An Intercomparison of Surface Observations and High-Resolution Forecasting Model Output for the

Lake Okeechobee Region

By Kathryn ShontzJuly 19, 2006

Department of Marine and Environmental SystemsFlorida Institute of Technology

150 W. University Blvd.Melbourne, Florida 32901

Introduction

• Purpose

• Idealized model of a Lake Breeze

• Observational and Analytical Methods

• Lake Breeze on June 8, 2006: Graphical and Satellite Data

• What is the Weather Research and Forecasting Model?

• Model Output: Image and Graphical Data

• Comparison between Observed and Model Data

• Conclusions

• Future Considerations

Purpose

• Gauge Weather Research and Forecasting (WRF) model

representation of the lake breeze phenomenon with

respect to Lake Okeechobee

• Evaluate the model performance in terms of forecasting

capabilities

Idealized Lake Breeze

• Meso-gamma scale turbulent vertical flow (2-20 km)

• Occurs in afternoon due to solar heating and flows inland less than

characteristic width of lake (Segal, 1997)

• Known to extend vertically for several hundred meters (Segal, 1997)

• Most events occur in the month of lowest average wind speed and

maximum solar heating (Laird, 2001)

www.islandnet.com/.../wxdrphotos/lakebrz.gif

+ easterly large scale (synoptic flow)

Synoptic scale influence on the lake breeze evolution

270

360

180

90

~150

Methods and Observations

• Weather Station Data: K4JHI

• Only Okeechobee Station

• Sensible Weather Elements

• WRF Model Output

• Data Processing

• Grads Output and Images

K4JHI

Lake Okeechobee

Mesowest Achieve, 2006

Palmdale

Sensible Weather Elements from K4JHI on June 8, 2006

0

1020

3040

50

6070

8090

100

0:00 6:00 12:00 18:00 0:00

Time

De

gre

es

F

ah

ren

he

it

1010

1010.5

1011

1011.5

1012

1012.5

1013

1013.5

1014

1014.5

Pre

ss

ure

(m

b)

Temperature

Dew Point

RelativeHumidity

Temperature(Palmdale)

Dew Point(Palmdale)

Pressure

Results

Sunrise

Lake Breeze

Wind Direction at K4JHI and Palmdale Stations on June 8, 2006

0

50

100

150

200

250

300

350

0:00 6:00 12:00 18:00 0:00

Time (hours)

Dir

ectio

n (d

egre

es)

K4JHI

Palmdale

Results ContinuedWind Speed at K4JHI and Palmdale Stations on

June 8 2006

0

2

4

6

8

0:00 6:00 12:00 18:00 0:00

Time (hours)

Sp

ee

d (

mp

h)

K4JHI

Palmdale

Satellite Imagery

Lake Okeechobee

Sea Breeze Front

Lake Breeze Front

What is the Weather Research and Forecasting (WRF) Model?

• Most current regional forecast model

• Numerical weather prediction in 4-dimensional space

• Spatial resolution from meters to tens of kilometers

• Prognostic dynamical model that incorporates actual data

with physical parameterizations (e.g., radiation, boundary

layer, cloud physics).

T, p, u, v, w,q

WRF ConfiguationDomain size

Hz Resolution (4 km), Vertical Resolution?

Initial/Boundary Conditions (NAM)

950 Model Winds at 5:00 PM

WRF Model Run of June 8, 2006: 5 am - 8 pm

5:00 AM8:00 AM11:00 AM2:00 PM5:00 PM8:00 PM

Time Series Data from WRF Output

www.jimporter.orglakesokeechobeelake.jpg

N

E

S

W

WRF Output Temperature Around Lake Okeechobee for June 8, 2006

22

23

24

25

26

27

28

6/7/2006 12:00 6/8/2006 0:00 6/8/2006 12:00 6/9/2006 0:00 6/9/2006 12:00

De

gre

es

Ce

lsiu

s

NorthOkeechobee

EastOkeechobee

SouthOkeechobee

WestOkeechobee

WRF Output Dew Point Around Lake Okeechobee for June 8, 2006

14

16

18

20

22

24

6/7/2006 12:00 6/8/2006 0:00 6/8/2006 12:00 6/9/2006 0:00 6/9/2006 12:00

De

gre

es

Ce

lsiu

s

NorthOkeechobee

EastOkeechobee

SouthOkeechobee

WestOkeechobee

Temperature Comparison between Observed Data and WRF Output on June 8, 2006

20

22

24

26

28

30

32

34

6/7/2006 12:00 6/8/2006 0:00 6/8/2006 12:00 6/9/2006 0:00 6/9/2006 12:00

De

gre

es

Ce

lsiu

s

NorthOkeechobee

EastOkeechobee

SouthOkeechobee

WestOkeechobee

K4JHI

Comparison of Observations and Model Data

Dew Point Comparison between Observed Data and WRF Output for June 8, 2006

14

16

18

20

22

24

6/7/2006 12:00 6/8/2006 0:00 6/8/2006 12:00 6/9/2006 0:00 6/9/2006 12:00

De

gre

es

Ce

lsiu

s

NorthOkeechobee

EastOkeechobee

SouthOkeechobee

WestOkeechobee

K4JHI

Relative Humidity Comparison between Observed Data and WRF Output for June 8, 2006

30

40

50

60

70

80

90

100

6/7/2006 12:00 6/8/2006 0:00 6/8/2006 12:00 6/9/2006 0:00 6/9/2006 12:00

Pe

rce

nt

NorthOkeechobee

EastOkeechobee

SouthOkeechobee

WestOkeechobee

K4JHI

sunrise/mixing

Conclusions• Possible lake breeze boundary observed in temperature, winds, and dew point at station K4JHI

• Temperature, dew point and relative humidity are not handled well by the WRF model (especially the diurnal temperature cycle)

• 4-km resolution model is too inaccurate to use instead of weather observations

• Possible problems/issues

• Sparse observations

• Rounding of data

• Observed lake temperature ~ 29 C, model ?

• Temporal model output insufficient

• Timing/distribution of convection

• model parameterizations (land surface, radiation, skin temperature, soil moisture)

•Synoptic scale flow appears to be different than observed

Future Considerations

• Repeated trials especially during other pressure regimes

• 1-km resolution or smaller output

• Enhanced monitoring equipment on all lake shores

www.nasa.gov/.../71654main1_florida_mosaic_t.jpg

References

Laird, N.F. et al. “Lake Michigan Lake Breezes: Climatology, Local Forcing, and Synoptic Environment.” Journal of Applied Meteorology: Vol. 40, no. 3, pp. 409-424. 2001.

Segal, M. et al. “Small Lake Daytime Breezes: Some Observational and Conceptual Evaluations.” Bulletin of the American Meteorological Society: Vol. 78, no. 6, pp. 1135-1148. June 1997.

Weather Station History: K4JHI in Okeechobee City, FL. Taken from Mesowest database. http://www.met.utah.edu/cgi-bin/droman/meso_base.cgi?stn=AR914

Questions?

Christopher Flanary, Natalie Lamberton, Kelli Zargiel

Vertical Wind Profile: Surface to 1.5 km at 5:00 PM

1000 mb950 mb900 mb850 mb