UK Hourly Weather Observations data - .hwx (weather observations) file format


PLEASE NOTE: The file format described below refers to the Met Office Land Surface data (1900-2000) dataset which has been superseded by the Met Office MIDAS dataset (1853-present) at the BADC.


The surface observation data are in a simple ASCII format.

A list of UK stations for which the BADC holds .hwx files is available (.hwx stations).

The file name convention is (STATION_NAME)(YEAR).(MESSAGE_TYPE).(FILE_EXTENSION)

-999 indicates a missing value.

The first line of the data file is the fields headers (which are detailed in the table below).

The fields in the .hwx data files are :

HEADER PARAMETER FIELDS COLUMNS UNITS COMMENTS
ID Station Ref. Number 1 1-8 - Station identification
IDTYPE - 2 9-17 - Station identification
MET_DOM Meteorological Domain 3 18-28 - Message types
YEAR Year 3 29-35 - 4 characters
MON Month 4 36-43 - 1 or 2 characters (from 1 to 12)
DAY Day 5 44-51 - 1 or 2 characters (from 1 to 31max)
HOUR Hour 6 52-59 - Hour of observation from 0 to 2300
DIR 10 minutes wind direction 7 60-67 Degree true From 0 to 360 degrees, clockwise. Note that zero values in both wind speed and wind direction fields indicate that there was no wind blowing at the time of observation.
See Met Office documentation
SPEED 10 minutes wind speed 8 68-75 Knots NB. A mean wind for the hour up until the reporting time. Note that zero values in both wind speed and wind direction fields indicate that there was no wind blowing at the time of observation.
See Met Office documentation
PRST Present weather 9 76-81 WMO Code See Met Office documentation
PAS1 Most significant Past weather 10 82-87 WMO code See Met Office documentation
PAS2 Least significant Past weather 11 88-93 WMO code See Met Office documentation
TCA Total cloud amount 12 94-98 WMO code See Met Office documentation
LCT Low cloud type 13 99-103 WMO Code See Met Office documentation
MCT Medium cloud type 14 104-108 WMO Code See Met Office documentation
HCT High cloud type 15 109-113 WMO Code See Met Office documentation
CBA Cloud base amount 16 114-118 WMO code See Met Office documentation
CBH Cloud base height 17 119-126 DAM DAM = Decameters
See Met Office documentation
VIS Horizontal visibility 18 127-133 DAM DAM = Decameters
See Met Office documentation
MSLP Mean Sea Level Pressure 19 134-146 0.1 mb Atmospheric pressure is expressed in millibars (1 millibar = 100 pascals = 100 newtons per square metre). Precision aneroid barometers are now in general use for measuring pressure and a correction for altitude is applied to obtain the value at mean sea level (MSL).
CA1 Cloud amount - level 1 20 147-151 WMO code See WMO documentation
CT1 Cloud type - level 1 21 152-156 WMO code See WMO documentation
CB1 Cloud base - level 1 22 157-164 DAM DAM = decameters
See WMO documentation
CA2 Cloud amount - level 2 23 165-169 WMO code See WMO documentation
CT2 Cloud type - level 2 24 170-174 WMO code See WMO documentation
CB2 Cloud base - level 2 25 175-182 DAM DAM = Decameters
See WMO documentation
CA3 Cloud amount - level 3 26 183-187 WMO code See WMO documentation
CT3 Cloud type - level 3 27 188-192 WMO code See WMO documentation
CB3 Cloud base - level 3 28 193-200 DAM DAM = Decameters
See WMO documentation
CA4 Cloud amount - level 4 29 201-205 WMO code See WMO documentation
CT4 Cloud type - level 4 30 206-210 WMO code See WMO documentation
CB4 Cloud base - level 4 31 211-218 DAM DAM = Decameters
See WMO documentation
VVIS Vertical visibility 32 219-226 DAM DAM = Decameters
See Met Office documentation
TEMP Dry-bulb air temperature 33 227-234 0.1 Degrees Celsius See Met Office documentation
DEW Dew-point temperature 34 235-242 0.1 Degrees Celsius The dew point temperature (in degrees Celsius) is the temperature to which the air must be cooled to produce saturation with respect to water at its existing atmospheric pressure and humidity.See Met Office documentation
WETB Wet-bulb temperature 35 243-250 0.1 Degrees Celsius The web-bulb temperature is the lowest temperature (in degrees Celsius) that can be obtained by evaporating water into the air. It measures the humidity of the air.See Met Office documentation
STNP Station level pressure 36 251-262 0.1 mb Atmospheric pressure (in mb) as measured at the station level. Correction for altitude is not applied.
ALTP Altimeter pressure 37 263-270 mb -
SOG State of ground 38 271-275 WMO Code -
MGS 10 minutes maximum gust speed 39 276-283 knots See Met Office documentation


More information about the Met Office surface data is available in the documentation provided by the Met Office.