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#Reigate storm forecast : grand finale of the Spanish Plume?

July 3, 2015 — 2 Comments

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UK thunderstorms July 3-4 2015 analysis chart modified spanish plume

Very quick update on the (grand?) finale of the Spanish Plume that has ebbed and flowed this week. (directly above is the analysis UKMet synoptic chart posted this morning after the event.  “In the event” round up see foot of this post (please send photos, I didn’t get any ;-( )

500hPa chart
850 temperature chart

Today, Friday sees a final push of warm/hot continental air into Southern England with Tmax 28C or more today.  The synoptic and upper air charts above show a Modified Spanish Plume set-up which is potentially conducive to MCS (big storms) pushing further north across the UK. The chart below shows this matches one of the three types of Spanish Plume identified by Lewis and Gray (2010) and further by Nat Melia (2012).

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modified spanish plume (after NatMelia 2012)

Winds charts below show a sheared wind environment with SE surface winds and a jetstream from the south.  This is conducive to thunderstorms and some rotation which organises storms and produces possible tornadic features.

Tonight thunderstorms are forecast to develop locally across S UK as elevated features and move north into N / NE England.  Models disagree on the track of these storms so some places are likely, as usual, to miss out.

estofex
estofex
convective wx
convective wx
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The development as whole is debated too so could change during today.  Models show vastly differing rainfall patterns.

Nevertheless, the potential is there for severe thunderstorms, even a meso-scale convective system (MCS) which is a group of sustained thunderstorms.  Intense rainfall and large hail is also possible.

The charts below are a collection that illustrate the set up in more detail. These are posted for future reference and reanalysis of any event or non-event that occurs. Interestingly the storms arrive overnight (as usual) and surface based cape is therefore extremely limited with no solar heating. These are therefore likely to be elevated thunderstorms. During this potential episode overnight do stay weather aware in case you come across one of these potential beasts! Equally the set up is, as usual, not certain with convective forecasts so check weather professional media for updates.

The outlook is for cooler Atlantic (still tropical) air to sweep away the continental plume during the weekend.  Thereafter, mostly dry pleasant temperatures for the SE. Wetter further west with chance of showers as troughs drag fronts (mostly weak) across the north.

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GEFS outlook

In the event:

Big storms erupted quickly from 10-11pm and intensified as they drifted north / NE.  Reigate experienced some heavy rain and plenty of lightning. The storms produced over 93000 lightning strikes over the course of the night. The SE, always hit and miss with models for this event, scored only 17418 strikes. Below is an animation of radar and strikes.

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Locally Reigate had some early action from developing storms before and through midnight.  Storms then intensified further N/NE. Note the rainfall rate before midnight 135.6mm/hr giving approx 10mm (tbc) and associated pressure spikes with descending air from storms. Nice event, some spectacular lightning but not as much or as intense as further north. Pictures and video below from local photographer Simon Spiers who caught some amazing lightning shots around the area. Thanks for sharing.

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In Analysis, Forecast, Reigate , ,
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