Thursday September 12, 2024
It was a wet and thundery night across parts of northeastern NSW - that's was courtesy of an upper low that tracked into southern NSW overnight. The same upper low was responsible for an isolated hailstorm north of Melbourne yesterday afternoon dumping large amounts of 1-2cm hail near Castlemaine.
Water Vapour, Radar & Lightning Loop showing the upper low rotating across southern NSW overnight. Source: Weatherwatch MetCentre
Upper lows often generate instability because they contain large amounts of cold air in the upper atmosphere. Since warm air rises, when the atmosphere is very cold it facilitates increased rising motion which allows air to rise and condense into clouds, often bringing showers and storms.
GFS 500mb temperatures showing the very cold air present across Victoria and NSW in the upper atmosphere. Source: Weatherwatch MetCentre
We'll continue to see that band of rain and embedded storms track eastwards today, pushing through the remainder of northeastern NSW and even nudging into southeastern Queensland late in the day bringing some more rainfall. We could also see some more small hail redevelop through parts of central NSW as the upper low tracks through.
Forecast rainfall from the G3 model for today and tomorrow morning. Source: Weatherwatch MetCentre
The presence of the upper low will also induce a surface low developing off the NSW coastline as it interacts with the warm and above average sea surface temperatures. The result? Expect a strong and gusty band of southerly winds to track northwards along the NSW coastline today, pushing up into the southern Queensland coastline tomorrow.
Forecast winds showing a gusty, southerly change moving up the coastline today and tomorrow in response to a developing low. Source: Weatherwatch MetCentre