GRIB Data Warning...Great Example

[weatherman]

Hi again ,

A deep area of low pressure (~980mb) is going to be crossing Scotland this weekend. By 6am Sunday morning it is expected to be off northern Scotland...




Now, given this area of low pressure, it's depth, development and track, wind speeds across outhern and western Scotland as the feature passes through, can be expected to be around 35-45kt (F 8 -F9) gusting in excess of 60kt (F10-F11) over exposed coasts and hills.

Many of you will have access to GRIB data and can check the speeds predicted by the models. This data will be the same as the chart below...



Notice how the mean wind speeds from the GRIB data shown here are of the order of 20-25kt (although the orange colours in the far NW of the chart indicated mean speeds of 30kt).

This is a good example of how GRIB data will smooth out wind speeds and, although very useful, GRIB is only a tool in the forecasting box, especially in potentially dangerous situations.

Thought you might be interested.

Simon

[tcm]

well, um, the two maps don't match - the first is over atlantic, second centred on europe. And as you say, the one over scotland shows the 30something knots which we all know means add a bit in open sea. Anyway, i see the point.

The "gusting 60knots" should cover it, you weather forecasters eh?...

[sahona]

Well, something just 'flipped' in the Clyde, we've gone from brisk Easterlies to strong Southwesterlies in the last 1/2 hour (with rain) .
Looks like PSC cancelled their dinghy racing , but still the golfers plod their weary way among the gorse.
That's where all the hard men have gone
(everybody-) long time passing....




Ramble over

[Silkie]

Simon has linked to actual forecasts unfortunately rather than saving the ones in question and linking to them as jpgs. I am currently seeing 48hr forecasts valid for 1200 Tuesday 27/10 and for quite different areas as tcm has said.