CYC Weather Challenge 2020

The challenge: forecast six weather elements for a given weather reporting station (generally a major airport – see the schedule below) on a daily basis.  You will be forecasting daily high temperature; daily low temperature; maximum daily wind speed; wind speed at local noon; and wind direction at local noon.   You will be forecasting for three cities:

Chicago, IL (KORD)May 18-22
Providence, RI (KPVD)May 25-29
Miami, FL (KMIA)June 1-5

The goal: become a better weather observer and forecaster by getting into the routine of doing a daily forecast. Along the way, you’ll learn something about available weather resources and maybe understand a bit more about the process of forecasting and just how hard and humbling it is.

Scoring: Forecasts will be scored daily by assigning error points to each forecaster, representing the difference between the actual measurements of those variables and your forecast.  Low scores are better.

Here are the detailed rules.


We are forecasting for a major airport because they are official weather reporting stations. The official station at the airport is the one we are using when comparing your forecasts, not what you may see on TV or what any other weather station in the area may tell you.

Forecasts are due Sunday evening through Thursday evening at 0000 UTC (technically, Monday – Friday UTC)  (generally around dinner time local – see the schedule below)  and are valid for midnight – midnight local time for the following day. Each forecast consists of:

  • High temperature (in whole number degrees F)
  • Low temperature (in whole number degrees F)
  • Maximum sustained wind speed (in whole number knots; not gusts)
  • Cumulative liquid precipitation (in inches, to two decimal places accuracy – e.g. 0.50, 0.25, 1.25)
  • wind speed at local noon (in whole number knots; not gusts)
  • wind direction at local noon (true direction – not magnetic – rounded to the nearest 10 degrees)

Forecasts will be submitted via a Google Form, which will time-stamp your forecast. It is up to each forecaster to submit his/her forecast and to follow the rules. If your forecast doesn’t comply with these rules, it will be deemed a ‘missed forecast’. While the Google form is the main method for submitting forecasts, e-mail is to be used ONLY in the event the Google form cannot be reached due to server issues. This email method of submitting a forecast is only allowed in the case where the Google form is unreachable and is not to be used in any other case. It can be rejected if this is abused. We’re running this on a volunteer basis, so please use the Google Form.   All e-mails must be time stamped before 00 UTC to be considered valid forecasts. If a forecaster submits more than one forecast, the last one submitted before 00 UTC will be considered their forecast for the day. No exceptions can be made to the deadline.

Missed forecast: A missed forecast will receive the climatological average high temperature, low temperature, average wind speed, and average precipitation for the forecast date. In addition to the calculated error points, a 10 point penalty will be added to the forecast score representing the noon wind score and a penalty for not entering. The climatological values used in the scoring procedure are based on the 30-year mean from the National Climatic Data Center, and are available here.

Official temperature and precipitation verifications are taken from the Daily Climatology Report issued by the local National Weather Service office. For the local noon wind speed and direction, the verification will be taken from the local noon METAR (which is often issued a few minutes before the exact hour). If the climatological report is missing or deemed to be invalid, then the METAR values will be used. These standard reports (not special observations) typically run between 51 and 56 minutes past the hour and will have the 6-hour codes included. You are forecasting for wind speed as defined by the NWS, not gusts.

A note on time

Weather forecasting occurs worldwide, so to reduce confusion it uses Universal Time Coordinated (UTC) (Formerly known as Greenwich Mean Time, or GMT). This is often abbreviated as UT or UTC, and times are often expressed with a “Z” (for “Zulu”). We attempt to convert all times for you into local time but see the schedule table below for details. Just know that, for example, noon (1200) at Chicago O’Hare local time (Central Daylight Time, or CDT) is the same as 1700 UTC, or 17Z, or 17UT. These are all the same time.

Forecasting Schedule

Forecast locationForecast DaysForecast DueForecast Period in UTCLocal noon in UTCLocal Time Zone and UTC Offset
Chicago IL (KORD)May 18 – 2200Z / 7 pm local the day before05Z – 05Z17ZCDT= UTC – 5 hours
Providence RI (KPVD)May 25 – 2900Z / 8 pm local the day before04Z – 04Z16ZEDT= UTC – 4hours
Miami, FL
June 1- June 500Z / 8 pm local the day before04Z – 04Z16ZEDT= UTC – 4hours
Note – Forecast period is midnight – midnight local time – the calendar day in local time

Daily Scoring

Here’s how the daily forecasts will be scored:


  • Temperature measurements are rounded to the nearest degree Fahrenheit
  • Wind speed measurements are to the nearest knot
  • Precipitation measurements are to the nearest one-hundredth of an inch.
  • Wind direction forecasts are rounded to the nearest ten degrees


The following error points will be accessed for non-perfect forecasts:

Max and Min. Temperature: One error point for every degree difference Fahrenheit between your forecasted high and low and the verified high and low temperatures.

Wind speed: 0.5 error points for every knot difference between your forecasted wind speeds and the verified wind speeds.

Wind direction:

0.2  points for each 10 degrees of error in the range from 10-60 degrees

0.4 points for each 10 degrees of error in the range from 60-180 degrees

Wind Direction Examples:

If a forecaster gave a forecast of 270 and the verification was 290, the score would be 0.2 *2 =  0.4

If a forecaster gave a forecast of 270 and the verification was 100, the score would be 0.2* 6 + 0.4 *11=5.6


0.2 error points for each 0.05″ (or fraction thereof) of error.

(Note: A verification of trace precipitation will be scored as 0.00″ of precipitation.)

For each day, a daily score will be calculated by summing the error points from the high temperature, low temperature, wind speed, and precipitation forecasts. Any penalty points for non-human forecasts will also be added into the daily score.

Weekly Scoring and Overall Championship Scoring

For the weekly score, the forecasters’ daily scores will be totaled with no throw outs. Lower scores are better, representing lower error. The weekly winner is the forecaster with the lowest total score for the week.  Prizes will be awarded for each week.

At the end of the entire tournament, we will throw out each forecaster’s worst score in each City and then total the scores. The forecaster with the lowest total score wins.

Club Champions

At the end of the tournament, the Chicago Yacht Club member with the lowest score as described above shall be deemed the CYC Weather Forecasting Champion.

At the end of the tournament, the Storm Trysail Club member with the lowest score as described above shall be deemed the STC Weather Forecasting Champion.

At the end of the tournament, the non-CYC CASRA Club member with the lowest score as described above shall be deemed the CASRA Weather Forecasting Champion.


We’re running this as volunteers. There is no money involved. We’ll do our best to be accurate, but please understand that this is intended to be for fun, and for education, and we cannot devote unlimited time to troubleshooting your problems and we cannot provide technical support. If we make any mistakes, we apologize in advance. Please keep the tone fun and civil. We reserve the right to terminate the challenge or to kick any individual out of the challenge if we deem their behavior to be inappropriate or disruptive.

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