university of nairobi, nairobi, kenya department of meteorology, august 15-19, 201111th...

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August 15-19, 2011 11th Inter'l RSM Workshop -National Central Univers ity, Jhongli, ROC 1 University of Nairobi, Nairobi, Kenya Department of Meteorology, www.uonbi.ac.ke Predictability of Weather on Extended NWP Timescales over Kenya Using the GFS Model Franklin J. Opijah University of Nairobi, Kenya www.uonbi.ac.ke

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Page 1: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

1

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Predictability of Weather on Extended NWP Timescales over Kenya Using the GFS

Model

Franklin J. OpijahUniversity of Nairobi, Kenya

www.uonbi.ac.ke

Page 2: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

2

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Early-Warning Systems may reduce vulnerabilityto floods, disease, pestilence, strong winds, hazardous air

Dust Storms/Hazardous AirDust Storms/Hazardous AirMalaria EpidemicsMalaria Epidemics

Communication ImpairmentCommunication ImpairmentStrong WindsStrong Winds

Page 3: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

3

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

EWS can reduce vulnerability to pests, drought and famine

Food InsecurityFood Insecurity

Livestock ManagementLivestock ManagementPest InvasionsPest Invasions

Food AvailabilityFood Availability

Water Resource ManagementWater Resource Management

Heat WavesHeat Waves

Hydropower GenerationHydropower Generation

Page 4: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

4

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Strong Linkage between Weather Conditions and Disease

• Malaria is rife in humid, high temperature areas

• Meningitis is rife in dusty, low-humidity areas

Page 5: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

5

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Traditional Forecasting Techniques in Kenya

(UNDP Report)

• Is it possible to forecast impending weather using indigenous knowledge (IK)?

• Modelling Challenge: Is NWP Superior to IK?

Indicator Coming rains

Dry spell

Croaking frogs

Pronounced Reduced

Migrant birds Appearance Disappearance

Indigenous trees

Leaving, flowering

Shedding

Cattle Stampedes

Bird nests (weaver birds )

More nests Fewer nests

Red ants Appearance

Human body Discomfort (hot)

Discomfort (cold)

Page 6: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

6

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Outline of Presentation

• Introduction• The Global Forecast System• Prevailing Weather Conditions over Kenya (OND

2008)• Error and Skill Analysis (Formulation and

Techniques)• Is RFE Data useful over Kenya? • Predictability of Daily Rainfall and Temperature• Predictability of Seven-Day Weather Outlooks• Summary and Conclusions

Page 7: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

7

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Outline

• Introduction• The Global Forecast System• Prevailing Weather Conditions over Kenya (OND

2008)• Error and Skill Analysis (Formulation and

Techniques)• Is RFE Data useful over Kenya? • Predictability of Daily Rainfall and Temperature• Predictability of Seven-Day Weather Outlooks• Summary and Conclusions

Page 8: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

8

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Global Forecast SystemHorizontal Resolution 35 km (T382)

Solution technique Spectral triangular; Nonlinear advection: Leapfrog Gravity waves: Semi-implicit

Vertical grid Hybrid p-sigma; 64 levels

PBL Bulk-Richardson approach + Monin-Obukhov similarity

Radiation scheme (LWR/3hr; SWR/1hr)

GHGs (O3, H2O, CO2, CH4, N2O, O2, CFCs ), atmospheric aerosols, Cloud-radiative properties

Convection Deep: Arakawa and Schubert (1974):

Shallow: bulk mass-flux parameterization

Gravity-wave drag: Nonlinear function of the surface wind speed and the local Froude number

Page 9: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

9

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Outline

• Introduction• The Global Forecast System• Prevailing Weather Conditions over Kenya (OND

2008)• Error and Skill Analysis (Formulation and

Techniques)• Is RFE Data useful over Kenya? • Predictability of Daily Rainfall and Temperature• Predictability of Seven-Day Weather Outlooks• Summary and Conclusions

Page 10: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

10

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Weather/Climate Controls over Kenya

• Quasi-permanent systems– ITCZ– Anticyclones

• Unusual systems – El Niño/La Nina– IOD– QBO

• Migratory Systems– Tropical cyclones – Easterly waves– MJOs

• Mesoscale systems– Great lakes– High mountains– Urban areas

Page 11: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

11

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Domain of Study Topography & Homogeneous Climate Zones

ARC

BAM

BAR

BAR COL

DAG

ELD

ELG

GAL

GARB

GAR

IS I

K ISU

KAJ

KAK

KAP

KAS

KAT

KER

K IBW

KINA

K IR I

K IS I

KAIS

LAIK

LAM

LOD

MAC

MAG

MAK I

MAL

MAN

MARL

MARS

MAT I

MBO

MOM

MON

MOY

MUT

NAIV

NAK

NAN NYK

NAR

NK IN

NYA

NYEOLEN

RUM

TAV

T IMAT IMB

ADU

VOI

WA

TOD

HOR

RHA

ELW

34.00 35.00 36.00 37.00 38.00 39.00 40.00 41.00

-4 .00

-3 .00

-2 .00

-1 .00

0.00

1.00

2.00

3.00

4.00

5.00

34.00 35.00 36.00 37.00 38.00 39.00 40.00 41.00

-4 .00

-3 .00

-2 .00

-1 .00

0.00

1.00

2.00

3.00

4.00

5.00

1

2

3

4 5

6

8

91 0

1 1

1 2

7

Rainfall climatic zones

Page 12: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

12

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Observed Weather Patterns over Kenya in the 2008 OND SeasonObserved Rainfall and Maximum and

Minimum Temperature at Dagoretti, Kenya

0

10

20

30

40

50

60

70

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

Date

Rai

nfa

ll (

mm

)

0

5

10

15

20

25

30

Tem

peratu

re (C)

Rainfall Tmax Tmin

Observed Rainfall and Maximum and Minimum Temperature at Eldoret, Kenya

05

1015202530354045

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

Date

Rai

nfa

ll (

mm

)

0

5

10

15

20

25

30

Tem

peratu

re (C)

Rainfall Tmax Tmin

Observed Rainfall and Maximum and Minimum Temperature at Lodwar, Kenya

0

2

4

6

8

10

12

14

16

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

Date

Rai

nfa

ll (

mm

)

0

5

10

15

20

25

30

35

40

Tem

peratu

re (C)

Rainfall Tmax Tmin

Observed Rainfall and Maximum and Minimum Temperature at Voi, Kenya

0

5

10

15

20

25

30

35

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

Date

Rai

nfa

ll (

mm

)

0

5

10

15

20

25

30

35

40

Tem

peratu

re (C)

Rainfall Tmax Tmin

Page 13: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

13

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Outline

• Introduction• The Global Forecast System• Prevailing Weather Conditions over Kenya (OND

2008)• Error and Skill Analysis (Formulation and

Techniques)• Is RFE Data useful over Kenya? • Predictability of Daily Rainfall and Temperature• Predictability of Seven-Day Weather Outlooks• Summary and Conclusions

Page 14: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

14

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Verification Techniques• Signal/direction test

– Space-time graphical analysis – Correlation analysis

• Accuracy test– Root mean square error analysis

• Skill analysis: – Hit rate (HR)– Proportion Correct (PC)– Equitable Threat Score (ETC)– True Skill Statistic (TSS)– Heidke skill score (HSS)– Two-Alternative Forced Choice Test (2AFC)

Page 15: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

15

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

OMOMr ),cov(

221

iii OM

NRMSE Forecast

‘Yes’Forecast

‘No’

Observed ‘Yes’

a b

Observed ‘No’

c d

ba

aHR

dcba

daPC

)(

)(

aRcba

aRaETS

dcba

cabaaR

))((

)(

))(( dbca

bcadTSS

)()(

)(

aR-dcba

aR-d)(a= HSS

)(

))(())(()(

dcba

dbdc+caba= aR

))(( dcba

bdacadP 2

1

AFC2

Page 16: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

16

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Outline

• Introduction• The Global Forecast System• Prevailing Weather Conditions over Kenya (OND

2008)• Error and Skill Analysis (Formulation and

Techniques)• Is RFE Data useful over Kenya? • Predictability of Daily Rainfall and Temperature• Predictability of Seven-Day Weather Outlooks• Summary and Conclusions

Page 17: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

17

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Station-Averaged Error Analysis: RFE and Observed Rainfall over Kenya

2004 2005 2006 2007 2008April Corr coef (%) -2.5 -12.6 -4.5 6.9 -7.4November Corr coef (%)

-6.5 -8.0 8.6 4.4 -6.3

April RMSE (mm) 12.8 8.9 15.4 9.6 9.6November RMSE (mm) 8.5 5.7 15.0 8.0 12.2

Page 18: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

18

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Spatial Distribution of Correlation Coefficients and RMSE between Observed and RFE Rainfall over Kenya

April 2008 November 2008

Root mean square error

Correlation coefficients

34 35 36 37 38 39 40 41 42

Longitude

R M SE Analysis of R FE vs O bserved R ainfa ll over Kenya for April 2008

-5

-4

-3

-2

-1

0

1

2

3

4

5

Latit

ude

3 m m

6 m m

9 m m

12 m m

15 m m

5 m m

8 m m

10 m m

13 m m

15 m m

18 m m

20 m m

34 35 36 37 38 39 40 41 42

Longitude

R M SE Analysis o f R FE vs O bserved R ainfa ll over Kenya in N ovem ber, 2008

-5

-4

-3

-2

-1

0

1

2

3

4

5

Latit

ude

34 35 36 37 38 39 40 41 42

Longitude

C orre lation Analysis Betw een O bserved andR FE R ainfa ll over Kenya for April 2008

-5

-4

-3

-2

-1

0

1

2

3

4

5

Latit

ude

-0 .25-0.20-0.15-0.10-0.050.000.050.100.150.200.25

34 35 36 37 38 39 40 41 42

Longitude

C orre lation Analysis Betw een O bserved andR FE R ainfa ll over Kenya in N ovem ber, 2008

-5

-4

-3

-2

-1

0

1

2

3

4

5

Latit

ude

-0 .2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

Page 19: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

19

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Outline

• Introduction• The Global Forecast System• Prevailing Weather Conditions over Kenya (OND

2008)• Error and Skill Analysis (Formulation and

Techniques)• Is RFE Data useful over Kenya? • Predictability of Daily Rainfall and Temperature• Predictability of Seven-Day Weather Outlooks• Summary and Conclusions

Page 20: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

20

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Comparison of Observed and GFS Rainfall : November 2008

GFS Model 7-Day Rainfall Forecast over Nyahururu, Kenya

0

5

10

15

20

25

30

05-Nov-08

06-Nov-08

07-Nov-08

08-Nov-08

09-Nov-08

10-Nov-08

11-Nov-08

Target Date

Rai

nfa

ll (

mm

)

Observed Forecast

GFS Model 7-Day Rainfall Forecast over Kisumu, Kenya

0

10

20

30

40

50

60

70

05-Nov-08

06-Nov-08

07-Nov-08

08-Nov-08

09-Nov-08

10-Nov-08

11-Nov-08

Target Date

Rai

nfa

ll (

mm

)

Observed ForecastGFS Model 7-Day Rainfall Forecast over Lodwar, Kenya

02468

1012141618

05-Nov-09

06-Nov-09

07-Nov-09

08-Nov-09

09-Nov-09

10-Nov-09

11-Nov-09

Target Date

Rai

nfa

ll (

mm

)

Observed Forecast

GFS Model 7-Day Rainfall Forecast over Mombasa, Kenya

05

1015202530354045

05-Nov-08

06-Nov-08

07-Nov-08

08-Nov-08

09-Nov-08

10-Nov-08

11-Nov-08

Target Date

Rai

nfa

ll (

mm

)

Observed Forecast

Page 21: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

21

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Rainfall Spatial Distribution in Kenya: 1 November 2008 and 3 November 2008

GFS Observed Reanalysis RFE

Page 22: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

22

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Observed and GFS Rainfall, Maximum and Minimum Temperature (7 November 2008)Observed 1-Day Lead Time 4-Day Lead Time 7-Day Lead Time

Page 23: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

23

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

RMSE and Correlation Analysis: Rainfall, Maximum and Minimum Temperature

Averaged RMSE and Correlation Coefficients between GFS 7-Day Forecasts and Observed Rainfall over

Kenya at Various Lead Times

9.5

10.0

10.5

11.0

11.5

12.0

12.5

1 2 3 4 5 6 7

Lead Time (Days)

RM

SE

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Co

rrelation

C

oefficien

t

RMSE Corr Coef

Averaged RMSE and Correlation Coefficients between GFS 7-Day Forecasted and Observed Maximum Temperature over Kenya at Various Lead times

4.404.454.504.554.604.654.704.754.804.854.90

1 2 3 4 5 6 7

Lead Time (Days)R

MS

E

0.35

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0.75

Co

rrelation

C

oefficien

t

RMSE Corr Coef

Averaged RMSE and Correlation Coefficients between GFS 7-Day Forecasted and Observed Minimum Temperature over Kenya at Various Lead Times

2.65

2.70

2.75

2.80

2.85

1 2 3 4 5 6 7

Lead Time (Days)

RM

SE

0.07

0.12

0.17

0.22 Co

rrelation

C

oefficien

t

RMSE Corr Coef

RMSE and Correlation Analyses between Averaged GFS 7-Day Forecasts and Observed Rainfall over

Kenya for Various Lead Times

1.5

2.5

3.5

4.5

5.5

6.5

7.5

1 2 3 4 5 6 7

Lead Time (Days)

RM

SE

-0.7

-0.5

-0.3

-0.1

0.1

0.3

0.5

0.7

0.9

Co

rrelation

C

oefficien

t

RMSE Corr Coef

RMSE and Correlation Coefficients Between Averaged GFS 7-Day Forecasts and Observed Maximum

Temperature over Kenya at Various Lead Times

4.1

4.2

4.3

4.4

4.5

4.6

4.7

1 2 3 4 5 6 7

Lead Time

RM

SE

0.400.450.500.550.600.650.700.750.800.850.90

Co

rrelation

C

oefficien

t

RMSE Corr Coef

RMSE and Correlation Coefficients Between Averaged GFS 7-Day Forecasts and Observed Minimum

Temperature over Kenya at Various Lead Times

1.8

1.9

2.0

2.1

2.2

2.3

2.4

1 2 3 4 5 6 7

Lead Time (Days)

RM

SE

0.29

0.31

0.33

0.35

0.37

0.39

0.41

0.43

0.45

Co

rrelation

C

oefficien

t

RMSE Corr Coef

Page 24: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

24

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

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.uonbi.ac.ke

Averaged Hit Rate and Proportion Correct for Rainfall and Temperature

• Rainfall

• Temperature 0

10

20

30

40

50

60

70

80

90

100

1 Day 2 Days 3 Days 4 Days 5 Days 6 Days 7 Days

Lead Time

Sc

ore

(%

)

HR PC

0

10

20

30

40

50

60

70

80

90

1 2 3 4 5 6 7

Lead Time

Sc

ore

(%

)

Tmax_HR Tmax_PC Tmin_HR Tmin_PC

Page 25: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

25

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

GFS Skill Score Indices (%): Rainfall, Maximum and Minimum Temperature

Rainfall Maximum Temperature

Minimum Temperature

2AFCETSHSSTSS

Two-alternative forced choice test scoreEquitable threat scoreHeidke skill score True skill statistic

Averaged Skill Score Indices for the GFS Model Rainfall for Various Lead Times over Kenya

-30

-20

-10

0

10

20

30

40

50

1 2 3 4 5 6 7

Lead Time (Days)

Skill

Scor

e (%)

2AFC ETS HSS TSS

Averaged Skill Score Indices for the GFS Model Maximum Temperature for Various Lead Times over

Kenya

20

25

30

35

40

45

50

55

60

1 2 3 4 5 6 7

Lead Time (Days)

Skill

Score

(%)

2AFC_mean ETS_mean HSS_mean TSS_mean

Averaged Skill Score Indices for the GFS Model Minimum Temperature for Various Lead Times over

Kenya

3

5

7

9

11

13

15

1 2 3 4 5 6 7

Lead Time (Days)

Skill

Score

(%)

2AFC_mean ETS_mean HSS_mean TSS_mean

Page 26: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

August 15-19, 2011 11th Inter'l RSM Workshop-National Central University, Jhongli, ROC

26

University of N

airobi, Nairobi, K

enya

Departm

ent of Meteorology, w

ww

.uonbi.ac.ke

Outline

• Introduction• The Global Forecast System• Prevailing Weather Conditions over Kenya (OND

2008)• Error and Skill Analysis (Formulation and

Techniques)• Is RFE Data useful over Kenya? • Predictability of Daily Rainfall and Temperature• Predictability of Seven-Day Weather Outlooks• Summary and Conclusions

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Spatial Distribution of 7-day cumulative Rainfall :

1-7 November 2008

GFS Model Observed Reanalysis RFE

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Spatial Distribution of 7-day Maximum and Minimum Temperature:

1-7 November 2008

Page 29: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

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Rainfall Bias: GFS minus Observed Rainfall

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Temperature Difference: GFS minus Observed Maximum and Minimum Temperature

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7-day GFS and Observed Total Rainfall and Average Temperature

Rainfall Tmax Tmin

Eldoret

Mombasa

Narok

Temporal Variability of GFS and Observed 7-Day Total Rainfall at Eldoret, Kenya

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.51-

7

3-9

5-11

7-13

9-15

11-1

7

13-1

9

15-2

1

17-2

3

19-2

5

21-2

7

23-2

9

Dates

Sta

ndar

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Observed Model

Temporal Variability of GFS and Observed 7-Day Mean Maximum Temperature at Eldoret, Kenya

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

1-7

3-9

5-11

7-13

9-15

11-1

7

13-1

9

15-2

1

17-2

3

19-2

5

21-2

7

23-2

9

Dates

Sta

ndar

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d A

nom

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Observed Model

Temporal Variability of GFS and Observed 7-Day Mean Minimum Temperature at Eldoret, Kenya

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

1-7

3-9

5-11

7-13

9-15

11-1

7

13-1

9

15-2

1

17-2

3

19-2

5

21-2

7

23-2

9

Dates

Sta

ndar

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d A

nom

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Observed Model

Temporal Variability of GFS and Observed 7-Day Total Rainfall at Mombasa, Kenya

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1-7

3-9

5-11

7-13

9-15

11-1

7

13-1

9

15-2

1

17-2

3

19-2

5

21-2

7

23-2

9

Dates

Sta

ndar

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d A

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Observed Model

Temporal Variability of GFS and Observed 7-Day Mean Maximum Temperature at Mombasa, Kenya

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

1-7

3-9

5-11

7-13

9-15

11-1

7

13-1

9

15-2

1

17-2

3

19-2

5

21-2

7

23-2

9

Dates

Sta

ndar

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d A

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Observed Model

Temporal Variability of GFS and Observed 7-Day Mean Minimum Temperature at Mombasa, Kenya

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

1-7

3-9

5-11

7-13

9-15

11-1

7

13-1

9

15-2

1

17-2

3

19-2

5

21-2

7

23-2

9

Dates

Sta

ndar

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d A

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Observed Model

Temporal Variability of GFS and Observed 7-Day Total Rainfall at Narok, Kenya

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1-7

3-9

5-11

7-13

9-15

11-1

7

13-1

9

15-2

1

17-2

3

19-2

5

21-2

7

23-2

9

Dates

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ndar

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d A

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Observed Model

Temporal Variability of GFS and Observed 7-Day Mean Maximum Temperature at Narok, Kenya

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

1-7

3-9

5-11

7-13

9-15

11-1

7

13-1

9

15-2

1

17-2

3

19-2

5

21-2

7

23-2

9

Dates

Sta

ndar

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d A

nom

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Observed Model

Temporal Variability of GFS and Observed 7-Day Mean Minimum Temperature at Narok, Kenya

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

1-7

3-9

5-11

7-13

9-15

11-1

7

13-1

9

15-2

1

17-2

3

19-2

5

21-2

7

23-2

9

Dates

Sta

ndar

dize

d A

nom

aly

Observed Model

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Station-averaged Temporal Variability Rainfall, Maximum and Minimum Temperature

Temporal Variability of GFS and Observed 7-Day Total Rainfall Averaged over Kenya

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

1-7

3-9

5-11

7-13

9-15

11-1

7

13-1

9

15-2

1

17-2

3

19-2

5

21-2

7

23-2

9

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Observed ModelTemporal Variability of GFS and Observed 7-Day Mean Maximum Temperature Averaged over Kenya

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

1-7

3-9

5-11

7-13

9-15

11-1

7

13-1

9

15-2

1

17-2

3

19-2

5

21-2

7

23-2

9

Dates

Sta

ndar

dize

d A

nom

aly

Observed Model

Temporal Variability of GFS and Observed 7-Day Mean Minimum Temperature Averaged over Kenya

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

1-7

3-9

5-11

7-13

9-15

11-1

7

13-1

9

15-2

1

17-2

3

19-2

5

21-2

7

23-2

9

Dates

Sta

ndar

dize

d A

nom

aly

Observed Model

Page 33: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

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and Minimum Temperature (C)

Correlation Coefficient (%) Root Mean Square Error

Rain-fall

Max Temp

Min Temp

Rain-fall

Max Temp

Min Temp

12-Station Mean

57 76 21 26.6 4.6 2.5

Area Average 82 -12 38 14.8 7.1 1.3

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Skill Score Indices (%) : Rainfall, Maximum and Minimum Temperature

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Outline

• Introduction• The Global Forecast System• Prevailing Weather Conditions over Kenya (OND

2008)• Error and Skill Analysis (Formulation and

Techniques)• Is RFE Data useful over Kenya? • Predictability of Daily Rainfall and Temperature• Predictability of Seven-Day Weather Outlooks• Summary and Conclusions

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Summary of Results

• RFE rainfall estimates may not be representative indicators of the rainfall distribution over Kenya & should only be used with caution

• GFS displaces the location of the observed rainfall over the region and underestimates the observed rainfall (but also gives false alarms for some ASALs areas)

• The accuracy of the model-generated rainfall and maximum and minimum temperature decreases with increasing prediction lead time

• The skill for rainfall beyond 5 days is unreliable

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Summary of Results• GFS generally captures the locations of

highest and lowest maximum and minimum temperatures but exaggerates their areal extent

• GFS underestimates maximum temperature but overestimates minimum temperature

• GFS has better skill in predicting daily maximum temperature than it does with rainfall, and worst for minimum temperature

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Conclusions• GFS is a useful tool for predicting the cycle of 7-

day rainfall and maximum temperature, but not minimum temperature over the domain

• GFS has better skill in predicting rainfall, maximum and minimum temperature for seven day averaged forecasts than for daily forecasts over a seven-day period

• Seven-day averaged quantities are not superior to daily forecasts within the first two to four days of the forecasts, but may be useful for predicting mean quantities on extended NWP range

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Recommendation

• The model needs some fine tuning to improve its ability to predict the maximum temperature and rainfall. The model, in its current form, is not suitable for predicting minimum temperatures over the domain

• There is need to recalibrate RFE and improve the quality of reanalysis data

Page 40: University of Nairobi, Nairobi, Kenya Department of Meteorology,  August 15-19, 201111th Inter'l RSM Workshop-National Central University,

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• Thank you for your attention

• Merci boucoup

• Ahsante sana

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