Damaging Storms Hit Lawrence

Powerful thunderstorms developed and pushed into Lawrence starting about 4 PM Saturday, part of a long band of storms extending from eastern Iowa to south-central Kansas.  The storms brought torrential rains, powerful and damaging lightning bolts and locally very strong and damaging winds in what appeared to be a ‘wet microburst’ event.

In the lead-up to the storms conditions were warm and muggy.  The high at the Lawrence Airport was 80 and the low only 59.   My personal weather station registered 81 for a brief period around 3 PM with lower to mid 70s prevailing from 8:45 AM to 7:30 PM.  The dew point was about 70 degrees all the way from around 9 AM to 7 PM, but bounced up to an unusually high 74 degrees from 3:40 to 4:00 PM just before the storms hit.

As the late afternoon storms finally rolled in, lightning hit numerous power poles and transformers, knocking out power in places. Locally strong winds damaged power poles and trees.  Small hail was reported.  While the entire city was hit, damage was primarily in the northeast quarter of town, which seemed to bear the brunt of the storms locally.  My home weather station in southwest Lawrence recorded three quarters of an inch of rain in a 45 minute period starting at 3:52 PM and totaled 0.79 inches in 50 minutes when the heavy storm was done.  Thirty-five hundredths of this fell in 10-minute period from 4:17 and 4:27 PM.

Personal Account:  The storms hit soon after I dropped my last passenger of the day at Vermont Towers (11th and Vermont) on my para-transit bus route.   Torrential rains were then ongoing when I arrived in the bus yard, as they apparently had been for some time already.  During the short walk from my bus to the dispatch office, the rain and wind got me pretty well soaked, despite my wearing a large protective hat and carrying an umbrella.  Scary nearby lightning bolts pummeled the immediate area.   The dispatch office had suffered a power hit and was on back-up generator power.  A bit of a lull in the rain when I left the bus facility for home was short-lived as another powerful batch of storm cells moved in.  As I was traveling west on Lake View Road (on the way toward my turn south on Kasold Drive), through the rear view mirror I happened to see a bolt of lightning hit a power pole, sparks then flying in a small explosion.  Several more powerful bolts hit very nearby in close succession.   As I glanced toward the south, I happened to see a powerful rain shield advancing rapidly eastward a mile or so in the distance, having all the appearance of a wet microburst (strong winds associated with torrential thunderstorm rainfall in a saturated atmospheric environment).  At the same time, water was running high in the streets, requiring a very slow speed to avoid hydroplaning.  As well,  winds had blown many small twigs and leaves off of the trees which were scattered across the road.

As I was driving west on Bob Billings Drive between Monterey way and Inverness Drive, on the north side of the road was an upside down trampoline.  No houses were in the immediate area, so it must have landed there from some distance away.  Heavy rain,  lightning and much running water in the streets continued until I made it to my driveway and pushed the ‘open’ button on the garage door opener which, thankfully, worked.  Surprisingly, power had been uninterrupted, as my PC and home weather station were both operating fine and none of the clocks in the place were flashing.  There is certainly something to be said for the underground power lines.

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At 4:15 PM Saturday:  Strong thunderstorms were moving across Lawrence, part of a line of storms extending from eastern Iowa, and even Chicago and Detroit, southwestward across south-central Kansas into Oklahoma.

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Saturday morning 500 MB chart showing the upper trough moving smartly east-southeastward across northern Utah (and not digging so much across Nevada this time).

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At 700 MB Saturday morning (about 10,000 ft ASL):  A moist southwest flow is over northeast Kansas ahead of the upper trough over the Rockies.  Meanwhile, as is typical in this type of pattern with troughs digging across the intermountain west, a dry northeast flow aloft is over northern and central California, providing the wildfires with a continued pro-growth atmospheric environment.

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The upper air sounding at Topeka Saturday morning.  Later coverage in the Lawrence Journal World quoted multiple NWS representatives as saying a micro burst was not involved in the strong wind event that hit mainly the northeast part of town.  Unfortunately, the morning sounding from Topeka refutes that.  This is a good ‘wet microburst’ sounding – plenty of moisture, a relative dry area at the mid levels around 850 to 700 mb, instability (strong lapse rate above the surface inversion) and strong winds aloft.  Add a surface trough moving through ahead a vigorous upper trough and throw in some degree of afternoon heating, and you have all the ingredients necessary – and then some!

Below is an example of a wet microburst sounding and description from the NWS at: www.weather.gov/bmx/outreach_microbursts

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Forecasting Microburst Potential
Forecasting for microbursts is typically done on a near-term basis, generally within 6-12 hours before convection is expected to develop.  There are several atmospheric parameters that forecasters use to help determine the microburst potential on any given day, primarily during the summer months. Instability, high precipitable water (PW), dry air in the mid levels, and strong winds in the dry layer are just a few of the parameters necessary for the development of microbursts.  The ideal conditions typically come together during hot and humid summertime afternoons in the Southeast. 

 

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At 12:45 PM CDT the frontal band associated with the western trough extends across Kansas.  For the longest time this band was quasi-stationary, with rain lurking just to the north and west of Lawrence. I thought it might never move in.  But, that ‘point of cloud’ just east of the center of Kansas marks the southwest end of strong thunderstorm development poised to move in later in the day.  Meanwhile, the smoke plume can be seen pushing out to sea from the North SF Bay Area fires, re-invigorated by a fresh surge of dry air from the northeast.

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At 3:45 PM CDT:   Storms explode from northern Illinois across eastern Iowa and northwest Missouri, on through northeast to south-central Kansas.  Note the moisture connection all the way into northwest Mexico.  Meanwhile, the smoke plume heads out to sea from the North Bay region, indicating still very active wildfires in the bone-dry northeast winds continuing across coastal California.

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Regional image at 4:45 PM PDT, shows the active smoke plumes heading well out to sea from the northern California coastal ranges fires, all the way up to the redwood country north of Ukiah.  Meanwhile, the smoke from the Sierra Nevada Mountain fires heads westward, over the Central Valley.  It looks  miserable to be stuck in that thick pall of smoke, day after day, even if you are not directly effected by the fires themselves.  Truly awful looking smoke pollution.   It could be worse, though: A good portion of it is blowing out to sea in this off-shore flow pattern.

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500 MB Chart Saturday evening:  The southwest flow ahead of the upper trough kept showers going for quite a while after the line of thunderstorms went through.  In fact, while the main band of thunderstorms was through Lawrence by 5 PM, off and on showers continued to generate and move in from the west until around 9 PM.

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Saturday evening at 250 MB, jet stream level:  Eastern Kansas is in the right-rear entrance region of the jet stream east of the trough, an area that often brings more intense uplift due to divergence aloft.  The strong jet, in general, imparts energy and wind that can be channeled toward the surface in downdrafts due to the very high rainfall rates produced by the moisture-laden storms.

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At 700 MB Saturday evening (10,000 ft ASL), lots of moisture being channeled ahead of the upper trough over the eastern Kansas area.  A light, dry southeast wind at this level over California is bringing the Sierra Nevada wildfire smoke plumes westward, over the central Valley, around a ridge of high pressure from the Pacific across Oregon.

 

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Saturday evening surface chart shows the surface low over eastern Iowa with the surface trough and storms extending across Missouri into southeast Kansas.  A strong pressure gradient behind the surface trough and front is bringing drier, cooler air in on strong northwest winds.

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Radar precipitation estimate as of 10:53 PM Saturday.  The one-inch plus area (green) starts at about Lawrence and extends into the north KC Metro Area.

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The view is a little more clear from the Pleasant Hill (KC) radar, with the heaviest swath in the Lawrence area seen just west through north of town, where 1.3 to 1.5 inches of accumulated rainfall is indicated.  This seems very close to reality.  Accuracy past about Lawrence from the Pleasant Hill radar site decreases, as the beam gets too high above the ground to reflect actual precipitation as accurately as it does closer in.  This tends to cause areas farther from the radar to indicate more rainfall than actually occurred.

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CoCoRaHS Network rainfall amounts in the 24 hour period from 7 AM Saturday to 7 AM Sunday.   From trace amounts up to about 4 hundredths fell in the previous 24-period between 6 and 7 AM Saturday, so event totals for some of the Lawrence sites shown here are a few hundredths too low.  A six station average for Lawrence starting at 6 AM Saturday comes in at 1.14 inches.   The airport automated site went down at the height of the storm, possibly as a result of lightning or a power hit caused by lightning.  So the Lawrence Airport precipitation will be missing or incomplete for this event.  If one was to extrapolate between the Leavenworth County site to the east (1.57 total event) and the two north-central Lawrence sites (1.34 for the total event) one could come up with a reasonable estimate of 1.45 inches for the Lawrence Airport.  My observation time on this network is 6 AM (due to the early hour I often have to be at work), so the total event at my residence is all shown on this chart (1.02 inches).  As can be seen, too, the heavier precipitation was in the north county with southeast Douglas County only receiving around a quarter inch of rainfall.

Here is the last hourly observation from the Lawrence Airport before the equipment went kaput:

KLWC 142052Z AUTO 35005KT 9SM -TSRA FEW055 FEW075 OVC100 24/22 A2976 RMK AO2 LTG DSNT ALQDS RAB31 TSB48 SLP073 P0001 60002 T02390222 55029 

The time is 3:52 PM.  The wind is still light out of the north.  0.01 inches of rainfall in the last hour and 0.02 inches in the last three hours since 18 GMT.

Here is the last automated special aviation weather observation from the Lawrence Airport before the equipment went out:

KLWC 142113Z AUTO 28012G24KT 1/2SM +TSRA FG BKN020 BKN055 OVC095 22/21 A2979 RMK AO2 WSHFT 2056 LTG DSNT NE AND SW AND W P0049 T02170211

Translated, the time is 2113 GMT, or 4:13 PM.  This is just as the part of the storm with the most frequent lightning was moving in.  Winds were now west, gusting to 24 knots (28 MPH).  Visibility was 1/2 mile in a thunderstorm with heavy rain (FG means ‘fog,’ but that is an artifact of automated observations; the rain is causing the obscuration, or reduced visibility, not ‘fog.’) The ‘P’ group is the precipitation, which is 0.49 inches since the last hourly observation 21 minutes ago.  (That is, about a half inch of rainfall has fallen in 21 minutes.  This is a rate of about two inches an hour – comparable to the most torrential rains of summer.  This is very heavy rainfall, especially for October.  The 0.49 inches  added to the 0.02 from 18 to 21 GMT and 0.04 inches between 6 and 7 AM adds up to a total of 0.55 inches measured up to 4:13 PM Saturday, at which time the equipment got zapped, and that was the end of that event, officially, for Lawrence.

Here is the next automated special observation:

KLWC 150445Z AUTO 31010KT 10SM OVC022 14/12 A3003 RMK AO2 T01390117

Apparently the technician came out and repaired the equipment and observations resumed at the above time, which is 11:45 PM CDT.

The next hourly observation did not come in until the midnight observation.  Now the front is past Lawrence and winds are northwest gusting to 24 knots (28 MPH):

KLWC 150452Z AUTO 30017G24KT 10SM OVC023 14/12 A3003 RMK AO2 SLP166 T01440117

Strongest post frontal winds overnight occurred at the 2 AM observation, when winds gusted to 33 knots (38 MPH):

KLWC 150652Z AUTO 31022G33KT 10SM OVC028 12/07 A3012 RMK AO2 PK WND 32033/0646 SLP196 T01170072

Now we go to our usual NWS precipitation measuring conundrum:  Since the automated equipment did not measure all the rainfall for this event, which I estimate at about 1.45 inches at the airport (see previous caption above), this event will not be counted in the monthly and yearly precipitation amounts for Lawrence.  Rather, all the rainfall with this storm event will be treated as if it did not occur, rendering the officially reported rainfall figures for October in Lawrence not only useless, but misleading, as about half the rainfall for the month so far is now ‘missing.’  This is why we utilize the CoCoRaHS network for the Lawrence precipitation amounts on this blog.  You should, too!

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Parting shot:  Looking west-northwest at 6:18 PM Saturday, after the big storms went though.  However more showers and a few storms are percolating out west as the supporting upper trough approaches.  These dropped another 15 hundredths at my residence between about 8:10 and 9:15 PM.  Event total at my residence was 1.02 inches.  Highest amount in Lawrence was at a site in north-central Lawrence near Trail and Lawrence Avenue with 1.35 inches.  Another measuring site near Peterson and Folks came in a close second with 1.33 inches.  The 6-station Lawrence City average for the event was 1.14 inches.  Clinton Lake came in with 0.95 inches.

10/25/17:  Here are the storm reports from NWS Topeka on the Lawrence storms:

0420 PM     TSTM WND DMG     1 N LAWRENCE            38.97N 95.26W

10/14/2017                   DOUGLAS            KS   EMERGENCY MNGR

            TREE  LIMB SNAPPED 12 INCH DIAMETER AT 6TH

            AND LAWRENCE. ALSO REPORTS OF PEA SIZE HAIL.

            AND MINOR TREE DAMAGE WITHIN THE AREA.

            DELAYED REPORT.

0420 PM     TSTM WND DMG     1 N LAWRENCE            38.97N 95.26W

10/14/2017                   DOUGLAS            KS   EMERGENCY MNGR

            DELAYED REPORT. MULTIPLE REPORTS OF POWER

            LINES DOWN, TREES DOWN. GENERALLY NORTH OF

            9TH ST. AND EAST OF IOWA STREET.


Lastly, in the comments section of the rainfall report from one of our Lawrence CoCoRaHS observers, located just west of the corner Trail Road and Lawrence Avenue: “Thunderstorms late Saturday afternoon; severe with very strong winds (microburst?) for a few minutes beginning at 4:18 PM. Much tree damage in my neighborhood, but appeared to be less just to the west near Kasold Drive and south of 6th Street on Lawrence Avenue.  Suspect measured total precipitation is less than accurate as rain was “falling” sideways during the strong winds.”

The observer actually reported the highest precipitation of the Lawrence measuring sites in the network with 1.35 inches for the entire event, which started with light showers around 6 AM.  A site near Peterson and Folks came in second place for the Lawrence sites 1.33 inches.

These reports are further evidence of a localized ‘wet microburst’ event across northeast Lawrence, starting around the Lawrence Ave and West 6th area at 4:18 PM and rapidly moving northeastward with the other reports being timed at 4:20 PM.

Why the NWS out of Topeka insists that a microburst event did not occur is beyond me.  It clearly did occur.   There is not doubt about it.

 

One thought on “Damaging Storms Hit Lawrence

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