Addition of Mean Sky Cover to the 1200 UTC GFS MOS MEX Alphanumeric Message

On or about November 5, 2013 we will implement new forecast equations to update the 0000 UTC mean total sky cover guidance and add mean total sky cover to the 1200 UTC extended-range GFS-Based MOS (MEX) guidance. This will change the format of the 1200 UTC bulletin slightly, completing the message with the addition of the weather element CLD. The format of the 0000 and 1200 UTC messages will become identical.

In addition, 322 sites from 0000 UTC bulletin will now have mean total sky cover guidance.

Format of 1200 UTC Message Before November 5, 2013

 IAD   GFSX MOS GUIDANCE   3/04/2013  1200 UTC                       
 FHR  24  36| 48  60| 72  84| 96 108|120 132|144 156|168 180|192      
      TUE 05| WED 06| THU 07| FRI 08| SAT 09| SUN 10| MON 11|TUE CLIMO
 N/X  21  45| 32  42| 32  45| 29  45| 31  51| 30  57| 34  55| 41 29 53
 TMP  24  40| 35  39| 34  41| 32  40| 34  45| 33  49| 37  49| 44      
 DPT  15  22| 28  27| 28  27| 23  26| 25  27| 26  30| 28  33| 37      
 WND  10   5| 14  20| 20  19| 18  21| 14  12|  6   8|  6   8|  7      
 P12   3  55| 98  90| 20   6|  0   7|  5   3|  4   7| 10  20| 47 23 24
 P24      55|    100|     20|      7|      5|      7|     25|       34
 Q12   0   1|  4   2|  0   0|  0   0|  0   0|  0   0|       |         
 Q24       1|      5|      0|      0|      0|      0|       |         
 T12   0   1|  1   5|  1   1|  2   1|  1   1|  1   2|  0   2|  1      
 T24        |  1    |  7    |  3    |  1    |  1    |  2    |  2      
 PZP   8  19| 26   2|  8  10|  8   7|  8   9|  6   3|  5   4|  4      
 PSN  90  42| 44  14| 51  46| 57  49| 46  26| 22  17|  3   8|  6      
 PRS   0  29| 20  27| 30  25| 17  17| 19  11|  3   2|  9   5|  4      
 TYP   S   S|  Z  RS|  S   S|  S   S|  S  RS|  R   R|  R   R|  R      
 SNW       0|      4|      0|      0|      0|      0|       |    
 
Format of 1200 UTC Message After November 5, 2013

 IAD   GFSX MOS GUIDANCE   3/04/2013  1200 UTC                       
 FHR  24  36| 48  60| 72  84| 96 108|120 132|144 156|168 180|192      
      TUE 05| WED 06| THU 07| FRI 08| SAT 09| SUN 10| MON 11|TUE CLIMO
 N/X  21  45| 32  42| 32  45| 29  45| 31  51| 30  57| 34  55| 41 29 53
 TMP  24  40| 35  39| 34  41| 32  40| 34  45| 33  49| 37  49| 44      
 DPT  15  22| 28  27| 28  27| 23  26| 25  27| 26  30| 28  33| 37      
 CLD  PC  OV| OV  OV| OV  PC| CL  PC| CL  CL| PC  OV| OV  OV| OV      
 WND  10   5| 14  20| 20  19| 18  21| 14  12|  6   8|  6   8|  7      
 P12   3  55| 98  90| 20   6|  0   7|  5   3|  4   7| 10  20| 47 23 24
 P24      55|    100|     20|      7|      5|      7|     25|       34
 Q12   0   1|  4   2|  0   0|  0   0|  0   0|  0   0|       |         
 Q24       1|      5|      0|      0|      0|      0|       |         
 T12   0   1|  1   5|  1   1|  2   1|  1   1|  1   2|  0   2|  1      
 T24        |  1    |  7    |  3    |  1    |  1    |  2    |  2      
 PZP   8  19| 26   2|  8  10|  8   7|  8   9|  6   3|  5   4|  4      
 PSN  90  42| 44  14| 51  46| 57  49| 46  26| 22  17|  3   8|  6      
 PRS   0  29| 20  27| 30  25| 17  17| 19  11|  3   2|  9   5|  4      
 TYP   S   S|  Z  RS|  S   S|  S   S|  S  RS|  R   R|  R   R|  R      
 SNW       0|      4|      0|      0|      0|      0|       |    
 
Current 0000 UTC Message (format not changing)

 IAD   GFSX MOS GUIDANCE   3/05/2013  0000 UTC                       
 FHR  24| 36  48| 60  72| 84  96|108 120|132 144|156 168|180 192      
 TUE  05| WED 06| THU 07| FRI 08| SAT 09| SUN 10| MON 11| TUE 12 CLIMO
 X/N  47| 34  42| 32  44| 29  45| 32  50| 33  57| 38  58| 40  54 29 53
 TMP  42| 36  39| 34  39| 32  41| 34  44| 37  50| 42  52| 43  47      
 DPT  23| 26  28| 24  29| 24  25| 25  29| 30  34| 34  38| 34  28      
 CLD  OV| OV  OV| OV  PC| CL  PC| CL  CL| PC  OV| OV  OV| OV  PC      
 WND   5| 18  20| 20  16| 13  22| 14   8|  5   8|  5  10| 18  14      
 P12  36| 99  93| 36   5|  0   7|  5   5|  7  17| 30  35| 31  24 24 24
 P24    |    100|     36|      7|      6|     19|     53|     46    34
 Q12   0|  5   5|  0   0|  0   0|  0   0|  0   0|  1    |             
 Q24    |      5|      0|      0|      0|      0|       |             
 T12   1|  1   7|  2   1|  0   1|  1   1|  1   2|  1   5|  4   6      
 T24    |  1    |  9    |  2    |  1    |  1    |  2    |  6          
 PZP  13| 27   4| 13   9|  6   6| 17  13|  6   5|  4   4|  4   5      
 PSN  25|  4  28| 16  45| 64  52| 32  24| 16   2|  3   4|  4  21      
 PRS  28| 47  29| 45  26| 16  15| 18   8|  3   4|  4   3|  9  14      
 TYP  RS|  Z  RS| RS   S|  S   S|  S  RS|  R   R|  R   R|  R   R      
 SNW    |      4|      0|      0|      0|      0|       |             
  • FHR = Forecast hour, i.e. how many hours from the model run time
  • X/N = daytime max/nightime min temperatures
  • TMP = temperature valid at that hour
  • DPT = dewpoint valid at that hour
  • CLD = mean total sky cover over the 12-hr period ending at that time
  • WND = maximum sustained surface wind (WND) during a 12-h period
  • P12 = 12-hr probability of precipitation (PoP) ending at that time
  • P24 = 24-hr PoP ending at that time
  • Q12 = 12-hr quantitative precipitation forecast (QPF) ending at that time
  • Q24 = 24-hr QPF ending at that time
  • T12 = 12-hr probability of thunderstorm ending at that time
  • T24 = 24-hr probability of thunderstorm for the 1200-1200 UTC time period ending at that time
  • PZP = conditional probability of freezing pcp occurring for the 12-hr period ending at that time (seasonal)
  • PSN = conditional probability of snow occurring for the 12-hr period ending at that time (seasonal)
  • PRS = conditional probability of rain/snow mix occurring for the 12-hr period ending at that time (seasonal)
  • TYP = conditional precipitation type for the 12-hr period ending at that time (seasonal)
  • SNW = snow fall categorical forecasts during a 24-h period ending at the indicated time (seasonal)
  • CLIMO = derived from 1970 - 2000 PRISM normals, to be updated from NCDC 1980 - 2010 normals soon.
 

Definitions of Categorical Elements

MEX 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


MEX 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
MEX Cloud (CLD) Categories
CL mostly clear                  
PC partly cloudy
OV mostly cloudy


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