Archive for August, 2011

An Amazing Light Show

Wednesday, August 3rd, 2011

A cold front interacting with a very warm humid air mass resulted in explosive growth of thunderstorms during the evening hours of Aug 2, 2011. The day had been very hot and humid with the temperature topping out at 95° and the dew point hovering around 80°. A band of severe storms moved out of Wisconsin and affected the far northeast counties in Illinois…north of Chicago. At the time I thought the show was over. Later however storms developed rapidly over portions of the Rock river valley and began moving southeast and eventually made it to Grundy county.  Here is a list of storm reports for Grundy county as of 1PM 8/23/11 courtesy NOAA/NWS Chicago:

1001 PM     TSTM WND DMG     COAL CITY               41.29N 88.28W
08/02/2011                   GRUNDY             IL   PUBLIC

            TREE DOWN ON HOUSE.

1001 PM     TSTM WND DMG     COAL CITY               41.29N 88.28W
08/02/2011                   GRUNDY             IL   PUBLIC


1001 PM     TSTM WND GST     2 W COAL CITY           41.29N 88.32W
08/02/2011  M64.00 MPH       GRUNDY             IL   MESONET

1008 PM     TSTM WND GST     SSE MINOOKA             41.45N 88.26W
08/02/2011  M57.00 MPH       GRUNDY             IL   MESONET


My Boltek lightning detector definitely got a workout. At the time it detected a peak lightning rate of 2094 strikes per minute. Most were in cloud but there were many close cloud to ground strokes as well. The following images show the lightning display and radar image around that time.  Note: this detector is not nearly as accurate as those used in professional detection networks (costing much, much more).

Aug 2, 2011 Radar Image (severe thunderstorm warnings denoted by red polygons)

August 2, 2011 Lightning Display

July 2011 Climate Summary – Hot, Humid, and …dry

Monday, August 1st, 2011

If you think it was warmer than usual for July, you are correct. We recorded 21 days with high temperatures of 90° or greater. Last year we had 10.  The average temperature for the month was 79.2° and although not making it to the century mark, we did reach 99° on July 19th. Another factor that made it unbearable at times was the high humidity. Dew point is a measure of the amount of moisture in the air and generally begins to feel somewhat uncomfortable when the dew point reaches 70° although each individual has his/her own comfort level.  The heat and humidity are oppressive when dew points reach or exceed the upper 70’s. We had many days with dew points hovering around 80°. That, combined with temperatures in the low to mid 90s resulted in heat indices of 115 to 120° at times.

In addition to the heat, July will be remembered for a lack of rainfall. Total rainfall for the month was 2.00 inches. While not the driest recorded here, it was well below normal. The total monthly precipitation value does not always tell the whole story however, especially with regards to summer storms. I like to look at the days with 0.50 inch of rain or greater to get a better feel for how wet or dry a summer may have been. For this July we recorded only 1 day during the month when rainfall exceeded 1/2 inch. Most gardeners know that a typical garden needs around 1 inch per week during the summer. But in reality, that rarely occurs. Summer thunderstorms can produce rainfall rates that exceed 1 inch per hour so if you do get rain, it generally comes all at once.  Chicago actually recorded the wettest July on record with a whopping 11.15 inches of rain! This was due to torrential rain that fell on July 23rd and deposited a calendar day total of 6.86 inches.

Here are some stats for the Goose Lake Weather station:

 Averages\Extremes for the month of July 2011

 Average temperature     = 79.2°F
 Average humidity        = 76%
 Average dewpoint        = 70.3°F
 Average barometer       = 29.913 in.
 Average wind speed      = 1.4 mph
 Average gust speed      = 2.9 mph
 Average direction       = 165° (SSE)
 Rainfall for month      = 2.00 inches.
 Maximum rain per minute = 0.04 in on day 24 at time 08:15
 Maximum temperature     = 99.2°F on day 19 at time 16:19
 Minimum temperature     = 58.0°F on day 09 at time 05:46
 Maximum humidity        = 100% on day 31 at time 07:50
 Minimum humidity        = 34% on day 08 at time 15:00
 Maximum dewpoint        = 83.1°F on day 28 at time 14:57
 Minimum dewpoint        = 53.1°F on day 07 at time 20:21
 Maximum pressure        = 30.09 in. on day 31 at time 08:41
 Minimum pressure        = 29.73 in. on day 20 at time 19:46
 Maximum windspeed       = 18 mph from 293°(WNW) on day 11 at time 08:12
 Maximum gust speed      = 28 mph from 293°(WNW) on day 11 at time 08:12
 Maximum heat index      = 122.0°F on day 21 at time 16:31
 Avg daily max temp :90.5°F
 Avg daily min temp :68.3°F
 Total windrun = 1004.6miles

Here is an interesting graphic depicting the July 2011 departure from normal precipitation. The red circle is our location.