national weather service – reno [email protected] northern nevada 2015 streamflow forecast...
TRANSCRIPT
Reno National Weather ServiceForecasting for the Sierra and western Nevada since 1905
National Weather Service – [email protected]
Northern Nevada 2015 Streamflow Forecast Meeting
Mar 20, 2015
2
El Niño StatusEl Niño Advisory issued in early March. It’s weak, but it’s there.Oceanic and atmospheric conditions have become coupledWhat does that mean? Normally El Niño Conditions in winter would bring this type of response across North America.But…
www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisorywww.climate.gov
3
El Niño StatusA look at past events show only about 3 of the last 10 El Niño years had above average rainfall in California.There is very little correlation between El Niño and precipitation over North America during the spring months.Note over northeast Nevada there is better correlation that conditions will be dry!
www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisorywww.climate.gov
4
El Niño Status50-60% chance weak El Niño will continue through the summer and about 50% that it will continue into fall.Again no real strong correlation to expected precipitation patterns in the coming months.Impacts from El Niño tend to be weak during spring and summer.
www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisorywww.climate.gov
• Model Solutions for early Monday morning; differences in timing • GFS (upper left) is faster, colder, wetter and farther south• Could produce up to a foot of snow in the Tahoe Basin above 7000 feet; lesser
amounts to the south• Models don’t show much chance of precipitation for the rest of March
GFS ECMWF
GEMUpper Level Winds
6
Updated April 2015 OutlookOfficial outlook – slight favoring of above normal precip in the southeast and far eastern Nevada; equal chances of above, below and near normal elsewhere. Confidence – low to medium. Weak ENSO signal introduces a bit of uncertainty.Temperature – favors above normal with medium to high confidence (higher than average snow levels).
www.cpc.ncep.noaa.gov
7
Official outlook – favoring equal chances of above, below and near normal precipitation overall; low-medium confidenceTemperature – favors continued above normal with medium to high confidence.
www.cpc.ncep.noaa.gov
Spring/Summer 2015 (May-Jul) Outlook
CNRFC Streamflow Volume Predictions
Forecasts updated daily; based on current weather and historical dataStart with current conditions and 30-40 years worth of model dataProbability distribution derived from multiple runs; 50% chance of exceedance is taken as daily forecastUpper Humboldt in better shape than the Lower HumboldtPalisade currently forecast at 30%Imlay at only 3%
8http://www.cnrfc.noaa.gov/water_supply.php
CNRFC Streamflow Volume Predictions
Forecasts updated daily; based on current weather and historical dataStart with current conditions and 30-40 years worth of model dataProbability distribution derived from multiple runs; 50% chance of exceedance is taken as daily forecastTruckee River at Farad forecast at 48%
9http://www.cnrfc.noaa.gov/water_supply.php
CNRFC Streamflow Volume Predictions
Forecasts updated daily; based on current weather and historical dataStart with current conditions and 30-40 years worth of model dataProbability distribution derived from multiple runs; 50% chance of exceedance is taken as daily forecastCarson River at Carson City forecast at 20%Fort Churchill forecast at 15%
10http://www.cnrfc.noaa.gov/water_supply.php
CNRFC Streamflow Volume Predictions
Forecasts updated daily; based on current weather and historical dataStart with current conditions and 30-40 years worth of model dataProbability distribution derived from multiple runs; 50% chance of exceedance is taken as daily forecastWest Walker River above Coleville forecast at 39%
11http://www.cnrfc.noaa.gov/water_supply.php
12
Key TakeawaysMaybe some high elevation snow in the Tahoe Basin next week. April – Maybe an increase in precipitation over southeast and eastern Nevada; no clear signal anywhere else.Seasonal forecasts for spring and summer show no clear signal in terms of precipitation.Better confidence in warmer than normal temperatures overall – increased frequency of high snow level storms in April and May. ESP Volume forecasts from CNRFC are well below average and trending down for main points