Understanding the Preliminary
Climate Data (WS Form F-6)

The preliminary climate data pages
consist of 3 parts.

__Part1__ is the site information including the
station location, the month and year of the report, and the latitude
and longitude of the station. __Part 2__ is the
daily information which consists of 18 columns of data, with one row of data
for each day of the month. The day runs from 0000 to 2359 Local Standard Time (0100 to 0059
Daylight Savings Time). __Part 3__ of the report (noted as Page 2)
is the monthly section which consists of various averages and totals for the
month.

An excerpt of a WS Form F6 is shown
below. An explanation of each column of the data can be found below the
example.

PRELIMINARY LOCAL CLIMATOLOGICAL DATA (WS FORM: F-6)

STATION: WASHINGTON NATIONAL MONTH: MARCH YEAR: 2003 LATITUDE: 38 50 N LONGITUDE: 77 2 W

TEMPERATURE IN F: :PCPN: SNOW: WIND :SUNSHINE: SKY :PK WND ================================================================================ 1 2 3 4 5 6A 6B 7 8 9 10 11 12 13 14 15 16 17 18 AVG MX 2MIN DY MAX MIN AVG DEP HDD CDD WTR SNW DPTH SPD SPD DIR MIN PSBL S-S WX SPD DR ================================================================================

1 40 33 37 -5 28 0 0.01 0.1 3 5.7 14 190 M M 10 18 15 190 2 52 36 44 2 21 0 0.41 0.0 1 9.2 21 320 M M 9 1 28 320 3 42 20 31 -11 34 0 T T 0 13.3 28 340 M M 2 35 340 4 46 23 35 -8 30 0 0.00 0.0 0 6.0 10 180 M M 7 M M 5 68 38 53 10 12 0 0.07 0.0 0 5.8 16 350 M M 9 18 18 360 6 49 30 40 -3 25 0 0.22 0.0 0 13.6 26 20 M M 9 1 29 10 7 89 69 79 3 0 14 0.14 0.0 0 6.3 25 240 M M 6 13 33 250 8 87 71 79 3 0 14 0.00 0.0 0 6.8 25 280 M M 7 32 260 9 91 72 82 6 0 17 0.28 0.0 0 7.5 23 250 M M 8 13 31 260 10 76 69 73 -3 0 8 0.23 0.0 0 9.2 16 50 M M 10 138 18 60 11 86 67 77 1 0 12 0.04 0.0 0 6.3 20 280 M M 7 138 25 280 12 85 61 73 -4 0 8 0.34 0.0 0 7.0 23 220 M M 5 138 30 220 13 83 62 73 -4 0 8 T 0.0 0 3.7 13 360 M M 6 18 350 14 79 67 73 -4 0 8 T 0.0 0 6.3 16 90 M M 7 1 21 50 31 45 31 38 -13 27 0 T T 0 12.7 31 300 M M 4 8 39 320 ================================================================================ SM 1767 1152 549 0 4.20 0.1 276.6 M 205 ================================================================================ AV 57.0 37.2 8.9 FASTST PSBL % 7 MAX(MPH) MISC ----> 37 330 44 330 ================================================================================ NOTES: # LAST OF SEVERAL OCCURRENCES

**Note: An "M" in any column means
the data are Missing for that element.**

Column | ||

1 | DY |
The day of the
month. |

2 | MAX |
The highest temperature for the
day in degrees Fahrenheit (F). |

3 | MIN |
The lowest temperature for
the day in degrees Fahrenheit (F). |

4 | AVG |
The average temperature for the
day, computed by finding the average of the values in columns 2 and 3,
then rounding (if necessary). Example; 55.5 rounds up to 56, 55.4
rounds down to 55 degrees. |

5 | DEP |
Departure from normal. The
difference between column 4 and the 30 year normal temperature for this
date. A minus (-) is number of degrees below normal. A zero (0)
indicates that the average for that day was the Normal. |

6a & 6b | HDD& CDD |
A
gauge of the amount of heating or cooling needed for a building using 65
degrees as a baseline. To compute heating/cooling degree-days, take the
average temperature for a day and subtract the reference temperature of 65
degrees. If the difference is positive, it is called a "Degree Day:Cooling Degree
Day". If the difference is negative, it is called a "Heating Degree
Day". The magnitude of the difference is the number of days. For
example, if your average temperature for a day is 50 degrees in September,
the difference of the average temperature for that day and the reference
temperature of 65 degrees would yield a minus 15. Therefore, you have 15
Heating Degree Days that day. If the average temperature is 77 degrees for
a day, you would have 12 Cooling Degree Days (77-65). If the average
temperature for the day is 65 degrees, there are no Heating or Cooling
degree days. Electrical, natural gas, power, and heating, and air
conditioning industries utilize heating and cooling degree information to
calculate their energy needs.
The Heating season runs from July
1st through June 30th. The Cooling season runs from Jan
1st through Dec 31st. |

7 | WTR |
Total precipitation for
the day to the nearest hundredth of an inch. This includes all forms of
precipitation, both liquid and water equivalent of any snow or ice that
occurred (T = Trace, some precipitation fell but not enough to measure). |

8 | SNW |
Total snowfall for the day to
the nearest tenth of an inch. |

9 | DPTH |
Snow depth on the ground to the nearest inch
at 1200UTC. 7am EST., 6am CST, 5am MST, 4am PST, 3am AST, etc. |

10 | AVG SPD |
Average wind speed for the day
in miles per hour (mph). |

11 | MX SPD |
The highest wind speed in mph
averaged over a 2 minute period. |

12 | 2MIN DIR |
The direction (in compass
degrees divided by 10) from which the wind speed in column 11 came
from. ( N=36 S=18 W=27 E=09, etc.) |

13 | MIN |
The number of minutes of
sunshine received at the station. Not reported at all locations. |

14 | PSBL |
The percentage of possible
sunshine. Computed by dividing the minutes of sunshine in column 13 by the
total possible minutes. Not reported at all locations. |

15 | S-S |
The average sky cover between sunrise and sunset in tenths of sky covered. The minimum of "0" means no clouds observed, "10" means clouds covered the entire sky for that day. |

16 | WX |
A coded number representing
certain types of weather observed during the day. 1 = Fog 2 = Fog reducing visibility to 1/4 mile or less 3 = Thunder 4 = Ice pellets 5 = Hail 6 = Glaze or rime 7 = Blowing dust or sand: visibility 1/2 mile or less 8 = Smoke or haze 9 = Blowing snow X = Tornado In the example above on the 12th, you see "138" coded for the day. That means Fog, Thunder and Smoke or Haze were observed at some time during that day. |

17 | SPD |
Peak wind speed for the day in
mph. The highest wind speed observed at the station. |

18 | DR |
The compass direction from which
the peak wind speed came. |

**SM **is the Sum of that column. Note; these MAY not
line up exactly under the column! Using the example shown above, the
monthly snowfall (0.1)inch is offset slightly to the right.

**AV **is the Average for that column

* An excerpt from the third part of a WS Form F6
(Page 2) is shown below. An explanation of each column of data can be found below the
example.

[TEMPERATURE DATA][PRECIPITATION DATA]SYMBOLS USED IN COLUMN 16AVERAGE MONTHLY: 42.7 TOTAL FOR MONTH: 5.97 1 = FOG DPTR FM NORMAL: 3.0 DPTR FM NORMAL: 1.95 2 = FOG REDUCING VISIBILITY HIGHEST: 80 ON 30 GRTST 24HR 2.05 ON 19-20 TO 1/4 MILE OR LESS LOWEST: 13 ON 4 3 = THUNDER SNOW, ICE PELLETS, HAIL 4 = ICE PELLETS TOTAL MONTH: 10.8 INCHES 5 = HAIL GRTST 24HR 6.5 ON 3- 3 6 = GLAZE OR RIME GRTST DEPTH: 9 ON 4 7 = BLOWING DUST OR SAND: VSBY 1/2 MILE OR LESS 8 = SMOKE OR HAZENO. OF DAYS WITHWEATHER - DAYS WITH9 = BLOWING SNOW X = TORNADO MAX 32 OR BELOW: 2 0.01 INCH OR MORE: 11 MAX 90 OR ABOVE: 0 0.10 INCH OR MORE: 9 MIN 32 OR BELOW: 22 0.50 INCH OR MORE: 4 MIN 0 OR BELOW: 0 1.00 INCH OR MORE: 2HDD (BASE 65)TOTAL THIS MO. 687 CLEAR (SCALE 0-3) 10 DPTR FM NORMAL -122 PTCLDY (SCALE 4-7) 15 SEASONAL TOTAL 1767 CLOUDY (SCALE 8-10) 6 DPTR FM NORMAL -348CDD (BASE 65)TOTAL THIS MO. 4 DPTR FM NORMAL 4PRESSURE DATASEASONAL TOTAL 4 HIGHEST SLP 30.45 ON 22 DPTR FM NORMAL 4 LOWEST SLP 29.50 ON 6REMARKS

TEMPERATURE DATA |
Cumulative temperature information for the month including averages, departure from normal, and the highest/lowest temperatures observed and on what day they occurred. |

NO. OF DAYS WITH |
Number of days during the month that meet the criteria shown. |

HDD (BASE 65) |
Heating degree day information based on an average temperature of 65 degrees. Included are the Total this Month, Departure from Normal for the Month, the Seasonal Total and the Seasonal Departure from Normal. The Heating season runs from July 1st through June 30th. |

CDD (BASE 65) |
Cooling degree day information based on an average temperature of 65 degrees. Included are the Total this Month, Departure from Normal for the Month, the Seasonal Total and the Seasonal Departure from Normal. The Cooling season runs from Jan 1st through Dec 31st. |

REMARKS |
Additive remarks made by observer. |

PRECIPITATION DATA |
Cumulative precipitation (for both rain and frozen precipitation) information, for the month including total for the month, departure from normal for that month, greatest 24 hour amount not necessarily midnight to midnight, and greatest snow depth at 1200UTC. |

WEATHER - DAYS WITH |
Number of days during the month that meet the temperature, precipitation and sky cover criteria shown. |

PRESSURE DATA |
Magnitude of highest and lowest sea level pressure (in inches) and the day on which it occurred. |

SYMBOLS USED IN COLUMN 16 |
A coded number representing certain types
of weather observed during the day. 1 = Fog 2 = Fog reducing visibility to 1/4 mile or less 3 = Thunder 4 = Ice pellets 5 = Hail 6 = Glaze or rime 7 = Blowing dust or sand: visibility 1/2 mile or less 8 = Smoke or haze 9 = Blowing snow X = Tornado |