My main concern is clouds. While models are adept at forecasting large areas of clouds associated with weather systems, they are less adept at forecasting fair weather cumulus which could be equally fatal to the 2 minutes of totality. I have some tricks which are helpful: 850mb mixing ratios and mesoscale areas of lift and subsidence, none are foolproof. What is everyone doing for cloud forecasting?
The eclipse chasers discussion group that I mentioned earlier is at
https://groups.yahoo.com/neo/groups/SEML/info - all of you are welcome and encouraged to join.
Jay Anderson, a meteorologist from Canada, is very experienced in eclipse climatology and weather. His site
http://eclipsophile.com/ is very valuable. You can see the climate data for various locations along the track of totality at
http://eclipsophile.com/overview/ (go to the bottom and click on each state)
As one person said once and many have repeated: "Climate is what you expect; weather is what you get."
So, Jay has also created a page showing some good forecast sites:
http://eclipsophile.com/eclipsewx/
Actually, fair weather cumulus has a decent chance of dissipating partially or completely as the temperature drops. And if you're near a large lake, it can create a clear patch in the direction of the sun (see the South Carolina page for good examples of that) But other clouds may form as the temperature drops. Of course, if there's a large scale weather system, then the best bet is to try to escape from it- but then there may be traffic issues.
I posted this to the group the other day:
"Sites like
http://www.skippysky.com.au/NorthAmerica/ and
http://clearoutside.com/ give forecasts for high, middle, and low level clouds (anyone know of any others?) Are clouds at a certain altitude more likely to dissipate as totality approaches? If clouds are present at a certain level of the atmosphere a few hours before the eclipse, are they likely to return as the temperature drops? I know, for example, that "popcorn cumulus" have the best chance of dissipating- which level of the atmosphere are they in? I know that fog (esp Oregon coast) has a chance of re-forming- I guess this would be "low clouds"?"
and got this response from Jay:
"Typically, small convective clouds with their “roots” on the ground will dissipate as the shadow approaches as the ground cools far more than the atmosphere and their forcing is cut off. Having said that, convective clouds of sufficient depth or amount (broken cloudiness) may also spread out into a layer of stratus, though I think that is more likely in mountain environments (i.e. 1988 in the Philippines, 1991 in Baja). Surface-based convective clouds may have bases that reach the mid-levels, but those clouds will most often be towering cumulus (TCU) or thunderstorms (CB) since it takes a lot of heating to force a parcel of dry air to saturation at mid-cloud levels (but it makes for great storm chasing). They may weaken but likely won’t dissipate during the eclipse. Also, TCUs and CBs both produce mid-level cloud during their lifecycle. Fog may reform if it only a short time elapsed since it first dissipated (Baja 1991 but not Egypt 2006). If an hour or two has passed, the moisture is likely distributed through a greater depth of the atmosphere and will not reform in the duration of an eclipse. Of course, if a persistent fog bank lies nearby (offshore?), all bets are off. To completely answer your questions, you will have to know how the numerical model calculates and defines the various cloud levels. Mid and upper clouds are usually associated with upper-level disturbances and will not respond to the eclipse. Some notes about models: The GFS model is geared toward the forecast of system cloud. The NAM model focusses on convective clouds. Typically they will have (sometimes significant) differences. The HRRR and the RAP focus on convection as well, but they are very short range models. These models have specific uses – the GFS goes out 16 days, the NAM, 84 hours, the HRRR 18 hours, and the RAP 21 hours. The Canadian GDPS goes out 10 days (15 on the right web site) and the RDPS goes out 48 hours. All of these forecast cloud and some forecast layer cloud (actually, they all do, but certain fields are hard to find online). Skippy-Sky uses the GFS model; I don’t know what clearoutside does, but I seem to recall that it used a mixture of models from different countries though certainly the GFS is in there.
The question you will have to answer is “which model is right?” One source that I know of will let you compare these at a single location: spotwx.com, a fairly sophisticated Canadian site. Just click on their map, or insert a city name and the available model forecasts can be examined. The College of DuPage site at weather.cod.edu will give you regional or continental maps of the cloud forecasts of the various models if you want a landscape view (weather analysis tools >numerical models>(select model)). When different models begin to agree, you can be more confident of your local forecast. For other eclipses, only two models are freely available worldwide: the Canadian GDPS and the American GFS. Spotwx.com works globally and will show both models and some others (try it on Paris), but the comparison may or may not leave you any wiser until the eclipse is fairly close (~3 days). And finally, as a fairly experienced storm chaser, I’d like to point out that the actual (convective) weather often bears only an approximate relationship to the model prediction."
I have the experience in eclipses; all of you have the experience in weather. Let's help each other out.
