City #3: Louisville, KY (KSDF)

I don't know about you, but I couldn't be happier to be moving on from forecasting for KBIL. The USL model, NAM and NWS forecasts had the least errors for KBIL but still rarely verified within 1 degree for temperature or 1 kt for wind. I guess it's just another example that forecasting for a point with discrete values is exhausting. Oh well, we all must soldier on! Let's travel southeast to KSDF!

Louisville, Kentucky is located in north-central Kentucky near the Kentucky-Indiana border which is the Ohio River. We are forecasting for KSDF or Strandiford Field, KY aka Louisville International Airport (NOT KLOU or Bowman Field!) found in the map below. The station ID is 72423. The city is located in a flood plain of the Ohio River with slightly higher terrain around, especially to the east but still less than 1,000 ft AMSL. I think that forecasting for this area will be determined by local radiative forcing for high and low temperatures and advection of warmer air from the south, cooler air from the north and storms from the west. But, we shall see.



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We are forecasting for KSDF from 22 October - 1 November for the 24-h period from 06 UTC - 06 UTC. 06 UTC is 2 AM EDT or local time. We are finally forecasting for our own time zone! The local NWS WFO is located conveniently in Louisville. I really, really like their formatting of their area forecast discussion so I think you will too. 

*PSA (Public Service Announcement): The local 88-D is getting an upgrade so for radar data, you'll have to check out the mosaic or surrounding radars (more information).*

Just to briefly say what the climate normals are-- high temps are usually in the upper 60's and low temps are usually in the upper 40's in late October. However, I don't want to harp on climate normals too much because it looks like we will be dealing with an amplified and slightly anomalous pattern early on. 

Large-scale Pattern:

Holy ridge, Batman! A look at forecast 500-hPa heights according to the GFS shows that the ridge looks to build for almost the entirety of this week. There may be a shortwave embedded in the flow that may provide some lift but with the question of moisture availability, I doubt there will be measurable precip until the ridge moves out and the trough brings a system on Friday. After that system, the GFS is showing troughiness (yes that's a word... now) in the Louisville region and then more zonal flow.


What to watch out for (IMO):

• Cloud cover affecting daytime highs and nighttime lows.
• Large diurnal swings in temperature especially with anomalous heights over the region- don't be afraid if you have a couple more degrees added to your temperature range than you are comfortable with.
• Moisture availability with weak forcing.
• Wind direction should be very important for the advection of warm, moist air from the south and cooler, dry air from the north. Pretty standard but still pay attention.
  

 Tips/Comments for Forecasting in General:

• Check out the current weather first via satellite, radar, surface observations, METAR, etc. You have to understand the present before you can look to the future.
• Get a feel for general pattern from NAM, GFS, etc. (available from here and here, for example). Identify the general pattern of low and high surface pressure systems and their progression, temperature advection at 850 mb, moisture at 700 mb, vorticity at 500 mb and the general jet structure at 300 mb. Make sure you are focusing your attention on Louisville.
• Look at forecast model soundings for the period for KSDF.
• Compare your idea for values with MOS (model output statistics).  Keep in mind these are instantaneous output values and you can always have values above/below that between output times. 
• Read the Louisville, KY WFO forecast discussion for KSDF.

Tips/Comments for Forecasting for High/Low temperature (Fahrenheit):

• Recall such basics as nighttime radiative cooling and daytime solar radiative heating, both of which are affected by cloud cover. 
• Frontal passages can affect your temperature forecast. Pay attention to the forecast timing of such frontal passages.

Tips/Comments for Forecasting Wind Speed (knots):

• NWS outputs wind speed in mph so if you are comparing your forecast value to theirs keep that in mind. Otherwise the models output wind speed (WSP) in knots.
• Look through METAR or surface obs for wind direction and temperature changes or try to spot it on the regional radar and know whether to take it into consideration for certain days with weak synoptic flow.

Tips/Comments for Forecasting Precipitation (inches):

• Take a look at some higher-resolution models (e.g. WRF)
• What does the HPC show?
• Take a look at some ensemble data (e.g. SREF)
• Most products you will be looking at will output the QPF in inches already so no conversion is necessary.
• KSDF will likely be a target for convection along cold fronts that move through after warm, moist air was advected from the south out ahead of the system. At least that's what one would expect if the ridging pattern we are starting with should ever break!

Alright guys- grab your fried chicken and get to forecasting! Hopefully Louisville is a little bit better to forecast for than Billings was. If you have any questions or want to discuss anything, feel free to comment on this post. Best of luck forecasting! Go SBU!