Deutscher Wetterdienst Central Forecasting DWD ECMWF Forecast Product Users Meeting 15 - 17 June 2005 1 Predicting severe weather by EPS tools - current

DWD ECMWF Forecast Product Users Meeting 15 - 17 June 2005

Deutscher WetterdienstDeutscher WetterdienstCentral Forecasting

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Predicting severe weather by EPS tools - current results

Thomas Schumann, Deutscher Wetterdienst, Zentrale Vorhersage D-63067 Offenbach,

GermanyE-Mail: [email protected]

NOAA12, 03 June 2005, 15:33 UTC (University of Bern)



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Outline

1. Introduction - current situation

2. EPS products used for severe weather prediction

3. Case studies

4. Preliminary verification results

5. Conclusions



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1. Introduction - current situation

Forecaster: a great variety of products

ECMWF EPS and derivedproducts www.ecmwf.int

ECMWF EPS and derivedproducts www.ecmwf.int



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SRNWP PEPS

PEPS Udos model market (DWD Intranet, in future included into NinJo)

COSMO-LEPS

Decision, which EPS tool will be used, depends from

• Purpose of my forecast (overview,

• ECMWF• GME• GFS• UKMO• LFPW• CMC (still not used)

Plots for global models:

Availableparameters:Z500T850MSLP

detailled view, ... severe weather) • lead time• expected scale of the event



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Problems (or advantages?):

Forecaster has to keep in mind:

• Clustering always provides a compromise. Different clustering methods could lead to different results.

• selection of available models allows to create a EPS as well from global models as from LAMs (different model physics, parametrisation scheme and resolution, ...)

---> SRNWP EPS

• No model is perfect, models more or less inconsistent („jumping“, caused from changes in initial and boundary conditions).

• The EPS mean / the best populated cluster / the majority of global • models not always shows the szenario that finally will happen.



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EPS product lead time used for ... able to predictECMWF Clusters/Tubes, EPSmean

H+72 ... 168 General overview ( ... the most likely szenario) –main synoptic pattern

Multi - plots fromUdo´s modelmarket (Intranet)

H+72 ... 168 Planetary waves, Blocking situations, longpersisting anomalies, central low, largethrough, . . .

EFI H+24(36)...H+168(240)

Patterns provided by the EPS related to possiblesevere weather or rare events. Highly scalable in

Stamps, plumes,EPSgrams

H+24(36)...H+168(240)

parameter and timeEvents in synoptic scale (major synopticstorms, cold outbreaks, heat waves,

Probabilities H+36 ... 168...240

large-scale precip events, snow melt...)

COSMO-LEPS H+24 ... 120 High spatial resolution. Allows to evaluateorographic effects (overestimated ?)

SRNWP EPS H+12 ... 42 Events of sub-syn scale, effects trigerredby orography (catabatic winds, heat islands)

2. EPS Products used for severe weather

prediction



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3. Case studies

A) Late frost - 20/21/22 April 2005

B) Heavy precipitation - 14 May 2005

C) „Hot day“ .... 03 June 2005

D) Thunderstorm - Squall line 03/04 June 2005

How did COSMO-LEPS and SRNWP-PEPS perform

• against observations ?

• against probabilities of the „pure“ (uncalibrated) ECMWF EPS?

SRNWP-PEPS (PEPS): http://www.dwd.de/en/FundE/Projekte/ PEPS/index.htm (forecasts password-protected)



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A) Late frost - 20/21/22 April 2005

MSLP analysis, 20 April, 06 UTC

Tmin Observations, 20 April, 06 UTC(NE-Part of Germany)



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PEPS forecast, 19 Apr 05, 12 + 18 ... 30 H(EPS-mean)

COSMO-LEPS,17 April 05, 12 + 42 ... 66 H

COSMO-LEPS, 18 April 05, 12 + 18 ... 42 H

SRNWP-PEPS: Temp below 3C in the N-partof Germany likely, frost 2 m above sfc not !

COSMO-LEPS: Frost in theNE-part of Germany likely !



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ECMWF EPS probabilities for Tmin > 0 C18 April, 12 + 36 H

ECMWF EPS probabilities for Tmin > 0 C19 April, 00 + 24 H

Frost in the NE-part of Germany likely !

Frost in the NE-part of Germany likely !



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MSLP analysis, 22 April, 06 UTC

Two days later... The climax of the cold outbreak

Tmin Observations, 22 April, 06 UTC



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Event well predicted by COSMO-LEPS as well as by the ECMWF EPSeven in the early medium-range !

ECMWF EPS, 17 April 05, 12 + 96 ... 120 H

ECMWF EPS, 17 April 05, 12 + 96 ... 120 H

18 April 05, 12 + 72 ... 96 H

18 April 05, 12 + 72 ... 96 H

ProbabilitiesTmin < 0 C22 April, 06 UTC



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B) Heavy precipitation - 14 May 2005

Precip (obs, 24 hr-accumulated), 15 May 2005, 06 UTC

MSLP analysis, 14 May, 18 UTCPrecip locally above 50 mm / 24 hin the W-part above 30 mm



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PEPS, 14 May, 00 + 06 ... 30 H24 hr-acc precipprobab > 50 mm

PEPS, 14 May, 00 + 06 ... 30 H24 hr-acc precipprobab > 20 mm

PEPS, 14 May, 00 + 06 ... 30 HEPS mean



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COSMO-LEPS forecasts: probab´s > 50 mm / 24 h (top) and > 20 mm / 24 h (bottom)11 May 12 + 66 ... 90 H 12 May 12 + 42 ... 66 H 13 May 12 + 18 ... 42 H



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ECMWF-EPS forecasts 15 May 12 UTC (24 hr accum precip: probab´s > 20 mm / 24 hSignal became weaker with decreasing lead time and approaching of the event

11 May 12 + 72 ... 96 H 12 May 00 + 60 ... 84 H 12 May 12 + 48 ... 72 H

13 May 00 + 36 ... 60 H 13 May 12 + 24 ... 48 H 14 May 00 + 12 ... 36 H



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C) „Hot day“ .... 03 June 2005

MSLP analysis, 03 June, 15 UTCTmax (Obs), 03 June, 18 UTCFew stations in SW-Germany > 30°C !



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PEPSmean, 02 June, 12 + 06 ... 30 H 03 June, 00 + 06 ... 30 H Probabilities not available !

PEPS forecasts based on 02 June, 12 UTC and 03 June, 00 UTC didn´t show Tmax above 30 C over SW Germany (EPSmean) !



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COSMO-LEPS probabilities T > 30 C30 May 12 + 90 ... 114 H31 May 12 + 66 ... 90 H

01 June 12 + 42 ... 66 H

Tmax above 30 C over SW-Germany very likely !Persistent signal

EPS (ECMWF) withoutof any signal !

02 June 12 + 18 ... 42 H



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ECMWF EPSprobab´s Tx > 30 C(03 June, 18 UTC)

ECMWF EPSprobab´s Tx > 25 C(03 June, 18 UTC)

02 June, 00 + 36 ... 42 H 02 June, 12 + 24 ... 30 H

Tmax underestimatedcaused from the„lower“ resolutionof the EPS



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D) Thunderstorm - Squall line 03/04 June 2005

Observed gusts (m/s), 03 June, 18 UTC 04 June, 00 UTC



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Damages by the storm in theforests near Offenbach(picture by Klaus Paetzold)

Hail in Northern Germany(picture by Matthias Jaenicke)



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PEPS, prob fx > 20 m/s03 June, 00 + 06 ... 18 H

prob fx > 20 m/s03 June, 00 + 18 ... 30 H

PEPS, prob fx > 20 m/s, 03 June, 12 + 06 ... 18 H

Most severe gusts over NW and N-Part of Germany ?



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COSMO-LEPS fx > 20 m/s30 May 12 + 96 ... 120 H31 May 12 + 72 ... 96 H

01 June 12 + 48 ... 72 H

Weak signals for gusts over the W- and S-part of GermanySignal over N-Germanyfor lead time > 48 h only

02 June 12 + 24 ... 48 H



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ECMWF EPS probabilities for gusts > 20 m/s (03 June, 18 ... 24 UTC)

01 June, 00 + 66 ... 72 H 01 June, 12 + 54 ... 60 H

02 June, 00 + 42 ... 48 H 02 June, 12 + 30 ... 36 H

Signal over N-partof Germany not consistent

Increased prob´slater...

No indications overthe central part ofGermany !



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4. Preliminary verification results

COSMO-LEPS: • still subjective verification, carried out by the medium-range shift meteorologist• Tables: Verification against observations

Main results:

• Tmin, Tmax: useful, able to add value to forecasts (improved)• Wind gusts: good, orographic effects overestimated• Conv wind gusts: signals mostly too weak (Improvement ?)• Large-scale precip: good, orographic effects overestimated• Convective precip: not useful• CAPE: still under evaluation• Snow: good, orographic effects overestimated



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PEPS: • operational experimental suite since beginning of this year • Forecaster collecting experience • Set of forecasts (weather parameter, leading time) will be increased

Parameter: 24h-accumutated precipitation (00 UTC +06...+30h)Observations: Max. 217 synoptical stationens of the DWD (06...06 UTC)

N: Sample sizePOD: Probability of Detection (hit rate). Perfect score: 1FAR: False Alarm Ratio. Perfect score: 0HSS: Heidke Skill Score. Perfect score: 1TS: Threat Score. Perfect score: 1

HSS=100*(a+d-R)/(a+b+c+d-R)R=((a+b)(a+c)+(c+d)(b+d))/(a+b+c+d)

TS=100*a/(a+b+c)

. Obs yes Obs nofc yes a bfx no c d

. Obs yes Obs nofc yes a bfx no c d



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PEPS - "Probability of Detection" and "False Alarm Rate"

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0,80

0,90

1,00

Date

POD

FAR



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Categorical verification of PEPS - Heidke skill score, Threat Score and Correlation Coefficient

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0,80

0,90

1,00

Date

HSS

TS

r²



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5. Conclusions

• Forecaster hat to deal with and to check a great collection of products in a limited time frame before making a decision

• EPS-products: more and more accepted by the forecaster - content has to be condensed and compressed

- products valid for different temporal and spatial scales- tailored products predicting severe weather in the meso-scale -----> COSMO - LEPS, SRNWP PEPS

• preliminary verification results of COSMO - LEPS and SRNWP PEPS encouraging (daily use by the forecaster, case studies)

- COSMO - LEPS: quasi-operational use, improvements to be seen- SRNWP PEPS: experimental, first results promisingly

Problem presenting EPS forecast customer-friendly not been solved



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CentralForecasting

That´s it ! Thank you for your attention!

Headquarterof the DWDin Offenbach

Documents

Deutscher Wetterdienst Central Forecasting DWD ECMWF Forecast Product Users Meeting 15 - 17 June 2005 1 Predicting severe weather by EPS tools - current