Homework # 3 Solutions
Decode the following
METAR observation taken in January.
KDFW 051356Z 24022G28KT 6SM SCT220 BKN350 OVC400 4/M9 A2984
RMK A02 SLP132
T00411089 P0052=
City and State: (KDFW)
Date (Day of Month): 051356Z - The green
section indicates it is the 5th day of the month
The next question asks for the time of the observation in
Zulu time and then to convert it to Central Standard Time and Central Daylight
Time. (There was some confusion as to which blank went where, so as long as
you had the correct values somewhere, I gave your credit.)
051356Z The green section indicates, the time of the observation in
Zulu. Therefore in Zulu time, it is 1356
Z.
CST is Z minus 6 hours = 1356Z 6
=
CDT is Z minus 5 hours = 1356Z 5
=
Temperature (to a tenth of a degree):
An important thing to remember is
that there are two separate temperature observations in the METAR code. The first is 4/M9,
however, this is a rounded value. However,
you must use this T00411089, to find the temperature.
Therefore, this is given by the blue part:
T00411089 which is 4.1
degrees Celsius
The temperature in Fahrenheit is
(1.8 * 4.1) + 32 = 39.4 degrees Fahrenheit
Dewpoint (to a tenth of a degree):
This follows the same procedure as
the temperature.
T00411089, the blue section
gives the dewpoint.
Remember that the leading one means that the temperature is
negative. Therefore the dewpoint is -8.9 degrees Celsius.
The
dewpoint in Fahrenheit is (1.8 * -8.9) + 32 = 15.9
degrees Fahrenheit
Visibility: 6SM This is decoded to 6 statute miles
The next 8 questions asked for cloud cover conditions (ie: part of the sky covered and height level clouds).
SCT220 This means Scattered skies at
22,000 feet. (You must add two zeroes to
the number given).
BKN350 This means Broken skies at
35,000 feet.
OVC400 This means Overcast skies at 40,000 feet.
The last two two
blanks are there in case there was a fourth cloud ob, which in our case, was
not present.
Precipitation:
P0052 This value gives the precipitation in hundredths of an inch
(ie: how many times the tipping bucket rain gauge
tipped). Therefore, with 0052, the
hourly precipitation is 0.52 inches of precipitation.
How long did it take to precipitate this amount? One
hour. This is because METAR reports are
given every hour.
Wind Direction: This is given in this section - 24022G28KT
24022G28KT The colored piece indicates the wind direction in degrees,
which is 240 degrees
(Direction using N, S, E, W) 240 degrees corresponds to roughly the SW (southwest)
Wind Speed:
24022G28KT METAR reports give the
wind speed in knots, which is shown to be 22 knots.
In
miles per hour it is (22 knots) * (1.15 mph / knot) = 25.3 miles per hour
Wind Gust:
24022G28KT Finally, wind
gusts are given when preceded by the G designator. In our case, the wind gusts were at 28 knots.
Sea Level Pressure
SLP132 The sea level pressure is given by this section in millibars. To decode
it, you must put a 9 or 10 in front of the numbers given and place a decimal
point between the 3 and 2. I will first
use a 9, giving a sea level pressure of 913.2 millibars. However, this is outside of the typical
pressure range of 970 1030 millibars. Therefore I know I must put a 10 in front giving, 1013.2
millibars as my sea level pressure.
To convert this to inches of
mercury:
Altimeter Setting:
This is shown by A2984 and is in units of
inches of mercury. The only decoding
needed is to put a decimal point between the 2nd and 3rd digits. Therefore the setting is 29.84 inches of
mercury.
To convert to millibars:
Precipitation Descriminator
This can be found in the RMK
section and is given by A02.
To interpret this, a 01 means that
there is no descriminator, while a 02 means there is
one. Therefore, in our METAR code, there
is a precipitation descriminator.