CWOP Information for CW4591 (C4591) in Tok, AK, US

The following information is known about CW4591. If you think that any information is incorrect, then please follow the instructions for correcting that data item.

It is possible that this page will report a problem where no problem exists. If you believe that this has happened, then please contact me (address at the bottom of this page) and explain clearly why you think this page is in error. Note that any changes that you make may take a few days to show up here, so please give it a week before commenting.

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Registered Location

Latitude: 63° 12' 0" N (deg min sec), 63.2000° (decimal), 6312.00N (LORAN)
Longitude: 143° 0' 0" W (deg min sec), -143.0000° (decimal), 14300.00W (LORAN)
Elevation: 541 metres (1775 feet) -- validated against 538 metres (1765 feet) from Geonames
Location: Tok, AK, US
Borough: Southeast Fairbanks, AK
Forecast Offices: Anchorage (AFC), Fairbanks (AFG)
Weather station Manager/Operator: Katy
Station type/software: Davis Vantage Pro 2/Vue with Weatherlink-IP

The site coordinates appear to be of low precision, and the station may be anywhere within the marked area. Clicking within the map area (or you can drag the 'CW4591' marker) will display the latitude/longitude of that point.

If the displayed location (or elevation) of the weather observing location is incorrect, please drag the marker to the right location (or click in the right location), and then send the updated information. Please note that we are trying to spot either the Stevenson Screen (or equivalent) or the location where the barometric readings are taken.

NOTE: The Registered Location is the location that the station owner provided when they signed up with CWOP. Show location history.

The station (or view from the station) is shown here. You can choose the view direction to see the surroundings. Other information (and somewhat larger images) can be found by clicking on the picture.

You can try to find photographs from the area surrounding the site marker by clicking on Find nearby photographs.

Data Status

Over the last 28 days, no data was seen on the following dates: 2020-02-01, 2020-02-04 to 2020-02-25.

All the means and standard deviations shown below are from the last 28 days. Change analysis period to Last 3 days  Last 7 days  Last 14 days  Last 8 weeks  Last 13 weeks  Last 26 weeks  Last 39 weeks  Last 52 weeks  

A recently received weather report from this station was


Average barometer error: -3.6 milliBars
Error standard deviation: 4.8 milliBars
Worst daily average barometer error: -9.9 milliBars
Mean error value of -3.6 exceeds limit of 2.0
MADIS rating 89% QC OK

Latest daily graph:

Latest daily graph

The standard deviation of your readings is higher than expected. This can be caused by a broken sensor that always reports the same value. It can be caused by a faulty sensor that sometimes reports values way out of range (such as 0). Check that your sensor is operating correctly.


  24 hours  Day time  Night time
Average temperature error3.0 °F0.3 °F8.5 °F
Error standard deviation4.1 °F1.5 °F1.7 °F
Worst average temperature error-1.0 °F-1.0 °F-1.0 °F
Worst standard deviation0.0 °F0.0 °F0.0 °F

NOTE: If the error above is POSITIVE, then it means that the analysis temperature is HIGHER than the reported temperature. This means that your sensor is reading COLDER than expected.

MADIS rating 92% QC OK

Latest daily graph:

Latest daily graph

It appears that your station is sited in a location where cool air collects at night. This is often near the bottom of a valley. The cool nighttime readings are probably correct, and the analysis values are not taking into account the local topography.

Dewpoint -- or switch to Relative Humidity

  24 hours  Day time  Night time
Average dewpoint error2.0 °F0.3 °F5.6 °F
Error standard deviation2.7 °F1.4 °F0.7 °F

NOTE: If the error above is POSITIVE, then it means that the analysis temperature is HIGHER than the reported temperature. This means that your sensor is reading COLDER than expected.

MADIS rating 100% QC OK

Latest daily graph:

Latest daily graph

These values are within the acceptable range. This probably means that your sensor is sited correctly and is calibrated correctly.

Wind Vector

The wind vector is the average wind over the relevant period. Note that if the wind blows North for half the time at 2 knots, and then blows South for the other half of the time at 2 knots, then the result is zero -- i.e. North wind and South wind will cancel out. Over time, the direction of the wind and of the analysis should match pretty well. If the lengths of the vector are different, then it could mean either that your anemometer reads high or low, or that you are in a more shielded or more open space.
MADIS rating 91% QC OK
TodayLast 7 days
Wind vector chartWind vector chart for last 7 days


Sometimes, larger than expected values of the standard deviation can be caused by the analysis process itself. If there is a stuck sensor on a neighboring station, this can cause a 'sawtooth' or 'jaggy' analysis. This will cause the standard deviation to be higher than it ought to be. If this happens to your station, then please ignore the warnings above. The analysis process is being upgraded to try and eliminate these problems.

Neighboring Stations

This is a list of stations that are close to this station. Note that this is not the list of stations that are used in the data analysis. That list of stations is known only to MADIS. You can see all the stations at MADIS Data Display. Your station should be in the middle of the display. If you think that the analysis is incorrect, then maybe one of the close stations has failed.

You can look at those for comparison purposes. The average difference between your station and each station below is listed as well. This may allow you to detect local stations which are erroneous. You can also use these numbers to adjust your instruments -- especially if a number of ASOS stations have similar differences to your station. Also, try increasing the analysis period to more than the default 28 days. The difference is only given if both stations report reasonably often during each day. Some stations only report every 6 hours, and this makes the average of less interest. In this case, the average is not displayed. The values reported are the differences between this station and the neighboring station. I.e. if the difference is positive, then this station is reading higher than the neighboring station. Since this station has not been reporting continuously during the analysis period (it missed 23 days out of 28), the offsets below may not be accurate.

You can also subscribe to an RSS feed to tell you when new stations come online in this area. Choose either within 100 miles or 250 miles . For stations covered by your Forecast Office: Anchorage (AFC),Fairbanks (AFG) .

CW368497.0 milesSouthwest Gulkana, AK, US (lat 62.2932°, long -145.3353°, altitude 505 metres)
DW9260179.4 milesSouthwest Valdez, AK, US (lat 61.1337°, long -146.3620°, altitude 13 metres)
KL1YC207.8 milesNorthwest Nenana, AK, US (lat 64.5578°, long -149.0918°, altitude 108 metres)
EW1088226.5 milesSouthwest Palmer, AK, US (lat 61.6250°, long -149.2047°, altitude 131 metres)
CW1074231.3 milesSouthwest Wasilla, AK, US (lat 61.6190°, long -149.3690°, altitude 136 metres)
EW9414232.3 milesSouthwest Wasilla, AK, US (lat 61.5608°, long -149.3295°, altitude 40 metres)
EW6470235.1 milesSouthwest Wasilla, AK, US (lat 61.6152°, long -149.4988°, altitude 129 metres)
KL7GG245.5 milesSouthwest Eagle River, AK, US (lat 61.2970°, long -149.4397°, altitude 140 metres)
EW8287246.8 milesWest Willow, AK, US (lat 61.7138°, long -150.0217°, altitude 86 metres)
ERTA2247.4 milesSouthwest Eagle River Kantishna, AK, US (lat 61.3188°, long -149.5430°, altitude 177 metres)

Quality Control Notes

This page reports on the quality control checks performed by MADIS. The green check mark and red cross are chosen based on the average performance during the analysis period (which is selectable above). The red cross can appear even if MADIS reports that all observations pass the MADIS QC checks.

The 'MADIS rating' reports on the percentage of observations that pass the MADIS checks. You should aim for two thumbs up!

Location Formats

The location is shown in three different formats. Each of these is used in some software, and is shown on some websites.

Degrees Minutes Seconds: VWS/VWSAPRS, WeatherLink 5.5, WeatherLink (5.2-5.4), WeatherView (Linux)

Decimal degrees: FreeWX, WeatherView32 (PC application)

LORAN: WeatherDisplay, WUHU, Henriksen WServer


CWOP Home: This describes the whole CWOP program and has a large amount of useful information.

CWOP Siting Guide (PDF): This is a guide to siting and operating a CWOP station. This is a must-read document.

Another CWOP Guide (PDF): This is another guide to siting and operating a CWOP station. This is a must-read document.

Urban Siting and Operations (PDF): This is a guide to siting and operating a CWOP station in an urban environment.

APRS WX Message format: This describes the actual format of the messages transmitted that carry WX information.

WXQC Mailing List: This is a mailing list where data quality issues are discussed. Assistance with software configuration can often be found here.

Topo Map Reading Guide: How to read USGS topographic maps, with a good section on reading contours.

Geographically nearby web pages: Use Geourl to find web pages that deal with locations geographically close to this site.

Overall website comments, problems etc to Philip Gladstone
Page layout last modified Sunday, 28 February 2016
Questions for this weather station owner/operator to Katy
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