Convective Outlook: Fri 05 Jun 2020 |
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What do these risk levels mean? |
VALID 06:00 UTC Fri 05 Jun 2020 - 05:59 UTC Sat 06 Jun 2020
ISSUED 06:31 UTC Fri 05 Jun 2020
br> br>ISSUED BY: Dan
Negatively-tilted longwave trough continues to strengthen over the North Sea on Friday, evolving into a large, broad upper low. Mid-levels will continue to cool as a result, especially associated with a shortwave sliding across eastern England during the day where mid-level lapse rates will steepen substantially. A strip of shear vorticity will straddle Northern Ireland - north Wales - East Anglia along the northern periphery of a strong upper jet, slowly sinking southwards through the day. Strong deep layer shear will be present as a result of this jet, although shear will be much weaker north of the jet. In any case, convection will likely be restricted in height, moreso the further southwest you go, and so is unlikely to grow tall enough to utilise the strong flow aloft. Diurnal heating will yield 100-200 J/kg CAPE fairly widely in a broadly unstable airmass, but as high as 300-500 J/kg CAPE across eastern England into East Anglia. Here, a better overlap of CAPE, shear vorticity, steep mid-level lapse rates and some 20-30kts shear will occur (more especially East Anglia, where a narrow NW-SE zone of more enhanced shear could overlap favourably with cells to aid in organisation), and consequently it is this zone that is likely to see the deepest convection and greatest potential for some sporadic lightning, with ELTs potentially as low as -30C to -40C. A low-end SLGT (30%) has been issued to highlight the main area of interest. Elsewhere ELTs of -10C to -20C are more likely, limiting the lightning potential somewhat.