** Winter Weather Options **


** DEFINITIONS **

[CPR]  = Combined probability (Prob_Field_1 x Prob_Field_2 x ... x 
         Prob_Field_N)
[MAX]  = Maximum from any member at each grid point
[MD]   = Median
[MDXN] = Median value contoured.  The dashed red line is the union of 
         all members at the lowest contour value plotted (i.e., where 
	 at least one of the 16 members exceeds the value of the first 
	 median contour).  The dashed blue line is the intersection of
	 all members at the lowest contour value plotted (i.e., where 
	 all 16 members exceed the value value of the first median 
	 contour).
[MIN]  = Minimum from any member at each grid point
[MN]   = Mean
[MNSD] = Mean and Standard Deviation
[PM]   = Probability Matched Mean Value
[PR]   = Probability (percentage of members meeting/exceeding some 
         condition)
[SP]   = Spaghetti



** SPECIFIC INFORMATION ON AVAILABLE FIELDS **

[PR]:Prob_Ptype_Snow_or_Ice ->Probability NCEP precipitation type
			      algorithm indicates snow OR freezing
			      rain OR ice pellets
[PR]:SnowRate_>=_1"/Hour ->Probability snowfall rate exceeds 1"/hour
			   for a 3h period.  Conversion of liquid
			   amount to snowfall uses a snow density 
			   (kg/m^3) = 109 + 6*(TMP - 273.15)
			   [from J. Hydromet, Aug 2001, pg 377] where 
		           TMP is the maximum temperature of the surface
		           or from the saturated layer up to 300 mb AGL
[MN]:Snowfall_(3hrs) ->SREF mean snowfall over the previous 3h period.
                       Conversion of total precip to snow uses a snow
		       density (kg/m^3) = 109 + 6*(TMP - 273.15)
		       [from J. Hydromet, Aug 2001, pg 377] where 
		       TMP is the maximum temperature of the surface
		       or from the saturated layer up to 300 mb AGL		       			   
[MAX]:Snowfall_(3hrs) ->As above, except the maximum from any SREF
                        member		   
[PR]:Blizzard_Conditions ->Probability of snow or ice pellets AND
			   wind >= 30 kts AND visibility <= 1/4 mile
[PR]:1000-500MB_Thck<=528 ->Probability 1000 to 500 mb thickness
                            <= 5280 meters
[PR]:1000-500MB_Thck<=534 ->As above but for thickness <= 5340 meters
[PR]:1000-500MB_Thck<=540 ->As above but for thickness <= 5400 meters
[PR]:Dendritic_Depth>=50mb ->Probability dendritic growth conditions
                             occur over a 50 mb depth.  Dendritic
			     growth conditions are defined here as:
			     omega < 0; dew point depression <= 3 degC
			     in the layer; -11 degC <= temp <= -17
			     degC.
[SP]:1000-500MB_Thck_5400m ->Spaghetti plot of 5400 meters 1000 to
                             500 mb thickness
[SP]:850MB_Temp_0C ->Spaghetti of 850 mb temperature at 0 degC


All SREF information presented herein is for guidance purposes 
only and should not be confused with official SPC operational 
forecasts.  Links to official SPC operational products are found 
at the bottom of every menu.

Many of the SREF products were developed for testing the utility 
of SREF analysis in the prediction of SPC mission critical items, 
including: thunderstorms and severe thunderstorms, large scale 
critical fire weather conditions, and mesoscale areas of hazardous 
winter weather. In order to accomplish this goal and test new and 
unqiue methods of SREF application in an operational environment, 
many fields not produced in the NCEP postprocessor were calculated 
locally for SPC purposes.



Close Window