The tone of yesterday's notemay be a bit too glib (ie "not to worry"). Now Tuesday and we did see light fog on the Sound, but not near yesterday's coverage, even though the WRF meteogram from yesterday would seem to imply even more today.The forecast this morning, however, did include "patchy fog," so the computer models may have looked out the window yesterday.
Synopsis: PZZ100-081900- 254 AM PDT Tue Aug 8 2017 .Synopsis for the northern and central Washington coastal and inland waters...High pres offshore with lower pres inland will maintain onshore flow of varying strength through Thursday. A layer of smoke from wildfires in British Columbia will continue to drift across the area today which may impact visibilities this morning before improving during the day today. $$
Today
Light wind becoming N to 10 kt in the afternoon. Wind waves 1 ft or less. Smoke and patchy fog in the morning then patchy smoke in the afternoon.
Tonight
N wind to 10 kt in the evening becoming light. Wind waves 1 ft or less. Patchy smoke in the evening then smoke after midnight.
The air temp at WestPoint Lighthouse did not get close to the dew point as early, but still within 1º and maybe getting closer even at 7 am. Generally we would think that reduced visibility is one of the easier things to forecast since it is determined by broad air mass properties (temp and dew point)... in contrast to wind, which in Puget Sound is extremely sensitive to just a slight rotation of the isobars. But it seems that adding a lot of smoke to the equation complicates the results, which makes it more difficult to predict temperatures as precisely as we need for this. Recall we were warned of record breaking temp records, that did not quite materialize, in large part because of the smoke.
But despite the wording of the visibility notices in the forecasts, the UW WRF model did do a good job on forecasting (T-TD) temperature difference, ie suppression of the wet bulb temp—a term that originates from the way dew point is measured using two thermometers, with one covered by a wet wick so it gets cooled by evaporation by an amount that depends on the relative humidity of the air.
UW forecast from 5pm last night shows lowest suppression coming at 8 am today, which is about what we saw. The one anomalous low point right at 8 am is likely a coincidence.
These are the actual measurements from West Point Lighthouse (WPOW1). Vertical scale is T - Td (ºF) (suppression of the wet bulb) and the data points are an hour apart with the scale indicated in red. There is a link at WPOPW1 for past hourly data, which can be copied and pasted into a spreadsheet to compute and plot the results.
So it seems the message of this amateur analysis is that looking at T dropping to TD is a dependable way to predict the onset of fog, but figuring the thickness of the fog does not come out of that simple analysis; that will take further analysis.
...standing by for meteorologists to tell us how we do that. See related note on UW Sounding Generator, which shows the temperature inversion we are having.
Smoke is clearly on our minds these days here in Puget Sound, and for good reason. But it seems to have distracted our local weather forecasters. They are forecasting "patchy smoke" that does indeed put a haze over the local waters, but they are omitting completely the pea soup fog we are having in the early mornings over Puget Sound. What is limiting the visibility here is fog, not smoke. The smoke is just damaging our lungs.
Synopsis: PZZ100-080100- 852 AM PDT Mon Aug 7 2017 .Synopsis for the northern and central Washington coastal and inland waters...High pres offshore with lower pres inland will result in onshore flow of varying strength through midweek. $$
Today
N wind 10 kt or less. Wind waves 1 ft or less. Patchy smoke.
Tonight And Tue
N wind 10 kt or less. Wind waves 1 ft or less. Patchy smoke.
Tue Night Through Thu
N wind 10 kt or less. Wind waves 1 ft or less.
Fri
SW wind 10 kt or less. Wind waves 1 ft or less.
But not to worry.... We can forecast the fog ourselves very easily, especially with the aid of the UW Atmospheric Sciences Meteogram on the Fly. Here was the meteogram yesterday (1.3 km, WRF model).
When the air temp drops to the dew point, or within a couple degrees in a forecast like this, we can expect fog. Should be even more fog tomorrow.
Here is a 3-min video on the use of the UW meteograms.
This is just a printed note of a method described in more detail in the video link at the end. It is one way to study local wind forecasts, and especially the use of the US WRF model, whose high-quality data are otherwise only available to us as rather large scale graphic images, with wind speeds presented on a color scale. In short, this note is a quick way to decide if you want to sit through a 11-minute video!
We use the UW WRF model, one of the best for this region of Puget Sound (though typically older forecasts than we want on race day), but nevertheless very good for planning the day before.
Choose latest run, 1.3 km resolution, click the point of interest to load the lat-lon, then reset the elevation to 0. The 3 marks here are about the places we tested here.
It takes a minute or so to get each picture back, but there is a warning about this in red.
The data look like this:
The video discusses these in more detail. For now we care only about the second panel of wind speed and direction.
The three regions in study were then cut from this type of picture and pasted into one graphic.
The 0 h here is the run time at UW, that was 12 aug 8, or 5 am PDT. Then the time scale goes from there.
The video first points out that this is not best example, as there is not much wind in this case, not to mention we have a layer of smoke over the Sound at the moment, which is bound to affect any forecast. Nevertheless, we proceed while the method is fresh in the mind. It is also explained that the apparent chaotic wind directions are just an artifact of how they are plotted. We still see clearly veering and backing, and pretty well by how much. the scale is not optimum for this.
If interested, the details are below:
The next step will be to get hi-res CONUS NDFD data and load it into a program like Expedition which offers the option to build a meteogram at any point from the stored data. Quick checks shows it all works as intended, but the ultimate role of the meteograms is not clear.
For example, below is a 4-min video looking at these same WRF winds discussed above but in the conventional way using the graphic images. We see a lot from the graphic presentation, so it could be the meteograms might best serve as simply a way to more precise or digital values. We have a convenient link to this graphic WRF data from UW at www.starpath.com/local in the model forecast section. (To clarify a question that comes up in the video, it appears the 1.3km WRF model is run every 12h and generates 1h forecasts out to 72h.)
LuckGrib is a Mac app for downloading and viewing grib files. It offers the most functionality of any similar product, as well as offering the largest selection of grib data for download. All the files it can download can then be exported to use in navigation programs for optimum routing, provided they are compatible with latest grib formats. LuckGrib will download and display all of the various grib2 format options, but many nav programs do not yet display these formats or map projections. Grib1 data, on the other hand, are more or less universal amongst viewers and nav programs.
Among the many unique features of LuckGrib, this note is about its ability to add custom instances of what it calls "draw styles" and "style sets," and why we might need this. A draw style is the prescription of how you want the data to appear on the compute screen. Showing wind, for example, as barbs, feathers, contour lines, color or gradient background scaled to speed, or streamlines is one example of a set of draw style options for wind. Then each of these can in turn be set to specific colors, line widths, spacing, and even the gradients can be digitally defined over speed ranges. (In another part of the program you can specify how dense you want interpolation between actual data points, or no interpolation at all.)
More specifically, a LuckGrib draw style applies to a specific parameter and level, or set of levels. In a display of surface wind and pressure for example, you can define a draw style for wind that includes, say, barbs (an arrows option) and background colors (an images option), and another draw style for pressure (say contours only). This combination of two draw styles can then be named and saved as a draw style set, which you can recall or apply to other grib files. When combining wind, current, and waves, for example, we can use this freedom in display to emphasize one parameter with one style set, and another using a different style set.
But that unmatched versatility is not the subject at hand.
LuckGrib not only can access almost any valid grib file, it will also import it and make the data available to the user. In the GFS model, for example, we typically get wind and pressure, precip, and maybe gusts, and maybe winds and altitudes at the 500 mb level, but in fact there are some 300 GFS parameters available, and LuckGrib lets you ask for any of them. This makes the app a tremendous tool for inland weather analysis.
If we were to ask, for example, for the soil temperature 1 meter below the ground, we would indeed get that data for any location in the US, and if we loaded that grib file and put the cursor over a chosen location, we would read that temperature from the panel in the top right of the screen. But there would be no graphic display of this data because it was not anticipated in the marine oriented product. There is no predefined draw style for this. Without a draw style, say color vs temp with contours of equal temp, we cannot tell at a glance where the best place to plant our corn in Kansas might be... for example.
We come back to more realistic examples shortly, but here is the soil temp + wind + press selected over WA state. The cursor does not capture, but the top right shows read out at cursor location.
There is no draw style for this parameter, so we must add one.
(1) click the arrow on the (highlighted) active grib file, and we see which draw styles are missing
(2) We see TSOIL is the only missing one. Note that the parameter name is TSOIL and the level of the data is @ 1-2DBLL (1 to 2m depth below land level). Click the arrow next to draw styles, then in the next popup, uncheck the box that says Show only draw files referenced by file.... which really means show only draw files referenced by file that have been so far activated. TSOIL will not show up at this point, we have to add it.
(3) For other parameters, you can scan the long list that then shows up to see if your parameter is there, but just not with the level you care about. But in this case there is no TSOIL, so we have to use + button and add it.
(4) When you press + you get the choices: Contour, Scalar image, Arrow, or Streamline. For this parameter we would want to add contour and then scalar image, which is the one needed for a color gradient background.
Once you type in the official parameter abbreviation that we read from an earlier screen, it will know what this is and print the name as soon as you click the level field. In this case, we can just use the default for all levels, since this is the typical draw style we would use for temperature.
You can sniff around the main grib file display with the cursor to see the range of temperatures you might like and enter them here, but this can always be changed easily once this style is saved.
Then do the same for an image style, and just drag one of the gradient patterns onto the template. (I will need to add a video on this, which shows the process).
Then you are done and you can go back to the grib display and show these new styles for a clear picture of where to plant the corn.
We see several hot spots, the red peaks are 66º F and higher. The yellow is about 48 and the turquoise is just under 40. Not sure what this means.... it is a random exercise (this is not even Kansas), but ends up sort of interesting. Portland and Tacoma are the two red areas on the left, but not sure at all what the other hot areas mean. This is left as an exercise. There is nothing in those red areas with any similarity to Tacoma and Portland that I can think of—other than, (it appears) having high soil temperatures 1 to 2 meters below the ground. Also, why Tacoma and not Seattle? ... all beyond our present scope.
I will add a video to outline the process, and discuss the real example that forces mariners into this operation. It has to do with pressure contours referenced to ground level (not what we want) rather than to mean sea level, which is the convention used in some Norwegian grib files.
On the other hand, LuckGrib is a fantastic tool for making your own inland weather station to predict thunderstorms, rain, cloud cover, and air temperature. This use of the program on land will call for several of these custom draw styles. Keep in mind, too, as you play with this exercise, you can't hurt anything. There are numerous buttons that take all draw styles, or selected ones, back to default.
Video on just adding a level to an existing parameter ... the motivating operation for this exercise.
Here is a video showing the steps of the above article, which is the full process of adding a parameter and draw styles.
