SEPTEMBER 2017 MONTHLY SUMMARY ROCKVILLE 2.8 WNW MARYLAND By Kevin Shaw, Observer in Charge

SEPTEMBER 2017 MONTHLY SUMMARY ROCKVILLE 2.8 WNW MARYLAND By Kevin Shaw, Observer in Charge

September 2017 was warmer and drier than usual.  The 2.58″ of rain this month was considerably less than August’s 4.09″ amount. The days of measurable rain were quite low (6) and all occurred on the first 14 days of the month. In fact rainfall on the very first 6 days of the month accounted for over 95% of the total monthly precipitation amount. Tropical activity was quite busy early in the month, but we did not get any big hits of rain. On the second of the month, 0.81″ fell from the weakened remnants of once powerful hurricane Harvey. Coincidentally the lowest maximum temp of the month also occurred on this day (60.6″). Another weakening storm Irma which had really caused havoc well to the south and southeast of my location only yielded light rain (0.12″) on the 13th and early on the 14th with little wind and slight pressure drops. The rainiest day of the month (0.89″) on the 5th also resulted in my modest lowest pressure reading of the month (29.72″). Powerful thunderstorms produced this rain on the 5th and was not directly tropical related. On the 6th the only other significant September rain fell, a cooler, stratiform rain under still relatively low barometric pressure. After a meager .02″ fell early on the 14th, we went totally dry the rest of the month with not even a trace of rain falling. Interestingly enough, on the 10th, I registered my highest pressure of the month (30.42″) along with my lowest minimum temperature (50.9°).

After that first half of the month generally wet and cool period, the rest of the month had mother nature’s spicket turned off and got the heat and humidity turned on most days. The average max temp from the 15th-30th was 79.4° with 80° maxtemps reached on 9 days, reversing the common sense usual trend of max temps turning cooler as September days progress towards October. And the streak of 16 straight days with minimum temps of 60° or more from the 13th-28th was quite impressively telling.  At least there were no days of max temps of 90° or greater.   The highest temperature of the month of 86.5° on the 27th was not really that high, but was made more oppressive being at the end of the long string of over 80° maxs and over 60° mins. At least the dew point temperature managed to drop to more fall like values at the end of the month (43° on the 30th) after hitting a max of 73° on the 5th and 27th.

There were 33 heating degree days (HDD) and 146 cooling degree days (CDD) during the month.

My maximum temperature frequencies included 11 days between 80° and 89°, 13 days between 70° and 79°, and 6 days between 60° and 69°.  On the minimum temperature frequency side of things, there was 12 days between 50° and 59°  and 18 days between 60° and 69°.

 

The diurnal range daily monthly average was 15.3°. Diurnal ranges were somewhat suppressed due to the lack of any really hot or cool days. The maximum daily range of only 23.0°occurred on the 3rd (79.1°- 56.1°). There were only 4 days total with daily ranges at or above 20.0°. The lowest daily temperature range of 4.0° (60.6°- 56.6°) which occurred on the 2nd was the 2nd wettest day of the month and by far had the coolest max temp of the month. Also interestingly enough these extreme diurnal temperature ranges for the month occurred only 2 days apart from each other. Just like in July and August, there were only a total of 3 days with minimum diurnal temperature ranges less than 10.0°.

With a full month to study the instrument changes made in mid-August, it appears to be a data quality improvement success. Recently both rain gauges were cleaned up well. Decisions upcoming include where to place my snowboards and whether or not to move my cocorahs rain gauge closer to the building to ease efforts for winter reading and recording, especially during icy/snowy periods. The sprinklers should be turned off for the season on or around November 1. Please ask me any questions you want at any time through any means available to you.

 

Average high temperature                         76.4°

Average low temperature                           61.1°

Mean temperature                                      68.8°

Precipitation                                               2.58″

Greatest daily amount (date)                      0.89″  (5)

Snow                                                           0.0″

Year to date precipitation                        32.87″

High temperature for the month (date)      87°  (27)

Low temperature for the month  (date)      51°  (10)

Highest barometric pressure (date)         30.42” (10)

Lowest barometric pressure (date)          29.72”  (5)

Peak wind gust (date/direction):               N/A

Heating degree days for the month:           33

Cooling degree days for the month:           146

Greatest diurnal range (date):                  23.0°  (4)

Least diurnal range (date)                        4.0°   (2)

Number of days:

Fog                                                              6                  

Thunder                                                      2

Cloudy                                                         6

Partly Cloudy                                              11

Sunny/Clear                                               13

Max temp => 90°                                         0

Min temp < 50°                                            0

Leave a Reply

Your email address will not be published. Required fields are marked *

%d bloggers like this: