Rochelle (IL) - On January 17, 2009, the National Weather Service threw out a claim that Rochelle, IL had the coldest temperature ever recorded in the state (on January 16, 2009) at -38 degrees Fahrenheit. They cite AWOS temperature recording equipment as being less reliable than other nearby ASOS equipment, which did not show a record cold temperature.
A "Public Information Statement" was originally posted on www.weather.gov, but has since been altered. Its original contents are still observable via a Google search for some keywords, but the current Google cached document includes a snapshot taken today (January 20, 2009) where the following text has since been removed (as the actual link also shows).
The original report appears below and was posted in the article linked at the bottom of this story. It is a public statement by the National Weather Service regarding the record cold temperature claim which reads in part:
PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE CHICAGO IL
432 PM CST FRI JAN 16 2009
...REGARDING ROCHELLE`S LOW TEMPERATURE THIS MORNING...
THE AUTOMATED WEATHER OBSERVING SYSTEM (AWOS) AT THE ROCHELLE AIRPORT RECORDED A TEMPERATURE OF -36F AT 745 AM THIS MORNING. WHILE THE THERMOMETER ON THE AWOS WAS RE-CALIBRATED YESTERDAY AND MAY INDEED BE ACCURATE...AWOS OBSERVATIONS ARE NOT QUALITY CONTROLLED OR CALIBRATED BY THE NATIONAL WEATHER SERVICE AND ARE ALSO NOT DESIGNED FOR CLIMATE PURPOSES.
THEREFORE…THE STATE CLIMATOLOGIST DOES NOT CONSIDER THIS TEMPERATURE AN OFFICIAL MEASUREMENT FOR THE PURPOSE OF DETERMINING WHETHER OR NOT AN ALL TIME RECORD LOW FOR THE STATE WAS REACHED. FOR THE PURPOSE OF DETERMINING RECORD TEMPERATURES FOR THE STATE…ONLY ASOS AND COOPERATIVE OBSERVER OBSERVATIONS WILL BE USED SINCE BOTH OF THESE OBSERVATIONS ARE QUALITY CONTROLLED BY THE NATIONAL WEATHER SERVICE.
Note: This article is included on TG Daily as part of our ongoing desire to bring science articles to our readers. The technology used to record official temperature data is impressive as these are official, somewhat massive units. Their reliability has been brought into question, however, by several PhD scientists and those who have physically visited more than half of the over 2,000 official temperature recording sites in the United States where this temperature sensing equipment is installed. They have reported anomalies in many of these installations which follow the observed temperature increases seen over the past two decades. The link below includes references to this - search for "HO-83" on that page. Some reported anomalies have come from physical equipment location - such as being too close to other sources which would alter temperature reliability, while others relate to physical replacements of the temperature recording devices with newer models that now show notably warmer readings which are reported to be in line with the recent warming trend observances.
See Anthony's full response.