Wet, Wet, Wet

Steady rain in Tawa yesterday came close to marking it as the wettest day since Tawa Weather began operating an automatic weather station in January 2005.

Impressions of weather conditions can be unreliable, with a day of relentless, steady rain seeming to be drier than a day on which a spectacular downpour causes storm drains to overflow, roads to close with surface flooding, and water to pool in unexpected places.

Yesterday was one of those days. An advancing low pressure system, which is passing through Cook Strait as I write this, drove two bands of moist tropical air over central New Zealand ahead of it. The low pressure system slowed down yesterday, and the leading moist band of warm air also slowed, dropping its rain over the lower North Island and upper South Island. Wednesday the 10th of October 2007, got off to a wet start, with steady rain at Tawa commencing just after midnight.

Rain fell steadily throughout the day, allowing the ground and plants to soak it up and run-off on sloping land was surprisingly low. By the middle of the day, the ground hereabouts was dinstinctly “squishy” and run-off rates were slowly increasing, but at a rate that storm drains could easily accommodate.

By the end of the day, 46 mm had been recorded at Tawa, 2mm less than the wettest day that has been recorded since the weather station was commissioned in January 2005. The record daily rainfall of 48 mm still belongs to the 5th of July 2006, closely contended by the 5th of January 2005 when 41 mm fell in one hour during a spectacular downpour.

Yesterday’s 46 mm brings the total rainfall measured by Tawa Weather for the first 10 days of October 2007 to 89 mm, and the year to date to 618 mm. During the first 10 days of October 2006, 29 mm fell, bringing the year to that date to 901 mm. Rainfall in 2005 was lower than this year, with 57 mm falling during the first 10 days of October, bringing rainfall to that date to 576 mm.

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