West Virginia Floods June 2016 NROW 2016 Albany NY Richard Grumm National Weather Service State College PA

Overview Where, when and how intensely it rained Was it Predictable Start with what happened and where it happened Was it Predictable Large scale signatures and QPFs Leveraging ARI and M-Climate Mesoscale Guidance Helps a bit but we still have a way to go Biggest issue: Our expectations and Uncertainty

Total Rainfall: Where it rained Stage-IV mainly 150 to 200 mm

When did it rain and where Figure 6. As in Figure 1 except for Stage-IV QPE in 6 hour increments from a) 0600 UTC 23 June through e) 0600 UTC 23 June and the summation of the 5 times in panel f. Values in mm based on the color key. Return to text.

How Hard did it rain verse 100 year ARI 6-hour return periods Figure 7. As in Figure 6 except for the ratio of the 6-hour Stage-IV QPE to the 6-hour 100 year recurrence interval data a-e and relative to the 24 hour 100 year recurrence interval in panel f. Values of the QPE/ARI ratio are expressed as a percentage of the ratio as per the color bar. Return to text.

Pattern was Favorable for heavy rainfall

Low-level inflow at 850 hPa Strong low-level westerlies anomalous Figure 5. As in Figure 3 except for CFSR 850 hPa wind vectors and the u-wind anomalies (shaded) in 6-hour increments from a) 0000 UTC 23 June 2016 through f) 0600 UTC 24 June 2016. Return to text.

The Pattern was pretty good Strong subtropical ridge with above normal heights Surge of high precipitable water (PW) air over the ridge Boundary became more east-west with time Strong westerly flow at 850 hPa And deep westerly flow over the ridge So inflow on west side of system

Could Guidance Forecast the pattern? Of course and where was the lift?

GEFS had the pattern as shown in PW Each member produced lift and thus useful but inexact QPF

The GEFS Produced A significant QPF Event in the model internal Climatology

GEFS had heavy rainfall But too far north GEFS had the rain too far north Most of Pennsylvania was missed and Missed heavy rainfall to the south Salient point: GEFS had the pattern and knew there would be a big QPF event. But our expectations of location were off. Uncertainty is part of forecasting

GFS QPF verse ARI GFS too knew a big event had errors

Traditional Guidance Will mesoscale guidance improve our abilities? Can produce the patterns for heavy rainfall In these pattern they can produce record and near record rainfall Thus they have clear signals which may be useful BUT They are inexact with huge spatial and temporal problems How we leverage this information matters

Mesoscale Guidance HREF NCEP HREF had a better signal Note matched mean gives texture NCEP HREF forecasts initialized at 1200 UTC 23 June 2016 showing 24 hour QPF for the 24 hour period ending at 1200 UTC 24 June 2016 showing left) the matched mean QPF and right) the probability of 6 inches or more QPF in 24 hours. Return to text.

HRRR-HRRR-TLE QPF>3 inches Time Lagged Ensemble (TLE)

NCAR 4km Ensemble Figure 15. NCAR 10 member 3km Ensemble initialized at 0000 UTC 23 June 2016 showing the hourly probability matched mean of 1 inch or more QPF for the 1 hour periods ending 20 and 22 UTC 23 June 2016. The second yellow color appears to be bleached out in these images. Return to text.

Convective allowing Mesoscale Guidance Is getting better Still had some issues with location and timing Out performed the larger scale guidance Higher resolution produced higher QPF maximum Rapid updates helped (did not show all the HRRR cycles) Got better at shorter ranges. Most CAMS had rainfall too far north and missed area of maximum rainfall Perhaps our expectations are too high

Summary This was a good example not a perfect one We know where, when and how intensely it rained The pattern was a relatively familiar heavy rainfall And thus the pattern was predictable Forecasters knew there would be big rainfall Guidance knew there would be big rainfall and ARI and M- Climate showed this Mesoscale Guidance had the rainfall develop in this favorable pattern Provided better clues and higher rainfall amounts But the biggest issue may be our expectations and how we deal uncertainty to include spatial and temporal issues