Flood

Summer Personified: July 2018 Recap

August 3, 2018 - 11:45pm -- Dave Robinson

Flash flood photo

July 2018 had a classic variety of summer weather. There was: 1) an ongoing heatwave to begin the month; 2) dry conditions for the most part in the first half of the month; 3) some warm, exceedingly humid conditions with widespread, at times heavy, showers the second half of the month (courtesy of the subtropics); and 4) some “top 10” sunny dry days following several cold front passages (thank you Canada).

The average statewide July temperature was 76.4°. This is 1.8° above the 1981–2010 average and ranks as the 13th warmest July in 124 years of records (2.6° above the full period of record average). Eleven of the 18 warmest Julys since 1895 have occurred in the past 20 years (since 1999). The average daily maximum temperature across the state was 87.2°, which is 2.2° above average and ranks as the 15th warmest on record. The 65.6° average minimum was 1.4° above the 1981–2010 average and comes in as the 17th warmest.

Statewide, August precipitation averaged 5.63”. This was 1.53” above the 1981–2010 average and ranked as the 32nd wettest since 1895. It was the wettest August since the record wettest month in 2011. As is often seen in the summer, the majority of the precipitation fell in scattered showers and thunderstorms. This resulted in a wide range of monthly totals around the state, with some serious flash flooding occurring in several locations when moisture ladened storms parked themselves over an area for multiple hours. Where storms missed time and time again, rainfall totals were below average. The northern NJ climate division (Hunterdon, Somerset, and Union counties northward) saw their 10th wettest August on record, with an average of 8.28” falling. This is 4.17” above average. Since 1990, only August 2011 was wetter in this division.

A Slow Green Up: April 2018 Summary

May 4, 2018 - 2:17pm -- Dave Robinson

Flash flooding photo

If you think it has been a long time since New Jersey experienced as chilly an April as this past one, you are correct. With snow accumulating in a storm on the 2nd to snow showers on the 30th, one was hard pressed to find many days when pleasant spring conditions could be found. Toss in two mid-month days when temperatures soared into the middle 80°s and another with strong thunderstorms delivering flash flood-producing rains, and weather-oriented heads kept spinning. However, overall, it was the persistent chill that captured the most attention, with the green up of lawns and foliage, accompanied by the blossoming of spring flowers, delayed from normal by upwards of two weeks.

Statewide, the April average temperature of 47.7° was 3.2° below the 1981–2010 mean (2.0° below the 1895–2017 mean). This ranks as the 28th coolest April since 1895 and the chilliest since 1982 (also 47.7°). The highest temperature observed in NJ was 87° at Stewartsville (Warren County) on the 14th and the coldest 16° at Walpack (Sussex) on the 11th.

April precipitation across NJ averaged 4.20”. This was 0.21” above the 1981–2010 mean (0.48” above the period-of-record mean). This was the 38th wettest April on record. Plentiful precipitation since February has eliminated drought concerns as we enter the summer water consumption season. Reservoirs and ground water levels are in good shape. However, this never means we should let our guard down and not use water in a responsible manner.

Rainfall Corridors: July 2017 Summary

August 4, 2017 - 4:20pm -- Dave Robinson

Valley fog photo

July 2017 proved to be an active month of weather throughout the Garden State. Time and time again, storms traversed the state, often depositing the heaviest rainfall in 30–40 mile west-to-east “corridors,” while elsewhere totals were much lighter. Such is the nature of showery summer rainfall, although in one case, the swath of heavy rainfall was associated with an out-of-season coastal storm. When all was said and done, rainfall occurred frequently enough to leave most locations with average to well above average monthly totals. The statewide average July rainfall was 6.33”. This is 1.76” above the 1981–2010 average and ranks as the 19th wettest July of the past 123 years. Last year with 6.97” (ranking 13th) and 2004 with 7.51” (ranking 8th) were the most recent Julys to be wetter than this year. The statewide average temperature of 75.5° was 0.9° above average. This ranks as the 22nd warmest July on record. There have been nine warmer Julys since 2002, including last year at 77.1° (ranking 7th).

Talk of Drought Evaporates: May and Spring 2017 Recaps

June 5, 2017 - 4:19pm -- Dave Robinson

Bayonne street flooding

It is always comforting to enter the water demand season, namely summer, with a bit of a hydrological cushion. Such is the case this year across NJ, thanks to ample rain and some late-season snow in recent months. This timely precipitation has eliminated drought concerns that stemmed from drier-than-normal intervals during 2016. As a result of the precipitation deficits, ground water, streamflow, and reservoirs all dropped to precarious levels, thus the issuance last fall of a drought warning by the NJ Department of Environmental Protection over northern NJ and a drought watch in some southern counties. Aside from two reservoirs in west central NJ remaining below average, at the moment all other hydrological signs are positive. However, no one should let their guard down and fail to appreciate the finite nature of our fresh water resources, and how quickly a period of abundance can lapse again into drought.

More will be noted regarding spring (March–May) conditions later in this report. First taking a look at May, New Jersey experienced its 9th wettest on record, with observations extending back to 1895. The statewide average rainfall of 6.62” was 2.63” above the 1981–2010 average and the wettest May since 1990. Frequent clouds and rain resulted in many chilly days, however, a mid-month heat wave was impactful enough such that the average statewide temperature of 59.8° was only 0.7° below the 1981–2010 average. It was the 61st coolest May of the past 123 years, with none cooler since 2008.

A Return to Hot Julys After a Two-Year Respite; Awfully Wet Too: July 2016 Recap

August 3, 2016 - 5:01pm -- Dave Robinson

Flooding photo

The second half of the 2016 NJ weather and climate year began with plenty to talk about. Maximum temperatures were 90° or higher somewhere in the state on 20 afternoons. This, along with many warm nights, helped boost the mean monthly temperature into the top 10, based on statewide records back to 1895. Yet, remarkably, this was only NJ’s 5th warmest July in the past 11 years. The 77.2° mean was 2.2° above the 1981–2010 average.

On 15 July days an inch or more of rain fell somewhere in NJ. This included eight days with greater than 2” in spots and four days where a few locations exceeded 4”. Statewide, the average rainfall was 6.85”. This was 2.33” above average and ranks as the 14th wettest July since 1895. It was the wettest July since 2004, and the 4th wettest in the past 41 years. The northern half of the state (Mercer/Somerset/Union northward) averaged 7.27” (+2.49”, 14th wettest), while the southern region averaged 6.77” (+2.38”, 12th wettest). This all came in a month where the northern half of the state remained classified as being in moderate drought (D1) on the US Drought Monitor, with about half of south Jersey considered abnormally dry (D0). Also, on July 26th the NJ Department of Environmental Protection placed the northern half of the state in a drought watch. These actions were the result of notable rainfall deficits dating back to the early spring, with the warmth of the month exasperating low soil moisture, stream flow, ground water, and reservoir conditions. Clearly, the late-month heavy rainfall in a good portion of the state warrants a re-evaluation of drought status as NJ heads into August.

Leaning Warm, Leaning Dry: July 2015 Recap

August 1, 2015 - 8:23pm -- Dave Robinson

Flooding photo

In most respects, July 2015 was a rather common one in the weather department. The statewide average temperature of 75.5° was 0.5° deg above the 1981–2010 mean. This past June had the same positive anomaly. This ranks as the 28th warmest July since 1895. It may seem strange to have such a small departure from normal yet rank in the top quartile for warmth. This can be explained by the fact that New Jersey has gotten warmer since the end of the 19th century. Compared to all Julys since 1895, this past July was 1.3° above average. Again, this might not seem like a large difference, however, given that temperatures do not vary from year to year nearly as much in summer as in winter, this change over the past century is notable.

Drought? What Drought?: June 2015 Recap

July 4, 2015 - 7:34pm -- Dave Robinson

Roll Cloud photo

Toward the end of May, the threat of a significant drought loomed over the Garden State, as May proved to be the 3rd driest on record. Crops were in bad shape or not growing at all, and reservoir levels were declining at a faster than seasonal rate. However, New Jersey had yet to reach the point where average and timely rainfall could not remedy the situation. Not only was this prescription filled, it was done in abundance. June rainfall averaged 8.21" across NJ. This was 4.19" above the 1981-2010 normal and ranked 4th wettest since 1895 (Table 1). It joined four other Junes in the past 13 years to rank in the top eight over this 121-year period. As explained in last month's report, the rains that fell during the daytime and evening hours of May 31st factored into the June total, much as the localized afternoon and evening rains on June 30th (discussed below) will count toward the July total.

New Jersey Hurricane Hunting: A brief recap of a small state’s big hurricane history

August 21, 2014 - 1:35pm -- Tom Karmel

Doria flooding photo

With more than a third of the 2014 Atlantic hurricane season behind us, many may assume this season has been quiet. However, the two hurricanes already named mark the first time since 1992 when the first two named storms have reached hurricane strength and the first time there have been two hurricanes by this date since 2008. With the peak of the tropical season yet to come, the question is whether the heart of the season will be active or quiet. The National Weather Service’s Climate Prediction Center recently updated their seasonal forecast, projecting only a 5% chance of an active season and 70% chance of a less than normal one. Still, it only takes one storm to seriously impact NJ, so we can never let our guard down. With this in mind, here is a brief history of memorable tropical cyclones affecting New Jersey and a summary of the frequency of storms through the hurricane season.

Mid-Atlantic Deluge

August 13, 2014 - 5:40pm -- Dave Robinson

Rainfall estimate map

Extremely heavy rain drenched portions of the Mid-Atlantic during the daytime hours on August 12 until after sunrise on the 13th. Starting off in the Washington-Baltimore area and moving up into central Long Island, a narrow ribbon of rainfall exceeding 5”, and over 10” in a few locales, resulted in flash flooding that resulted in water rescues and many damaged roads and vehicles. Excessively heavy rains, occasionally accompanied by lightning, traveled up a frontal boundary that was associated with an unusually strong August low-pressure system situated over the Great Lakes. The atmospheric impulses riding up this front joined forces with abundant atmospheric moisture (in the top 1% for the region) to bring multiple inches per hour rainfall rates…for multiple hours.

The heaviest rain was situated within less than a 10-mile wide path. Within 20 miles on either side, totals fell off to a mere inch or two, or even less. Such is the nature of these events, where despite the abundant atmospheric moisture, there is a finite amount of water available. The dynamics concentrated the atmospheric lifting, thus the condensation of the majority of the moisture and resultant rainfall, while adjacent areas balanced out the lifted air with subsiding air that greatly limited rainfall totals.

A Rather Average July, Believe It or Not: July 2014 Summary

August 4, 2014 - 6:26pm -- Dave Robinson

Thunderstorm photo

Despite a general feeling amongst NJ residents that July 2014 was a cold summer month, in actuality, compared to long-term records, it was rather average. The statewide average temperature of 74.5° was 0.5° below the 1981-2010 mean. However, it was 0.3° above the 1895-present mean and ranked as the 45th warmest July of the past 119 years. Even the number of afternoons with temperatures of 90° or higher was close to normal. So why the common misperception? Some armchair psychology brings me to four possibilities:

1) The first half of the month was above average, while the more recent weeks were on the cool side. Our perceptions are biased toward the most recent.

2) People have yet to “recover" from the cold start of 2014. The dubious media ramblings of the “polar vortex" returning to the eastern US in mid-July fueled these thoughts.

3) The most recent four NJ Julys all rank in the top six for warmth over the past 119 years. This was an amazing run of hot Julys.

4) Those sticking their toes in the Jersey surf in early July were shocked by water temperatures in the 50°s and may have equated this to the cool July atmosphere. The cold surf was actually indicative of persistent southerly winds that brought atmospheric warmth. This wind flow led to coastal upwelling that pushed warmer surface waters offshore and introduced cool deeper waters to the surf zone.

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