DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
1
Verification of LEPS products at the DWD - first results
Thomas Schumann, Deutscher Wetterdienst, Zentrale Vorhersage
D-63067 Offenbach, GermanyE-Mail: [email protected]
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
2
Content
1. Introduction
2. A subjective verification method
3. Some case studies
4. Results
5. Conclusions and outlook
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
3
1. IntroductionA lot of parameters and thresholds available ... at time steps H+24 . . . 120
Parameter Thresholds (> ... , Tn < ...)
fx 10 m/s 15 m/s 20 m/s 25 m/s
precip 24h 20 mm 50 mm 100 mm 150 mm
precip 72h 50 mm 100 mm 150 mm 250 mm
Tx 20°C 30°C 35°C 40°C
Tn < 5°C < 0°C < -5°C < -10°C
Selection for verification !
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
4
2 Examples ...
Prob fx > 20 m/sMay 04, 12 + 24 ... 48 H
Prob Tx > 30°CMay 05, 12 + 18 ... 42 H
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
5
Datenblatt zur Verifikation der LEPS-Vorhersagen
Datum Tmax Betroffene RegionZieltermin > 30 °C
Obs T+42 T+66 T+90 T+114
02.04.03 12 003.04.03 12 0 004.04.03 12 0 0 0 Südwesten (Obs)05.04.03 16 0 0 0 0 Südwesten (Obs)06.04.03 10 0 0 0 0 Rhein(Obs)07.04.03 8 0 0 0 0 Niederrhein(Obs)08.04.03 10 0 0 0 0 Freiburg(Obs)09.04.03 11 0 0 0 0 Südwesten (Obs)10.04.03 10 0 0 0 0 Bamberg(Obs)11.04.03 12 0 0 0 012.04.03 17 0 0 0 0 Rhein(Obs)13.04.03 20 0 0 0 0 Oberrhein(Obs)14.04.03 24 0 0 0 30 Oberrhein(114),Oberrhein(Obs)15.04.03 26 0 0 0 0 Niederrhein(Obs)16.04.03 25 0 40 40 0 Rhein(90),Oberrhein17.04.03 24 50 60 20 40 Westen(114),Westen(90),Südwesten, Stellenweise am Rhein(42)18.04.03 21 0 0 0 20 Westen(114)
2. A subjective verification method
Permanent Verification (Excel-Sheet) or Case Studies ...
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
6
Problem: Lack of severe events (permanent blocking)a few cases only
SLP Analysis, May 05, 06 UTCPrecipitation Anomaly 2003Dresden and Duesseldorf(www.cpc.ncep.noaa.gov)
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
7
3. Some case studies3.1. Temperature - late cold outbreaks Date: April 09/10 and 10/11, 2003
ECM April 7, 12 + 72 h, SLP (blue) and T850 (red) ECM April 8, 12 + 72 h
L
L
H
H
H
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
8
Tn forecasts 09/10 AprilApril 08, 12 + 18 ... 42 H (left top), April 07, 12 + 42 ... 66 H (left bottom)
Tn forecast 10/11 AprilApril 06, 12 + 66 ... 90 H
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
9
EPS ECMWF Prob Tmin < 0°C April 10/11April 06, 12 + 72 ... 84 H
April 08, 12 + 18 ... 42 H
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
10
Observed Tn April 10, 06 UTC
Observed Tn April 11, 06 UTC
Late frost over widespread areas
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
11
... The snow forecast has been performed well ... (excerpt Southern Germany)
April 07, 12 + 72 ... 96 H April 11, 06 UTC 24-hr snow amount (cm)
April 09, 12 + 24 ... 48 H
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
12
EPS ECMWF prob snow > 1 cmApril 09, 12 + 24 ... 48 H
Snow fc fromthe EPS:
No signal !
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
13
3.2. Temperature - daily Temperature Maximum
ECM March 22, 12 + 72 h, SLP (blue) and T850 (red)
Date: March 25, 2003Tmax exceeding 20°C over SouthernGermany is likely
H
Observed Tmax
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
14
March 24, 12 + 18 ... 42 H (left top), March 23, 12 + 42 ... 66 H (left bottom)
March 21, 12 + 90 ... 114 H (right)
Forecasts perform well, even the effect oflarge cities (London) is visible !
Useful forecasts also in similar situations !
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
15
3.3. Total precipitation, accumulated over 24 hours
ECM April 1, 12 + 72 h, SLP (blue) and T850 (red)
Case: April 03/04, 2003
large-scale precip at thenorthern side of the Alpsand the Pyrenees
mostly convective precipat the Algerian coast andthe Croatic and Slowenicmountains
L
L
L
H
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
16
Obs 24-hr precip values, April 4, 06 UTC (top)and April 5, 06 UTC (right)
Gaps caused bycountries, doesn´treport 24-hr preciptotals
a better verification ifLEPS could predict12-hr precip totals at06 and 18 UTC (synop)
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
17
March 31, 12 + 72...96 H April 1, 12 + 48...72 H
April 1, 12 + 72...96 H March 31, 12 + 96...120 H
LEPS fc valid forApril 4 (top)threshold: 20 mm
LEPS fc valid forApril 5 (bottom)threshold: 50 mm
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
18
3.4. Wind gustsDate: April 05/06, 2003
MSLP Analysis April 05, 12 UTC
• Through situation, in transistion to a cut-off over eastern Europe• instable conditions over eastern Germany and Poland ---> gusts
April 06, 12 UTC
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
19
Max wind gusts (obs) April 05, 18 UTC
gusts up to 24 m/sover northeasternparts of Germany and the North Seacoast
April 03, 12+24...48 HThreshold: 20 m/s
Excellent Forecast
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
20
Max wind gusts (obs) April 07, 00 UTC
gusts up to 24 m/snear the Baltic Seacoast
April 03, 12 + 48...72 HThreshold: 20 m/s
Gusts overestimated !
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
21
EPS ECMWF prob fx > 20 m/sApril 03, 12 + 48 ... 60 H,valid at April 05, 12 ... 24 UTC
April 04, 12 + 48 ... 60 Hvalid at April 06, 12 ... 24 UTC
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
22
April 19, 12 UTC Sat picture (vis) andGeopotential 500hPa ECM 12 + 00 h
Small cut-off low over central Germany
caused convectiveprecipitation up to32 mm (10460)
3.5. Convective precipitation eventsCase study: April 19 - cut-off low
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
23
Obs April 19, 18 UTCweather, lightning,radar
Obs April 20, 06 UTC24-hr precip totals
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
24
24-hr Precip totals (right)April 19, 00 UTC, GME + 24 h April 18, 12 UTC, ECM + 36 hBoth models gave valuable signals !
LEPS April 18, 12 UTC + 24...48 hNo signal !
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
25
EPS ECMWF prob precip_24hr > 10mmApril 18, 12 + 24 ... 48 H
ECMWF T511 precip_24hrApril 16, 12 + 66 ... 90 H (left)April 18, 12 + 18 ... 42 H (right)valid April 19/20, 06 UTC
T511-forecast: event was predictedquite well, but the EPS: No signal
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
26
4. Results
• preliminary status - experiences obtained from several forecasters during semi-operational use
• Case studies ...
• Subjective verification method takes a lot of time ...
• High expectations to the LEPS• well-known problems of the LM- and the ECMWF (EPS- and T511)-forecasts (wind gusts, convective precipitations)
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
27
Parameter Results Comments
Minimum temperature No signal Don´t use the LEPS !Maximum temperature fair, useful realistic regional assignment of
the signals, some skill in med-range
Wind gusts fair, useful gusts sometimes overestimated (LM)realistic presentation of orographiceffects, without skill in med-range
Snow not very well realistic presentation of orographiceffects, one case study only
precipitationlarge scale fair, useful realistic regional assignment of the
signals, rapid lost of predictabilityby increasing leading time
convective mostly no The use if LEPS is not signal recommendable !
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
28
5. Conclusions and outlook• LEPS wasn´t able to meet our expectations (no skill in med-range)
• predictions of convective precipitations and gusts, caused by convective events, not useful
• forecasts of late cold outbreaks: results very poor, no signal
• Acceptance by forecasters
Results of this workshopexperiences from otherCOSMO-LEPS members
Further development ofthe LEPS systemSimulation of „historic“extreme weather events
Continuing verification ?Continuous or case-sensitive ?
Improvements of the LEPSforecasts in the near future ?
Enhanced operational use of the LEPS system by forecaters ?
DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003
Deutscher WetterdienstDeutscher WetterdienstZentrale Vorhersage
29
Thank you for your attention !