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Convective/Thunderstorm Discussion Spring/Summer 2018
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Wouldn't go beyond +48hrs when looking at convective weather forecast in Ireland. Each day's convective potential depends so much on the previous day's remenants. Especially when theres high pressure around.
Looking into tomorrows potential.
Some good heating in the boundary layer with temps/DPs in the high/low teens respecitively leading to several hundred cape (j/kg) in places.
Risk area - Just west of the spine of the country. ( weirdest area name I know but it works :rolleyes: )
Low Deep layer shear will mean storms will be of the pulse type ( short lived) , so short heavy downpours with some lightning.
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Plume of warm moist air moving across from the UK tomorrow into rising temperatures in the afternoon,Cloud bubbling up producing showers with some looking heavy, will be interesting to see if some become electrified.
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http://www.convectiveweather.co.uk/forecast.php?date=2018-05-24
Day 2 Convective Outlook
VALID 06:00 UTC Thu 24 May 2018 - 05:59 UTC Fri 25 May 2018
ISSUED 20:59 UTC Wed 23 May 2018
ISSUED BY: Dan
Several episodes of thunderstorms are possible during this forecast period - in general, for England / Wales the risk of lightning is mainly across the southern half of the SLGT during Thursday daytime, the focus then shifting to the northern half of the SLGT on Thursday night / early Friday. Main focus for Northern Ireland / Republic of Ireland will be Thursday afternoon and early evening.
... THURSDAY DAYTIME: ENGLAND / WALES ...
Elevated convection will likely be ongoing at the start of this forecast period, associated with destabilisation of relatively high WBPT plume, over southern England / south Midlands, moving westwards into S Wales and parts of SW England. Some sporadic lightning continues to be possible with this activity, although instability reduces as storms continue to drift to the west, so probably with a weakening trend as they move into Wales / SW England.
By the afternoon, there is fairly good model agreement for any thunderstorm potential to become primarily focussed along the moisture plume, in a SE-NW corridor from Cen S England to S Wales. By this point, rain will be evolving into a messy mix of dynamic and embedded convection elements, though should any thunderstorms develop along this zone then they will quite likely be elevated - however, there is scope for some to become rooted in the boundary layer if enough surface heating can occur, either along or to the north of this frontal boundary. Some high-resolution model guidance suggests the potential for a couple of surface-based thunderstorms during the second half of the afternoon near or just north of the M4, drifting west into E / SE Wales towards evening. This area therefore has the potential to be upgraded to MDT; should thunderstorms develop here lightning could be quite frequent, accompanied by hail and gusty winds.
Main threats will be surface water flooding from prolonged heavy rain running over similar areas, particularly Cen S England and along the M4 corridor into the SW Midlands. Depending on developments, the SLGT may also need extending into parts of Devon and Cornwall.
... THURSDAY DAYTIME: NORTHERN IRELAND / REPUBLIC OF IRELAND ...
Remnants of mid-level convection / instability (from Wales) will drift westwards into southern and eastern Ireland on Thursday morning - this airmass then destabilising further in response to surface heating, yielding 500-900 J/kg CAPE. Low-level convergence will aid in the development of a few scattered surface-based showers and thunderstorms along a N-S line, starting on the eastern side of the SLGT mid-afternoon and drifting slowly to the west into the early evening, before decaying as nocturnal cooling of the boundary layer commences.
Shear is not particularly strong, and so most showers/storms will tend to be of the pulse variety, an individual cell lasting less than an hour etc. This is also somewhat dependent on how much cloud will spill from the east, reducing surface heating. An isolated heavy shower / thunderstorm is also possible in western Northern Ireland.0 -
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Meteorite58 wrote: »Looks like a bust, nada !
Seems to be a recurring theme this past year, I know thunderstorms are scarce here at the best of times but its been a fairly pathetic year for storms. I can't recall a single day all Spring so far that's had more than a handful of sferics either.
Here's hoping for something like this over the summer to make up for it
https://www.youtube.com/watch?v=E8cMSyzFoLs0 -
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http://www.convectiveweather.co.uk/forecast.php?date=2018-05-26
Day 2 Convective Outlook
VALID 06:00 UTC Sat 26 May 2018 - 05:59 UTC Sun 27 May 2018
ISSUED 22:40 UTC Fri 25 May 2018
ISSUED BY: Dan
Plume events are often fraught with uncertainty, primarily due to poor NWP modelling of deep convection generated by mid-level instability. In these types of situations, including today, it is best to take a broad-brush approach and try to highlight trends, rather than specifics - basically, expect the unexpected! The latest model guidance is much further north and a lot quicker with developments than data had been suggesting just 12 hours ago. It is likely some areas within the SLGT could remain lightning free, and the forecast may need to be altered if confidence improves - it rarely goes to plan...
There are reasonable signs for an area of elevated convection to be drifting across S / SE England at the beginning of this forecast period, continuing to move NW-wards through Saturday morning. Questionable as to how much lightning there will be with this activity given weakening instability, though forecast profiles do suggest some reasonable shear to help with some organisation. Either way, whatever activity there is will likely weaken with time as it continues to migrate across the Midlands and into Wales.
A secondary pulse of elevated convection may develop and move NW-wards across SW England late morning into the afternoon, which would have a better chance of producing lightning - but this is a weaker signal amongst model guidance.
This then leaves a window of opportunity during the afternoon for surface-based thunderstorms to occur. However, the atmosphere will be largely capped by a warm nose at 850-900mb, and so despite increasing instability it is possible very little will actually develop. Greatest potential perhaps across Dorset, Somerset and Gloucestershire, but this very much dependent on enough surface heating to break the cap, which is uncertain due to the potential for extensive mid/upper level cloud associated with earlier elevated convection. Should an isolated thunderstorm develop, it may be severe, capable of producing hail up to 2.0cm in diameter and localised surface water flooding.
The potential for thunderstorms then increases during Saturday evening and night, with numerous elevated thunderstorms likely to develop over the English Channel containing frequent lightning and perhaps some hail. The vast majority of model guidance would suggest thunderstorms will move to the NW, putting SW England and the West Country at greatest risk, broadly Isle of Wight westwards. However, ECMWF has been very consistent over several runs (now joined by 12z EURO4) to produce a much more bifurcated flow, which would then take a very active cluster of thunderstorms NE-wards over Hampshire, Sussex and towards the London area by the early hours of Sunday.
Given the large spread of possible areas affected, it is difficult to pin down a MDT area with any significant confidence - though worth stressing the ECMWF (and EURO4) tends to have a good handle of elevated convection, and its consistent signal over multiple runs is somewhat reassuring. As a result, have followed these trends for the MDT - though if other models are correct, this may need shifting westwards to cover more of Devon and Cornwall.0 -
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Update
UPDATE 06:49 UTC All areas extended north to cater for quicker arrival in latest model guidance. MDT expanded westwards to include Devon and Cornwall. Note: bifurcating flow tends to leave a gap between two main clusters of thunderstorms, so it is possible not everywhere in the MDT will be affected by lightning - but hard to specify exactly which areas might remain lightning-free0 -
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Big storm pushing closer to Ireland, a few hours off it would seem.
https://twitter.com/EUStormMap/status/10004440123843543040 -
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