Verification of the ARPS and Verification of the ARPS and NAM Model Forecast Winds NAM Model Forecast Winds in the East Central Florida in the East Central Florida Coastal ZoneCoastal Zone

Arlena MosesArlena MosesDepartment of Marine and Environmental SystemsDepartment of Marine and Environmental SystemsFlorida Institute of TechnologyFlorida Institute of TechnologyMelbourne, FL 32901Melbourne, FL 32901

OverviewOverview

Introduction Analysis Methods Model Performance Performance During Tropical Storm Arlene Summary

Why are We Interested in Wind Why are We Interested in Wind Forecasts?Forecasts? Winds direction and speed can affect

Atmospheric stability Convective Development (or lack thereof) Commercial and Recreational Boating Interests Dispersion of smoke and toxic substances Rocket and Shuttle Launch Conditions

Inaccurate wind forecasts can cause feedback in other portions of the forecast

Why Choose These Models?Why Choose These Models?

Wet season weather is often dominated by local circulations

WFO Melbourne provides gridded forecasts at 5km resolution

These models provide good resolution of local and mesoscale features

ModelModel NAM12NAM12 ARPSARPS

Horizontal Horizontal ResolutionResolution 12 km 4 km

Vertical Vertical ResolutionResolution 60 layers 40 layers

Temporal Temporal ResolutionResolution 3 hr 0.5 hr

Turbulence Turbulence SchemeScheme

Mellor-Yamada 2.5-Level Closure

1.5 TKE Closure

Model Run Model Run UsedUsed 0Z 3Z

Table 1: Model ResolutionsTable 1: Model Resolutions

MethodsMethods The study was conducted 1-30 Jun

2005 The ‘nighttime’ hours of 03Z to

12Z (11pm-8am EDT) were considered for each day

To evaluate development of nighttime land breezes

To correspond with the 3Z ARPS run

Seven parameters evaluated Five sites within coastal zone of

the WFO Melbourne CWA

ParametersParameters

Surface Wind Direction (°)

Surface Wind Speed (kts)

Surface Temperature (°F)

100 ft Temperature (°F)

200 ft Temperature (°F)

500 ft Temperature (°F)

1000 ft Temperature (°F)

Inversion Height (m)

Table 2: Evaluated Forecast ParametersTable 2: Evaluated Forecast Parameters

Figure 1: Sites evaluated in the study (Pink Dots) within the NWS Melbourne CWA Figure 1: Sites evaluated in the study (Pink Dots) within the NWS Melbourne CWA

(shaded in gold). Other cities provided for reference(shaded in gold). Other cities provided for reference

(009)

Model PerformanceModel Performance

Table 3: Averages for June 2005Table 3: Averages for June 2005

ModelModelSurface Wind Surface Wind

DirectionDirectionSurfaceSurface Wind Wind

SpeedSpeedSurface Surface

TemperatureTemperature

Difference (°) Difference (kts) Difference (°F)

Model Average-Model Average-ARPSARPS -25.92 -1.88 1.58

Standard Standard Deviation-ARPSDeviation-ARPS 17.17 2.51 1.41

Model Average-Model Average-NAM12NAM12 -5.19 -2.75 0.03

Standard Standard Deviation-Deviation-

NAM12NAM1218.29 2.28 1.53

Model PerformanceModel Performance The NAM12 performed better overall in

forecasting wind direction and surface temperature ARPS performed better in direction at Buoy 41009

The ARPS provided more accurate forecasts for wind speeds at all sites

Both models show a tendency to forecast higher winds than observed Most noticeable at Buoy 41009 and TTS Possibly due to the model handling of nighttime surface

boundary layer over water

TS Arlene – 10 June 2005TS Arlene – 10 June 2005TS Arlene passed into the Gulf of Mexico and west

of the Florida peninsula between 10 and 11 June

Figure 2: 10 June 2005 12Z Surface Map Figure 2: 10 June 2005 12Z Surface Map http://www.hpc.noaa.govhttp://www.hpc.noaa.gov

TS Arlene – 10 June 2005TS Arlene – 10 June 2005 ARPS

No error in direction forecast at VRB Forecasted winds tended more southerly than observed

directions Average difference at DAB was -25.00°

NAM12 No error in direction forecasts at MLB

Least Accurate at DAB (-22.50°) Speed most accurately forecasted at DAB (-1.50kts) and VRB

(-1.75kts)

Both models least accurate speed forecasts at TTS and 009 Forecast errors may be due to inaccurate forecasting of

storm position

Figure 3: NAM12 and ARPS Forecast vs Observed Wind Direction on 10 June 2005 at DABFigure 3: NAM12 and ARPS Forecast vs Observed Wind Direction on 10 June 2005 at DAB

0102030405060708090

100110120130140150160170180

3 6 9 12Hour (UTC)

Dire

ctio

n (d

egre

es)

Forecasted-NAM12 Forecasted - ARPS Observed

Figure 4: ARPS NAM12 Forecast vs Observed Wind Speed on 10 June 2005 at TTS and 009Figure 4: ARPS NAM12 Forecast vs Observed Wind Speed on 10 June 2005 at TTS and 009

0123456789

1011121314151617181920212223

3 6 9 12Hour (UTC)

Win

d Sp

eed

(kts

)

Forecasted NAM12 - 009 Forecasted ARPS - 009 Observed - 009 Forecasted NAM12- TTS Forecasted ARPS-TTS Observed - TTS

Summary and RecommendationsSummary and Recommendations

Wind direction and speed can have a variety of impact on weather and operations

The NAM12 performed better overall in wind direction and surface temperature, the ARPS in wind speeds

Tendency to forecast higher winds than observed

Forecast errors during Arlene possibly due to misplacement of storm

Longer time period/More hours needed for more comprehensive comparison

AcknowledgementsAcknowledgements

A special thanks to the National Weather Service Office in Melbourne, Florida for data and

assistance

ReferencesReferences Case, J.L. 2002: Final Report of Land-Breeze Forecasting. NASA Contractor CR-2002-211181,

Kennedy Space Center, FL, 56 pp.

NOAA-National Weather Service. [http://www.noaa.gov]. Accessed 15 Jul 2005.

North American Surface Analysis. Hydrometeorological Prediction Center. [http://www.hpc.ncep.noaa.gov]. Accessed 15 Jul 2005.

Operational Models Matrix. Meteorology Education and Training. [http://meted.ucar.edu/nwp/pcu2/index.htm] Accessed 15 Jul 2005.

Real Time Operational and Analysis Network (ROMAN). [http://raws.wrh.noaa.gov/roman/]. Accessed 15 Jul 2005.

Tropical Weather Summary-June 2005. National Hurricane Center [http://www.nhc.noaa.gov]. Accessed 15 Jul 2005.

Weather Observation Station Record. National Climatic Data Center. [http://www.ncdc.noaa.gov]. Accessed 15 Jul 2005

Xue, M., Droegemeier, K., Wong, V. "The Advanced Regional Prediction System and Real-time Storm-scale Weather Prediction." International Workshop on Limited-area and Variable Resolution Models. Beijing, China, October, 1995.

Questions?Questions?

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