Update for storm prospects for Reigate: an intense low pressure is forming out in the far west of the Atlantic this evening where frigid air from Canada is meeting humid warmer sub-tropical air circulating from the south round the Azores high pressure. This confluence of winds causes lift to occur at the polar front but a fast jetstream blowing at 180mph directly overhead will cause additional lift of the air lowering pressure extremely rapidly.
This process is called rapid cyclogenesis and gives birth to a deep low pressure with tropical air circulating into the storm from the SW and polar air sweeping round the head of the storm to follow in its wake.
The low will deepen and race 1300 miles across the Atlantic to arrive off the NW UK coast by midnight Thursday. For inland Reigate and SE England the impacts will be lower than in the west and NW but the English Channel will experience significant gales overnight in the warm sector of the depression with gusts possible of 70mph. NW Britain and especially NW Irish coast might see the biggest gusts in the wrap around winds on the south side of the low core where stingjet winds are possible even as high as 100mph.
Winds for SE and Reigate will build through Wednesday from late afternoon and through the evening and are likely to peak at possibly 50mph gusts as the squally cold front passes sometime 4-6am. Exposed places on the Downs could experience stronger gusts. Winds will ease after the cold front moves through by breakfast time but Thursday will stay blustery with showers and feel cooler. There is a chance that our record wind gust recorded in Reigate of 52mph will be broken in this storm but the town is sheltered from southerly / SW winds which will be the dominant wind throughout the event so this might keep wind gusts lower.
For Reigate the rain is likely to arrive mid evening on Wednesday. Rainfall will be persistent throughout the event and heavy at times and possibly with isolated thunderstorms as the active cold front moves across early Thursday morning. Rainfall totals could amount to over 20mm, most of it falling in a short period probably at the cold front.
The weather on Wednesday will be interesting: starting with cold temperatures and scattered snow showers courtesy of frigid air originating from Canada and Greenland on a brisk NW wind and then warming through the day as the storm arrives with a deluge of rain arriving in sub-tropical air from the deep south Atlantic.
Finally, the storm is due to usher in cold polar winds which eventually swing to the north as pressure builds in the Atlantic to bring an Arctic flow across the UK during the weekend. Various troughs and any low pressures sliding down the edge of the developing high pressure could cause a more significant snow event any time from Sunday and through the week. This wintry spell is likely to last into next week so dig out the warm woollies! Any snow that we get in Reigate will be the first since March 2013. Lots going on and very changeable so stay tuned!