On the cusp of a storm.

I posted this some time ago with the title of:
A Four Year Cycle.

That was because besides the embarrassingly inexplicable minutes of the time of the phases involved, there was very little else that offered an obvious denoumon.

Then I got to an old PDF written by Will Hand for the Met Office about flash floods. And the penny dropped. …

But first let me clean up the original to correct the version I may have posted saome time ago. (Just in case. I think it was a work in progress though and may have dropped it.)


This is from a weather station near Glasgow:

20th March, 1986

The date of this storm is well documented, many wind speed records were set in Scotland.

The Burns day storm (25th January, 1990)

It lasted for hours and peaked here around 10pm. 60-70mph �mean� wind speeds over most of the country, gusts up to and over 100mph.

Other parts of the country suffered far worse. Taking many lives UK-wide (over 50 deaths) and setting many wind speed records. It was also one in a line of a few nasty storms that month

The tempest (26th December,1998)

Otherwise referred to as the "Boxing day storm".

The peak of that storm was around 11pm, I recorded a gust of 103mph. The top ten minute mean wind speed was 56mph, qualifying it for Overland/Inland storm classification. Around 20% of the mature trees were down, all uprooted.

Severe Gale of 28th January, 2002

Nothing like as bad as the ones described above in this area, but as it struck in daylight hours it created it's own brand of headaches and tragedies. The top gust recorded on my anemometer that day was 74mph.

Sadly there were a few deaths that day, particularly affecting high sided vehicles which had been blown over on exposed roads


20th March, 1986

10th Mar 14:52
18th Mar 16:39
26th Mar 03:02

The Burns day storm (25th January, 1990)

18th Jan 21:17
26th Jan 19:20

The tempest (26th December,1998)

18th Dec 22:42
26th Dec 10:46

Severe Gale of 28th January, 2002

21st JAN. 17:46
28th JAN. 22:50

The hours: 10; 2; 4 and 8 are difficult ones to forecast as I can only do positive anomaly spells. Those for the hours:
5 and 11 for fine spells
1 and 7 for wet ones
12 and 6 for dull overcast
And 3 and 9 for thundery spells.
(Which of course went haywire this year with its unexplained penchant for flaccid weather vortexes.)

The other spanner in the works is the minute values of a phase. I have exactly the same collywabblers with phases that occur on the 20 minutes past or twenty minutes to the hour as I have with those difficult spells.

However, the difficulty with them all is that they have a tendency to be flaccid cyclones and anticyclones. And they are associated with tornadoes. And from what I can see in this PDF, I think a degree of flaccid pressure systems is endemic:

Numerical Weather Prediction
A historical study of extreme rainfall events in the 20th Century
Forecasting Research Technical Report No. 384
Will Hand
email: nwp_publications@metoffice.com
©Crown Copyright

A historical study of extreme rainfall events in the 20th Century
By W. H. Hand

Extreme rainfall events by their very nature are rare but common enough to require consideration of the possibility and associated serious flood risk by DEFRA. It is therefore vital that signals of the likelihood of such events occurring in any given region be recognised as early as possible, preferably 24 hours or more in advance.

The primary aim of this study was to examine events in the 20th century in order to ascertain any common hydrological and meteorological features that could be used operationally to provide early recognition of the possibility of an extreme rainfall event that could lead to serious flooding.

The aim of the research was to investigate the nature of very extreme rainfall events, particularly the meteorological situations leading to their occurrence and the susceptibility of river catchments.

Rainfall events that give rise to serious flooding involve four main ingredients. They are intensity and duration of precipitation, the wetness of the ground and the response of the rainfall catchment. The key items considered in this study were the first two, which are the meteorological ones. Hydrological contributions and other factors were noted when applicable.

A small matter but I suppose I aught to keep it to myself until I actually take the time to check. I am not even sure what sort of pressure we have for rainfalls in Britian. Now isn't that omission strange. I mean it's not something a weather nut would miss is it?

Good job nobody reads my stuff.


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