Flood

Fall and spring months are considered to be seasonal transition ones. At times, the change of season takes place rather slowly. Then there are months like this past September when the turn is quite abrupt. September 2023 began with the hottest day and week of 2023. Several rainy periods, some with severe storms, ensued as temperatures began to decline and Hurricane Lee, while remaining far offshore, brought rough surf and some clouds to NJ. Soon after came chilly conditions with the remnants of Tropical Storm Ophelia twice bringing heavy rain into portions of the state and over a week of minor to occasional moderate coastal flooding at times of high tide.

Statewide, the average temperature of 68.1° was 1.2° above the 1991–2020 normal. This ranked as the 16th warmest September since records commenced in 1895. The average high temperature was 77.4°, which 0.2° above normal and ranks 35th warmest. The average low temperature of 58.8° was 2.2° above normal, ranking 8th warmest. The northern climate division averaged 65.8° above (+0.9°, 21st warmest), southern +69.5° (+1.4°, 14th warmest), and coastal 69.9° above (+1.2°, 14th warmest).

September rainfall was excessive, with the southwest and northwest the driest regions of the state yet averaging above the statewide 30-year normal. The wettest area was along the northern coast with rainfall as much as 3 to 4 times above the climatological mean. Statewide, September precipitation averaged 7.55”, which is 3.39” above normal and ranks as the 9th wettest. The northern division averaged 7.73” (+3.27”, 11th wettest), southern 7.38” (+3.39”, 11th wettest), and coastal 8.01” (+4.12”, 3rd wettest).

Post tropical storm Ida moved across the Garden State during the afternoon of September 1st into the early hours of the 2nd. It brought with it torrential rainfall, leading to flash and river flooding that took the lives of approximately 30 individuals and the rescue of countless more from raging waters. Additionally, it brought three tornadoes to southwestern and central areas, including the first EF-3 twister to strike New Jersey in 31 years. There were only minor injuries and no deaths from the tornadoes.

Ida developed in the Caribbean, being named a tropical storm on August 26th. From there, it moved northwestward, attaining hurricane status on the 27th as it passed over extreme western Cuba and moved into the Gulf of Mexico. It maintained a steady course as it strengthened into a major category 4 hurricane, making landfall in Louisiana on the 29th with sustained one-minute wind speeds as high as 150 mph. Once inland, winds diminished rather quickly but rainfall associated with the tempest remained heavy as the storm began to curve toward the northeast. This track remained quite steady as the storm weakened to a tropical depression on the 30th and became an extratropical low-pressure system as it approached the central Appalachians. On September 1st, Ida’s remnants merged with an advancing cold front as the system entered the Mid-Atlantic and crossed New Jersey before moving into southeast New England on the 2nd.

The summer of 2019 concluded on a warm and a bit dry note when averaged across the Garden State. The warmth was a common theme throughout June to August, while the earlier summer months were on the wet side. The average August temperature of 74.4° was 1.4° above the 1981–2010 mean and is tied with 1983 and 1973 as the 14th warmest since 1895. On 12 days, the temperature topped out at 90° or hotter at one or more Rutgers NJ Weather Network station, but never exceeded 96°. The heat was somewhat tempered by seven mornings with lows in the 40°s at some northwestern NJWxNet locations.

August precipitation averaged 3.75” across NJ. This was 0.35” below normal and ranks as the 52nd driest of the past 125 Augusts. As expected during a summer month that is dominated by hit and miss showers, rainfall totals varied quite a bit, even on a local scale. The driest location in the state was Lambertville in Hunterdon County where 1.48” fell, while the wettest was Lebanon, also in Hunterdon County, with 7.99”. When and where the storms struck, they were, at times, intense. This included small tornadoes and more widespread strong winds, dangerous lightning, and flash flooding.

The moist and mild pattern of late spring and early summer has left the Garden State quite green. There is nothing new to this pattern, as the first six months of 2019 totaled 27.22” of rain and melted snowfall, some 4.92” above the 1981–2010 mean, and a 49.0° average temperature, which is 1.3° above average. Each of these ranks 13th highest of the past 125 years.

Even more impressive, the past 12 months have seen 10 wetter than average and 10 warmer than average. The two drier-than-average months (March and April) were closer to their 30-year mean than any of the wetter ones. The precipitation total for the past 12 months is 65.28”. This is the second wettest 12-month period on record out of all 1483 12-month periods dating back to 1895. The wettest was 66.62” for the period ending this past January. The majority of the top 20 such periods have occurred this decade. They have included the two wettest calendar years on record (2018 and 2011) and appear to have lasted longer than earlier wet intervals. Meanwhile, the warmth of the past 12 months (54.5°) would rank as the 9th warmest calendar year but not within the top 20 for any 12-month period.

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.