conditions part of the page are the temperature, humidity, and winds measured at the NOAA affiliated weather monitoring station closest to the geographic location you picked (which may be miles away). And they're only measured once per hour. (The time of measurement is usually given in small font.)

[The reason I did this is that I've been told by several people over the years that there are certain spots along the foothills that are true banana belts where it rarely gets below freezing even in the cold winters we occasionally get. There was a guy who used to live along a stretch U.S. highway 101 that that hugged the beach and was backed by very tall mountains and he had the only commercial banana plantation on the west coast of the U.S. It was buried in a really bad mudslide one winter. His research indicated that he might be able to plant a similar plantation in one of these true banana belt microclimates along the foothills of the mountains in my area. I'd love to buy a house in one of these areas if I could locate one and I could afford it. Then I would worry much less about my more tender plants!]

--Lee Poulsen
Pasadena, California, USA - USDA Zone 10a
Latitude 34°N, Altitude 1150 ft/350 m

On Jan 16, 2013, at 5:03 PM, jonathan wrote:

> Leo said: "...  one may click quite precisely on one's location on a map on the right side of the page for a more accurate prediction..."
>> I've been using the NOAA site for some years but always had to make adjustments since my postal zip code referred to a town several miles away.  I didn't realize I could pinpoint my location. It's now pinpointed and I have my accurate predictions.  Leo, thank you!
>> Jonathan Lubar
>> Alachua, Florida z8b

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