Endless Summer?
September 2010 Overview

Dr. David A. Robinson
New Jersey State Climatologist
Center for Environmental Prediction, School of Environmental and Biological Sciences/NJAES, Rutgers University
October 6, 2010

For those who covet warm weather, has this been the year for you! The first time a thermometer somewhere in New Jersey exceeded 90° this year was on April 7 and maximum temperatures continued to frequently exceed this mark in much of the state through September 25. That's likely it for the year, but not before New Brunswick (Middlesex County) equaled or exceeded 90° on 51 days. This establishes a new record, topping the previous maximum of 49 in 1900, and is well above the 1981-2010 average of 19. Other locations that topped the 50 day mark include Newark (Essex) with 54 and Hillsborough (Somerset) with 55. Pomona (Atlantic) reached the mark on 46 days, and even right along the shore at Seaside Heights the total was 21 days. Only the highest elevations of northwest Jersey escaped the hottest of the hot weather, with the High Point Monument station only reaching the 90° mark on three days this season.

September 2010 was the 4th warmest on record across NJ (table 1). It marked the 7th consecutive month with average temperatures in the top ten of the 116 years dating back to 1895. This is one of the more remarkable climate anomalies I have run across in my almost 20 years as state climatologist. As discussed in last month's narrative, this year continues to be neck in neck with 1998 and 2002 as the warmest on record (table 2).

Rank Year Sept Temp
1 1961 71.4°
2 2005 71.0°
3 1931 70.1°
4 2010 69.4°
5 1998 68.9°
6 1959 68.8°
7 1945 68.7°
8 2002 68.4°
9 1970 68.3°
10 2007 68.3°

Table 1. Ten warmest Septembers across New Jersey since 1895

Rank Year Avg Temp year-to-date
1 1998 58.5°
2 2010 58.4°
3 2002 58.4°
4 2006 57.5°
5 1991 57.5°
6 1949 57.5°
7 2008 57.1°
8 1921 57.1°
9 1999 56.9°
10 1953 56.9°

Table 2. Warmest January-August intervals across New Jersey since 1895

The September mean of 69.4° was 4.1° above the 1971-2000 average. Seven days had afternoon highs in the 90s at more than one location. They came in three periods, the first continuing on from late-August heat and bringing maximums as high as 99° at New Brunswick on the 1st when most of NJ was in the 90°s, and 98° at Hillsborough on the 2nd. The maxes were tightly bunched on the 7th, with Hillsborough at 93°, New Brunswick and Berkeley Township (Ocean) at 91° and eleven other stations in our network at 90°. The 8th saw Sicklerville (Camden) top out at 93°, with ten other stations at 92°. Sicklerville reached 91° on the 22nd, with eight stations at 90°. Piney Hollow (Gloucester) and Sicklerville reached 94° on the 24th and New Brunswick 91° on the 25th.

With the nights growing longer and skies clear much of the month, the opportunity for some cool nights arose. On eight mornings temperatures dropped below 45° at Pequest, a valley location in Warren County. Before continuing, it must be noted that our perennially cold Walpack (Sussex) station was out of commission this month, thus allowing Pequest to reign supreme. Pequest's cool mornings started with lows of 42° on the 5th and 39° on the 6th, when Berkeley Township in the Pine Barrens fell to 40°. The 11th brought 42° to Pequest and 45° to Basking Ridge (Somerset), the 15th was 40° at Pequest and 43° at Berkeley Township and Basking Ridge, and the 16th was 41° at Pequest and Basking Ridge. Pequest fell to 44° on the 18th and 20th, with the coldest morning of the month occurring on the 21st, when Pequest reached 36°, Basking Ridge 37° and Kingwood (Hunterdon) 39°.

Precipitation for September averaged 2.96" around the state. This is 1.19" below average and is the 52nd driest of the past 116 Septembers. It marks the 6th consecutive month with below-average rainfall. On average, 25.22" should have fallen over this period, while this year only saw 17.10" statewide (68% of average). Totals from April 1 through September 30 range from 14.42" in Hillsborough Township (Somerset) to 27.21" in Bethlehem Township (Hunterdon).

Before continuing, it must be noted that the bulk of the September 30th precipitation observations at the long-running National Weather Service Cooperative Observing Stations that go into the state average were taken at 7AM on the 30th. Thus any rain falling after that time is accounted for on October 1. There were only five stations that observed at midnight on the 30th out of the 25 total stations. I am confident that given the rainfall distribution that day that the monthly average would not have climbed to normal, as the bulk of the statewide rain from this event fell in the early morning hours of October 1. Again, excluding rain that fell after approximately 7AM on September 30th, NJ CoCoRaHS stations received as much as 4.67" in Belmar (Monmouth) for the month. Other totals on the high end include South Plainfield (Middlesex) with 4.51", Howell (Monmouth) at 4.45" and New Providence (Union) with 4.43". The lowest totals for September include the 1.32" at Wanaque (Passaic), 1.66" in Middle Township (Cape May), 1.75" in Boonton (Passaic) and 1.86" in Wantage (Sussex).

The month started on a dry note. Light showers fell in coastal counties on the 3rd and in the central area on the 8th, otherwise no appreciable rain fell until the 12th. On that day, 0.85" and 0.66" was reported from two stations in Mt. Olive Township (Morris), 0.68" in Blairstown (Warren) and 0.66" at Fairhaven (Monmouth). Evening thunderstorms brought 1.06" to Lafayette Township (Sussex) and 0.97" to Denville (Morris) on the 13th. Nighttime thunderstorms soaked the north coast from the 16th into the 17th, with 1.65" at Belmar (Monmouth), 1.61" in Berkeley Township (Ocean) and 1.55" in Shrewsbury Township (Monmouth).

More storms arrived in northern areas during the evening of the 22nd. The largest total was the 1.15" at West Milford (Passaic), with 0.81" in High Bridge (Hunterdon) and 0.75" and 0.72" at stations in Liberty Township (Warren). An extended rainy period brought periods of light to heavy rain across NJ from the 26th -28th. Most of the state saw more than 0.50", with the eastern half exceeding an inch. The largest totals included 2.47" at Estell Manor (Atlantic), 2.25" in Eatontown (Monmouth), 2.15" in Wall Township (Monmouth) and 1.79" at Hammonton (Atlantic).

Rather than break up the major storm that occurred on September 30 and October 1 into each separate monthly summary or wait until October ends to summarize it, here we will take a look at was a notable event for much of the state, as well as through the east coast from North Carolina to the Canadian maritime. Storm totals exceeded 7" at five stations in Warren County, including the townships of Allamuchy (7.54"), Greenwich (7.24"), Liberty (7.23" and 7.02") and Independence (7.10"). Five western and northern counties from south to north had stations observing as much as 6-7" (Salem, Hunterdon, Warren, Morris, Passaic). Stations in these last four counties as well as Sussex, Gloucester and Burlington saw 5-6", and twelve counties received at least 4". Only Cape May County failed to have stations receive more than an inch, as two Middle Township stations caught 0.54" and 0.57" and Sea Isle City reported 0.57".

Atmosphere pressure peaked in the 30.25" to 30.30" range on the 6th, 18th and 21st. The lowest pressure of the month was close to 29.50" on the 3rd. Winds gusted to 40 mph or better on six September days. High Point Monument (Sussex) led the way on the 8th, with a gust to 41 mph and Wantage (Sussex) reached 40 mph on the 9th. A windy mid-month period saw 41 mph gusts at the Atlantic City Marina (Atlantic) and Upper Deerfield (Cumberland) on the 16th, 51 mph and 41 mph gusts at Wantage and High Point Monument, respectively, on the 17th and 48 mph at Wayne (Passaic) on the 18th. The highest gust in the late-month storm was 49 mph at Bivalve (Cumberland) on the 30th.

September weather and climate impacts were varied. Tropical systems posed threats, particularly Earl early in the month. However, other than beach concerns, the state was not impacted greatly by any system. The 8th saw the entire state declared to be in a drought watch. This was issued by the commissioner of the NJ Department of Environmental Protection. Up to that date, only the northeast drought zone (of six statewide) had been in a watch, that since mid August.

The late afternoon of the 16th saw an EF1 tornado strike near Woodruff in Ocean County and a microburst impact Perth Amboy in Middlesex County. Roof and tree damage were the major impacts of these severe events.

Drought conditions generally continued to build throughout the state until the last week of this warm month. The second in a series of drought hearings was held by the NJDEP on September 29th (the first was on August 25th). This was in anticipation of perhaps having to go to drought warning or emergency status in all or parts of NJ. While some rain had fallen earlier in the week before the Wednesday hearing and the forecast was for heavy rain on the 30th and 1st, it was necessary (and perhaps prudent) to hold it because announcements of this hearing were first publicly posted approximately two weeks prior.

And as noted above, the heavy rain certainly arrived. The deluge focused on the entire Delaware Basin in New York, Pennsylvania and New Jersey. This led to the 12th highest flood crest on the Delaware River at Easton/Phillipsburg and the 21st highest at Trenton, each river gauge with records extending back to the early 20th century. Fortunately, damage was minimal. The gusty winds of the 30th resulted in over 21,000 customers losing power in various locations across New Jersey.

For those seeking more detailed information on hourly, daily and monthly conditions, please visit the following Office of the NJ State Climatologist's websites:

NJ Weather and Climate Network
NJ Community Collaborative Rain, Hail and Snow Network
NJ Snow Event Reports

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