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Convective/Thunderstorm Discussion Spring/Summer 2018
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Just wondering could the second cold front crossing the country tomorrow produce a few isolated thunderstorms. A nice convergence sets up and the models showing some CAPE available. Decent low and deep level shear. Lapse rates not great though. Maybe too much mixing and not enough heating. It will be interesting watching the fronts go through tomorrow and the winds backing. Temperatures fluctuating during the day as the fronts pass over.
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I think I got a photo of a shelf cloud yesterday (Southern France), not 100% sure though. I was kicking myself I didn't go outside to get a better shot:
The resulting storm was impressive, 1000 strikes in the department and gusts of up to 120Km/h. The airport is nearby and there were planes trying to land in this :eek:0 -
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Convective Weather
In Ireland, elements of embedded mid-level instability release may occur within the frontal rainfall slowly tracking eastwards during Thursday daytime. A few isolated lightning strikes will be possible, before potential starts to reduce by evening hours.0 -
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Very active again the UK tomorrow and could lead to some severe storms there. Best chance for Ireland tomorrow evening. Still think Sat is our best chance of Thunderstorms.
Day 2 Convective Outlook
VALID 06:00 UTC Fri 27 Jul 2018 - 05:59 UTC Sat 28 Jul 2018
ISSUED 20:03 UTC Thu 26 Jul 2018
ISSUED BY: Dan
... FRIDAY MORNING ...
Elevated thunderstorms will likely be ongoing on Friday morning along the ThetaE plume from Cen S England, through eastern England to perhaps the Northern Isles. These should continue to drift north along the same corridor through the day, but probably with some reasonable gaps developing as forcing aloft and instability weakens temporarily in the wake of each thunderstorm cluster.
... FRIDAY AFTERNOON / EVENING ...
Strong surface heating with temperatures in the mid 30s Celsius and dewpoints of 18-20C will create a very unstable environment by the afternoon, with CAPE values in excess of 1,500 J/kg possible. This combined with elements of low-level convergence and stronger upper forcing arriving, as a shortwave drifts northwards on the forward side of an approaching upper trough, should provide the trigger for scattered surface-based thunderstorms, particularly during the late afternoon and into the evening hours. There is also some signal for orographic forcing during the evening hours to allow a few thunderstorms to develop over the northern Pennines, drifting north into southern Scotland, hence the inclusion of a small MDT.
Given the magnitude of instability, strongly-sheared profiles and dry intrusion in the mid levels, a supercell or two will be possible capable of producing large hail over 3cm in diameter along with damaging outflow winds and very frequent lightning. Some surface water flooding could occur in a few places. As such, a SVR has been issued to cover the risk of large hail, damaging winds and torrential downpours.
... FRIDAY NIGHT ...
On Friday evening and night, increased forcing aloft will destabilise the instability plume more widely, with an increasing coverage of elevated thunderstorms likely to erupt over eastern England, gradually clearing to the east - perhaps bending back westwards over parts of northern Scotland and the Northern Isles. A MDT and HIGH have been issued to cover this potential combined with earlier surface-based storms - though should model guidance trend eastwards, the focus will naturally shift eastwards to the North Sea instead, and the HIGH may need to be removed / MDT trimmed.
... SW ENGLAND / S + W WALES / CELTIC SEA / S IRELAND ...
The secondary cold front will be subject to strong forcing as a sharp upper trough over-runs it during Friday night. Several hundred J/kg CAPE will be present, with some lightning activity and gusty winds possible as the cold front surges eastwards. A SLGT has been introduced to cover this potential.0 -
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