On the first day of October, we did our first Halloween update. The update involved having a brief look back to previous Halloweens since 2000 in terms of weather in the UK along with discussing what the long range models, CFSv2 and Beijing Climate Centre (BCC), were showing for Halloween 2018 at that time. Both models were hinting at the chances of a pretty chilly Halloween but largely settled.

For the second update, we’re going to be looking at the same long range models of the CFSv2 and BCC but we also have the Global Forecast System (GFS) this time around to add to the update as it now generates as far out as Halloween. This will be another just for fun update like the first as Halloween is still two weeks today on the 17th October. This means to not take the forecast too seriously and wait ’til time passes closer to the event.

GFS

To start off this update, we’ll be having a look at our new addition to the updates, the GFS model. The charts below are from the twelve o’clock run generated by the GFS today. The model shows an area of high pressure building over and just to the east of the UK drawing in a southeasterly wind with air coming from continental Europe. This wind direction in Summer time would be very hot but as it’ll be late October and the continent is ever gradually cooling, this would be fairly chilly. The 850hPa temperatures prove this as they’re around freezing along eastern regions of the UK whilst out west ranging between 0-4°C, which is still relatively below average. Under this high pressure, there would be the potential for air frost, most certainly ground frost especially up north, mist and low cloud. Temperatures on the surface would range between 6/7°C in northern regions and those under persistent low cloud to 13/14°C sheltered in sunny spells. However, it would be a very settled Halloween.

This GFS run is very similar to how the CFS was in our previous Halloween update.

CFSv2

The CFSv2 is similar in terms of 850hPa temperatures for Halloween 2018 with chilly values all around the UK. However, it is a more unsettled solution compared to the GFS. The winds are from a westerly to northwesterly direction so it is a zonal pattern. There would be scattered showers, possibly falling as wintry on northern hills. Winds not overly strong, in fact rather calm but it would feel chilly. Nice sunny spells around the country especially in the south. Surface temperatures would likely range from 7/8°C in the north to 14°C in the south.

BCC

The BCC model is different to the other two models shown above in that it generates forecasts as 10 day tri-monthly period. The 10 day tri-monthly period that includes Halloween 2018 shows an area of below average heights i.e. low pressure parked right over top of the UK. It would be a very unsettled period; though not overly mild, for the UK that the BCC is hinting at here for the 26th October to 4th November 2018 which is largely on odds with other models like the GFS. Good thing this update is just for fun eh?

Summary

There you have it, that’s the second Halloween update from us here at Metcast. Unlike the first update which strangely enough should be the more divided update in terms of model outlook, this update shows disagreement among the models but one thing’s for sure in all of them, mild temperatures aren’t a common appearance with each one showing the potential for some quite chilly conditions on or around Halloween 2018. We will start to think more seriously in the next update as other models come into range of Halloween 2018 and the period is closer to the more reliable timeframe. Stay tuned.

Sean Bruen is a forecaster for Metcast (and Snow Watch). His main interests are historical and long range weather. He LOVES snow (his Twitter account is @SnowbieWx, go figure!) and his favourite season is Winter.