Archives For upper atmosphere

Reigate should see 30ºC Tmax for the first day of August and high 20’s on Friday. The cause is a warm tropical plume of air flooding over the south of the UK from Iberia (Spain) and Africa brought in as the jetstream moves north and a LOW to our west and HIGH to the east builds a brisk Southerly airstream. Thursday will be dry and bright and the night will feel very muggy with high dew points and lows of over 20ºC at midnight: warm and damp, the air will feel close! Friday will be warm too but slightly less so for Reigate, dawning bright but with cloud spilling in associated with a weakening cold front pushing east across the country. Little frontal rain is expected but the cooler upper temps could release the huge heat energy built up in the lower atmosphere and kick off heavy / thundery showers for a while, especially Friday morning. Confidence is low currently but this might occur, the potential is there with all that heat.  

Every thunderstorm indicator is giving green lights to thunderstorms in the SE sometime in the next few days BUT the airstream is capped with warm uppers: this appears to be the only factor stopping convective action. This means heat building in the lower atmosphere will stay put until forced to rise into the unstable layers above (see sounding graph above). The approaching cold front might be sufficient to produce something of convective interest on Friday, morning especially… before the warm Euro air retreats back to east. So far Reigate has seen little of the impressive thundery activity elsewhere in the UK this summer. You might be forgiven for thinking it must be our turn soon! It’s unlikely to be in the next few days as the risk is small for any major thundery outbreak.
The synoptic situation remains similar over the next few days with HIGH pressure over the continent and LOWS edging close to the NW of the UK bringing rain and wind to the NW. The SE should escape with any trailing fronts weakening and Reigate should remain largely dry but for any threat of isolated thunderstorms in building heat.


Has the sun set on the first and last day of Spring?!  Spring will return but certainly not for a while.  The rest of this week will be rather wet but mild. An octopus-like LOW sitting out west in the Atlantic will sweep several tentacle-like fronts across the country (count them = 8) and this will bring frequent, mostly light rain to Reigate, heavier rain does threaten on Thursday: check back for details. The big news is the temperature drop between Saturday (+11C) and Sunday (+2C!): this temperature plunge will feel bracing after our all-too brief flirt with Spring and the mild conditions this week. Over the weekend the LOW looks like it will track south of the UK and drag in amazingly chilly air from a BLOCKING HIGH developing over Scandinavia to the NE.  The HIGH will force the LOW to the south and east of the UK and we will pick up a NE / E air flow.  This air flow could stick around for much of next week.  By Tuesday things could be really cold in the upper atmosphere (1500m= -14C!). Down here in Reigate things will return to a wintry feel with hard frosts, cold temperatures around freezing and possible snow now and again. If the coldest upper air temps reach us then heavier snow from the E and NE is a possibility.  Tricky to tell this far out.  Brace yourselves and keep watching for updates!

 

The very cold upper atmospheric pool of air which put Reigate in the freezer this half term (-11ºC at 1500m, -35ºC at 5000m!) is moving off South… to be replaced by warmer air aloft moving in from the North (-1°C at 1500, -25ºC at 5000m).  Watch the video below to see the warm air moving in from the north and pushing the cold air south.  This is rather upside-down to what we would normally expect and is being caused by warm air being squeezed through by an active jetstream in the Atlantic: this is feeding warmer air into the HIGH pressure sitting atop the UK currently.  Reigate weather will be dominated by the HIGH pressure during this week making things mostly dry but, as we are located on the edge of the high pressure weak fronts will be able to influence our weather as they nudge across the Channel early in the week and bring light snow turning to drizzle through Monday and maybe more light rain on Tuesday. Temperatures remain uninspiring at 5°C.