Weather School Musing ... What a Difference a Day Makes!

[simonjk]

Hello,

I hope you had a good weekend.

What a difference a month makes (although who can tell for how long?

Take a look at the skew-t diagrams below. Now, these are essentially graphs of temperature against height. The right hand red line is air temperature, the blue line to the left is dewpoint. Where the two touch is totally saturated air, hence cloud.

Below are three skew-t’s one for Birmingham and they show what the profile of the air was like above Birmingham.

The first is for 9am Sunday morning (yesterday). See how wet the skew-t is? Totally saturated all the way up through the atmosphere, hence the reason it was raining so much.

But now, look at today. See how the lines are spreading apart. It shows that the air is drier and that is certainly what it is like outside. Lots of sunshine (although frosty) today.

And then tomorrow (skew-t 3) at 9am is even drier. So a couple of fine days ahead.

Skew-t’s are really useful diagrams for showing you how moist air is, and what height clouds are at. You can see them at (http://www.weatheronline.co.uk/cgi-...&MODELLTYP=4&VAR=pslv&HH=0&BASE=-&WMO=&ZOOM=0)

Don’t forget you can now watch Weatherweb.TV 24-hours a day at http://www.weatherweb.tv and I’ve added a video today about the weather this week.

Best wishes,
Simon

 

[Bosun Higgs]

Hi Simon

1/ what are the wind vectors off to the side - are they the wind speeds at various heights in which case does the angle show descending wind as in high pressure etc

2/ what are the mix ratios?

3/ why are the ASL levels there when the graphs are against height?

4/ what do the radar diagrams show?

5/ On another subject, what happened to Sundays original 45 kn forecast. We were out on the boat and it was never more than 10 kn or so - and bone dry as opposed to the deluge forecast.

 

[simonjk]

Watcha,


1/ what are the wind vectors off to the side - are they the wind speeds at various heights in which case does the angle show descending wind as in high pressure etc

Yes, these are wind directions and speeds at various heights. One full feather= 10knots, half =5knots and the blind-arrow points to the direction from which the wind is coming from.
There is no strict rule as to the directions with height, it all depends on where the upper high and low are positioned.

2/ what are the mix ratios?
These are Humidity Mixing Ratios (HMR's). These are the ratio of water vapour mass (g/kg) for a given pressure. Practically they are used when assessing fog probabilities, but I won't go into that here.

3/ why are the ASL levels there when the graphs are against height?
Aha, these are Atmospheric Standard Levels (for those who don't know what ASL means). We actually measure the height in mb, but the true height changes each day dependent on temperatures. However, meteorologists measure the height for each of these pressure surfaces.

4/ what do the radar diagrams show?
This is a Hodograph. It is used to shaow where from, and at what speed warm or cold are are advecting towards the station.

5/ On another subject, what happened to Sundays original 45 kn forecast. We were out on the boat and it was never more than 10 kn or so - and bone dry as opposed to the deluge forecast.
This one was always overplayed. I could not believe the graphics which were being shown on the TV through Friday. I think it was overdone just in case it actually came further north and ion which case we could have seen the problems along the south coast which France have experienced.

Hope these answers help?

Simon