Archives For October 2012

An unusual weather pattern exists right now: High pressure in the Atlantic is stopping our normal south/westerly winds and allowing cool north and north westerlies to dominate.  Once the rain on Monday shifts from the South East, Tuesday will be our best day – especially out west where a ridge of high pressure briefly flirts with the UK.  After that an ugly low pressure system swoops down from Iceland and the Low will centre over NW Scotland.  Strong winds and heavy rain will affect much of the country, especially the western half.

However, a tricky beast of a storm (a wave depression) might rapidly develop to the SW of the UK and rip across the south rather quickly sometime around Friday / Saturday.  Look at the jetstream chart below for next Saturday and see how the jetstream really picks up over the South during this time, dragging the storm along on the surface, like an unruly dog on a lead! This “dog” has a pretty big bark and a big bite and could deliver a deluge of rain and strong gales over the south.  Let’s wait and see: some bonfire nights might be wet and windy.


In Reigate: our first air frost of the Autumn was recorded last night at 3.00am: -0.3C.

An “air frost” is when the air temperature recorded by thermometers placed at 1.25m above the surface (a standard height) falls below freezing (0C).  A “ground frost” is when the temperature recorded by thermometers placed on the ground, usually over grass, record 0C or lower.  This is often quoted as “grass minimum”.  Reigate Grammar weather station currently records air temperatures but we hope to record grass temperatures in the future.

Hello winter!

October 25, 2012 — Leave a comment

Temperatures are falling across the UK tonight.  Reigate temperatures have fallen from a high of 13.3C at 2:30am Thursday morning to 9.3C now at 10:28pm and expected to fall much further.

Look at the jetstream forecast chart below for Saturday 27 October.  This shows a 100mph jetstream blowing from the North across much of the UK.  This means cold air from the polar regions will take less than ONE DAY to reach the UK!  This will give it very little time to warm up, other than picking up some moisture over the North Atlantic ready for snow over the Scottish hills.  A very chilly thought!

Sunday 21 October will be wet for Reigate, with Monday through Tuesday getting unseasonably warm – but probably remaining cloudy and autumnal.  Make the most of it because thereafter things get interesting with a HIGH pressure building to the North, LOW pressure drifting into Biscay and feeding COOL air from more easterly and northerly winds blowing across the UK.  How quickly this cold air feeds down to Reigate is uncertain but Wednesday onwards looks increasingly cool but dry for the South East.

Update: CANCEL the “dry” bit!  The charts below show a big cold polar low drifting down over the East of the UK and North Sea from Iceland and Greenland: this will bring a chilly blast of Arctic air across the UK with snow in Scotland, sleet over Wales and a real taste of winter for the rest of us.

Some models are predicting a COLD northern hemisphere winter this year: the Japanese global forecast and UK Met Office long range both agree that average temps will be about 1.5C below normal.  This means perhaps 4 or 5 spells of really cold weather interspersed with warmer spells.

Dig out your winter coats over half term: will winter start in mid november as this CFS model suggests?

A little unsettled throughout this week October 15 onwards, but not so bad except mid-week.  Models look unsettled and wet for our region Wednesday: heavy rain on the cards again!  Low pressure dominates throughout the week but some warmer air flows from the south on occasions keep day time temperatures up reasonably.  A more significant dip in temperature is looking likely in the next week.

Here’s an update for London temperature forecasts through to the end of October according to the GFS.  Note the significant dip to cooler temperatures around mid week on 25 October… no real surprise as we enter autumn proper but it’s interesting to note when these inevitable falls kick-in.

Forecasts remain uncertain because Raphael, a decaying Atlantic Hurricane, is sitting off our shores.

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Some forecasts are suggesting thunderstorms in our region Thursday pm.

Keep an eye on approaching fronts here:

Looks like this at the moment: rain clearing away overnight Thursday and should be dry Friday.  Rain spreading overnight Friday night and some showers through Saturday morning. Temperatures a cool 10C during Friday morning, climbing to a max of 12C, then falling to a chilly 5 or 6C by dawn on Saturday. Wrap up campers!

The LOW predicted yesterday for Sunday has seemingly melted away, but likely to get significantly cooler next week.

One to watch: GFS models are suggesting a nasty polar depression threatening all of UK on Sunday but bringing especially strong winds to southern UK: it’s 25 years since the Great october Storm – time for an anniversary?.  Or not (it’s a way off!).