Smethport, Pennsylvania 1942 Storm

[Ptarmigan]

I notice that Smethport, Pennsylvania got 34.30 inches of rain in 12 hours, including 28 inches in 3 hours on July 18, 1942! I checked 1942 tropical records and there was no tropical system that made landfall and remnant low that dumped heavy rain, which has happened in the past. The first tropical system recorded for the 1942 season was in mid August. I wonder what caused this incredible rain event?

[senorpepr]

I haven't found any full data, but after reading some DCR-Virginia briefs this is what I suspect:

A high pressure system located in the Northern Great Plains helped to curve the jet stream--which a frontal boundary was attached--over the area. An extension of the sub-tropical ridge over the Atlantic keep the front from progressing. I've also attached an image from Google Earth. This shows the terrain surrounding Smethport. Between a strong, high-moisture stationary boundary and enhancing effects from upsloping... it could squeeze out extra moisture... allowing the record rainfall to occur.

That's my best guess...

[Ptarmigan]

I haven't found any full data, but after reading some DCR-Virginia briefs this is what I suspect:

A high pressure system located in the Northern Great Plains helped to curve the jet stream--which a frontal boundary was attached--over the area. An extension of the sub-tropical ridge over the Atlantic keep the front from progressing. I've also attached an image from Google Earth. This shows the terrain surrounding Smethport. Between a strong, high-moisture stationary boundary and enhancing effects from upsloping... it could squeeze out extra moisture... allowing the record rainfall to occur.

That's my best guess...

That makes sense. I tend to think there may have been a tropical depression that went undetected and made landfall somewhere in the Gulf Coast.

[Aslkahuna]

Could also have been a slow moving intense MCC as they can produce very large rainfall amounts as well. Would also be interesting to see what produced the 12 inches of rain in 42 minutes in MO during a storm-rain rate sensors on Post here have measured such rates for short periods of time during monsoon thunderstorms but they are not long lasting.

Steve

[Ptarmigan]

Could also have been a slow moving intense MCC as they can produce very large rainfall amounts as well. Would also be interesting to see what produced the 12 inches of rain in 42 minutes in MO during a storm-rain rate sensors on Post here have measured such rates for short periods of time during monsoon thunderstorms but they are not long lasting.

Steve

It wouldn't surprise me if there was a MCC/MCS involved. They are responsible for heavy rain and flooding. The 1977 Johnstown Flood was caused by a MCC that formed over South Dakota. As for the rain event in Holt, MO in 1947, my guess is that a MCC was involved too. Perhaps maybe a tropical depression or troical storm could of made landfall in June, which could of been treated as a low pressure system at the time. Some tropical cyclones have formed from MCC. Here is an article about Hurricane Alberto (2000), which was traced to a MCC that formed over Ethiopia. I wonder how if all these tropical waves in the Atlantic come from MCC in Africa?

http://www.agu.org/pubs/crossref/2003/2 ... 6655.shtml

Hurricane Alicia formed from a MCC/MCS/MCV that went over the GOM.

[vbhoutex]

Could also have been a slow moving intense MCC as they can produce very large rainfall amounts as well. Would also be interesting to see what produced the 12 inches of rain in 42 minutes in MO during a storm-rain rate sensors on Post here have measured such rates for short periods of time during monsoon thunderstorms but they are not long lasting.

Steve

It wouldn't surprise me if there was a MCC/MCS involved. They are responsible for heavy rain and flooding. The 1977 Johnstown Flood was caused by a MCC that formed over South Dakota. As for the rain event in Holt, MO in 1947, my guess is that a MCC was involved too. Perhaps maybe a tropical depression or troical storm could of made landfall in June, which could of been treated as a low pressure system at the time. Some tropical cyclones have formed from MCC. Here is an article about Hurricane Alberto (2000), which was traced to a MCC that formed over Ethiopia. I wonder how if all these tropical waves in the Atlantic come from MCC in Africa?

http://www.agu.org/pubs/crossref/2003/2 ... 6655.shtml

Hurricane Alicia formed from a MCC/MCS/MCV that went over the GOM.

Yep she did. We were visiting my folks in Shalimar when that system come off the coast. My dad and I were watching it and we both commented on the fact it appeared to be becoming more than just what it started as. Sure enough, we headed home and 3 days later wham, there she was right on our doorstep-literally!!!

[Ptarmigan]

Hurricane Mitch also formed from a MCC.

MCC's can also originate in the Amazon basin during the latter portion of the tropical cyclone season and migrate into the Caribbean. Hurricane Mitch (Oct-21-Nov 3, 1998) a 180mph monster and the deadliest (over 11,000 killed) hurricane to strike North America in the 20th Century, developed from a disturbance that can be traced back to the Amazon basin.

http://www.accd.edu/sac/earthsci/sgirha ... /chap5.htm