About the NAM MOS (MET) Text Product

The NAM-Based MOS guidance is generated from 0000 UTC and 1200 UTC model output from the Environmental Modeling Center's NAM Model. This guidance is valid for stations in the Continental United States, Alaska, Hawaii, Puerto Rico, and the U.S. Virgin Islands. Forecast elements are valid from 6 to 72 hours in advance.

Detailed Documentation can be found in the following documents:

The NAM MOS Message (New Format, starting January 2016)

Sample Message
WASHINGTON          
 KDCA   NAM MOS GUIDANCE    1/28/2016  0000 UTC                      
 DT /JAN  28            /JAN  29                /JAN  30          /  
 HR   06 09 12 15 18 21 00 03 06 09 12 15 18 21 00 03 06 09 12 18 00 
 X/N                    39          33          39          28    42 
 TMP  33 32 31 34 36 37 37 37 37 36 35 36 37 36 33 32 31 30 30 38 39 
 DPT  21 22 24 27 29 29 30 31 31 30 29 28 24 20 18 19 20 20 21 29 32 
 CLD  SC CL SC FW SC FW OV OV OV SC OV BK BK FW CL CL CL SC FW BK SC 
 WDR  01 08 14 17 16 18 18 20 31 30 30 29 30 30 31 32 30 30 20 20 18 
 WSP  02 01 02 04 04 04 04 03 03 05 05 11 17 16 14 13 06 04 03 08 06 
 P06         2     3     1     2     3     3     2     3     4  4  5 
 P12                     3           5           4           4     6 
 Q06         0     0     0     0     0     0     0     0     0  0  0 
 Q12                     0           0           0           0     0 
 T06      0/ 0  0/ 3  0/ 0  0/ 0  0/ 0  0/ 3  0/16  0/ 5  0/ 1  0/ 3 
 T12            0/ 3        0/ 0        0/ 3        0/16     1/ 1    
 POZ   0  5  8  6  8  3  0  1  0  1  5  0  0  0  2  2  3 10 11  9  1 
 POS  82 87 74 70 25 21 22 19 23 30 65 72 94 90 98 98 94 86 77 22 10 
 TYP   S  S  S  S  R  R  R  R  R  R  S  S  S  S  S  S  S  S  S  R  R 
 SNW                                 0                       0       
 CIG   8  8  8  8  8  8  8  7  8  8  6  7  6  8  8  8  8  8  8  8  8 
 VIS   7  7  7  7  7  7  7  7  7  7  7  7  7  7  7  7  7  7  7  7  7 
 OBV   N  N  N  N  N  N  N  N  N  N  N  N  N  N  N  N  N  N  N  N  N 
  • DT = The day of the month, denoted by the standard three or four letter abbreviation
  • HR = Hour of the day in UTC time. This is the hour at which the forecast is valid, or if the forecast is valid for a period, the end of the forecast period.
  • N/X = nighttime minimum/daytime maximum surface temperatures.
  • TMP = surface temperature valid at that hour.
  • DPT = surface dewpoint valid at that hour.
  • CLD = forecast categories of total sky cover valid at that hour.
  • WDR = forecasts of the 10-meter wind direction at the hour, given in tens of degrees.
  • WSP = forecasts of the 10-meter wind speed at the hour, given in knots.
  • P06 = probability of precipitation (PoP) during a 6-h period ending at that time.
  • P12 = PoP during a 12-h period ending at that time.
  • Q06 = quantitative precipitation forecast (QPF) category for liquid equivalent precipitation amount during a 6-h period ending at that time.
  • Q12 = QPF category for liquid equivalent precipitation amount during a 12-h period ending at the indicated time.
  • SNW = snowfall categorical forecasts during a 24-h period ending at the indicated time.
  • T06 = probability of thunderstorms/conditional probability of severe thunderstorms during the 6-hr period ending at the indicated time.
  • T12 = probability of thunderstorms/conditional probability of severe thunderstorms during the 12-hr period ending at the indicated time.
  • POZ = conditional probability of freezing pcp occurring at the hour.
  • POS = conditional probability of snow occurring at the hour.
  • TYP = conditional precipitation type at the hour.
  • CIG = ceiling height categorical forecasts at the hour.
  • VIS = visibility categorical forecasts at the hour.
  • OBV = obstruction to vision categorical forecasts at the hour.

 

The NAM MOS Message (Old Format, prior to January 2016)

Sample Message

KDCA   NAM MOS GUIDANCE    1/24/2008  1200 UTC 
DT /JAN  24/JAN  25                /JAN  26                /JAN  27
HR   18 21 00 03 06 09 12 15 18 21 00 03 06 09 12 15 18 21 00 06 12
N/X                    15          24          20          30    28
TMP  36 35 30 24 21 18 16 21 23 22 23 21 20 21 22 24 27 29 29 29 30
DPT  14  9  3  0 -2 -4 -3 -3 -2  2  8 12 15 17 19 22 24 25 25 24 21
CLD  CL CL FW FW SC SC BK OV OV OV OV OV OV OV OV OV OV OV OV BK FW
WDR  34 33 34 35 34 36 36 06 14 08 05 04 02 02 03 05 05 06 03 35 34
WSP  07 14 14 11 10 10 08 03 02 05 07 11 11 12 10 07 04 04 07 11 10
P06         0     0     0     0    55    76    60    34    36 13  9
P12                     0          58          86          48    25
Q06         0     0     0     0     1     1     1     0     1     0
Q12                     0           1           2           1     0
T06      0/ 0  0/ 9  0/ 1  1/ 0  3/ 0  0/ 0  0/ 1  0/ 0  3/ 0  0/ 0
T12            1/ 9        1/ 1        3/ 0        1/ 1     1/ 0
SNW                     0                       6                 0
CIG   6  8  8  8  8  7  7  7  7  4  4  3  2  3  3  2  2  1  1  2  8
VIS   7  7  4  5  5  5  6  7  7  7  7  7  7  7  7  7  7  7  7  6  5
OBV   N  N BR BR BR BR  N  N  N  N  N  N  N  N  N  N  N  N  N HZ BR
  • DT = The day of the month, denoted by the standard three or four letter abbreviation
  • HR = Hour of the day in UTC time. This is the hour at which the forecast is valid, or if the forecast is valid for a period, the end of the forecast period.
  • N/X = nighttime minimum/daytime maximum surface temperatures.
  • TMP = surface temperature valid at that hour.
  • DPT = surface dewpoint valid at that hour.
  • CLD = forecast categories of total sky cover valid at that hour.
  • WDR = forecasts of the 10-meter wind direction at the hour, given in tens of degrees.
  • WSP = forecasts of the 10-meter wind speed at the hour, given in knots.
  • P06 = probability of precipitation (PoP) during a 6-h period ending at that time.
  • P12 = PoP during a 12-h period ending at that time.
  • Q06 = quantitative precipitation forecast (QPF) category for liquid equivalent precipitation amount during a 6-h period ending at that time.
  • Q12 = QPF category for liquid equivalent precipitation amount during a 12-h period ending at the indicated time.
  • T06 = probability of thunderstorms/conditional probability of severe thunderstorms during the 6-hr peri od ending at the indicated time.
  • T12 = probability of thunderstorms/conditional probability of severe thunderstorms during the 12-hr per iod ending at the indicated time.
  • SNW = snow fall categorical forecasts during a 24-h period ending at the indicated time.
  • CIG = ceiling height categorical forecasts at the hour.
  • VIS = visibility categorical forecasts at the hour.
  • OBV = obstruction to vision categorical forecasts at the hour.

Definitions of Categorical Elements

Ceiling Height Categories
1 < 200 feet
2 200 - 400 feet
3 500 - 900 feet
4 1000 - 1900 feet
5 2000 - 3000 feet
6 3100 - 6500 feet
7 6600 - 12,000 feet
8 > 12,000 feet or unlimited ceiling


Visibility (VIS) Categories
1 < 1/2 miles
2 1/2 - < 1 miles
3 1 - < 2 miles
4 2 - < 3 miles
5 3 - 5 miles
6 6 miles
7 > 6 miles


QPF Categories
0 no precipitation
1 0.01 to 0.09 inches
2 0.10 to 0.24 inches
3 0.25 to 0.49 inches
4 0.50 to 0.99 inches
5 1.00 to 1.99 inches
6 2.00 inches or greater
Cloud (CLD) Categories
CL clear
FW few > 0 to 2 octas
SC scattered > 2 to 4 octas
BK broken > 4 to < 8 octas
OV overcast


Obstruction to Vision (OBV) Categories
N none of the following
HZ haze, smoke, dust
BR mist (fog with visibility >= 5/8 mile)
FG fog or ground fog (visibility < 5/8 mile)
BL blowing dust, sand, snow


Snow Fall Amount Categories
0 no snow or a trace expected
1 > a trace to < 2 inches
2 2 to < 4 inches
4 4 to < 6 inches
6 6 to < 8 inches
8 >= 8 inches


Precipitation Type (TYP) Categories
S pure snow or snow grains
Z freezing rain/drizzle, ice pellets, or
anything mixed with freezing precip
R pure rain/drizzle or rain mixed with snow