A Drop Of Rain At Holt, Missouri

[knocker]

Frontal-wave depressions are complicated affairs and well outside my comfort zone but that doesn’t make them any less interesting.

It is complicated further by the fact that over central North America, cyclones forming in winter and spring depart considerably from the Norwegian model. In particular, they feature an outflow of cold arctic air east of the Rocky Mountains, forming an arctic front, a lee trough with dry air descending from the mountains, and warm, moist southerly flow from the Gulf of Mexico. The trough superposes dry air over warm, moist air, generating instability and a rain band analogous to a warm front. The arctic air flows southwards west of the low centre, causing lifting of warmer, dry air but giving little precipitation. There may also be an upper cold front advancing over the trough that forms a rain band along its leading edge.

Such a system is thought to have caused a record rainstorm at Holt, Missouri, on 22 June 1947, when 305mm fell in just 42 minutes!

It so happens there was a paper written about this event for the American Meteorological Society in 1995 and is available online.

A World Record Rainfall Rate at Holt, Missouri: Was It Due to Cold Frontogenesis Aloft?

John D. Locatelli and Peter V. Hobbs

http://journals.ametsoc.org/doi/pdf/10.1175/1520-0434%281995%29010%3C0779%3AAWRRRA%3E2.0.CO%3B2

[Terminal Moraine]

I'd almost give my right arm to witness rainfall of that intensity.

There would be some serious practical difficulties in recording it though as most standard gauges will only hold about 150mm of rain at most, perhaps another 80 or 90mm in the body of the gauge itself.

It's the prospect of one day recording something even halfway as exceptional which makes weather recording so fascinating.

[knocker]

I must admit I find it difficult to envisage what it must have been like.

[reef]

Its puts it into perspective when you consider on the day of the floods in 2007 I recorded 97.9mm in 24 hours. I cant imagine the result if three times that fell in 42 minutes. Absolutely mindblowing!

[Terminal Moraine]

Thinking back to the most severe thunderstorms I've witnessed in this country I would think a maximum rainfall rate of 150-200mm an hour for perhaps 5 mins at a time; it seemed impossible for it to rain any more heavily.

The rainfall rate in the Holt storm was 435 mm/hr, it must have seemed as though the whole atmosphere was water and it was all falling earthward.