Question about Highest Minimum

[RayProudfoot]

Steve,

I have a feeling we discussed this a while back but I can't find or remember the outcome.

Overnight 30/6 to 1/7 the temp never dropped lower than 20.0C. I expected that come midnight 1/2 July that would be reflected in my all-time records.

However, midnight has now passed and the old record back in 2009 is still current. I'm trying to work out why it hasn't been updated. Can you offer any insight please? My meteorological day ends at midnight, not 09:00 if that's a factor.

Happy to supply any logs you need.

[steve]

That may be true, but you had a lower temperature later in the day. According to your 'yesterday' data (and supported by the temperature graphs), your minimum temp on the 1st July (just before midnight last night) was 19.1C. Your record highest minimum is 19.6C.

[RayProudfoot]

Sorry Steve but I'm struggling to understand this. The record is for the highest minimum so if 20.0 is higher than 19.1 shouldn't 20.0 be stored as the higher of the two?

[steve]

Your minimum temperature for July 1st (midnight to midnight) was 19.1C, not 20.0C. 19.1C is not higher than 19.6C, so your record from 2009 was not broken.

[RayProudfoot]

So despite the fact that the lowest temperature between 00:00 and 06:00 on 1 July was 20.0 that is effectively ignored because later that day the minimum dropped lower than 20.0?

It seems this can only happen when the recording day ends at midnight. If it ended at 09:00 the record would have been broken. I can now understand why the Met Office uses 09:00 as the end of the recording day.

I assume there must be a downside to choosing 09:00 compared to 00:00 as the end/start point.

And finally, if I wish to set 20.0 as a new high min record can this be done using the editing facility provided?

[steve]

Yes, it's one of the disadvantages of using midnight to midnight as your recording period; your night is split into two parts, midnight to morning at the beginning of the day and evening to midnight at the end of the day, and the weather can change between the two parts.

The main disadvantage I can think of for 0900 recording is the confusion it can cause for casual viewers of the data. There may be others. There's no 'perfect' recording period, you can still get anomalies.

Yes, you can use the editors to override the all-time and monthly records.

[RayProudfoot]

Thanks Steve. You're quite right about the pros and cons of 09:00 versus 00:00. The Weather Observer's Handbook describes events that will appear to show odd results whatever period is chosen.

I have now edited This Month / Year, Monthly Records and All-Time Records to reflect the new overnight low. I don't consider that a false record in any way. Just a victim of the quirks of the time reporting period.

This might help others in the UK who may wish to change their records. It's my oldest record after all and after an period of exceptional heat it would be a shame if it wasn't recorded.