 |
| Source |
KRDD is Redding Municipal Airport and is located to the southeast of the city center. It has a WMO ID of 72592 and an elevation of 153 m which is actually pretty low considering all of the surrounding terrain and that parts of the outskirts of Redding rise to about 800 m. The representative NWS WFO is Sacramento, CA and after looking at some satellite imagery I'd totally read up on what these expert forecasting for NORCAL have to say in their area forecast discussion (AFD).
Given that we are forecasting for a site entrenched in terrain on the West Coast of the United States, I think it would be a good idea to review the concept of orographic precipitation. We all know that if air is sufficiently moist and is lifted that it reaches a point in which the air becomes saturated and the water vapor condenses into cloud. If that parcel keeps rising then some of that water can precipitate out. That's the simple idea about stable orographic flow over terrain that can cause precipitation on its windward slopes. The situation can be a bit more complex when you have preexisting synoptic features translating across areas of terrain; then you can have orographically-enhanced precipitation. And don't be fooled if the moisture is coming directly from the west and Redding lies within the shadow of the Coastal Mountains-- it may not be safe from precipitation for many reasons including that the Cascades are higher (can wring out more moisture) and perturbed flow can develop over the Coastal Mountains that can actually form a wave-like appearance and cause air to lift downstream and produce precipitation. It's a little bit long and you'll have to zoom-in, but a great guide to forecasting out west for these types of situations was put out by the Warning Decision Training Branch of NOAA and a pdf going through a whole bunch of orographic precip. goodies is found here.
Summarizing Thoughts & Large-Scale Pattern:
The pattern looks to be drying out just as we start to forecast for RDD. According to the 500 hPa heights of the GFS, a trough (that we are all very much paying attention to for its potential role in weather for us on the East Coast!) is moving out of the area and a ridge builds in its wake that remains and builds throughout our first full week of forecasting for Redding. Therefore, the forecast challenges for our first week of forecasting will be catching the temperature trends and getting those winds right. There may be some moisture to play with next week, but we'll have to wait and see.
In general-- I'd focus my particular attention to the large-scale synoptic pattern, with land falling mature cyclones and their associated moisture plumes being the most important thing to watch out for. I'd use the available hi-resolution models to get a better feel for wind patterns and diurnal temperature variations (see sections below for links).
Tips/Comments for Forecasting in General:
- Check out the current weather first via satellite, radar (beware of beam blockage out west!), 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 Redding.
- For forecasting for Redding, I'd look hemispherically or look at the Pacific specifically which can be done at the following links (Note: can only be done with global models for obvious reasons, i.e. domain boundaries):
- Look at forecast model soundings for the period for KRDD.
- 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. Here's a winter-specific SREF page just for fun.
- 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 Sacramento, CA WFO forecast discussion for info on KRDD. These are the experts for that location, after all!
- Other universities have great WxChallenge-specific pages:
- The GFS-WRF run by the University of Washington has Redding in their 36-km domain and a list of all of the types of qpf products can be found here:
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, snow 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 KRDD!
- 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.
- The terrain around KRDD makes it a little complex to associate a specific wind direction with a specific temperature effect.
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.
Tips/Comments for Forecasting Precipitation (inches):
- Take a look at some higher-resolution models (e.g. WRF, hi-res NAM) or compare a whole bunch at once using a meteogram (ISU)
- The GFS-WRF run by the University of Washington has Redding in their 36-km domain and a list of all of the types of qpf products can be found here:
- 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 or for a zoomed-in national look try here. And for a winter-weather specific SREF page then check this out.)
- Most products you will be looking at will output the QPF in inches already so no conversion is necessary. Recall that we are forecasting for the liquid precipitation so if the forecast calls for snow, make sure you aren't forecasting 4 inches-- use the liquid equivalent.
Be sure to check out a previous post found here for a long list of great resources that you should check out! Most of them are also found on Dr. Colle's Coastal Meteorology and Atmospheric Prediction (COMAP) group's website. Please feel free to comment below with any cool sites or tools that you've discovered from your experience!
I don't know much about Redding except that a former boy band singer-turned solo artist Ashley Parker Angel of O-Town fame was born there. If you don't know who he is then A) I'm really old and B) you're better off.
I hope you're excited to forecast for this very different area of the country! Go Team SBU!
