Very Steep Pressure Field Between 965mb Icelandic Low and 1030mb Azores High! 70-80+mph Winds Tonight!

Written by on September 3, 2012 in Rest of Europe, United Kingdom & Ireland with 0 Comments

Satellite image courtesy of WeatherOnline

A very steep pressure field is setting up over the Atlantic between deepening Icelandic low and strong Azores high. Bteween the expected bombing out at 965mb tomorrow am and the 1030 ridge, very strong upper level winds are likely to mix down the the surface thanks to alignment with good vertically ‘stacked’ winds from jet stream level to the surface. As pressures tighten, so winds blow harder to compensate the imbalance and with winds align from top down, these much stronger upper level winds can mix down to the ground and so winds may get clocked at 70-80 mph or more between the Northwest Scottish Mainland, the Outer Hebrides, Northern Isles and Faroe Isles.

With the low not yet reached maximum depth within it’s centre, prefrontal winds above 4,000 feet are already strong with gusts being reported on top of 4084 foot Cairngorm Mountain at 81 mph.

Check out this GFS surface pressure forecast over the North Atlantic tomorrow morning off the WeatherBELL site!

GFS chart courtesy of WeatherBELL Models

Note the GFS has the Icelandic low down to an impressive 965mb. Problem is, the Azores ridge to it’s south is 1030mb and that is a very steep pressure gradient. The atmosphere must compensate for this large imbalance and Scotland finds itself beneath these strong winds. Alignment within the vertically stacked winds tonight should support hurricane-force conditions between Scotland and the Faroes tonight and much of Tuesday.

Note the below upper level winds expected at jet stream level tomorrow am off the GFS. Note the brighter colours indicating stronger winds racing out of the SW between Scotland and the Faroes due not only pressure difference but thermal contrast between the hot air mass within the Azores ridge and the cold drawn down from Greenland on the north side of the circulation. This intensifies the jet.

GFS Upper level wind forecast (Courtesy of WeatherBELL Models)

Front-right-rear-entrance region warming over the UK this afternoon!

With good dynamics in place. The UK sits in the perfect place this afternoon for strong surface warming within the front right rear entrance region of the jet as it approaches the UK from the west. The front right rear entrance is a region just east of an advancing SW to NE aligned frontal zone which can support sinking (subsidence) which erodes cloudcover and provides enhanced surface warming. This setup also merges with increased warming southwest winds which is transporting heat from the Azores up to Britain, helping with the heating process. The warmest places will be east of hills where southwest winds can downslope and so it’s no surprise that temperatures are up at 22C as of 1pm on the south shore of Moray Firth at Loossiemouth and areas east of the Grampians Scotland.

Did you notice clouds dissipated this afternoon. That because this region of subsidence arrived as the front approaches. This enhanced ‘sinking’, clears out clouds.

Less warm, sunny Tuesday for all with wind everywhere, strongest in the north

Tomorrow will see winds cranking everywhere, especially the further north you go with gales or severe gales from the Highlands north. Wouldn’t be surprised to hear of damage in the wsetern and Northern Isles as leaves are still on trees which addsd weight.

There may even be a period of southwest gales for a time across the Central Belt tonight into tomorrow morning as the front sweeps through and the pressure drops.

Strong west winds blow hard tomorrow as the low bombs out to the north but beyond tomorrow, the ridge rebuilds and with increasing heights, so the increased cloudiness of Tuesday should become sunshine Wednesday, especially in the South up towards Manchester with temperatures rebounding back towards the 23-24C mark. A little more mixed in the North with showers brought in by the strong west winds.

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