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Conference CallMarch 14, 2012

• Decay over land

• Update on modeling work

• Training material for WFOs

• Open discussion

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Decay over Land

Goals:

• Show how the wind speeds of “typical” landfalling tropical cyclones decay once over land

• Show how wind speeds compare to NHC guidance

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Decay over Land

Data set to use:

• ASOS station observations frequently go missing (see JB’s blog posting)

• HWIND analyses often not available once storm is over land

• RUC analyses chosen– Available from NCDC since 2002 (data not

online for 2006-2007—looking into this now)

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Decay over Land

• Only storms that actually made landfall used in study

• Only times the storm is over land used in analysis

• Storm list:– Gabrielle (2007) -Irene (2011)– Kyle (2002) -Gaston (2004)– Isabel (2003) -Hanna (2008)– Charley (2004) -Ernesto (2006)– TD7 (2003)

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Decay over Land—Strong StormsIsabel (2003) & Irene (2011)

Isabel (2003)

Irene (2011)

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Decay over Land—Weaker Storms

Kyle (2002) Gaston (2004)

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Decay over Land

• Strong storms show sharp reduction in wind over first 6-24 hours once over land; little change afterwards– Timing of sharpest decrease in winds

depends on angle with respect to coastline

• Weaker storms show little reduction once over land– Sometimes, outer radii actually have slightly

higher winds than closer to storm

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Land Decay Discussion

• Land decay and climatology: other data sets to you besides RUC? NARR? CFSR?

• Land decay and climatology: radii to use?

• Reduction vs. max. wind forecast for various radii: calculate ratio of RUC analyzed winds at various radii and compare to forecast at each time?

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Modeling Update

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Landfall Verification: Run 4

SIMULATED LANDFALL TIME: 08/27/1500 UTCLANDFALL CENTRAL SLP: 961 hPa

BEST TRACK LANDFALL TIME: 08/27/1200 UTCLANDFALL CENTRAL SLP: 952 hPa

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Run #7

• RTG SST data updated every 6 hours

• Initialized 8/27/00 UTC (12 hours prior to landfall)

• 9 km / 3 km nested run

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Best Track vs. Run #7 Track

Irene 5 (SST updated, 8/25/12z initialization)

Irene 7 (SST updated, 8/27/00z initialization)

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HWIND ANALYSIS, 8/27/1330 UTC ANALYZED MAX WIND: 80 KTSOBSERVED MAX WIND: 75 KTS

Model Run 7, 8/27/1300 UTC MODELED MAX WIND: 70.3 KTS

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Radar Loop: Run 7

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Landfall Verification: Run 7

SIMULATED LANDFALL TIME: 08/27/1300 UTCLANDFALL CENTRAL SLP: 959 hPa

BEST TRACK LANDFALL TIME: 08/27/1200 UTCLANDFALL CENTRAL SLP: 952 hPa

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Current/Future Modeling Work

• Zhu et. Al (2008): WRF-LES simulation for Ivan (2004)– Provides guidance for initial WRF-LES

simulation/namelist.input parameters

• 5 domains, two-way nested: 8.1 km, 2.7 km, .9 km, .3 km, and .1 km grid spacing

• Compare buoy/ASOS data to innermost domain

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Training Slides Outline (Gail Hartfield)

• Slide 1: Overview of project purpose and plans

• Slide 2: Basics of study: data/models used (could be combined with Slide 1)

• Slide 3: Results of observed wind analyses (Irene)

• Slide 4: NDFD verification summary (Irene)

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Training Slides Outline (Gail Hartfield)

• Slide 5: Summary of modeling results

• Slide 6: Potential TCWindTool improvements & Mike Brennan notes on TCM limitations

• Slide 7: Guidance for WFOs on speed reduction and gusts in TCs

• Slide 8: Future plans: Wind reduction & gust factors based on distance from center, topography, distance inland, etc.

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Open Discussion

• Training slides discussion

• Other topics?

• Next call date: Wednesday, April 11th at 11 a.m.