City #6: Austin, TX (KAUS)

Welcome back to forecasting for the WxChallenge! City #6 is the first city for the spring 2013 semester. We are forecasting for Austin, TX (KAUS) from 28 January - 7 February for the 24-hour period 06 UTC - 06 UTC which translates to midnight local Austin time (CST) if you are looking at NWS Austin/San Antonio forecast products. Forecasts are still due by 00 UTC which is 7 PM local Long Island time (EST).

Austin was the location for the most recent Annual Meeting of the American Meteorological Society earlier this month. Attending the AMS Annual Meeting or just the Student Conference is an amazing chance to see what the field of meteorology is really all about. If you are not a student member of the society, please consider doing so; a yearly fee of $20 can open up huge scholarship, networking, and educational opportunities. Okay, I'm off of my soap box and now you know why the WxChallenge is following their tradition of forecasting for the most recent AMS Annual Meeting city. Back to discussion forecasting.

Time to stalk the airport. KAUS is Austin-Bergstrom International Airport with a WMO ID of 74745. Austin, TX is located in south-central Texas, depending on how you slice up that oddly-shaped state, northeast of San Antonio, northwest of Houston, and south of Dallas & Fort Worth.
 



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So it is flat, in unimpeded (no real topography) proximity to the Gulf of Mexico, and pretty developed (more urban than not). So warm, moist air can likely surge up from the Gulf given strong southerly flow. We'll definitely keep that in mind.

Large-scale Pattern:
A look at forecast 500-hPa heights according to the GFS shows that the first player we will have to worry about is a large, digging upper-level trough causing a surface cyclone to form and strengthen lee of the Rockies. All of the models are showing this as it is in the very near-term. Ahead of this cyclone in the warm sector, there will likely be strong warm air advection off of the Gulf. This warm, moist air should allow for there to be a chance for some heavy rains with the passage of the cold front. Behind the cold front there should be clearer and cooler conditions. The models are showing predominately zonal flow for the remainder of the week. So we are starting Austin off with a bang but then things may be a bit boring.

What to watch out for (IMO):

• Amplified flow that allows strong southerly flow ahead of upper-level troughs to advect warm, moist Gulf of Mexico air into central Texas.
• Given quiet synoptic players, the evening dew point can act as a rough guess for the nighttime low (some forecasters use this as a first guess when they think MOS is bonkers). Therefore the wind direction may be a good indicator of humidity which may affect the nighttime temperatures, 
• i.e. southeasterly winds should be more moist which means a higher dew point which means a higher nighttime temperature and northeasterly winds will advect drier air which means a lower dew point which means the possibility for lower nighttime temperatures.

 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 Austin.
• Look at forecast model soundings for the period for KAUS.
• 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 Austin/San Antonio WFO forecast discussion for KAUS.

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 and fog.
• 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. For example, southerlies may bring warmer Gulf air inland to Austin.

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 (South Central option) or for a zoomed-in national look try here.)
• Most products you will be looking at will output the QPF in inches already so no conversion is necessary.

Alright guys- grab your cowboy hats and boots and try to lasso up some great forecasts! If you ever have any questions or want to talk about AMS student opportunities please feel free to stop by my office in Challenger 121. I have candy. That is all. Good luck with KAUS!