Grand Rapids, Michigan is located about 50 km (25 mi) east of Lake Michigan on the Lower Peninsula of Michigan and is situated on the Grand River. Even though it is displaced from the shore of the lake, it is still a susceptible city to lake effect or lake-enhanced precipitation. There is no real topography to deal with and KGRR is at an elevation of 245 m. Time to stalk the airport!
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KGRR is Gerald R. Ford International Airport and is located to the southeast of the city center. KGRR's WMO ID is 72635. There is no real topography around and there is a mixture of more developed land to the west versus more tree-filled neighborhoods to the east. Remember that "great" lake to the west, though. Be sure to check in with the local NWS WFO which is the Grand Rapids office. A convenient quality of KGRR is that it is located in our timezone (EST) to minimize conversions for us!
Large-scale Pattern:
The forecast upper-level pattern according to the GFS for the start of our first week of forecasting for Grand Rapids shows an amplifying pattern throughout the week that is associated with the development of a low pressure system sometime mid-week (there's some model disagreement about the timing). Throughout the week there's a pretty steady chance of light precipitation, especially within the next couple of days with the passage of a warm front ahead of the strengthening low pressure system. A good tactic for dealing with precipitation forecasts like this is to look at some plume diagrams that show the differences between the models and then return to each model and check out some key levels (e.g. is the 850 mb temperature advection too overdone or is there a stronger jet at 300 mb or more positive vorticity advection at 500 mb?).
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 Grand Rapids.
- Look at forecast model soundings for the period for KGRR.
- How are the models evolving in time? Check out d(model)/dt plots like this one that focuses on the GFS.
- Ensembles are your friend. Here's a cool page for some spaghetti from the GEFS.
- 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 Grand Rapids, MI WFO forecast discussion for the GRR CWA. Keep in mind that they are covering a few diverse landscapes (coastline and higher terrain). These are the experts for that location, after all!
- Other universities have great WxChallenge-specific pages:
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 especially right at the start of our first week of forecasting for KGRR!
- 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 the model output statistics (MOS) is bonkers). Therefore the wind direction may be a good indicator of humidity which may affect the nighttime temperatures.
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.
- Take a look at some higher-resolution models (e.g. WRF)
- What does the WPC show?
- Take a look at some GFS model-derived standardized anomalies of precipitable water (PWAT) to get a handle on any significant movement of the forecast of dry air or very moist air.
- 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.
I hope you are Team Jacob because Grand Rapids is Taylor Lautner's hometown as well as Reed Timmer's which is more appropriate given our field of study. Best of luck forecasting for KGRR! Go Team SBU!!! Have a very Happy Holidays and enjoy your Winter Break! We'll resume forecasting on 27 January 2014.
