1 HPC Winter Weather Desk Operations and Upcoming NCEP Model Changes Dan Petersen NROW Conference...

1

HPC Winter Weather Desk Operations and Upcoming NCEP

Model Changes

Dan PetersenNROW Conference Nov. 4, 2009

With contributions from David Novak and Keith Brill

2

HPC Winter Weather DeskHPC Winter Weather DeskOverviewOverview

Internal deterministic 6-h snow/ sleet/ ZR accumulation grids & graphics

Heavy Snow and Ice Discussion (QPFHSD)

Public products of 24-h exceedance probabilities for:

Snow/Sleet: 4,8,12 in.Freezing Rain: 0.25 in.Probabilities computed from deterministic forecast and model spread

Track forecasts for sfc. lows associated w/ significant winter weather

3

• Analysis of lift, instability, moisture, and thermal profiles of model solutions

• Use model/ensemble blender to generate first guess

Winter Weather Desk (WWD) Forecast ProcessWinter Weather Desk (WWD) Forecast Process

•Forecaster edits first guess, and sends to WFOs

- Precipitation type from thermal profile of blend - Snow-liquid ratio from Roebber technique /Climatology/ fixed ratio

4

• WFO input used to modify public snow/ice probabilistic forecasts

• HPC input used to modify grids within GFE to produce local forecast

• Results in final collaborated forecast

HPC/WFO Collaboration via instant message, phone and/or event conference calls

WWD Collaborative Forecast ProcessWWD Collaborative Forecast Process

5Courtesy Brian Montgomery, WFO Albany

(snow blue-green-orange, freezing rain pink-purple)

Advent of WWD Accumulation Grids in AWIPSAdvent of WWD Accumulation Grids in AWIPS

6

Snow, freezing rain, and snow to liquid ratio grids are available in six hourly increments for ingest at WFOs.

Requested at NROW 2008!

Courtesy Brian Montgomery, WFO Albany

Advent of WWD Accumulation Grids in GFEAdvent of WWD Accumulation Grids in GFE

7

Probabilistic snow forecast verificationProbabilistic snow forecast verification

-20-15-10

-505

1015

Brier Skill Score (x

100)

Day 1 Day 2 Day 3

Skill Relative to Automated Superensemble

4"8"12"

•Hypothesis: Probabilities for ≥12” threshold forecast over too small of area (i.e., under dispersive / too focused on a preferred solution or

cluster of solutions)

NAM + GFS + SREF members + GEFS members

8

2008-9 Day One Snow 2008-9 Day One Snow Accumulation Threat ScoresAccumulation Threat Scores

Green: Winter Weather Desk manual forecast

Blue: NAM+GFS+ SREF mean +GEFS mean

0

0.05

0.1

0.15

0.2

0.25

0.3

Threat score

4" 8" 12"

WWD

SUPERENS

9

0

0.05

0.1

0.15

0.2

0.25

Threat Score

4" 8" 12"

WWD

SUPERENS


Blue: NAM+GFS+SREF mean +GEFS mean

2008-9 Day Two Snow 2008-9 Day Two Snow Accumulation Threat ScoresAccumulation Threat Scores

10

00.020.040.060.08

0.10.120.140.160.18

0.2

Threat Score

4" 8" 12"

WWD

SUPERENS



2008-9 Day Three Snow 2008-9 Day Three Snow Accumulation Threat ScoresAccumulation Threat Scores

11

2008-9 Day One Ice 2008-9 Day One Ice Accumulation Threat ScoresAccumulation Threat Scores

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Threat Score

0.01" 0.25" 0.50"

WWD

SUPERENS



12

2008-9 Day Two Ice 2008-9 Day Two Ice Accumulation Threat ScoresAccumulation Threat Scores

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Threat Score

0.01" 0.25" 0.50"

WWD

SUPERENS



13

2008-9 Day Three Ice 2008-9 Day Three Ice Accumulation Threat ScoresAccumulation Threat Scores

0

0.05

0.1

0.15

0.2

0.25

0.3

Threat Score

0.01" 0.25" 0.50"

WWD

SUPERENS



14

Verification of HPC low tracks Verification of HPC low tracks (position at each forecast hour)(position at each forecast hour)

Average of GFS/NAM did best through 24 hours, while ECMWF

and HPC were best after 48 hours.

15

The NCEP Short-Range Ensemble Forecast (SREF)

System

Jun Du, Geoff DiMego and Bill Lapenta

NOAA/NWS/NCEPEnvironmental Modeling Center

http://www.nws.noaa.gov/om/notification/tin09-29aaasref_upgrade.txt

16

• Upgrade models: WRF-NMM, WRF-ARW and RSM

• Increase horizontal resolution:– ARW (45 km to 35 km)– NMM (40 km to 32 km)– RSM (45 km to 32 km)

• Total Membership = 21:– Adding 4 WRF members– Eliminating 4 Eta members

• Zhou cloud physics Ferrier (3 RSM members)

• Ensemble Transform (ET) perturbations (10 WRF members)

• Increase output frequency from every 3 hr to hourly for 1st 39hr

• Add/fix/unify variables in SREF output– radar (composite reflectivity + echo top) (aviation)– unify PBL height diagnosis with critical Ri (aviation)– fix cloud base (aviation)– BUFR broken out into individual station time-series (SPC)– Hurricane track

Upgrades to the SREF systemUpgrades to the SREF system (Implemented 27 Oct. 2009)(Implemented 27 Oct. 2009)

87 h forecast

17

SREF Plume – State College, PASREF Plume – State College, PAInitial time: 09 UTC 23 Nov 2008Initial time: 09 UTC 23 Nov 2008

Cold WRF v2.0 Members

18

SREF Plume – State College, PASREF Plume – State College, PAInitial time: 09 UTC 23 Nov 2008Initial time: 09 UTC 23 Nov 2008

19

SREF Future PlansSREF Future Plans • 2010:

– Post processed output of SREF members downscaled to 5 or 2.5km

– Addition of more variables to AWIPS

– Addition of more ensemble products requested by users such as AFWA

– Eta members discontinued

20

SREF Future PlansSREF Future Plans • 2010:

– Post processed output of SREF members downscaled to 5 or 2.5km

– Addition of more variables to AWIPS

– Addition of more ensemble products requested by users such as AFWA

– Eta members discontinued

• 2012: – SREF run at 20 km resolution

(2010 run at 32 km)

– Introduction of the NAM Rapid Refresh (10-12 km, hourly update to the 24 hour forecast)

– Introduction of higher resolution (3 km) nested rapid refresh for high impact events in CONUS, AK and HI

21

The NCEP Global Forecast System (GFS)

John Ward

NOAA/NWS/NCEPEnvironmental Modeling Center

http://www.nws.noaa.gov/om/notification/tin09-32gfs_changes.txt

22

December 15 ImplementationDecember 15 Implementation

• Gridpoint Statistical Interpolation (GSI) Analysis/GFS Fall Bundle

– Ingest new data types – primarily satellite

– Motivation: Simulating ECMWF initialization improved GFS forecast performance ams.confex.com/ams/pdfpapers/142644.pdf

– Benefits

» Better tropical cyclone definition» Small incremental improvement in forecast skill

23

24 h accumulated precip ending 12 UTC 15 July 2009Observed

Update Shallow convection, Deep Convection, PBL SchemesBenefits

Significant reduction in gridpoint stormsImprovement in forecast skill (QPF, wind, temp, etc)

72 h GFS Forecast

72 h GFSp Forecast

March 2010 ImplementationMarch 2010 Implementation

24

• GFS Resolution Increase

– T382L64 (~35 km) T574L64 ( ~27 km grid spacing)

– Benefits

» Overall improvement in forecast skill

May 2010 ImplementationMay 2010 Implementation

25

The NCEP Global Ensemble Forecast System (GEFS)

upgradesYuejian Zhu

Zoltan Toth, Richard Wobus, Dingchen Hou and Bo Cui

Global Ensemble GroupEnvironmental Modeling Center

http://www.nws.noaa.gov/om/notification/tin09-34gefs.txt

26

Planned Changes - SummaryPlanned Changes - Summary

• Effective late January, 2010• Upgrade horizontal resolution from T126 to T190• Use 8th order horizontal diffusion for all resolutions

– Improved forecast skills and ensemble spread• Introduce Earth System Modeling Framework(ESMF) for GEFS

– Allows concurrent generation of all ensemble members– Needed for efficiency of stochastic perturbation scheme

• Add stochastic perturbation scheme to account for random model errors– Increased ensemble spread and forecast skill (reliability)

• Add new variables (28 more)– Mostly stratospheric

27

Continuous Ranked Probability Skill Score for Northern Continuous Ranked Probability Skill Score for Northern Hemisphere (NH) 850hPa temperatureHemisphere (NH) 850hPa temperature

Summer (08/01-09/30/2007)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Lead Time (days)

GEFS GEFSp

Winter (11/01-12/30/2007)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Lead Time (days)

GEFS GEFSp

Extend current 5-day skill to 6.5-day

Extend current 5-day skill to 6-day

28

NH Anomaly Correlation for 500hPa HeightNH Anomaly Correlation for 500hPa HeightPeriod: August 1Period: August 1stst – September 30 – September 30thth 2007 2007

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

An

om

aly

Co

rrel

atio

n

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Forecast Lead Time (days)

GFS GEFS GEFSp

GEFSp is better than GFS at 48

hours

Parallel GEFS forecast skill at day 9 equals the GFS skill at day 7

24 hours better than current GEFS48 hours better than current GFS

29

Summary

• WWD continues to provide critical winter weather forecast guidance and collaboration– Gridded snow and ice accumulations and SLR in AWIPS

• Several upcoming model upgrades– SREF (Oct 2009)– GFS (several phases)– GEFS (January 2010)

• WWD products generally improve upon NCEP model guidance

Questions or Comments?Dan Petersen(301)763-8201

[email protected]

30

WWD Snow/Ice Verification Method

Where model forecasts snow:Model forecast snow accumulation = model QPF * Snow Liquid Ratio

where the SLR is a 4 member mean of Roebber technique1 applied to GFS, Roebber technique applied to NAM, Climatology2, and 10:1

1Roebber, P. J., S. L. Bruening, D. M. Schultz, and J. V. Cortinas, 2003: Improving snowfall forecasting by diagnosing snow density. Wea. Forecasting, 18, 264-287.

2Baxter, M. A., C. E. Graves, and J. T. Moore, 2005: A climatology of snow-to-liquid ratio for the contiguous United States. Wea. Forecasting, 20, 729-744.

WWD gridded forecasts compared against •“Superensemble” (NAM+GFS+SREF mean+GEFS mean)• Manually selected model blend

P-type mask applied based on station obs.

Where snow: First guess snow analysis = NPVU QPE x climatological SLR2. The resulting first guess is adjusted by Coop, CoCorahs, and METAR observations.

Model forecast P-type determined from each model’s p-type algorithm

To compare skill of WWD forecasts versus models, need to convert 6-hourly model QPF forecasts into model snow and ice forecasts

Where model forecasts freezing rain:Model forecast ice accumulation = model QPF

6 hourly Snow and Ice Gridded Analyses

6-hourly Snow and Ice Gridded Forecasts

Where freezing rain: First guess ice analysis = NPVU QPE. This is adjusted by METAR observations.

1 HPC Winter Weather Desk Operations and Upcoming NCEP Model Changes Dan Petersen NROW Conference...

Documents

Transcript of 1 HPC Winter Weather Desk Operations and Upcoming NCEP Model Changes Dan Petersen NROW Conference...