Spreadsheet data file for May 2018:

2018-05-Rockville-2.8-WNW

MAY 2018 MONTHLY SUMMARY ROCKVILLE 2.8 WNW MARYLAND
By Kevin Shaw, Observer in Charge

May 2018 featured significantly above normal rainfall and temperatures

in the region, based on statistics compiled at the three major airports in

the DC area and in general corroboration with my own statistics. There

were generally warm temperatures all month except for 5 days in the 60s

during some of our 16 rainy days during the month. Most of the warm days

were in the 80s, save for 2 days near the beginning of the month that just

tipped over the 90° mark. Extremes in temperature were quite muted this

month. The highest temperature of the month was 90.5° on May 3, and the

coolest was 46.4° just two days earlier on the 1st. There were no really

notable heavy precipitation days, just a lot of moderate amounts, topped

by the 4 days of just over an inch during the month (The 1.13” total on the

15th was the greatest daily amount for the month). A particularly wet period

(May 13-19) occurred with 7 straight days of measurable precipitation

totaling 4.77” and was about 67% of the total monthly amount (6.68”) for

May 2018. There were 16 days with measurable precipitation, assuredly

well above the normal amount.

 

As we approach the summer months, significant pressure differences

become less important because, among other things, they go away,

unless we get some significant tropical activity with the usual low

pressure associated with tropical storms and/or hurricanes. May started

to show this pattern as the extreme highest pressure for the month

(30.25” on the 8th) and the extreme lowest (29.80” on the 10th) weren’t

nearly as large apart as in the colder months. But please note that the

extreme values still exhibit the seemingly usual pattern of not being very

far apart in days. The month had 13 cloudy days, 10 partly cloudy days,

and 8 clear/sunny days.

 

There were only 16 heating degree days and 174 cooling degree days

during the month. There were 11 foggy days, 7 days with thunder and 6

windy days (mostly from thunderstorms). The windy day category is

subjective with no personal real data values to back it, just based on

my descriptive email daily weather posts that are also posted here on

http://kevinshaw.weathertogether.net

 

Daily max/min temperatures varied less than April throughout May.

My maximum temperature frequencies included 2 days of 90° or greater,

16 days between 80° and 89°, 8 days between 70° and 79°, and 5 days

between 60° and 69°. On the minimum temperature frequency side of

things, there was 1 day between 40° and 49°, 11 days between 50° and

59°, 17 days between 60° and 69°, and 2 days at or above 70°. The

coldest daily max temperature was 66.7° on the 18th and the warmest

daily min temp was 71.9° on the 26th.

 

The diurnal range daily monthly average was 18.6°. Our greatest daily

range of temperature was 35.8° on the 2nd°, formed from a high of 87.8°

and low of 52.0° as I was in short transition between the coldest and

warmest temperatures of the month on the 1st and 3rd. We had one

more day with a range over 30° (33.2° on the 1st) and an additional 10

days with daily ranges above 20°. Our lowest range of temperature was

3.6° (67.7°-64.1°)  on the 17th. It was one of our cloudy, rainy days of

the month. There were 4 other days with diurnal temperature ranges less

than 10.0°, mostly on cloudy, rainy days.

 

With yet another month to study the most recent instrument changes

made in mid-August, data appears to be stable and an overall data

quality improvement success. I am still constantly checking on my data

quality frequently along with some of my Maryland weather cohorts.

I am about to add a lightning detection component to my system. I had

problems with pollen clogging my tipping bucket gauge during May,

which inhibited my capacity for adding precipitation timing and max rain

rates to my daily records. I also have continued as close to daily

(as time allows) GLOBE Cloud observations, complete with submission

of sky pictures at the time of the observation, usually timed with the

passage of satellites and also solar noon about 70 minutes past actual

EDT noon. Please ask me any questions you want at any time about my

station setup and/or my data through any means available to you.

 

MAY 2018 – ROCKVILLE 2.8 WNW MARYLAND – SUMMARY STATISTICS

Average high temperature 79.4°
Average low temperature 60.8°
Mean temperature 70.1°

Precipitation 6.68″
Greatest daily amount (date) 1.13″ (15)
Greatest storm total (dates) 4.77” (13-19)
2018 year-to-date precipitation total 18.50″

High temperature for the month (date) 90.5° (3)
Low temperature for the month (date) 46.4° (1)

Highest barometric pressure (date) 30.25” (8)
Lowest barometric pressure (date) 29.80” (10)

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

Heating degree days for the month: 16
Cooling degree days for the month: 174

Greatest diurnal range (date): 35.8° (2)
Least diurnal range (date): 3.6° (17)

Number of days:

Fog 11
Windy 6
Thunder 7
Cloudy 13
Partly Cloudy 10
Sunny/Clear 8
Max temp ≥ 90° 2
Min temp ≤ 32° 0
Precip ≥ 0.01” 16