This is why Bathurst missed out on the rain bomb beast from the east

He says the west is best if Bathurst is looking for rain and this week's beast from the east simply couldn't maintain the momentum once it hit the sandstone curtain.

Katoomba, less than 100 kilometres from Bathurst, received just under 70 millimetres in the 24 hours to 9am on Monday, January 15; Bilpin, on Bells Line of Road; received 87mm and Kurrajong Heights received a barely believable 151mm.

Lithgow, meanwhile, finished with 15mm and Bathurst received a grand total of zero.

"Basically, we had a pretty strong easterly air stream pushing into eastern Australia," Weatherzone's Mr Levesque said.

"But, really, the depth of that easterly air stream was limited to probably just about the height of the Blue Mountains, so a lot of that moisture feeding into eastern NSW was actually coming up the Blue Mountains, falling as rainfall and then moisture [was] generally falling away from the atmosphere as it crossed over the Blue Mountains and back down towards Bathurst."

So was it the distance from the coast or the height of the sandstone curtain?

"Mostly the height of the mountains, but the distance from the coast as well led to precipitation falling out and the air stream drying out," he said.

"But definitely the main factor was climbing up the mountains and falling as it did so."

Rainfall in the 24 hours to 9am on Monday

Westbound traffic was affected on the Great Western Highway near Springwood on Monday morning due to water over the road and there was a swift rise in the Grose River, which flows into the Sydney basin.

"The air stream was very saturated with moisture," Mr Levesque said.

"The temperatures off the Sydney coast, the sea surface temperatures, are really warm, so there's lots of moisture in the atmosphere.

"It's just unfortunate that that air stream was very limited to below about 2000 or 3000 metres of the atmosphere, making it a real struggle to get over the ranges."

Bathurst, Mr Levesque said, is better off looking in a different direction for its rain.

"It's always better, west of the ranges, to look further to the west for low pressure troughs that move across the continent and draw tropical moisture from the north rather than from the east and then make their way."

At this time of year, that's likely to come in the form of thunderstorm outbreaks, he said.

"So it can be hit and miss, but it also can deliver some pretty heavy rainfall over western and central NSW."

MEANWHILE, the maximum of 21.2 degrees that was recorded at the Bathurst Airport weather station on Monday was the coldest in almost a month.

Strong southeasterly winds kept the temperature well down on the average so far this month of 27 degrees.

It was the airport weather station's coldest day since December 20, when just 19.1 degrees was recorded.