||Overview: An area of low pressure intensified rapidly as it moved slowly from the southeastern United States on the morning of Sunday, April 15th to near New York City by the morning of Monday, April 16th. The intense low over New York City in combination with high pressure over eastern Canada produced a very intense pressure gradient across the area which caused strong east to northeast winds to develop across the region. Over land, the strong winds downed numerous trees. The downed trees caused widespread power outages, especially near the coast, and numerous road closures. Over the marine areas, the strong winds caused a storm surge and large ocean waves of up to 30 feet to develop. The combination of astronomical high tides, storm surge, and large waves contributed to coastal flooding in coastal areas of the state and severe coastal erosion in areas south of Portland.|The storm also brought heavy rain to the region which, when combined with snow melt, produced widespread flooding across much of the region. The flooding of small rivers and streams was worst in southern and coastal areas and led to numerous road closures. In the mountains, the rain was preceded by heavy snow. Flooding was minor on most mainstem rivers. |The intense low drifted very slowly eastward from Monday morning through Friday morning as it gradually weakened. During this time, the pressure gradient slowly relaxed, the winds gradually diminished, and the seas slowly subsided. However, rain continued into Tuesday across the region and each high tide during the period brought a reoccurrence of coastal flooding and erosion to the area. Power outages persisted, and stream and river flooding continued across the region during this period. Many roads remained closed.|On Friday, April 20, high pressure built eastward from the Great Lakes ending the influence of the Atlantic storm. |Wind: The pressure gradient associated with the storm brought high winds to the region. The damage observed in the hardest hit areas was typical of wind gusts of 60 to 80 mph. While most observing sites reported winds below this range, topography, elevation, and exposure were likely factors in determining the amount of wind damage any location experienced. In addition, the heavy rain brought strong wind gusts to the ground level and contributed to the sporadic nature of the heaviest wind damage. In addition to the meteorological factors, damage from the wind was exacerbated because of the heavy rain that accompanied the wind and the soft, wet ground caused by the spring thaw.|The wind knocked over numerous trees and branches throughout the region and caused numerous and prolonged power outages throughout the region.
Coastal Flooding/Storm Surge/Waves: The coastal storm hit during a period of very high (and very low) astronomical tides. In addition to the astronomical tides, the prolonged period of strong northeast winds caused a prolonged storm surge along the coastline. Also during this period, the strong winds caused large and battering waves along the coast. The storm tides and large waves caused significant flooding and coastal erosion. |In Portland, flood level is 12 feet. During the storm, storm tides reached or exceeded the 12 foot flood level during 7 tidal cycles. In addition, due to the large waves, coastal erosion occurred throughout the week of April 15th to 20th when the Portland gauge was above or near the 12 foot flood level. Communication was lost with NOAA???s Portland Weather Buoy shortly after 6 am Monday when it was reporting 31 foot seas.|Precipitation: Rain developed across New Hampshire Sunday morning and spread northward. The rain became heavy during the afternoon and overnight. By morning, 3 to 5 inches of rain had fallen over much of southeastern New Hampshire and 1 to 3 inches across much of the remainder of the state. In the mountains of New Hampshire, 3 to 11 inches of snow had fallen. Although the heaviest precipitation fell from Sunday afternoon into Monday afternoon, precipitation persisted into Tuesday. |Flooding: The heavy rain combined with snow melt to cause small rivers and streams in much of New Hampshire to flood. The worst flooding occurred on the smaller rivers in Rockingham county. The U.S. Geological Survey in New Hampshire reported that 5 river basins recorded all time record flows and 9 river basins in southern and southeast New Hampshire recorded peak flows that were equal to or greater than the 100 year recurrence interval. Of these nine river basins in New Hampshire, seven had recorded record flows just 11 months earlier during the Mother???s Day flood. Damage to infrastructure was severe (roads, bridges, waste water treatment plants, public buildings). Homes and businesses were also damaged.