Convective Outlook: Sat 20 Jul 2019 |
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What do these risk levels mean? |
Convective Outlook
VALID 06:00 UTC Sat 20 Jul 2019 - 05:59 UTC Sun 21 Jul 2019
ISSUED 21:05 UTC Fri 19 Jul 2019
br> br>ISSUED BY: Dan
Confidence is fairly low in the forecast evolution for Saturday, although the broad pattern sees an upper trough close to the British Isles with a series of shortwaves lifting northeastwards around its southern flank.
Outbreaks of rain and embedded elevated thunderstorms may still be affecting parts of SE England / East Anglia first thing on Saturday morning, but these will clear to the North Sea. Provided sufficient insolation can develop, heating of the very moist low-level airmass (dewpoints 14-17C) could yield up to 1,000 J/kg CAPE for a time, with the potential for scattered showers and thunderstorms to develop across eastern England. In general, coarse-resolution global models favour more widespread convection, while higher-resolution regional models (and CAMs) suggest deep convection may be fairly isolated.
Instability will tend to peak around midday, with a slight reduction in the afternoon as subtle warming occurs aloft. Nonetheless, the risk of sporadic lightning will persist until the evening hours, with additional showers and a few scattered thunderstorms possible in E / SE Scotland and NE England. Any showers/storms that do develop will gradually decay through the second half of the evening as nocturnal cooling of the boundary layer occurs.