Wet June on the East Coast Raises Hurricane Flood Risk

By Dr. Jeff Masters
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Published: 1:41 PM GMT on July 16, 2013

June 2013 was the 15th warmest June in the contiguous U.S. since record keeping began in 1895, said NOAA's National Climatic Data Center (NCDC) in their latest State of the Climate report. Six Southwest U.S. states had a top-ten warmest June on record, and no states recorded a significantly below-average June for temperatures. Over three times as many record warm highs and lows occurred than record cold highs and lows during June. For the year-to-date period January - June, both temperature and precipitation over the contiguous U.S. have been above normal, ranking in the upper 33% and 23% of years, respectively.

According to NOAA's U.S. Climate Extremes Index (CEI), which tracks the percentage area of the contiguous U.S. experiencing top-10% and bottom-10% extremes in temperature, precipitation, and drought, June extremes were about 10% below average, and the year-to-date period January - June 2013 has been 20% below average.


Figure 1. Historical temperature ranking for the U.S. for June 2013. Six Southwest U.S. states had a top-ten warmest June on record, and no states recorded a significantly below-average June for temperatures. Image credit: National Climatic Data Center (NCDC).

Wet June on the East Coast raises hurricane flood risk
It was a very June for the contiguous U.S., ranking as the 13th wettest June since 1895. New Jersey and Delaware had their wettest June on record, and sixteen other eastern states had a top-ten wettest June. The very wet June has brought some of the highest soil moisture levels ever recorded for July along much of the coast from Florida to Maine, increasing the chances of extreme flooding should this region receive a hit from a tropical storm or hurricane during the coming peak months of hurricane season. The latest 2-week forecast from the GFS model keeps the East Coast under a wetter-than-average weather pattern into early August, and the latest 1-month and 3-month precipitation outlooks from NOAA's Climate Prediction Center also give above-average chances of wetter than average conditions. Lake Okeechobee in Florida is 1.4' above average for this time of year, and 5' higher than two years ago. While this still puts the lake 1.2' below what is considered high water, Lake Okeechobee water levels will need to be watched as we head into the peak part of hurricane season.


Figure 2. Historical precipitation ranking for the U.S. for June 2013. New Jersey and Delaware had their wettest June on record, and sixteen other eastern states had a top-ten wettest June on record. Utah had its driest June on record, and Arizona, Colorado, and Wyoming had a top-ten driest June. Image credit: National Climatic Data Center (NCDC).


Figure 3. Soil moisture for July 14, 2013, expressed as percent average of the soil moisture observed between 1916 - 2004. Portions of Florida, Georgia, South Carolina, North Carolina, Virginia, Maryland, New York, Vermont, and New Hampshire are near their highest soil moisture levels on record for this time of year, increasing the odds of extreme flooding in those states should a tropical storm or hurricane hit this year. Image credit: University of Washington Variable Infiltration Capacity Macro-scale Hydrological Model, which includes soil moisture, snow water equivalent, and runoff.

Drought conditions remained relatively unchanged during June. According to the July 9 Drought Monitor report, about 45% of the contiguous U.S. is still in moderate or greater drought, compared to 44% at the beginning of June. The U.S. Seasonal Drought Outlook issued on June 21 calls for little overall change in the U.S. area covered by drought conditions during the remainder of summer. Approximately 1.2 million acres of land burned in the U.S. during June, which is above average. However, the year-to-date total acreage burned is the second lowest in the past ten years.

Quiet in the Atlantic
There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for tropical cyclone formation is predicting development during the coming seven days.

Jeff Masters

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About The Author
Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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Wet June on the East Coast Raises Hurricane Flood Risk

June 2013 was the 15th warmest June in the contiguous U.S. since record keeping began in 1895, said NOAA's National Climatic Data Center (NCDC) in their latest State of the Climate report. Six Southwest U.S. states had a top-ten warmest June on record, and no states recorded a significantly below-average June for temperatures. Over three times as many record warm highs and lows occurred than record cold highs and lows during June. For the year-to-date period January...

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