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An overview of the Mid November Nor’ Easter of 2009

7:50 PM

The forecasting of the major Nor Easter that impacted the northern Mid Atlantic from November 11 through November 14 can best be described as very difficult and in the end the model guidance was not very helpful.

The potential for the storm was showing up on the model guidance by November 8th as then Hurricane Ida was intensifying off the Honduras coast.  By Monday night November 9th, Hurricane Ida had moved into the Gulf of Mexico and was falling under the influence of a strong mid level disturbance located at roughly 700 MB.  This disturbance initially improved the outflow of Ida, which allowed the hurricane to intensify over the southern portions of the central Gulf of Mexico.

Watervapor this morningBy Tuesday morning (11/10) Ida was under strong southwesterly shear and was taking on some extratropical characteristics.  Several model guidance at this point was suggesting that Ida or the remnants of Ida would either stall and meander over the Gulf of Mexico or would be shunted east into the Bahamas.  This clearly did not happen.

While Ida was becoming absorbed by the 700 MB disturbance, a deeper and stronger disturbance within the Sub Tropical jet stream was pressing to the east over Texas and southern Oklahoma.  Meanwhile, a Polar jet stream disturbance was organizing and dropping south of the Northern Plains.  The Sub Tropical jet stream would eventually catch up with the 700 MB disturbance and a weakening Tropical Storm Ida on Tuesday night.  A few key features were developing with this trough.  For one, the developing upper level low with the new coastal storm was much further to the west than expected and was the remnant moisture of Ida was pushing much further north and west than expected.  What caused this to happen?

The answer is a poorly forecasted and very influential upper low to the northeast of the Bahamas.  This upper low had several key contributions to this storm, but one of them was to slow the entire pattern ECW1-1down long enough to allow the new coastal low to develop.  On Tuesday night and Wednesday morning, the upper low over the Bahamas was able to enhance the western Atlantic ridge to the east of the Gulf Stream.  As a result, the Sub Tropical disturbance was not racing into the Atlantic as forecasted, but rather was pushing into the Tennessee Valley on Wednesday morning.  Moisture was racing ahead of a stalling cold front and pushed into much of southeastern Pennsylvania, New Jersey, and southeastern New York including Long Island.

By Wednesday evening, the further north trajectory of the developing Sub Tropical upper level low made the environment favorable for more interaction with the Polar jet stream.  At this point, model guidance now suggested that the Polar disturbance would force or kick the Sub Tropical disturbance into the Atlantic.  The ECMWF went as far as producing a large upper low off the Southeast coast for several days.  Again, neither of these solutions came to reality.  Instead, a piece of the Polar disturbance phased with the Sub Tropical Disturbance, which lead to a powerful upper low developing over the Tennessee Valley and later off the North Carolina coast.

An important change was also unfolding along the Southeast and southern Mid Atlantic coast by Wednesday night.  A stationary front was sitting off the coast and was an area favorable for new low pressure development.  Strong lifting was focusing towards the North Carolina coast and low level winds were strongly converging in these locations.  The low level center of Ida was quickly weakening and losing warm core characteristics.  By Wednesday night the center of Ida had dissipated and a new area of low pressure had developed along the North Carolina coast.

This is very important to state as many in the media (including some who should know better) continue to claim that this Nor Easter was the direct remnants of Ida.  Tropical storm Ida at no time become an extratropical low nor was the main low that produced the heavy rain and coastal flooding over much of New Jersey.  The actual Nor Easter was a completely different surface low pressure system from the circulation of Ida.  While the moisture and energy from Ida was entrained into this storm, this storm was not the direct remnant low of Ida.

While the new coastal low was developing off the North Carolina coast, a strong high pressure system was also strengthening over the Great Lakes.  This high pressure system eventually moved to a position over Northern New England, slowly moving over Vermont and New Hampshire.  The high pressure system had a significant impact on the evolution of this storm.  One impact was the introduction of very dry air at the lowest levels of the atmosphere, which lead to large bouts of virga over much of the New York City and Philadelphia metro and limited the advancement of moisture to the north on Thursday.

Through the day on Thursday, the coastal low continued to intensify down to a 994 mb low while the high pressure system strengthened to a 1030 mb high.  The combination of which produced a very impressive pressure gradient off the Mid Atlantic coast.  Through the day on Thursday, the strongest pressure gradient was focused over Virginia were gusts reached impressive levels over 75 mph at times.  Winds will also increasing throughout New Jersey with sustained winds ranging from 15 to 30 mph and gusts exceeding 40 mph along the coast.  The rainfall however, was limited to the central and southern New Jersey coast through the day as dry air prevented rain from falling over the rest of the northern Mid Atlantic.

The coastal low slowly drifted north towards the Virginia coastal waters on Thursday night into Friday morning.  Waves of rain moved through much of central and southern New Jersey, however the rest of the northern Mid Atlantic remained relatively dry.  The strengthening of the pressure gradient continued into Friday morning with the strongest shift of the pressure gradient directed towards the southern New acyn4_hgJersey coast.  The strong easterly fetch from the surface to 500 MB aided in forcing a marine air mass into the coastal plain, keeping the threat of fog, drizzle, and overcast conditions in place in locations that did not experience heavy rainfall.  Meanwhile, coastal flooding became a significant problem on Friday as wave heights built up to 7 to 8 feet, which lead to periods of moderate stages of coastal flooding.  Reports of roads being washed out, beach erosion, and  flooding of local streets throughout the southern New Jersey coast caused significant damage and costs in the millions.

Once again, the model guidance had a poor handled on the precipitation for much of the region as heavy ECW1rain was expected through much of the day.  However, the same upper low that caused the Sub Tropical disturbance to slow down and eventually stall the storm off the Mid Atlantic coast would eventually force the best upper level dynamics off the coast and southeast of Long Island.  The Bahamas disturbance was entraining into the storm, but the added divergence over the Gulf Stream caused a massive explosion of convection south and east of Long Island.  As a result of the rapidly rising air off the coast, air was sinking along the coast.  This sinking air inhibited any lifting developing at the lower levels along the coast.  Therefore, the heavy rain remained off the coast and did not push inland.  By Friday evening, the influence of this strong lifting off the coast was abating and rain worked back into the coast line once again.  The heaviest rain fell over Long Island and Connecticut on Friday evening as rain also redeveloped over central and southern New Jersey.  Waves of rain moved westward into much of New Jersey and into parts of eastern Pennsylvania as well on Friday night and through the day on Saturday.  The low pressure system was in a weakening state through Saturday, which allowed the winds to decrease from the northeast.

The following data shows the forecast in place on Wednesday morning, the actual observed rainfall map, and the official data and reports from the National Weather Service.


Rain Through Saturday

Forecasted


14

Official Observed Rainfall

Official NWS data:

Rainfall from 11/12 through 11/14

New Jersey

Atlantic City:  2.15”

Atlantic City CG: 3.59”

Atlantic City Marina: 3.39”

Cape May:  2.11”

Seaville: 2.69”

Green Creek: 2.33”

Flemington: .14”

Freehold:  0.27

Hightstown: 0.58

Millville: 1.59”

New Brunswick: .68”

Pottersville:  .14”

Sussex: .28”

Charlotteburg: .47”

Newark: .28”

Pennsylvania:

Allentown: .03”

Blue Marsh Lake: 0”

Glenmorre: 0.56”

Hamburg: 0.01”

Lehighton: 0.06”

Neshaminy: 0.7”

Philadelphia: 0.5”

West Chester: 0.63”

New York:

Bridgehampton: 1.70”

Islip: 1.16”

New York City: .06”

JFK: 0.47”

LGA: .51”

Westchester: .17”

Albany: 1.05”

Poughkeepsie: 0.61”

Upton: 1.81”

Middle Island 1.36”

Brookhaven: 1.35”

Oceanside: .53”

Connecticut:

Bridgeport: 0.76”

Danbury: 0”

Norwich: 1.77”

Wind Gusts:

NEW JERSEY

…ATLANTIC COUNTY…

ATLANTIC CITY MARINA    59   259 PM 11/12

ATLANTIC CITY           47   940 AM 11/13

…BURLINGTON COUNTY…

WRIGHTST/MCGUIRE        39  1057 AM 11/13

CHATSWORTH COYLE FIELD  38  1100 AM 11/13

…CAPE MAY COUNTY…

CAPE MAY                57   709 AM 11/13

OCEAN CITY              52

WILDWOOD                51   914 AM 11/12   MOREY`S PIER

CAPE MAY                50   537 AM 11/12   LA MER BEACHFRONT

WOODBINE                35   300 PM 11/12

…CUMBERLAND COUNTY…

MILLVILLE               41  1006 PM 11/12

…MERCER COUNTY…

TRENTON                 38  1036 AM 11/13

…MONMOUTH COUNTY…

SEA GIRT                43   300 PM 11/12

KEANSBURG               41  1100 AM 11/13

SANDY HOOK              38  1200 PM 11/12

…OCEAN COUNTY…

BARNEGAT LIGHT          59  1000 AM 11/13

TUCKERTON               55

HARVEY CEDARS           54   200 PM 11/12

SEASIDE HEIGHTS         52

BARNEGAT BAY            49

BRICK                   45

TOMS RIVER              38  1055 AM 11/13

WEST CREEK              38   800 AM 11/12

LAKEHURST NAS           35   550 AM 11/13

…SOMERSET COUNTY…

SOMERVILLE              39  1110 AM 11/13

…BERGEN COUNTY…

TEANECK                 44  1100 AM 11/14   MESONET

…ESSEX COUNTY…

NEWARK                  44   440 PM 11/13   ASOS

CALDWELL                29   354 PM 11/13   ASOS

…HUDSON COUNTY…

ROBINS REEF             56   536 PM 11/13   MESONET

JERSEY CITY             42  1100 AM 11/14   SKYWARN SPOTTER

HARRISON                36  1100 AM 11/14   SKYWARN SPOTTER

PENNSYLVANIA

…LEHIGH COUNTY…

ALLENTOWN               35  1053 PM 11/12

…NORTHAMPTON COUNTY…

FORKS TWP               38   100 PM 11/13

…PHILADELPHIA COUNTY…

PHILADELPHIA            40  1219 PM 11/13

PHILADELPHIA/NE         39  1142 AM 11/13

MARINE BUOYS

44009 26 NM SE CAPE MAY 60   350 PM 11/12

BRND1 BRANDYWINE SHOAL  57   321 PM 11/12

LWSD1 LEWES, DE         57   306 PM 11/12

AVAN4 AVALON, NJ        54   259 PM 11/12

BRBN4 BRANT BEACH       54   459 PM 11/12

CMAN4 CAPE MAY FERRY    47   230 PM 11/12

SJSN4 SHIP JOHN SHOAL   46   406 PM 11/12

SDHN4 SANDY HOOK        43   718 AM 11/13

CONNECTICUT

…FAIRFIELD COUNTY…

BRIDGEPORT              41   719 AM 11/14   ASOS

…NEW HAVEN COUNTY…

NEW HAVEN/TWEED         37   802 AM 11/14   ASOS

MERIDEN                 31   836 AM 11/13   ASOS

EAST HAVEN              25  1100 AM 11/14   MESONET

BRANFORD                24  1100 AM 11/14   MESONET

…NEW LONDON COUNTY…

GROTON/NEW LONDON       46   805 PM 11/13   ASOS

NOANK                   41  1100 AM 11/14   MESONET

STONINGTON              35  1100 AM 11/14   MESONET

NEW LONDON              21  1100 AM 11/14   MESONET

NEW YORK

…NEW YORK COUNTY…

NYC/CENTRAL PARK        39   330 PM 11/13   ASOS

…ORANGE COUNTY…

MONTGOMERY              31   449 AM 11/14   ASOS

…PUTNAM COUNTY…

LAKE PEEKSKILL          22  1100 AM 11/14   MESONET

…QUEENS COUNTY…

NYC/JFK ARPT            46   823 PM 11/13   ASOS

NYC/LAGUARDIA           45  1229 AM 11/13   ASOS

BREEZY POINT            39  1250 PM 11/13   COASTAL STATION

…SUFFOLK COUNTY…

SHINNECOCK HILLS        59  1027 PM 11/13   LIGHT TOWER

ISLIP                   46   446 PM 11/13   ASOS

WESTHAMPTON BEACH       46   547 PM 11/13   ASOS

FARMINGDALE             44   429 PM 11/13   ASOS

LINDENHURST             41   642 PM 11/13   SKYWARN SPOTTER

MONTAUK                 40   815 PM 11/13   ASOS

ORIENT                  37   920 PM 11/13   PUBLIC

SHIRLEY                 37   616 AM 11/13   ASOS

…WESTCHESTER COUNTY…

WHITE PLAINS            40   707 PM 11/13   ASOS

MILLWOOD                20  1100 AM 11/14   MESONET


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