Upcoming Changes in Winter Weather Operations at the Weather Prediction Center (WPC) Great Lakes...

Upcoming Changes in Winter Weather Operations at the

Weather Prediction Center (WPC)

Great Lakes Operational Meteorological WorkshopDan Petersen, Wallace Hogsett, Faye Barthold,

Mike Bodner, and Keith Brill

New ensemble membership of probabilistic snow/freezing rain forecasts for the 2014-15 season

Experimental winter weather ‘watch recommender’

Experimental Days 4-7 Winter Weather Forecasts

Presentation Outline

32-member ensemble: WPC deterministic forecast 21 Short Range Ensemble Forecast (SREF) members GFS Global Ensemble Forecast (GEFS) Mean, 5 GEFS

members ECMWF, ECMWF Ensemble Mean Canadian Global (GDPS) snowfall/freezing rain

forecasts

Previous Models/Ensembles Used to Compose Snow/Ice Probability Forecasts

24 Hour Forecast Liquid Equivalent Precipitation Valid 12z 04 Mar 2014

SREF Mean 87 hr precipitation forecast (left), Climate Prediction Center Analysis of observed precipitation (right)

Forecast

Observed

GFS 84 hr forecast (left), Climate Prediction Center Analysis (right)


Forecast

Observed

ECMWF 84 hr forecast (left), analysis (right)


Forecast

Observed

NAM 84 hour forecast (left), Climate Prediction Center Analysis (right)


Forecast

Observed

Weather Prediction Center 24 Hour Probability of Snow 12z 03 Mar to 12z 04 Mar 2014

The SREF, NAM further north axis of QPF results in northward expansion of probabilities in PA/NJ/NY/southern New England)

Run to Run Changes result in lower forecast confidence-03 Mar 2014

http://eyewall.met.psu.edu/rich/compare/

SREF Forecast 6 hour precipitation valid 18z 03 Mar 2014 (15z run left, 09z run right)

Later run (left) decreases precip across southern NY/New England

Run to Run Changes result in lower forecast confidence-17 Mar 2014

The high probability of QPF over PA/northern NJ/Long Island NY too high and not calibrated (courtesy Rich Grumm and Jeff Tongue)- 14 Mar runs of the SREF probability of 12.5 mm of precip

- 14-16 Mar runs of the SREF probability of 12.5 mm of precip

03z cycle 14 Mar

09z cycle 14 Mar

15z cycle 14 Mar

21z cycle 14 Mar

09z cycle 15 Mar

09z cycle 16 Mar

Need to include more datasets has resulted in the addition of 25 ECMWF ensemble membersFor the 2014-15 season: 57-member ensemble including WPC deterministic forecast* 25 ECMWF Ensemble members (transition to 0.5 degree

resolution during 2014-15 season) 21 SREF members GFS GEFS Mean, 5 GEFS members ECMWF, ECMWF Ensemble Mean Canadian Global (GDPS) snowfall/freezing rain

forecasts

2014-15 Models/Ensembles Used to Compose Snow/Ice Probability Forecasts

http://www.wpc.ncep.noaa.gov/pwpf/about_pwpf_products.shtml

Goal: provide maps of where the snow/freezing rain accumulation probabilities of watch/warning criteria exceed 50 percent for use in watch decisions

Maps of 12/24 hour forecasts will be posted on password protected winter weather page

2014-15 season: Experimental Winter Weather ‘Watch Recommender’

Step #1 – Compute probability of exceeding snow/ice accumulation thresholds and compare to local warning criteria to determine the probability of exceeding watch/warning criteria

Step #2 – If probability of exceeding watch/warning criteria ≥ 50%, area on map is highlighted

Step #3 – Produce map summarizing where >50% probability of exceeding watch/warning criteria occurs at any time during the 3 day period

Methodology

+ =WPC Snow Probability

12-hr warning criteria Probability of exceeding warning criteria

Probability of exceeding warning criteria

≥ 50% ?Highlight areas of >50% on map

Example – 12 March 2014

Summary map-all areas where >50% chance of exceeding 12 hr

criteria anytime during 72 hr period ending 00 UTC 3/15

Probability of exceeding 12-hr criteria ending 12Z 3/12





‘Watch Recommender’ is a tool to assist in collaboration between WPC and WFOs

Example – 7 March 2014

Blue highlights where probability of exceeding 24 hr snowfall

criteria>50%

Red highlights areas where

probability of exceeding 24 hr

freezing rain criteria >50%


Forecast Components: WPC QPF and international ensembles

WPC QPF-2 day QPF divided into 24 hour components

WPC Day 6-7 48-hr QPF Day 6 24-hr WPC QPF Day 7 24-hr WPC QPF


Forecast Components

Probability of WPC QPF >= .10

Ensemble Probability of Frozen Precipitation

Probability of Winter Precipitation > 0.10”

× ¿

Forecasters edited probability of winter precipitation for individual models/ ensemble members and means

Future Work • Expand precipitation type guidance to include all

GEFS, ECENS and CMCE members• Add ensemble QPF mean from other ensemble

systems (ECMWF, Canadian)

Multi-ensemble Precipitation Type

GEFS ECMWF GEFS+ECMWF


24 hr snow ending 00z 13 Mar 2014 www.nohrsc.noaa.gov

Examples of Experimental Days 4-7 Winter Weather Forecasts

Day 7 forecast verifying 00z 13 Mar 2014

Red contours WPC probability of 0.10” liquid equivalent frozen precipitation

Color filled graphic observed liquid equivalent precipitation (scale on left)

Snow and ice accumulation probabilities have been updated to incorporate 25 members of the ECMWF ensemble

Winter Weather ‘Watch recommender’ has been developed to match watch/warning criteria and produces maps of locations where the probability of the criteria being exceeded is >50%

Initial testing of days 4-7 winter weather outlooks has begun and more testing is forthcoming for 2014-15

Future: NWS proposal to expand winter weather desk to 24 hour/day operations

Summary: WPC Winter Weather Desk Updates

Questions or Comments?

[email protected] Forecast Operations Branch

(301) 683-1530

mailto:[email protected]

Future Improvements

Timing Output from watch recommender

currently available at the very end of each WWD shift

Warning Criteria Currently using estimates for Western

Region, much of Southern Region Not accounting for terrain


Forecast ComponentsProbability of WPC QPF >= 0.10”●WPC 24-hr QPF is used as a meanThe 24-hr QPF from each of the 20 GEFS members and 50 ECENS members are used as a variance to compute a cumulative distribution function (CDF) of the WPC QPF reaching or exceeding 0.10” (top right image)

Probability of WPC QPF >= .10

Ensemble Probability of Frozen Precipitation

Probability of Winter Precipitation > 0.10”

Frozen Precipitation Component●An ensemble probability of frozen precipitation isgenerated using the precipitation type fields for snow, sleet and freezing rain in each of the GEFS members (middle right image)● Probability of winter precipitation >= 0.10” is derived from multiplying ensemble probability of frozen precipitation by the probability of the WPC QPF >= 0.10” (Bottom right image)

2014 NCEP Ensemble Users workshop:http://www.emc.ncep.noaa.gov/gmb/ens/WkShopOct13/6th_User_workshop.shtmlSREF upgrade: http://www.emc.ncep.noaa.gov/gmb/ens/WkShopOct13/program/pdf/S1-02-SREF2014.pdfECMWF upgrade:http://www.emc.ncep.noaa.gov/gmb/ens/WkShopOct13/program/pdf/S4-04-RB_2014_03_NCEP_WSensUsers.pdfQPF Object oriented verification: http://www.wpc.ncep.noaa.gov/verification/mode/mode.php#page=page-1

Updates, Plans, and Applications

http://www.emc.ncep.noaa.gov/gmb/ens/WkShopOct13/program/pdf/S1-02-SREF2014.pdf




http://www.emc.ncep.noaa.gov/gmb/ens/WkShopOct13/program/pdf/S4-04-RB_2014_03_NCEP_WSensUsers.pdf




Impetus to Change Ensemble Membership in Probabilistic Snow

Forecasts

Analysis of Observed 24 Hr Snow ending 00z 04 Mar 2014

http://www.nohrsc.noaa.gov

Winter Weather Desk Forecast Snowfall Accumulation Ending 00z

Tue 04 Mar 2014

72 Hr 50th Percentile Snowfall ending 00z Tue 04 Mar 2014

DCA Forecast SREF mean snow 12.4 inches observed 7 inches

observed

DCA Forecast experimental SREF mean snow 11.7 inches observed 7 inches

observed

NAM B 84 hr forecast (left), Climate Prediction Center Analysis (right)


http://www.srh.noaa.gov/ridge2/snow/index.php?site=dtx

Upcoming Changes in Winter Weather Operations at the Weather Prediction Center (WPC) Great Lakes...

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