cloud level weather forecasts

[Adam__S]

does anyone know of weather forecasts that include cloud level? Something to distinguish between "mostly cloudy above the peaks" and "mostly cloudy socked in"?

 

thanks

[iain]

Skew-T plots are helpful if you are interested in where the cloud deck is. The plots are based off weather balloon data launched twice a day. Unfortunately it is not a forecast, but observation data. Basically wherever the dewpoint and temperature curves meet, you have clouds.

 

Upper Air Sounding Plot Information:

http://weather.unisys.com/upper_air/skew/details.html

 

Maybe someone with aviation experience can provide upper air forecast information.

 

Usually you can have a good idea of what's happening in the Cascades based on what's happening in the foothills, or what's coming off the coast.

[jmace]

You dont actually need to tread the skew T in ordr to get the cloud deck you need to read the metar/taf reports issued by your local airport.

 

METAR CYVR 041600Z 11007KT 8SM -RA SCT040 OVC068 13/11 A2995 RMK

SC3AC5 PCPN VRY LGT SLP142=

 

its usually one of the first codes, this one issued at 16z or 9am, says sctatterd clouds at 4000 feet and overcast at 6800 feet, sometimes if you look around they may decode them for you but its pretty easy to read.

 

Forecasting cloud decks is a whole other ball game.

[knelson]

The National Weather Service's forecast "discussions" have recently started adding aviation information at the end of the discussion.

 

Western Washington's discussion is here..

 

http://www.atmos.washington.edu/data/disc_report.html

 

(This is a feed from the UW, but if you poke around the NWS/NOAA website, you should be able to find it also.)

 

Most of the time, they give you figures for cloud ceiling.

 

-kurt

[ski_photomatt]

The MM5 run at UW has some web accessible cloud fields available:

 

http://www.atmos.washington.edu/mm5rt/

 

These are forecasts. MM5-GFS is usually the best, 12 km. Use at your own risk as they are often inaccurate, especially at this level of detail.

[jmace]

12km is not the smallest detail, MM5 is a great model, if you dont know what you are looking at then they can be quite innacurate. if you want to try and forecast cloud and rain use the 70 kpa relative humidity chart, 90% is rain and 70% is cloud. Using this alone can be difficult but it can give you an idea of cloud or precip in a more localized area, knowing the topograhy can help you help the computer forecast.

 

Good Luck

[Ricardo_Montalban]

METAR CYVR 041600Z 11007KT 8SM -RA SCT040 OVC068 13/11 A2995 RMK SC3AC5 PCPN VRY LGT SLP142=

 

if this makes as much sense to you as it does to me, here is another option...

 

 

Explanation:

-this is a meteogram that is roughly a forecasted skew-t

-time moves from right to left in 6 hour increments

-the solid black line is the freezing level

-i'm not sure what the dashed black line is

-elevation is loosely associated with the atmospheric pressure (numbers at left). unfortunately this model does not give equivalent elevation like the skew-t model (which is measured data), but you can look at the skew-t du jour and compare to get a rough idea. warning; the pressure/elevation relationship changes constantly so even the skew-t from 2 hours ago could mislead you.

-i'm not sure if the color spectrum refers to cloud and weather intensity or just weather intensity. read: just b/c there's no color doesn't necessarily mean there won't be clouds. given the forecast, i would guess that the colors do not display clouds.

-wind speed and direction is indicated by the flags and # and type of barbs

-this can be found on this link (or and wa) in the UPPER section; click on star nearest your destination!

 

This image (from portland airport today) shows that on 5/20 at midnight, the precip will stop for roughly 24 hours and sunday evening it's going to rain like hell for a couple of hours.

let's report back on monday and compare our observations with this!

[jmace]

1000 = 100 m, 300 ft

 

900 = 1000 m, 3300 ft

 

850 = 1500m, 5000 ft

 

750 = 2500m 8000 ft

 

STD Atmosphere

 

The colors more than likely refer to Relative Humidity, I.E Cloud or Rain, Dashed line is probably another temp contour probably -5

 

Pretty sure if there is no color then there is no FORECASTED cloud. The meteogram looks good, possible convective clouds in the afternoon today then nice tomorow with a rather decent storm moving in lat sat night/sun morn

[Ricardo_Montalban]

STD = standard atmospheric pressure?

 

if you look at the skew-t's from the last couple of days, the elevation varies as much as 100m. granted that difference doesn't mean too much to most of us. since i don't know what the range of variation is, i was just pointing out that it's not a static equivalency.

 

good point on cloud/no cloud. we are now in the middle of the blue on the right and it's not raining (not to say it won't). and about noon, there was a nice sun break.

 

hhmmm...i know where i'm going tonight!!!

[jmace]

yes on the std atmosphere, as we see low pressure or high pressure move in we see the elevations varie, but +/- 100m should be too much of a problem and if it is then you just look and see how much the pressure has dropped or will drop as the storm comes in and re-adjust accordingly, but the forecast meteogram is nice since you can see where the computer model beleives moisture will be and how it may affect you by looking at the upper winds.

[Ricardo_Montalban]

ahh! it's raining now.

i guess dark blue means cloud and light rain.

 

so, if a high pressure system was moving in, would the elevation drop on your scale? (i.e., 850mb = 4000')

[jmace]

sounds about right, for the pressure, there should be a scale for those colors on the site you took it from sort of like what I posted above about 70%...

 

you see so if blue is a low amt of moisture but we get a trigger like a trough or a mountain range then possibly we can tap into that moisture aloft and squeeze out a shower.

 

sounds like you know how skew T works so its like plotting somethnig like that when you know the dew pt or moisture forecast content...

[Ricardo_Montalban]

thanks for the confirmation jmace.

here's another vertical profile forecast link (with more info) and it's explanation

the 1st, 3rd, and 8th part of the graph are relevant to the mtns, the rest are ground level predictions.