What a Difference a Front Makes
posted 26th March 2020
Fig 2 Surface analysis 0000 UTC 26 Mar2020
By 26Mar2020 0000 UTC, as seen in figure 2, the warm front had moved south over mid Scotland in the east to southwest Scotland . At times over Glasgow.
The difference in weather either side of this front was very different. In this article I analysed the weather at half hourly intervals at Glasgow Airport and Manchester Airport (200 Km apart) and show comparisons.
Surface Pressure:
Fig 3 surface pressure comparison between Manchester and Glasgow 25 Mar 2020
Comment: Surface pressure at Manchester was stable with a mean of 1023 mb whilst Glasgow had rising pressure from 1017 to 1025 mb.
Temperature:
Fig 4 Temperature comparison between Manchester and Glasgow 25 Mar 2020
Comment: Temperatures at Glasgow were within 1°C either side of 9°C, in contrast temperatures fell to 5°C rising to 17°C then falling back to 5°C at Manchester. Glasgow has a spread of 1°C and Manchester a spread of 12°C. Out of interest London Heathrow had a temperature spread of 18°C with a temperature of 13°C and dew point -5°C.
Dew Point:
Fig 5 Dew Point comparison between Manchester and Glasgow 25 Mar 2020
Comment: Glasgow Dew Point had a small range between 6-9°C. In contrast Manchester Dew Point ranged between 5°C and -3°C
Relative Humidity:
Fig 6 Relative Humidity comparison between Manchester and Glasgow 25 Mar 2020
Comment: As depicted in the Dew Point temperatures, Relative Humidity at Glasgow was high between 80% and 100%. On the other hand, Manchester recorded a max of 76% and minimum of 27% (very dry air).
Wind Speed:
Fig 7 Wind Speed comparison between Manchester and Glasgow 25 Mar 2020
Comment: Glasgow showed a maximum of 10 m/s falling to 1 m/s as pressure rose. Manchester showed wind speeds between 3 m/s and 1 m/s
Visibility:
Fig 8 Visibility comparison between Manchester and Glasgow 25 Mar 2020
Comment: Visibility at Manchester was 10Km or greater throughout the 24 hours. Glasgow's visibility however ranged from 10Km or more around mid-day to less than 1 km in fog late in the day.
The airmass along and north of the warm front was mild, moist, cloudy, moderately windy, with poor visibility. Manchester was in a different airmass with southeasterly winds coming from the dry continent providing clear skies, a dry atmosphere, a cool start with rising temperatures until mid-afternoon, then falling back to cool in the evening, higher pressure gave a light breeze and visibility was excellent.
Learning points: Different airmasses produce very different sorts of weather, they always have done and mostly likely will in the future. When the sun shines in a dry airmass, temperatures increase rapidly in Spring, Summer and Autumn, not so much in the Winter. Greater water (gas, liquid or solid) content in the atmosphere suppresses temperature rise. Sun and water controls our weather, and accumulated weather - climate.
| Weather | Manchester | Glasgow |
|---|---|---|
| Pressure | High and steady | moderate rising to high |
| Temperature | Cool - Warm - Cool | Mild |
| Relative humidity | Low to very Low | High |
| Wind Speed | Low | Moderate to Low |
| Sunshine | Wall to wall | None |
| Visibility | Excellent | Moderate to poor |