Oct 28, 2012: Final Hurricane Sandy Forecast

Brief Overview:

Sandy continues to steadily approach the region as a 75 mph hurricane, with its center currently east of North Carolina moving northeast. Sandy remains a massive hurricane, with tropical storm force winds extending up to 520 miles outward of its center and its rain bands already moving into the Northeast, as shown in the latest radar to the left. Sandy will turn towards the NW on Monday, making landfall over central New Jersey in the evening, resulting in widespread damage that is set to make Sandy a potentially historic storm. Click below to read the full post for the latest analysis on Sandy.



Sandy’s Track: Sandy continued to move northeast throughout the day, although it is currently starting to lose its eastern component as the trough to its west becomes negatively tilted and captures it, which will cause Sandy to turn north and then northwest, aiming straight at the Mid Atlantic coast. The only question at this time regarding the short term track is where the landfall location will be; despite landfall being 24 hours away, the model guidance continues to have some differences, with some models taking Sandy into central NJ just south of NYC while the tropical model guidance takes Sandy into the Delaware Bay. Looking at the latest observations, Sandy is close to its expected location, and will be making the turn north tonight, followed by the northwest turn on Sunday. My final forecast for the landfall location is slightly south of yesterday’s forecast, back in central NJ.

It is very important to remember that Sandy is a very large storm and will have widespread impact. Regardless of the landfall location, there will be significant impact from Sandy across the entire region.

Sandy’s Intensity: Sandy continues to deal with dry air, although it remains a 75 mph hurricane. In fact, its minimum pressure has dropped to 950 millibars as of the latest NHC update; over the last 2 days, Sandy has generally maintained 75 mph winds except for a brief time yesterday when it became a tropical storm, while the minimum pressure has dropped 19 millibars during this interval. Despite the low sustained winds, Sandy is a massive storm; tropical storm force winds extent outward 520 miles of the center, and Sandy’s size is also evident with the latest observations as coastal areas along the Mid Atlantic coast have already seen flooding with wind gusts starting to increase in the NYC area, despite the center being east of North Carolina. As of 9 PM, most of Long Island is already seeing sustained winds of at least 20-30 mph with gusts up to 30-40 mph.

Sandy will remain a very large storm as it moves into the region. As Sandy phases and retrogrades, it will transition into a hybrid cyclone, losing some tropical characteristics while maintaining a warm core, with additional deepening of the low pressure likely. Sandy is likely to make landfall with at least 70 or 75 mph sustained winds, but as described in the impact section below, it will not behave like a regular tropical storm or minimal hurricane.



Impact in the Northeast

The latest regional radar image posted to the left shows rain is already affecting the majority of the Mid Atlantic, well ahead of Sandy. Additionally, coastal flooding has already been observed today along the Mid Atlantic coast, and winds are increasing along coastal areas, with Long Island reporting 30-40 mph gusts as of 9 PM. These impacts will only continue to worsen as Sandy moves into the region and makes landfall on Monday night, resulting in widespread and significant damage across the region, which will be prolonged as Sandy stalls on top of the region through the end of the week.

Winds: (Slightly revised) The biggest risk from Sandy for the NYC area and New England is the wind and storm surge threat. Sandy is a very large storm, and instead of having very strong winds confined to a small radius near the center, strong winds will be spread out across a large radius; the majority of the Northeast and Mid Atlantic is likely to observe wind gusts near or above 40 mph at some point, including parts of the Ohio Valley and the Great Lakes.

The strongest winds will be to the north and east of Sandy, somewhat close to the center but spread out across a larger area; with a central NJ landfall, this will be focused over the NYC area and southern New England. In this area, sustained winds of at least 40 to 50 mph expected for 6-12 hours. The main question is exactly how high wind gusts get, as winds aloft are very strong with some, perhaps most, of these winds mixing down to the surface. With tonight’s forecast, I am expecting frequent wind gusts of 65 to 85 mph across Long Island and southern New England, with isolated occasional gusts to 90 mph, especially with the heavier showers. A little more inland towards N NJ and SE NY away from the coast are expected to see wind gusts generally between at least 60 and 75 mph, locally up to 80 mph, with areas further inland across a large part of the region expected to see gusts of 45 to 60 mph.

There appear to be two periods of strong wind gusts. The first will be on Monday during the afternoon, focusing over Long Island and southern New England with strong NE winds. As Sandy’s center makes landfall in New Jersey, a second and potentially slightly stronger period of strong winds is expected but with the wind direction from the SE, sending water straight into coastal areas with more widespread gusts up to 60-80 mph. Winds will be weaker on Tuesday, with wind gusts of at least 35-45 mph expected across the area.

Storm Surge: Sandy will result in a significant storm surge for coastal areas that is expected to be worse than Irene. According to the National Hurricane Center, the highest surge from Sandy will be about 7 to 11 feet, with the worst over the Long Island Sound, the Raritan Bay, and the New York Harbor. The storm surge is expected to be higher than that of Irene and potentially approaching the highest surge recorded in NYC, from Hurricane Donna in 1960. If the expected surge verifies, there may be problems with water flooding into the NYC subway system; last year’s Irene stopped 6-12 inches short of flooding the subway system.

Rainfall: Significant rain amounts are also expected with Sandy across the region. The highest rain totals will be to the west and south Sandy, with widespread totals of 4 to 8 inches, locally above 8-10 inches, expected from Delaware to Maryland, northern Virginia, southern New Jersey, and Pennsylvania. To the north and northeast of Sandy’s track, there will be less rain, but the wind for interior areas and storm surge for the coast will be the main risks in these areas. Totals are generally expected to end up between 1 and 3 inches across most New England and the northern half of New York State, locally up to 4″, with at least 2 to 4 inches in most of the NYC area, locally up to 5″, with the highest amounts further west and the lowest amounts in eastern LI and southeastern CT.

Snowfall: As Sandy interacts with a much colder air mass, a significant snowstorm is expected for the mountains of West Virginia, North Carolina, western Virginia and far western Maryland. In these areas, at least 1 to 2 feet of heavy wet snow are expected, with snow amounts potentially higher in some areas. As of this evening, some of the higher elevations have already reported several inches of snow.



Impact in the NYC Area

As of this evening, Sandy is already starting to affect the area with windy conditions, as Long Island is reporting widespread gusts between 30 and 40 mph. Tonight will be mostly dry for the area with isolated showers possible, especially west and south of NYC. More widespread rain will move into the area by Monday morning as conditions gradually worsen and wind gusts steadily increase. By the late morning through the late afternoon hours, a steady heavy rain is expected to fall from NYC and further west and south, with moderate to locally heavy rain expected in Long Island, southern CT, and most of southeastern NY north of the NJ/NY border. By Monday afternoon, strong northeast wind gusts of 50 to 70 mph are expected north and west of NYC, with gusts of 65 to 80 mph, locally higher, in Long Island and southern Connecticut.

By the evening hours, the rain is expected to slightly weaken in intensity. Sandy will make landfall in central New Jersey early in the overnight hours, with heavier rain expected again from NYC and further west and south. As Sandy moves into New Jersey, winds will switch to the southeast as a second period of strong wind gusts is expected with a very strong low level jet. With steeper lapse rates expected, stronger wind gusts are possible during this time frame across Long Island, southern CT and the immediate NYC area, with gusts up to 65-80 mph again expected, perhaps up to 85-90 mph. Sandy will then continue to push inland into Pennsylvania, with the rain weakening across the area as winds decrease later into the overnight hours. Occasional showers will persist into Tuesday and Wednesday with wind gusts generally in the 30-45 mph range. Sandy will finally move out by Friday with clearing skies and drier conditions.

The storm surge will be the biggest risk for coastal areas including the NY harbor, with a surge of 6 to 11 feet expected which is expected to be worse than last year’s hurricane Irene. With the ground saturated from the rain, 6-12 hours of strong to damaging wind gusts will be capable of producing widespread power outages across the area and the region, with power outages likely lasting for days, perhaps as much as a week.

Please refer to the 5-Day Forecast for a more detailed forecast for each part of the area. As of 11 PM, this has not been updated yet, but will be updated by 12 AM.



Overall Impacts From Sandy:

Sandy will be a very dangerous and potentially life threatening storm, which is expected to be worse than Hurricane Irene and may rival other historic East Coast hurricanes, such as the 1938 Long Island Express. All preparations should have been completed or almost completed by now. People in mandatory evacuation areas along the coast are highly recommended to evacuate before conditions begin to significantly worsen. Important supplies such as food, water, flashlights, batteries, ect. should be gathered, with generators prepared for the possibility of days of no power, which will be made worse by chilly temperatures behind the storm, with lows in the upper 30s and 40s and highs in the upper 40s to mid 50s. All loose outdoor objects, including Halloween decorations, should be secured or moved indoors.

This is a dangerous storm, and must not be taken lightly. This is the final forecast discussion on Sandy; brief updates will be posted in the Twitter page on Monday morning, with the blog going into live update mode starting 4 PM on Wednesday unless I lose power, in which case updates will be suspended. In that scenario, occasional updates regarding Sandy and the status of the blog may be posted in the NYC Area Weather twitter page until power returns. Stay tuned for additional coverage of Sandy over the next few days.

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