Experimental aviation grids at national weather service marquette michigan
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Experimental Aviation Grids at National Weather Service Marquette, Michigan. Steven Fleegel NWS Marquette, MI. Great Lakes Operational Meteorology Workshop Webinar Series. May 14, 2013. Overview. Started as a part of experimental Fire Weather grid creation in February 2012

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Experimental Aviation Grids at National Weather Service Marquette, Michigan

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Experimental Aviation Grids at National Weather Service Marquette, Michigan

Steven Fleegel

NWS Marquette, MI

Great Lakes Operational Meteorology Workshop Webinar Series

May 14, 2013


  • Started as a part of experimental Fire Weather grid creation in February 2012

    • Creating Ceiling and Visibility grids

  • Tools and Procedures were modified and created in Graphical Forecast Editor (GFE) to use a consensus approach

    • Averaged the derived model ceilings and explicit model visibilities

    • Completely hands off for forecasters

Overview - cont.

  • This proved useful to the forecasters in giving a rough idea on potential ceiling/visibilities across the County Warning Area (CWA)

    • Very helpful with timing

  • Created hourly through first 12 hours and then every 3 hours after that through 72 hours

    • Originally created every 3 hours through 60 hours

What was done in GFE

  • Added Ceiling and Visibility (Vsby) grids to the Forecast (Fcst) database

    • Originally, the ceiling grids were derived on the fly and calculated based off model RH

  • Ceiling grids were converted to background processing (smartInits) with the transition to calculations based on RH with respect to Ice (March 2013)

    • Vsby grids were also converted to smartInits at this time

  • This conversion allowed the consensus calculations to be enhanced

    • Hourly calculations in the first 12 hours

      • Hourly model data when available and interpolated 3 or 6 hour model data.

    • Weights to increase emphasis on preferred models

Models Included




MET Guidance

NAM 4km Nest

MAV Guidance (Beyond 12-hours)

WRF-ARW (local 20km and 5km)


HRRR (Previous)

Gridded LAMP

Gridded LAMP (Previous)



  • NAM12

  • MET Guidance

  • GFS40

  • MAV Guidance (beyond 12-hours)

  • RAP X2

  • RAP (Previous)

  • WRF-ARW (local 5km) X2

  • RuMM1/2 (3 hourly local 3km WRF-ARW initialized off RAP)

  • Gridded LAMP

  • Gridded LAMP (Previous)

GFE and AWIPS data limitations exclude using GEM (NH and Regional), ECMWF, NCEP WRFs Ceiling data

How the Forecasters see the Data

  • Example of a Ceiling grid in GFE

  • Uses a color table to match Categorical Amendment Criteria (CAC)

    • Help forecasters quickly see areas of concern

What was done in AvnFPS

  • The data is also available to the Aviation forecasters through the AvnFPS TAF Editor

  • Forecaster feedback has been positive to this addition

    • Helps them with timing for TAFs

  • Did have to make minor background adjustments due to local labeling

    • Will likely be transitioning towards more consistent labeling with AWIPS 2




Case Study – March 11, 2013

Low pressure system moving northeast through the Great Lakes region

March 11, 2013 – 00Z



Surface Chart

March 11, 2013 – 06Z



Surface Chart

March 11, 2013 – 12Z



Surface Chart

Quick Verification Background

Categorical Amendment Criteria (CAC)

March 11, 2013 - Verification

KSAW – Sawyer International Airport

3/10 – 18Z

3/11 – 00Z

3/10 – 06Z

24hrs Out

12hrs Out

6hrs Out

MVFRMust File AlternateIFRAlternate Landing MinsAirfield Landing Mins

KCMX – March 19th, 2013 Snow

KCMX – Houghton County Memorial Airport

March 17, 2013 – 18Z Forecast

  • Low pressure system moving east out of the Northern Plains and across Lake Superior

  • Hit alternate landing minimum visibilities within an hour or two at 30 hours out

    • Extremely useful for Outlook portion of TAF forecast

Shallow Moisture Case – 03/08/2013

Light winds and lingering moisture trapped below subsidence associated with high pressure over the Great Lakes

Shallow Moisture Case – cont.

Model initial conditions – March 08, 2013 00Z




Shallow Moisture – cont.

  • With the reliance on model data, the Aviation Grids struggled

    • Forecasters also struggled with timing of wind becoming offshore

      • Forecaster Aviation discussion mention timing uncertainty on clouds

      • 00z TAF had conditions scattering out at 02Z

    • But at least the TAF forecast had the right idea


  • In order to quantify the biases and identify areas of improvement, verification was started in February 2013

  • Caveats

    • Local NDFD Verification

      • Only Hourly obs at the top of the hour

      • Looks at ceiling height with no restriction by cloud cover

      • Looked at 2 of our 3 TAF sites

        • Left out KIWD (Ironwood, MI) due to inconsistent observations

    • Stats on Demand (NWS Verification)

      • 5min obs and calculation

      • Has in-between obs (Specials)

KSAW – 0-6hr Verification

KCMX – 0-6hr Verification

KSAW – 6-24hr Verification

KCMX – 6-24hr Verification

Aviation Grids – Performance

  • Positives

    • Synoptic systems

      • As long as there is model consistency

    • Visibility

      • Values and timing

      • Model derived data versus calculated like ceilings

    • Recently improved ceilings in lake effect areas

      • Due to relative humidity calculations with respect to ice

Aviation Grids - Shortcomings

  • Shallow Moist Layers

    • Models have same issue

    • Plus, with GFE only having data every 25mb, it is easy for those shallow layers to be missed

  • Timing the end of lake effect snow and clouds

    • Models have same issue

  • Very low ceilings

    • Due to the way the consensus is averaged

      • One model showing 20,000 foot ceilings can quickly raise the other models consensus of 500 feet

    • Doesn't represent lower ceilings or vertical visibility (VV) due to Blowing Snow (BLSN) or heavy snow (+SN)

      • Potential improvement based off Forecast

        • Tool could use BLSN or +SN to adjust ceiling values to increase consistency with the forecast

CAC Category Distribution - KSAW

  • Issue with lack of lower ceilings can be seen in frequency comparisons

    • Biased towards VFR conditions

      • Misses IFR and lower

    • Visibility has a fairly even distribution in all categories

Recent Improvements

  • Changes made at the beginning of March have improved lower ceiling errors

    • RH with respect to Ice

    • Hourly Calculations in the first 12 hours

  • Has greatly reduced the high bias for MVFR and lower Ceilings

Future Work

  • Main focus will be improving Ceiling forecasts for IFR and lower conditions

  • Perform Summertime convection verification

  • Incorporate some influence of the Forecast to visibility and ceiling

  • Generate experimental TAFs like some NWS Eastern Region offices

    • Would help simplify verification, since it would be incorporated into Stats on Demand

Future Work – cont.

  • Expand Gridded Database to web for aviation customers

    • Point and Click and Forecast Graphics

      • Similar to Jackson, KY, Charleston, WV, etc.


  • Visibility Grids – Definitely shows skill

    • Verification over last two months indicates that it is as good or slightly better than our TAFs

  • Ceiling Grids – Showing improvement

    • But still struggles with IFR and lower values

  • A good start

    • Believe that using this as a starting point and then adding forecaster intervention would create a superior product for the TAF sites and our CWA as a whole

Contact Information

  • Steven Fleegel – [email protected]

  • NWS Marquette, MI

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