Tuesday, February 18, 2014

The Howard Pass Wind Chil and Meteorlogical Records

The discussion here on Deep Cold and elsewhere concerning the wind chill values reported from the Howard Pass RAWS platform over the weekend have been useful in helping to clarify the way the meteor/climatological community thinks about "records" and what constitutes a record.

From an operational viewpoint, "on the fly" data quality evaluation is a routine, every day, indeed every hour part of the job. Doing it correctly though requires a detailed understanding of not only the general meteorological situation but details through the meso and mircoscales, the dominant physical processes, the impact of orography on the variables in question and the details of instrumentation measuring and reporting the physical parameters of interest.

Alaska, with it's complex terrain and high latitude location is an exceptionally difficult arena for meteorological quality control. In Interior Alaska, it's boringly common in mid-winter for temperatures in two locations five miles apart to be 30ºF different, and for such differences to persist for days. How would that fly in Minnesota? Now in this case we happen to have a good physical understanding of how that happens. But temperatures are simple compared to winds.

Details of terrain and instrumentation are even more important for winds than temperatures. Consider the variability of winds but relative uniformity of temperatures in the heavily instrumented areas along the Delta River south of Fort Greely or in the Healy/Denali Park Entrance area. No one who has ever driven through Glitter Gulch in winter in  during a Chinook doubts the 70 mph winds reported at Antler Creek from the RWIS and at the same time the 15 mph or less winds at the AWOS at the Denali Park train station.

So how does all this play into the Howard Pass report? We know that outlets of constricted terrain can be remarkably windy in the appropriate meteorological conditions. We know the details of the instrumentation and know it is research grade equipment. We know it was installed and is maintained by experts in high latitude meteorological instrumentation (thanks Ken and Pam!). We know that the highest resolution numerical models routinely run over Alaska do capture something of the extreme winds and temperatures observed (thanks to Richard for this useful post illustrating this). I made an educated but incomplete scour of observations some years ago for this kind of information and Brian has now systematically checked hourly observations for most of the North Slope sites that might have ever have wind chills in the 90s below.

So, as I see it, to the best of our ability to determine, Howard Pass RAWS did observe the lowest wind chill reported in real-time in Alaska, and I think we can say so with confidence. That does not mean it is certain. And certainly we can argue whether the wind speeds should be adjusted due to the low height. But this is detail: the base observation has verisimilitude, and with no other observations anywhere close (KTZA2 is 67 miles away, and IMYA2, in a completely different physiographic setting, is 42 miles away), the best hope we have for verification would be higher, say 1km, horizontal resolution modeling. Even this will simply make the case more or less solid. There can be no proof.

In the past ten years we've seen a dramatic increase in the amount of quality surface data available in Alaska. but in winter. I expect we'll see more of these kind of "oddball records".


  1. Hmmmm Rick. In my experience with electronics and instrumentation, any equipment that was, and is, as wonky in reporting as that would be suspect and not support my confidence.

    Do the frequent recent caution reports have value? Is 23G96 (the last wind report) have value? What is real, and what is potential instrument or reporting error? And now the wind report is absent. Why?

    Believe what you wish and model what potential for extremes you can. I'd not put my professional hat in that ring for the above reasons, apparent new record or otherwise, and siting issues aside.

    As far as I can tell, no one as of yet has confirmed the quality of data and integrity of the equipment. Yes, at manufacture it was research grade and was installed properly. But now it's used and may have been compromised at some point in it's recent life.

    Gary...not here to argue or incite, just question.

    1. Gary, the final observation of 23G96 and subsequent missing values almost certainly indicates the anemometer failed that hour. Where rendered inoperative by damage or blown away we of course do not know. The fact that instrument has failed in the face of reported extreme winds is, too my mind, another indication that the winds were in fact very strong and not an instrument artifact.


    2. I agree Rick re: The failure. I also indicated earlier that I agreed that it was cold and windy at the Howard Pass RAWS site. To what degree I believe is the focus of these discussions.

      One aspect that hasn't been discussed here I believe is the potential for data overlap from the respective confidence intervals associated with the two most recent records of wind chill in Alaska.

      Sensors and their supporting electronics can have inherent errors due to calibration, processing algorithms, environmental influences among some. That's why I suggested elsewhere to recapture the RAWS' components and subject them to reanalysis in a controlled environment if the validity of the "Record" is important. I doubt that will happen, especially with the earlier reported wind chill from the Arctic Coast and its equipment.

      I'll leave this with the belief that some "Record Weather Events" can have subjective influences based upon best available data.

      With respect,


  2. "* 2/18/14 Update *

    Preliminary communication with the NPS technician (not by this blog entry's author) who installed and maintains the station indicated that the equipment is designed for this type of environment and that the wind readings are unlikely to be revised downward. The anemometer is replaced annually and the design makes readings that are too high improbable. In addition, data from the previous several seasons appears to confirm the fact that wind is funneled through the north-south oriented mountain gaps and that especially low temperatures are entirely plausible. As the data continues to accumulate, the confidence in the observations in increasing."

    I'm out of here in this Record deal. What I see is an effort to back fill for the NWS employee that made the record call, and NPS for the alleged quality of the current status of their instrumentation.

    The simple fix is to acknowledge that the Agencies ( I have no axe to grind with the the Feds…they paid 75% of my wages) are willing to accept Gray Science when it comes to records of Alaskan weather.

    When employed, we called that BAD: Best Available Data. And in some circumstances, it is in fact that.