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Experimental Short-Range Ensemble Forecast (SREF)
Dispersion Forecast for Washington, D.C. (+0 hours)

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Chicago 12 24 36
Los Angeles 12 24 36
Washington 12 24 36

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Probability that concentration exceeds Number of members Mean Variance
1% of maximum value 10% of maximum value 100% of maximum value
Probability that concentration exceeds 1% of maximum value Probability that concentration exceeds 10% of maximum value Probability that concentration exceeds 100% of maximum value Number of members Mean Variance

Concentration at
5th percentile 10th percentile 25th percentile 50th percentile 75th percentile 90th percentile 95th percentile
Concentration at 5th percentile Concentration at 10th percentile Concentration at 25th percentile Concentration at 50th percentile Concentration at 75th percentile Concentration at 90th percentile Concentration at 95th percentile

Individual member plots
eta_ctl1 eta_ctl2 eta_n1 eta_n2 eta_n3 eta_n4 eta_p1
eta_ctl1 member eta_ctl2 member eta_n1 member eta_n2 member eta_n3 member eta_n4 member eta_p1 member
eta_p2 eta_p3 eta_p4 nmm_ctl nmm_n1 nmm_p1 rsm_ctl1
eta_p2 member eta_p3 member eta_p4 member nmm_ctl member nmm_n1 member nmm_p1 member rsm_ctl1 member
rsm_n1 rsm_n2 rsm_p1 rsm_p2 em_ctl em_n1 em_p1
rsm_n1 member rsm_n2 member rsm_p1 member rsm_p2 member em_ctl member em_n1 member em_p1 member

This web page is under development and is experimental.
Products may change without notice.
Concentrations are relative to the source of 1 unit.
Contour values may vary from chart to chart.

Model Details:

The 6-hour HYSPLIT dispersion forecasts above are output using 21 members of the National Weather Service (NWS) National Centers for Environmental Prediction (NCEP) Short-range ensemble forecasts (SREF) for a source location of Washington, DC, Reagan National Airport (DCA). Members are composed of dispersion output using the following models: Eta, WRF/NMM, WRF/ARW (em), and RSM.

  • 10-minute release from the layer 10 - 50 m above ground beginning at 06 UTC
  • All output is for the layer 0 to 100 m
  • 03 UTC NCEP SREF forecast
  • No wet nor dry deposition
  • Eruption mass is arbitrarily set to one unit. Concentrations shown are with respect to the one unit source.

Probability that concentration exceeds:

These plots show the probability, in percent, that the concentration exceeds a concentration equal to the given percent of the maximum value. For example, the plot on the left labeled "1% of maximum value", shows the probability of the concentrations exceeding 1E-12 units of mass per cubic meter. This is indicated by the "C-12" label on the line of text above the plot. The center plots shows the probabilities of exceeding the concentration 1E-11 (C-11), and the plot on the right, 1E-10 (C-10).

Concentration at:

These plots show the concentrations at the given percentile. The plots are labeled "PC05", "PC10", "PC25", "PC50", "PC75", "PC90", and "PC95" in the line of text above each of the 5th, 10th, 25th, 50th, 75th, 90th, and 95th percentile plots, respectively. For instance, for each point on the PC75 plot, there is a 75% chance that the concentration is less than that shown.

Modified: January 6, 2010
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