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Paul Blight

@PaulBlight6

Dec 28, 2024

Storm Update 31st - 2nd Jan
Unfortunately we now have growing confidence of a very unsettled pattern developing over the UK over the New Year Period, with the likelihood of two deep depressions crossing the UK. There are however still sig. mismatches between the Models handling of upstream upper troughs/ Jet Patterns emanating over the Davis Strait which will impact our weather over the period.

1) A deepening area of low pressure will cross Scotland during New Year Eve, Multi Hazard low with heavy snow developing over the North Of Scotland & Gales developing to the South, Gusts to 70mph possibly slightly higher over N Ireland, Southern & Central Scotland. Perhaps gusts to 80mph NW Ireland. Models are in fair to good agreement on this first low, though there is still some doubt over the exact depth of the low.

2) The 2nd low crossing the UK on NYD is still causing forecasting major headaches due to the lack of agreement on the shape & depth of the shortwave 300-700mb trough which is swinging SE from the Davis Strait which will pick up a wave depression in the mid Atlantic developing on the cold front as it tries to move SE. The ECMWF insists that this upper trough will be sharper than the flatter more E/W trough that the GFS suggests. Study of the GFS Ensembles suggest that the model has about the right depth, but slightly too far south. The ECMWF Control a tiny bit too far north. The 30 GFS Ensemble + the 51 memnber ECMWF ensemble suggest the Control is a little too far to the North.
The UKMET Global would seem to represent a good multi model and multi ensemble compromise on a track across Ireland, across the Northern Irish Sea towards the Borders as best track i could suggest at this time.

This will likely be a multi hazard storm event, with gales or Severe Gales likely to develop across the South with gusts likely to 85mph+ around coasts and hills in the West, 70-75mph over parts of Ireland, 65mph+ across many Southern parts of the UK., Heavy snow will develop to the North of the storm centre as it sweeps east with 30-40cm across Southern Scotland, Far North England, though again on track , slightly further south and the snow risk increases markedly for major population centers as shown by the 00Z GFS .

The ECMWF Precip Phase ensemble suggests a nearly 100% chance of rain falling from the Low across the Midlands, which strongly backs up my suggestion of a track further north as discussed.

A lot of uncertainty in the detail remains which i will keep on top of over the next couple of days as we get more data on the crucial upper trough coming SE across the Atlantic from the Davis Straight. However I can say with increasing confidence that the risk of a multi hazard storm or storms over the New Year is increasing and we should all be prepared for the potential for some significant disruptive weather across the UK.
EDIT - 06Z GFS coming in further north as i suggested with a track across Ireland, the Borders with a very deep solution of 960mbs with blizzards to the North and 80-90mph gusts (potentially more) around the coasts of West Wales, Irish Sea. (upper trough is correcting towards ECMWF solution)

Paul - 28th December 2024
(Diagrams in the replies below)

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Paul Blight

@PaulBlight6

Feb 21, 2024

Thursday's Wave Low is continuing to cause me some concern & is proving troublesome to the Model Guidance. The 00Z Runs of the ICON, ARPEGE & some ECMWF Ensemble members indicate the risk of a much deeper wave depression developing over CS/SE England during the afternoon. >>

this leads to a spell of potentially very strong winds in those models over parts of coastal S/SE England before clearing into the North Sea. A very active squally cold front is going to move east during Thursday. This ALL models agree on, however the shape & extent of the upper

trough filament driving it is not agreed upon in the models. The upper trough then interacts with the frontal boundary over the Near Continent to form a wave low running NE. However in the ARPEGE & ICON this upper trough is sharper & more backed which allows for a deeper wave

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Paul Blight

@PaulBlight6

Nov 1, 2023

1/10) 1st November Morning Update #StormCiarán
The rapidly developing low is currently moving rapidly into the Eastern Atlantic around 987mbs, steady deepening occurring overnight, however it will soon move into the Left Exit region of the Powerful 200mph Jet. This will act like

(2) a giant chimney & at 300mb (5 miles up) the air will rush outward rapidly, this means that air from the surface has to rapidly take its place which will cause the pressure to drop rapidly at the surface deepening the Storm. (That is called Divergence aloft) This causes the

3) winds to begin to rapidly increase around the developing Storm. Unfortunately it now looks likely that the peak deepening phase will concur with the storm making its final approach towards NW Europe. Multiple Models now showing extremely strong gusts a probable over NW France

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Paul Blight

@PaulBlight6

Oct 31, 2023

(1) Tuesday Evening Update on #StormCiaran. Unfortunately we now have quite high confidence in a spell of potentially very damaging winds across NW France & the Channel Islands and preparations for #StormCiaran in #JerseyCI & #GuernseyCI should be completed as soon as possible.

(2) Ciaran could bring gusts over 90 & perhaps near to 100mph over the Channel Islands late on Wednesday Night & early on Thursday. Ciaran is currently SE of Newfoundland around 993mbs, currently sat under the Jet with only modest deepening. The 12Z St John's ascent analysed

(3) a 165Knt Jet broadly in line with expectations. The Low will move rapidly across the Atlantic tonight & on Wednesday & approach the SW of Cornwall Weds Night. Models are now in good agreement on a track from Cornwall across SW then CS England & NE into East Anglia. Strongest

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Paul Blight

@PaulBlight6

Oct 31, 2023

(1/) 31st October AM Update on #StormCiaran. Increasingly confident about damaging winds affecting West Cornwall & Channel Islands, Coastal Sussex & Kent Kent. Remains on a knife Edge for other Southern Coastal Counties this morning.50-100Mile bounds will make a huge difference

(2) #StormCiarán is currently located S of St Johns in Newfoundland, analysed at 997mbs at 07Z. The 00Z Ascent from Caribou Maine perfectly sampled the Powerful Jet across the far NE part of North America. This was at 180Knts or 207mph.This was under analysed by both the GFS &

(3) ECMWF. The ECM was expecting 163Knts & the GFS 168Knts. Therefore both of these models have underestimated the Jet at 00Z. The Jet 17Knts stronger than the models were anticipating. Given these starting errors one can only be moderately confident they have a good handle on

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Paul Blight

@PaulBlight6

Oct 29, 2023

(1/) The Embryonic Low which will highly likely become the next name storm is now developing along a developing frontal boundary over the Ohio Valley. This Low will move East across the Atlantic where it will come under the influence of the powerful 160-170Knt (nr 200mph) Jet

(2/) The low is set to deepen rapidly as it crosses the Atlantic, though there remains some uncertainty in the models with respect to when the most explosive phase of deepening will occur & how near this is to the UK. The 00Z Suite of models have backed off (thankfully) a little

3/) from the very concerning extreme solutions seen on Saturday evening. However there is still cause for serious concern with where this low tracks. There is 100-200m Spread in some of the solutions, which if the low is passing NW of the UK doesn't make that much difference

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