Isaac Rainfall in Kansas City

By: Skyzics , 1:18 PM GMT on September 02, 2012

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The Kansas City area experienced an unusually good 'hit' from the remnants of Hurricane Isaac. This helped make up for the August 25-26 big miss as I detailed on my previous blog entry.

As can be seen from historical paths, such storms rarely if ever move into the Kansas City area.

Historical Paths

Nevertheless, the storm was forecast to hit the area for several days by the NWS forecasters, though at the last minute they downgraded forecast amounts. However many in the area were sure the system would miss entirely, including myself.

Below is a statement from the local NWS Office at Pleasant Hill, issued after the event was well over:

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...Remnants of Hurricane Isaac Deliver Beneficial Rain to the Region...

A steady rain, falling for nearly 32 straight in some places, brought beneficial rains to the region as the remnants of what was once Hurricane Isaac drifted through central Missouri. As a tropical depression on Friday, Isaac slowly churned northward into Missouri, interacting with an existing front that extending from near Kansas City to Kirksville. An extensive plume of tropical moisture intersecting this front yielding a nearly stationary band of moderate to at times heavy rainfall that persisted during the afternoon and into the overnight hours. Even after the system had become post-tropical, Isaac continue to deliver a steady light rain to the region through much of the day Saturday as well before shifting into Illinois. In addition to the tropical feel to the air, this tropical system was far different than most storms that would have impacted the area during late August and early September. First was the absence of any thunderstorms. Second, pulsing gusty winds accompanied the rain squalls through much of Friday afternoon into early Saturday morning, with speeds of 35 to 40 mph observed around Kansas City. Thirdly, temperatures stayed rather warm despite the relentless rain, hovering the low-mid 70s.

The result was a widespread three to nearly 7 inches of rain as of Saturday evening, impacting all but far northwest Missouri. In the absence of thunderstorms, the rain fell steadily over the period, allowing almost all of it to soak in. No significant flooding was observed and rises along area rivers and creeks were generally minor. As a result, this rain will be extremely beneficial in helping to offset the extreme to exceptional drought across the area, with additional rain chances over the coming week likely to make additional improvements at both the short and long term drought.
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Radar precipitation estimates tell the story (from Topeka and Kansas City):

Topeka Radar Rain Isaac

Kansas City Radar Rain Isaac

Below is an NWS product of accumulated precipitation that was issued concurrently with their summary above.

48hr_ending_7am090212

The 8-inch gauge at KKSKANSA15, my station in Kansas City, KS, came in with a total of 4.83 inches, but precipitation was much less just 15 miles west through north of my station, which was located just at the edge of a steep gradient of reduced precipitation from southeast to northwest.

Summary of the exact total amounts in inches (calender day August 31st and September 1st accumulated rainfall) roughly from northwest to southeast across the area:

Lawrence...............................0.76
St Joseph:.............................0.99
Kansas City International Airport......1.48
Kansas City, KS (KKSKANSA15)...........4.83
Kansas City, MO (Downtown Airport).....4.92
Olathe, KS NE (Johnson Co Exec Arpt)...5.90
Olathe, KS SW (New Century Arpt).......5.36
Lees Summit, MO........................5.63
Pleasant Hill, MO (NWS Office).........4.61

Below are regional rainfall charts for the storm:

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About Skyzics

A former NWS meteorological technician and former FAA contract aviation weather observer and supervisor. My WU weather station is KKSKANSA15.