The U. S. Winter Outlook

Transcription

1 The U. S. Winter Outlook Michael Halpert Acting Director Climate Prediction Center

2 Outline CPC Overview About the Seasonal Outlook Potential Climate Features impacting U. S. Winter U. S. Winter (DJF) Outlook 2

3 CPC Mission Deliver real-time products and information that predict and describe climate variations on timescales from weeks to year(s) thereby promoting effective management of climate risk and a climate-resilient society. One of 9 NCEP Service Center; only NWS center issuing climate products Focus: weeks, months, seasons, years (i.e. short term climate) National temperature and precipitation outlooks Integral to NWS Seamless Suite of Products Temperature Outlook

4 Climate Prediction Products Focus on week-2 to seasonal-to-interannual 6-10 Day & 8-14 Day Precipitation & Temperature Outlooks Day 3-14 Hazards Outlooks (US, Global Tropics) Monthly & Seasonal Precipitation & Temperature Outlooks Seasonal Drought Outlook Seasonal Hurricane Outlooks (Atlantic and Eastern Pacific) Monthly ENSO Prediction Tools used to develop prediction products Dynamical Models Statistical Models Historical Analogs Historical Composites * Dynamical Models Climate Forecast System Global Forecast System ECMWF

5 6-10 Day Outlook Washington Below: 32% Near: 36% Above: 32% C. Texas Below: 17% Near: 33% Above: 50% Seasonal Maine Below: 33% Near: 33% Above: 33% 5 S. Nevada Below: 7% Near: 33% Above: 60%

6 Climate Monitoring Products Daily and monthly data, time series, and maps for various climate parameters and compilation of data on historical and current atmospheric and oceanic conditions Primary modes of climate variability (ENSO, MJO, NAO, PNA, AO,...) Atmospheric Circulation (global troposphere and stratosphere) Storm Tracks and Blocking Monsoons Oceanic Conditions (global and coastal) Precipitation and Surface Temperature (global and US) Drought (US, North America; NIDIS)

7 Outline CPC Overview About the Seasonal Outlook Potential Climate Features impacting U. S. Winter U. S. Winter (DJF) Outlook 7

8 Outlook Categories and Probabilities! Seasonal outlooks are prepared for average temperature and total accumulated precipitation category! Three categories are used (terciles). These are BELOW-,NEAR- and ABOVEnormal (median), for temperature (precipitation).! Regions where the likelihoods of the three categories are the same (33.33 % each) are designated as EC, for equal chances.! In non-ec regions the labels on the contours give the total probability of the dominant category. 8

9 About the Seasonal Outlook Each month, near mid-month CPC prepares a set of 13 outlooks for 3-month seasons (any set of 3 adjacent months) for lead times ranging from ½ month, 1 ½ months, 2 ½ months, 3 ½ months,, 12 ½ months. November 21 DJF DJF The outlook for each successive/prior lead time overlaps the prior/successive one by 2 months. This overlap makes for a smooth variation from one map to the next. 9

10 Temperature U. S. Seasonal Outlooks Interpretation Precipitation N. Washington Below: 45% Near: 33% Above: 22% N. Georgia Below: 29% Near: 33% Above: 38% Minnesota Below: 33% Near: 33% Above: 33%

11 Outline CPC Overview About the Seasonal Outlook Potential Climate Features impacting U. S. Winter U. S. Winter (DJF) Outlook 11

12 N A T I O N A L O C E A N I C A N D A T M O S P H E R I C A D M I N I S T R A T I O N How Does CPC Make Opera0onal Seasonal Climate Outlooks? Seasonal temperature and precipitation forecasts are based on a combination of statistical and dynamical forecasts An objective consolidation of forecast information provides a basis for a single outlook map A forecaster subjectively adjusts the forecast A team of seasonal forecasters reviews the forecasts with input from across NOAA and other agencies First conference call on Friday before release date to review the current climate state and previous forecasts Second call on Tuesday before release date to review the forecaster s preliminary maps Release date every third Thursday of the month Monthly ENSO forecast is always updated prior to the start of the seasonal forecast process 12

13 FACTORS INFLUENCING A CLIMATE FORECAST Climate Change - trends Natural Climate Variability organizes weather El Niño-Southern Oscillation (ENSO) Mid-latitude Oscillation modes (NAO, AO, PNA, ) Land Surface Processes (Soil moisture, Snow cover, ) Atmospheric Noise - unpredictable climate signals produced by chance through cumulative effects of weather. This is large in middle latitudes, small in the Tropics. Major cause of uncertainty in forecasts.

14 ENSO-neutral is expected to continue into the Northern Hemisphere summer 2014.

15 Pacific Niño 3.4 SST Outlook Most models predict ENSO-neutral (-0.5ºC to +0.5ºC) continuing through Northern Hemisphere summer Figure provided by the International Research Institute (IRI) for Climate and Society (updated 19 November 2013).

16 NORTH ATLANTIC OSCILLATION/ ARCTIC OSCILLATION A major source of intraseasonal variability over the U. S., Atlantic and Europe during winter. Modulates the circulation pattern over the high latitudes thereby regulating the number and intensity of significant weather events affecting the U.S., such as cold air outbreaks. Currently there is no reliable capability to forecast the seasonal phase. 16

17 Arctic Oscillation (AO) Positive Arctic Oscillation (left) and negative Arctic Oscillation (right). Source: J. Wallace, University of Washington

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20 NH Winter Arctic Oscillation (AO)

21 Individual Model Forecasts 21

22 National and International MultiModel Ensemble Forecast updated Oct. 9,

23 Optimal Climate Normal (OCN) OCN, as it is used as a tool at CPC is, quite simply, a measure of the trend. For a given station and season, the OCN forecast is the difference between the seasonal mean temperature during the last 10 years and the 30 year climatology. 23

24 Optimal Climate Normal (OCN) OCN, as it is used as a tool at CPC is, quite simply, a measure of the trend. For a given station and season, the OCN forecast is the difference between the seasonal mean temperature during the last 10 years and the 30 year climatology. 24

25 Global Land Decadal Trends G H C N - C A M S F A N

26 December - February OCN

27 Winter Outlook Rationale ENSO-neutral conditions across the Pacific have prevailed for over a year. ENSO-neutral is favored through NH winter. AO has been and continues to be erratic. Large swings possible in any year (e.g. DJF ). Temperature trends relative to base period are generally small over country; precipitation trends resemble La Niña. Forecast consistent with trends and most model forecasts, but confidence is low. 27

28 Outline CPC Overview About the Seasonal Outlook Potential Climate Features impacting U. S. Winter U. S. Winter (DJF) Outlook 28

29 December 2013 February 2014 Temperature Outlook C. Texas Below: 23% Near: 33% Above: 44% C North Dakota Below: 42% Near: 33% Above: 25% C Virginia Below: 33% Near: 33% Above: 33%

30 December 2013 February 2014 Precipitation Outlook C. New Mexico Below: 43% Near: 33% Above: 24% C. Montana Below: 23% Near: 33% Above: 44%

31 U. S. Winter Outlook: Forecast Summary Odds slightly favor: Warmer than average across the southwestern, south central, and northeastern portions of the nation Colder than average favored in Northern Plains Drier than average in parts of the Southeast and Southwest; Wetter than average Northern Rockies 31