A mass of thunderstorms sweeping over the Central West Slopes and Plains of NSW interacted with moisture flowing off the unusually warm Tasman Sea, resulting in a particularly intense and slow-moving group of storms.

The Mudgee Airport Weather Station recorded 18.6mm from Wednesday’s rain, a significant amount considering only 10mm fell during all 31 days of July. This took the October total to 37.6mm, the average for the tenth month of the year is 53.7mm which could still be reached with over a week remaining and showers likely for the weekend.

But more is still needed to bridge the January-to-October deficit, as of Thursday Mudgee has only had 345.2mm for the year to date, on average it should have had over 525mm.

Gulgong had 14mm in the rain gauges at 9am on Thursday morning, taking their September figure to 49.2mm (average 55mm). While at the Nullo Mountain Weather Station in the Rylstone/Kandos area 13mm was recorded, taking it past the October average (74.4mm plays 73.9mm).

Wednesday’s storms disrupted the visit to Dubbo by the Duke and Duchess of Sussex, Harry and Meghan, which was to see the affect of the drought on the area.

Prior to October, Dubbo had only received 118mm of rain during the first nine months of 2018. This was their driest January to September period on record, with data stretching back to 1870. As of 2pm on Wednesday, Dubbo had already received 78mm so far during October, making it the wettest calendar month in a year.

As the storms headed east that evening Penrith was inundated by 71mm of rain in just one hour.

The slow-moving low pressure trough crossing NSW this week caused more showers on Thursday, mainly during the afternoon and early evening. Storms will become more confined to the state's northeast on Friday as the trough weakens and moves further east.