Strong Jet Stream Brings Changeable Weather in October


The sunset as seen from the Clinton Lake Dam on Friday, October 13th.

October is the second of the three transition months of fall, with an 11-degree drop in average temperature during the course of the month.

October also often has some of the most pleasant weather conditions of the entire year,  with sustained mild and dry conditions quite common.  Yet, the month can also be a volatile, as still-available subtropical air from the south brings moisture and energy to any passing weather systems moving in on the strengthening autumn jet stream.

This October, we had both scenarios.

The month started warm and dry.  The warmest temperature of the month occurred on the 2nd with a high of 86.  The next day, October 3rdaveraged 15 degrees above normal with a high of 85 and low 66.  This was the warmest day overall and had the greatest daily deviation above normal, as well.

Temperatures fell to near normal from the 4th to the 7th.  There was also some 1.25 inches of rain over a 72-hour period by the morning of the 7th, thus assuring that October would not be a totally dry month.

The first truly autumn-like day was Tuesday, the 10th, a cloudy day with temperatures hovering in the mid to upper 40s.  There was also a notable shot of brief heavy rain in the early afternoon that brought two tenths of an inch in little more than a half hour.

Next came a strong warming trend with highs ranging from 65 on the 11th to 84 on the 13th.  These warmer and increasingly humid days lead up to the notable ‘wet microburst’ storm of Saturday, October 14th.

Speaking of which, some new information has come to light on this damaging storm event (described in detail in my previous post).  In short, winds at the airport were recorded at 37 MPH initially, building to 72 MPH four minutes later at 4:27 PM.  This coincided with a rainfall rate of over 4 inches per hour from 4:22 to 4:26 PM (0.27 inches in four minutes).  The automated observations from the airport were not transmitted during the high wind portion of the event due to a lightning-caused commercial power outage.  However, the data was recorded internally on backup battery power for a half hour, thus capturing the event at the airport.

The 4 PM storms dropped from three quarters of an inch to around an inch of precipitation within about 45 minutes across town.  During the course of the entire day, an average 1.13 inches of rain across town with an estimated 1.28 inches at the airport.

A cool day on Sunday, October 15th, was followed by a string of fine, mild days from the 16th to the 21st.  The 18th to the 21st averaged 7 to 10 degrees above normal.  An 80-degree high temperature occurred on the 19th, the last of six days reaching the 80s.  I think we can probably say good-bye to the 80s until next spring, at this point.

Late in the afternoon of Saturday, October 21st, another line of strong thunderstorms hit the area, nearly one week to the hour following the microburst event of the previous Saturday.  These storms intensified as they moved in from the west.  At the same time, the entire system slowed down as the upper system started to split off to the south.    When all was said and done, an average 2.41 inches had fallen across Lawrence with 2.32 inches recorded at the airport, making this the most significant rain event of the month.  This was followed by another fine, pleasant day on Sunday, the 22nd.

The first in a series of dry, windy cold fronts pushed in from the north on Monday, the 23rd.  Cold air continued to rush in behind this front under clear skies on Tuesday, the 24th.  Solar heating at the surface combined with a strong push of cold air on a powerful jet stream aloft brought very gusty north winds throughout the day.  These winds were strong and gusty enough to knock down good-sized tree branches around town, along with lots small branches, twigs and leaves.  Winds at the airport topped out a 44 MPH.

The last few days of lower 70s occurred on the 25th and 26th before two additional dry cold fronts swept in from the north.  Northwest winds at the airport gusted to 45 MPH on the 26th, 40 MPH on the 27th and 38 MPH on the 30th.

Low temperatures dropped to 23 degrees on the 28th and 29th at the airport, though most of town, away from the low-lying floodplain at least, was probably closer to 28 degrees, which is what I registered at my residence.

October was not done with us yet, however, as the trick-or-treaters had a trick pulled on them this year.  October 31st reached a high of only 38 under cloudy skies after a morning low of 21.  This averaged out to a deviation for the date of 21 degrees below normal – enough to bring the average for the month down by two thirds of a degree!  A few snowflakes fell around town in the afternoon.  Some areas in the region, such as Topeka, received a few tenths of an inch of snowfall on the grass and leaves.  At least we missed out on that fun.

October as a whole averaged near 70 for a high and 45 for a low.  That was 1.3 degrees above normal for the month overall.  Precipitation-wise, our seven volunteer weather observers across the city averaged out to exactly 5 inches, considerably above the normal of 2.88 inches.

For the year, the city average precipitation average stands at 44.06 inches.  Normal through October 31st is 34.90 inches.

November brings a 14 degree drop in average temperature – the greatest of the three months of autumn.  However, the month usually sees some mild and pleasant days.  So, enjoy the last month of fall while it lasts, leaves and all..!




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