East Coast High Impact Hurricane/Post Tropical Storm Sandy

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12 GFS:

12Z Euro:

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EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
226 PM EDT FRI OCT 26 2012

VALID 12Z MON OCT 29 2012 - 12Z FRI NOV 02 2012

...DANGEROUS HURRICANE/POST-TROPICAL CYCLONE SANDY IS LIKELY TO
SPREAD HIGH WINDS/HEAVY RAINS AND INTERIOR HEAVY SNOWS FROM THE
CAROLINAS AND CENTRAL APPALACHIANS NORTHWARD INTO CANADA...

GENERAL FLOW PATTERN
====================
A RETROGRADING POSITIVE ANOMALY MOVING FROM SOUTHERN GREENLAND
INTO NORTHERN QUEBEC FAVORS A QUASI-STATIONARY DEEP CYCLONE NEAR
THE NORTHEAST, IN THIS CASE HURRICANE SANDY AND ITS POST-TROPICAL
REMAINS. OTHERWISE...RIDGING IS GENERAL EXPECTED OUT
WEST...THOUGH FLOW ACROSS THE PACIFIC IS EXPECTED TO SEND AMPLE
ENERGY/HEAVY PRECIPITATION ACROSS THE NORTHWEST. GUIDANCE IS IN
EXCELLENT AGREEMENT ON THE GENERAL FLOW PATTERN, THOUGH ISSUES
REMAIN WITH SANDY'S FUTURE COURSE AND STRENGTH.

MODEL PREFERENCE
================
THE NATIONAL HURRICANE CENTER (NHC) TRACK NOW BEST RESEMBLES THE
00 UTC ECMWF ENSEMBLE MEAN. THE EXTRATROPICAL TRANSITION OF SANDY
MAY HAVE ALREADY BEGUN BASED UPON RECENT SATELLITE IMAGERY...A
PROCESS EXPECTED TO COMPLETE TUESDAY PER NHC. THE DETERMINISTIC
GUIDANCE (PARTICULARLY THE 00 UTC ECMWF) SHOW PRESSURE SOLUTIONS
WELL BEYOND WHAT HAS EVER BEEN OBSERVED NEAR THE NEW JERSEY/NEW
YORK COAST (EVEN EXCEEDING THE 1938 LONG ISLAND EXPRESS HURRICANE)
EARLY IN THE MEDIUM RANGE PERIOD. THE DETERMINISTIC GUIDANCE
(CANADIAN, GFS, AND ECMWF INCLUDED) HAS SHOWN A VERY STRONG BIAS
WITH TROPICAL CYCLONES GAINING LATITUDE AND/OR TRANSITIONING INTO
NON-TROPICAL STORMS OVER THE PAST COUPLE YEARS... INCLUDING (BUT
NOT EXCLUSIVE TO) LESLIE 2012...ISAAC 2012...DEBBY 2012 IN THE
WESTERN SUBTROPICAL ATLANTIC IRENE 2011 AND IGOR 2010. PLEASE
REFER TO THE NHC FOR UPDATED INFORMATION ON SANDY.

THE 00 UTC ECMWF ENSEMBLE MEAN ALSO DEPICTS AN OVERALL FLOW
PATTERN UPSTREAM ACROSS THE W-CENTRAL CONUS AND ERN PACIFIC THAT
IS ON THE MORE AMPLIFIED AND LESS PROGRESSIVE SIDE OF THE FULL
ENVELOPE OF GUIDANCE SOLUTIONS OVER THE NEXT WEEK. THIS SEEMS
QUITE REASONABLE CONSIDERING DOWNSTREAM BLOCKING.

WEATHER IMPACTS
===============
PER THIS SOLUTION FROM SUNDAY THROUGH WEDNESDAY...WINDS AS HIGH AS
HURRICANE-FORCE ARE EXPECTED TO LASH EXPOSED AREAS OF THE
NORTHEAST/MID-ATLANTIC STATES (THE COAST AND TOPOGRAPHY)...LEADING
TO POTENTIALLY SERIOUS COASTAL EROSION AND COASTAL FLOODING. THE
TIMING OF THE FULL MOON AND THE BUILD-UP OF TIDES OVER MULTIPLE
TIDAL CYCLES SHOULD EXACERBATE THE SITUATION ALONG THE
COAST...PARTICULARLY IN CORNERS SUCH AS THE NEW YORK BIGHT. HEAVY
RAINS ARE EXPECTED TO FOCUS WITHIN SANDY'S WARM CONVEYOR BELT
CIRCULATION AS WELL AS ALONG ITS DRAPING WARM FRONT FROM THE
NORTHERN MID-ATLANTIC STATES AND INTO NEW ENG AND ERN
CANADA...WITH LOCAL AMOUNTS EXCEEDING 10 INCHES POSSIBLE. THIS
SOLUTION WOULD MEANWHILE ALLOW SIGNIFICANT SNOWS WITHIN ITS COMMA
HEAD PATTERN UNDER THE SUPPORTING/COOLING MID-UPPER LEVEL TROUGH
TO FALL AS CENTERED/FOCUSING OVER THE CENTRAL THEN NRN
APPALACHIANS AND VICINITY. LAKE EFFECT SNOWS ACROSS THE EASTERN
GREAT LAKES ARE POSSIBLE THROUGH THE PERIOD WITHIN THE CYCLONIC
FLOW IN THE SYSTEM'S COLD SECTOR. AS THE CYCLONE GRADUALLY WEAKENS
AS IT PULLS NORTHWARD THURSDAY INTO NEXT FRIDAY...WINDS SHOULD
SLACKEN AS SHOULD NERN US PRECIPITATION AMOUNTS/COVERAGE...BUT
EXPECT THAT AMOUNTS WILL REMAIN SIGNIFICANT CONSIDERING TROPICAL
ORIGIN OF THE LOW.

UPSTREAM...A SOLUTION CLOSEST TO THE 00 UTC ECMWF ENSEMBLE MEAN
SLOWS FROM HPC CONTINUITY SLIGHTLY THE INLAND PROGRESSION OF ERN
PACIFIC SYSTEM ENERGY ACROSS THE WRN US MID-LATE NEXT WEEK...MORE
SLUGGISH TO BUMP INTO A LEAD AMBIENT MEAN MID-UPPER RIDGE
POSITION. THIS SOLUTION OFFERS STRONG POTENTIAL FOR HEAVY
PRECIPIATION/MOUNTAIN SNOWS ACROSS MUCH OF THE NWRN US NEXT
WEEK...INCLUDING THE THREAT FOR MEDIUM RANGE DAYS 4-7 LIQUID
AMOUNTS UPWARDS TO 5 INCHES OVER MOST FAVORED PAC NW COASTAL
TERRAIN AND THE CASCADES...WITH DECREASING BUT STILL WIDESPREAD
AMOUNTS SPREADING FURTHER INLAND.

ROTH/SCHICHTEL

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18Z Tracks & Intensity:

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HURRICANE SANDY DISCUSSION NUMBER 18
NWS NATIONAL HURRICANE CENTER MIAMI FL AL182012
500 PM EDT FRI OCT 26 2012

THE LOW-LEVEL CENTER OF SANDY REMAINS EXPOSED TO THE SOUTH OF THE
MAIN AREA OF DEEP CONVECTION AS STRONG SHEAR CONTINUES TO INFLUENCE
THE SYSTEM. THE LAST RECONNAISSANCE MISSION INTO THE TROPICAL
CYCLONE SUGGESTED THAT THE INTENSITY MAY BE DROPPING BELOW
HURRICANE STATUS. THE CURRENT WIND SPEED IS HELD AT 65 KT PENDING
THE NEXT AIR FORCE HURRICANE HUNTER MISSION SCHEDULED FOR A 0000
UTC CENTER FIX. THE SHIPS OUTPUT INDICATES THAT THE SHEAR WILL
REMAIN QUITE STRONG FOR THE NEXT DAY OR SO...AND THEREFORE THE NHC
FORECAST INDICATES WEAKENING FOR THE NEXT 36 HOURS OR SO.
THEREAFTER...THE GLOBAL MODELS SHOW DEEPENING OF THE CYCLONE
PRESUMABLE DUE TO BAROCLINIC FORCING. THIS IS ALSO INDICATED IN
THE OFFICIAL INTENSITY FOREACST. THE GLOBAL MODELS ALSO SUGGEST
THAT SANDY COULD TRANSITION INTO A FULLY EXTRATROPICAL CYCLONE IN 3
TO 4 DAYS.

THE MOTION CONTINUES TO BE RATHER SLOW AND...IN FACT...RECENT
VISIBLE IMAGES SUGGEST LITTLE SHORT-TERM MOVEMENT OF THE CENTER.
HOWEVER A MORE REPRESENTATIVE ESTIMATE OF THE MOTION IS NEAR 360/6.
AFTER SANDY ESCAPES THE INFLUENCE OF A MID- TO UPPER-LEVEL LOW TO
ITS WEST...THE CYCLONE SHOULD MOVE NORTH-NORTHEASTWARD TO
NORTHEASTWARD WITH SOME INCREASE IN FORWARD SPEED. BY AROUND 72
HOURS...A NEGATIVELY-TILTED SHORTWAVE TROUGH NEAR THE U.S. EAST
COAST AND A RIDGE OVER EXTREME EASTERN CANADA SHOULD CAUSE SANDY TO
TURN TOWARD THE NORTHWEST AND WEST-NORTHWEST TOWARD AND OVER THE
U.S. COAST. INTERESTS ARE REMINDED NOT TO FOCUS ON THE EXACT TRACK
OF THIS SYSTEM SINCE SIGNIFICANT IMPACTS WILL EXTEND WELL AWAY FROM
THE LOCATION OF THE CENTER.

FORECAST POSITIONS AND MAX WINDS

INIT 26/2100Z 27.3N 77.1W 65 KT 75 MPH
12H 27/0600Z 28.3N 77.0W 60 KT 70 MPH
24H 27/1800Z 29.7N 76.1W 55 KT 65 MPH
36H 28/0600Z 31.3N 74.3W 55 KT 65 MPH
48H 28/1800Z 33.1N 72.6W 65 KT 75 MPH
72H 29/1800Z 37.0N 71.5W 70 KT 80 MPH
96H 30/1800Z 39.5N 76.5W 55 KT 65 MPH...POST-TROP/EXTRATROP
120H 31/1800Z 41.0N 77.0W 40 KT 45 MPH...POST-TROP/EXTRATROP

$$
FORECASTER PASCH

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Morning e-mail from Jeff:

Historic storm system heading for the mid Atlantic and NE US.

Potentially life threatening destructive storm surge event for the New Jersey and New York coasts.

Discussion:
The transition of Sandy from a pure tropical cyclone toward more of mid-latitude cyclone has begun. Sandy is still located near the northern Bahamas this morning, but satellite and radar images along with recon data suggest that the system has made the expected turn toward the NNE and this motion should continue with an increase in forward speed. Aircraft data also shows the wind field is greatly expanding with TS force winds extending outward 435 miles from the center with the highest winds located across the western and northwestern flank of the circulation where sporadic deep convection is found.

Across the north Atlantic and the US, the upper air pattern continues to “block” with massive high pressure building over eastern Canada and a strong trough (our cold front) pressing into the eastern US. A shortwave over the western states this morning will swing through the base of the main trough and tilt it from SE to NW over the SE and mid Atlantic starting tomorrow. Sandy will become captured by this titling and instead of pushed out to sea, make a hard left turn (NW) back toward the US mid-Atlantic and NE US coast between the trough to her SW and the blocking high to her NE. Global guidance is in very good agreement on this pattern and in fact has very little spread in the track solution given the complex interactions that will be in place. Models show Sandy moving NW to WNW toward the New Jersey coast and making landfall Monday night or Tuesday morning and then slowing down as she moves inland.

As for intensity, Sandy is gradually taking on more and more mid latitude influences although her center core remains “warm” or tropical. Jet stream phasing with the system is starting to occur with temperature gradient developing on her outer flanks of the large circulation. As Sandy moves northward this process will intensify has the warm Caribbean air mass clashes with a very cold polar air mass resulting in strong baroclinic intensification. Sandy will also be located in the favorable region of the trough and jet stream axis to promote surface deepening of a cyclone. Models continue to advertise “incredibly” low pressures with the ECMWF showing a record 942mb low near landfall on the New Jersey coast which is an astounding 30mb lower than the 1991 Perfect Storm and 6mb lower than anything ever recorded in the NE US.

Given the continued very good model agreement on both track and the forecasted extreme low pressures, confidence is building that an extremely rare powerful storm system will impact the NE and mid-Atlantic coast from Sunday-Thursday.

Impacts:
Major travel disruption is likely as numerous major E coast airports will not be able to sustain operations and this will have ripple effects across the nation. Additionally, widespread power outages and down trees will greatly hamper surface and rail travel across the entire region with widespread and potentially prolonged impacts to commerce.

This will be a long duration multi-day event with prolonged impacts over the entire area from North Carolina to Canada and extending inland into the OH valley affecting some 55-65 million people.

Coastal flooding or storm surge flooding appears to be significant especially for the New Jersey and New York (NYC and Long Island) coasts. The angle of approach this storm will be taking from (SE to NW) strikes the coast at a right angle instead of the usual grazing by of the coast most storms in this region take (SW to NE or parallel to the coast). This direct hit on the coast will drive onshore winds and massive amounts of Atlantic seawater toward the central and northern New Jersey coast and into the “L” shaped New York Bight area of southern New York City and western Long Island (a worst case track for this area, that has never occurred before with this strong of a storm system). The fetch of wind across the entire north Atlantic will drive large waves and surge to the coast and this will last for several high tide cycles. Tides will be at their maximum due to the full moon on Monday. Massive beach erosion is likely with coastal structures experiences significant damage many to the point of total collapse. Seawater inundation will be extensive and widespread and long lasting and in some places potentially record setting. Due to the rare track of this storm, some locations that have never before experienced coastal flooding, may flood with this event.

Winds of 50-60mph with gust to 70-80mph will battered a wide area for 24-48 hours. Expect widespread tree damage and power outages which could rival some of the largest power outages ever in the US. The prolonged nature of the event will result in trees giving way over time as the ground saturates from the heavy rainfall. Winds will be higher in an near tall high rise buildings where funneling will take place. Structure damage will be mainly from trees falling into buildings and to roofs from the wind itself.

Rainfall amounts of 5-8 inches will be common over a very large area with totals of 8-12 inches over New Jersey into southern PA and New York. Isolated amounts of 15 inches are possible as the tropical moisture from Sandy’s air mass crashes into the eastern slopes of the mountains and a stalled frontal boundary. Rainfall of this magnitude over an area of steep terrain will produce life threatening flash flooding and major river flooding.

Ocean seas will be building to staggering heights over the next few days. Already buoys north of the Bahamas have been reporting 30 foot seas, and Wave Watch III guidance is maxed out at 42-48 foot seas over the NW Atlantic Ocean by early next week. The expanding area of strong winds of 50-60mph and the massive fetch of wind all the way from Europe will produce very large swells. Would not be surprised to see reports of wave greater than 50-60 feet over the NW Atlantic. Some of this wave action and energy will be directed toward the US coastline and this will worsen the beach erosion. Large wave setup will also trap water levels near the coast and worsen the coastal flooding threat.

On the extreme SW flank of the storm heavy wet snow will fall over parts of OH and WV with totals of 1-2 feet possible.

Power outages will likely last for 1-2 weeks or longer

Large scale evacuation orders for the New Jersey coast will be underway today with portions of New York also likely requiring evacuation due to the potential for coastal storm surge inundation.

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12Z Tracks & Intensity:

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HURRICANE SANDY DISCUSSION NUMBER 21
NWS NATIONAL HURRICANE CENTER MIAMI FL AL182012
1100 AM EDT SAT OCT 27 2012

NOAA AND AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT HAVE BEEN
SAMPLING THE CYCLONE THIS MORNING. THE AIR FORCE AIRCRAFT FOUND
AN AREA OF HURRICANE-FORCE SFMR WINDS TO THE SOUTHWEST OF
THE CENTER AND A PEAK 850 MB FLIGHT-LEVEL WIND OF 91 KT. A
DROPSONDE RELEASED FROM THE NOAA AIRCRAFT IN THE SAME AREA ALSO
SUPPORTED WINDS TO HURRICANE FORCE. THE AIR FORCE AIRCRAFT ALSO
REPORTED A MINIMUM PRESSURE OF AROUND 956 MB FROM A DROPSONDE
AROUND 1200 UTC...BUT THE PRESSURE IS UP A COUPLE OF MILLIBARS ON
THE LATEST FIX. BASED ON THE AIRCRAFT DATA...THE INTENSITY WAS
INCREASED ON THE 8 AM INTERMEDIATE ADVISORY AND SANDY IS ONCE AGAIN
A 65-KT HURRICANE. WHILE SANDY COULD WEAKEN SLIGHTLY DURING THE
NEXT 12 TO 24 HOURS...THE NHC FORECAST KEEPS THE CYCLONE AT
HURRICANE STRENGTH. THE GLOBAL MODELS INDICATE THAT THE CYCLONE
COULD INTENSIFY AS IT INTERACTS WITH A STRONG SHORTWAVE TROUGH
MOVING INTO THE EASTERN UNITED STATES BY LATE SUNDAY...AND THE
OFFICIAL FORECAST SHOWS A PEAK INTENSITY SLIGHTLY HIGHER THAN
THE PREPVIOUS FORECAST. THE CYCLONE SHOULD STEADILY WEAKEN
AFTER LANDFALL.

ALTHOUGH THE MOST RECENT AIRCRAFT FIX SHOWS THAT THE HURRICANE HAS
MADE A JOG TO THE EAST DURING THE PAST COUPLE OF HOURS...THE LONGER
TERM MOTION YIELDS AN INTIAL MOTION OF 030/8 KT. THE TRACK
GUIDANCE IS IN GOOD AGREEMENT DURING THE FIRST 36 TO 48 HOURS.
AFTER THAT TIME...THERE ARE SOME DIFFERENCES AS TO HOW SHARP A
WESTWARD TURN THE CYCLONE MAKES BEFORE REACHING THE EAST COAST OF
THE UNITED STATES. SOME OF THE GUIDANCE...SUCH AS THE GFS...
SUGGESTS THAT THERE WILL BE A CONTINUED NORTHWARD MOTION AFTER 48
HOURS AND THEN A VERY HARD TURN TO THE WEST...MEANING THAT SANDY
WOULD LIKELY COME ASHORE MOVING FROM EAST TO WEST...RATHER THAN
FROM SOUTHEAST TO NORTHWEST AS SUGGESTED BY DRAWING A STRAIGHT LINE
BETWEEN THE 48 AND 72 HOUR FORECAST POINTS. HAVING SAID THAT...IT
IS STILL TO SOON TO FOCUS ON THE EXACT TRACK OF THE CENTER...BOTH
BECAUSE OF FORECAST UNCERTAINTY AND BECAUSE THE IMPACTS ARE GOING
TO COVER SUCH A LARGE AREA AWAY FROM THE CENTER.

NOTE THAT WIND HAZARDS FOR SANDY NORTH OF THE TROPICAL STORM WARNING
AREA ARE BEING HANDLED BY HIGH WIND...STORM...AND GALE WATCHES AND
WARNINGS ISSUED BY LOCAL NATIONAL WEATHER SERVICE OFFICES. GALE
CONDITIONS ARE LIKELY TO FIRST REACH THE MID-ATLANTIC COAST BY LATE
SUNDAY.

FORECAST POSITIONS AND MAX WINDS

INIT 27/1500Z 29.0N 76.0W 65 KT 75 MPH
12H 28/0000Z 30.4N 75.0W 65 KT 75 MPH
24H 28/1200Z 32.2N 73.4W 65 KT 75 MPH
36H 29/0000Z 34.2N 72.1W 65 KT 75 MPH
48H 29/1200Z 36.4N 72.0W 70 KT 80 MPH
72H 30/1200Z 39.8N 77.0W 55 KT 65 MPH...POST-TROP/EXTRATROP
96H 31/1200Z 40.8N 77.5W 40 KT 45 MPH...POST-TROP/EXTRATROP
120H 01/1200Z 43.8N 76.8W 35 KT 40 MPH...POST-TROP/EXTRATROP

$$
FORECASTER BROWN

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12Z GFS msl pressure and surface wind gusts:

[Andrew]

Another update from Jeff:

Historic storm system heading for the mid Atlantic and NE US.

Potentially life threatening destructive storm surge event for the New Jersey and New York coasts.

Discussion:
The transition of Sandy from a pure tropical cyclone toward more of mid-latitude cyclone has begun. Sandy is still located near the northern Bahamas this morning, but satellite and radar images along with recon data suggest that the system has made the expected turn toward the NNE and this motion should continue with an increase in forward speed. Aircraft data also shows the wind field is greatly expanding with TS force winds extending outward 435 miles from the center with the highest winds located across the western and northwestern flank of the circulation where sporadic deep convection is found.

Across the north Atlantic and the US, the upper air pattern continues to “block” with massive high pressure building over eastern Canada and a strong trough (our cold front) pressing into the eastern US. A shortwave over the western states this morning will swing through the base of the main trough and tilt it from SE to NW over the SE and mid Atlantic starting tomorrow. Sandy will become captured by this titling and instead of pushed out to sea, make a hard left turn (NW) back toward the US mid-Atlantic and NE US coast between the trough to her SW and the blocking high to her NE. Global guidance is in very good agreement on this pattern and in fact has very little spread in the track solution given the complex interactions that will be in place. Models show Sandy moving NW to WNW toward the New Jersey coast and making landfall Monday night or Tuesday morning and then slowing down as she moves inland.

As for intensity, Sandy is gradually taking on more and more mid latitude influences although her center core remains “warm” or tropical. Jet stream phasing with the system is starting to occur with temperature gradient developing on her outer flanks of the large circulation. As Sandy moves northward this process will intensify has the warm Caribbean air mass clashes with a very cold polar air mass resulting in strong baroclinic intensification. Sandy will also be located in the favorable region of the trough and jet stream axis to promote surface deepening of a cyclone. Models continue to advertise “incredibly” low pressures with the ECMWF showing a record 942mb low near landfall on the New Jersey coast which is an astounding 30mb lower than the 1991 Perfect Storm and 6mb lower than anything ever recorded in the NE US.

Given the continued very good model agreement on both track and the forecasted extreme low pressures, confidence is building that an extremely rare powerful storm system will impact the NE and mid-Atlantic coast from Sunday-Thursday.

Impacts:
Major travel disruption is likely as numerous major E coast airports will not be able to sustain operations and this will have ripple effects across the nation. Additionally, widespread power outages and down trees will greatly hamper surface and rail travel across the entire region with widespread and potentially prolonged impacts to commerce.

This will be a long duration multi-day event with prolonged impacts over the entire area from North Carolina to Canada and extending inland into the OH valley affecting some 55-65 million people.

Coastal flooding or storm surge flooding appears to be significant especially for the New Jersey and New York (NYC and Long Island) coasts. The angle of approach this storm will be taking from (SE to NW) strikes the coast at a right angle instead of the usual grazing by of the coast most storms in this region take (SW to NE or parallel to the coast). This direct hit on the coast will drive onshore winds and massive amounts of Atlantic seawater toward the central and northern New Jersey coast and into the “L” shaped New York Bight area of southern New York City and western Long Island (a worst case track for this area, that has never occurred before with this strong of a storm system). The fetch of wind across the entire north Atlantic will drive large waves and surge to the coast and this will last for several high tide cycles. Tides will be at their maximum due to the full moon on Monday. Massive beach erosion is likely with coastal structures experiences significant damage many to the point of total collapse. Seawater inundation will be extensive and widespread and long lasting and in some places potentially record setting. Due to the rare track of this storm, some locations that have never before experienced coastal flooding, may flood with this event.

Winds of 50-60mph with gust to 70-80mph will battered a wide area for 24-48 hours. Expect widespread tree damage and power outages which could rival some of the largest power outages ever in the US. The prolonged nature of the event will result in trees giving way over time as the ground saturates from the heavy rainfall. Winds will be higher in an near tall high rise buildings where funneling will take place. Structure damage will be mainly from trees falling into buildings and to roofs from the wind itself.

Rainfall amounts of 5-8 inches will be common over a very large area with totals of 8-12 inches over New Jersey into southern PA and New York. Isolated amounts of 15 inches are possible as the tropical moisture from Sandy’s air mass crashes into the eastern slopes of the mountains and a stalled frontal boundary. Rainfall of this magnitude over an area of steep terrain will produce life threatening flash flooding and major river flooding.

Ocean seas will be building to staggering heights over the next few days. Already buoys north of the Bahamas have been reporting 30 foot seas, and Wave Watch III guidance is maxed out at 42-48 foot seas over the NW Atlantic Ocean by early next week. The expanding area of strong winds of 50-60mph and the massive fetch of wind all the way from Europe will produce very large swells. Would not be surprised to see reports of wave greater than 50-60 feet over the NW Atlantic. Some of this wave action and energy will be directed toward the US coastline and this will worsen the beach erosion. Large wave setup will also trap water levels near the coast and worsen the coastal flooding threat.

On the extreme SW flank of the storm heavy wet snow will fall over parts of OH and WV with totals of 1-2 feet possible.

Power outages will likely last for 1-2 weeks or longer

Large scale evacuation orders for the New Jersey coast will be underway today with portions of New York also likely requiring evacuation due to the potential for coastal storm surge inundation.

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18Z Tracks & Intensity:

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10272012_1955_goes13_x_vis2km_18LSANDY_65kts-961mb-298N-756W_97pc.jpg

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HURRICANE SANDY DISCUSSION NUMBER 22
NWS NATIONAL HURRICANE CENTER MIAMI FL AL182012
500 PM EDT SAT OCT 27 2012

FIRST A NOTE ON THE NWS WARNING STRATEGY FOR SANDY. IN ORDER TO
AVOID THE RISK OF A HIGHLY DISRUPTIVE CHANGE FROM TROPICAL TO
NON-TROPICAL WARNINGS WHEN SANDY BECOMES POST-TROPICAL...THE WIND
HAZARD NORTH OF THE TROPICAL STORM WARNING AREA WILL CONTINUE TO BE
CONVEYED THROUGH HIGH WIND WATCHES AND WARNINGS WARNINGS ISSUED BY
LOCAL NATIONAL WEATHER SERVICE OFFICES.

SATELLITE IMAGERY SHOWS THAT DRY MID-LEVEL AIR HAS WRAPPED AROUND
THE WESTERN AND SOUTHWESTERN PORTIONS OF THE CIRCULATION...WHICH MAY
HAVE CAUSED THE RECENT WEAKENING OF THE INNER-CORE CONVECTION. THE
AIR FORCE AIRCRAFT MADE ITS FINAL PASS THROUGH SANDY AROUND 1800
UTC AND REPORTED A MINIMUM PRESSURE OF AROUND 961 MB. WIND DATA
FROM THE AIRCRAFT AND A RECENT DROPSONDE FROM THE NOAA G-IV AIRCRAFT
CONDUCTING A SURVEILLANCE MISSION AROUND SANDY SUPPORT MAINTAINING
THE INITIAL INTENSITY OF 65 KT.

THERE HAS BEEN NO CHANGE TO THE TRACK OR INTENSITY FORECAST
REASONING. SANDY IS LIKELY TO REMAIN AT OR NEAR HURRICANE STRENGTH
DURING THE NEXT DAY OR SO. AFTER THAT TIME...THE CYCLONE WILL
INTERACT WITH A STRONG SHORTWAVE TROUGH AND ASSOCIATED COLD FRONT
MOVING INTO THE EASTERN UNITED STATES. AS THIS OCCURS...THE GLOBAL
MODELS INDICATE THAT THE CYCLONE WILL STRENGTHEN DUE TO BAROCLINIC
PROCESSES...AND THE OFFICIAL FORECAST CALLS FOR SOME INCREASE IN
INTENSITY IN A COUPLE OF DAYS. BY 48 HOURS...THE GFS AND ECMWF
MODELS SHOW COLDER AIR WRAPPING AROUND THE SOUTH PORTION OF THE
CIRCULATION AND SANDY IS LIKELY TO HAVE COMPLETED ITS
TRANSFORMATION TO A VIGOROUS EXTRATROPICAL CYCLONE AT THAT TIME.
AFTER LANDFALL...THE CYCLONE IS FORECAST TO STEADILY WEAKEN.

THE GFS AND ECMWF MODELS ARE IN BETTER AGREEMENT THIS AFTERNOON...
WITH THE ECMWF A LITTLE NORTH OF ITS PREVIOUS TRACK. SANDY IS
FORECAST TO MOVE NORTHEASTWARD DURING THE NEXT 24 HOURS...THEN TURN
NORTHWARD AHEAD OF THE APPROACHING MID-LATITUDE TROUGH. THE CYCLONE
SHOULD TURN NORTHWESTWARD...THEN WESTWARD AS IT ROTATES AROUND THE
EASTERN SIDE OF THE DEEPENING TROUGH. ONCE AGAIN...DRAWING A
STRAIGHT LINE BETWEEN THE 48- AND 72-HOUR FORECAST POINTS DOES NOT
QUITE DEPICT HOW CLOSE THE CENTER IS EXPECTED TO COME TO LONG
ISLAND. HAVING SAID THAT...IT IS STILL TOO SOON TO FOCUS ON THE
EXACT TRACK...BOTH BECAUSE OF FORECAST UNCERTAINTY AND BECAUSE THE
IMPACTS ARE GOING TO COVER SUCH A LARGE AREA AWAY FROM THE CENTER.

FORECAST POSITIONS AND MAX WINDS

INIT 27/2100Z 30.2N 75.2W 65 KT 75 MPH
12H 28/0600Z 31.5N 73.8W 65 KT 75 MPH
24H 28/1800Z 33.4N 72.1W 65 KT 75 MPH
36H 29/0600Z 35.4N 71.1W 65 KT 75 MPH
48H 29/1800Z 37.9N 72.0W 70 KT 80 MPH...POST-TROP/EXTRATROP
72H 30/1800Z 40.0N 77.0W 50 KT 60 MPH...POST-TROP/EXTRATROP
96H 31/1800Z 42.5N 76.5W 35 KT 40 MPH...POST-TROP/EXTRATROP
120H 01/1800Z 45.5N 74.5W 30 KT 35 MPH...POST-TROP/EXTRATROP

$$
FORECASTER BROWN

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Code: Select all

Hurricane Sandy’s Transition to a Post-Tropical Cyclone
The National Hurricane Center (NHC) issues advisories, forecasts, and warnings on tropical
cyclones - the generic term for hurricanes, tropical storms, and tropical depressions. Sometime
prior to making landfall, Hurricane Sandy is expected to lose its characteristics as a tropical
cyclone and take on the structure of a wintertime low-pressure area. Because the National
Hurricane Center only issues advisories on tropical cyclones, there will be changes in the flow of
information coming out of the NWS when this transition occurs.
The primary difference between a tropical cyclone and a wintertime cyclone is the energy
source. Tropical cyclones extract heat from the ocean and grow by releasing that heat in the
atmosphere near the storm center. Wintertime cyclones (also called extratropical or frontal
lows), on the other hand, get most of their energy from temperature contrasts in the
atmosphere, and this energy usually gets distributed over larger areas. Because of these
differences, tropical cyclones tend to have more compact wind fields, tend to be more
symmetric, and have a well-defined inner core of strong winds. Wintertime lows have strong
temperature contrasts or fronts attached to them, have a broader wind field, and more complex
distributions of rain or snow.
The official NWS term for a tropical cyclone that has evolved into something else is “Posttropical
cyclone”, where the post in post-tropical simply means after. Thus, once Sandy loses
its tropical cyclone status it will be known as “Post-tropical Cyclone Sandy” in NWS products.
Some aspects of this transition are already occurring, and NWS forecasts of storm impacts are
based on this expected evolution. Regardless of when this transition formally occurs, Sandy is
expected to bring significant wind, surge, rainfall and inland flooding hazards over an extremely
large area, and snowfall to more limited areas.
Because Sandy is expected to make this transition before reaching the coast, the NWS has
been using non-tropical wind watches and warnings, issued by local NWS Weather Forecast
Offices (WFOs), to communicate the wind threat posed by Sandy in the Mid-Atlantic States and
New England. (This is why NHC’s tropical storm warnings extend only into North Carolina.)
The NWS plans to continue using non-tropical watches and warnings issued by local offices in
the Mid-Atlantic States and northward throughout this event. By using non-tropical warnings in
these areas from the start, we avoid or minimize the significant confusion that could occur if the
warning suite changed from tropical to non-tropical in the middle of the event.
When NHC determines that Sandy has become post-tropical, NHC advisory products will cease.
The NWS will ensure a continuing flow of information through the following:
• NWS WFOs will continue, as they already are, to provide detailed information on local
impacts through their regular products. The non-tropical watches and warnings that are
in place at the time will remain in effect through the transition.
• The Hydrometeorological Prediction Center (HPC) will take over issuance of Public
Advisories on Post-tropical Cyclone Sandy every six hours, under the same product
headers as NHC Public Advisories. The HPC Public Advisories will include similar
information to the NHC Public Advisory on the current location and strength of the storm,
as well as information on the various hazards (wind, surge, and precipitation). The HPC
Public Advisories will also contain a track forecast.
• Assuming Sandy becomes post-tropical while its center is still over water, the Ocean
Prediction Center (OPC) will discuss the storm in its Marine Weather Discussion. The
Marine Weather Discussion will also include the same track forecast contained in the
HPC Public Advisory.
• OPC will host a web page for storm support. This page will contain a graphic showing
the forecast track of the storm and other information specific to Sandy.
• While NHC's web page will no longer display forecast information about Sandy once
responsibility is transferred to other offices, the NHC web page (www.hurricanes.gov)
will prominently display a collection of links to the other offices’ products, such as HPC’s
Public Advisories and precipitation forecast graphics, OPC’s support page and their
Marine Weather Discussion, storm surge information from NOAA’s Meteorological
Development Laboratory, current water levels data, and regional weather graphics from
weather.gov.
• NHC will continue to lead the coordination between NHC, HPC, OPC, and the WFOs
throughout the event to ensure consistency of information throughout the NWS.
• NHC will continue to lead the NWS’s coordination with FEMA.
In the event Sandy remains a tropical cyclone through landfall, NHC advisories and products
would of course continue. There would be no transition, however, from non-tropical wind
warnings issued by the WFOs back to Tropical Storm or Hurricane Warnings issued by
NHC, since both sets of warnings describe the same wind hazard.
Contact: NHC Public Affairs nhc.public.affairs@noaa.gov
October 27, 2012

http://www.nhc.noaa.gov/news/20121027_p ... sition.pdf

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12Z Tracks & Intensity:

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HURRICANE SANDY DISCUSSION NUMBER 25
NWS NATIONAL HURRICANE CENTER MIAMI FL AL182012
1100 AM EDT SUN OCT 28 2012

DATA FROM NOAA AND AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT
MISSIONS THIS MORNING HAVE REVEALED NO SIGNIFICANT CHANGES TO THE
INTENSITY OR OVERALL STRUCTURE OF SANDY...EVEN THOUGH SATELLITE
IMAGERY INDICATES A BANDING EYE FEATURE IS TRYING TO FORM AND THE
CENTRAL PRESSURE HAS BENE AS LOW AS 951 MB. THE AIRCRAFT DATA...
ALONG WITH DATA FROM SHIPS...BUOYS...AND SURFACE OBSERVATION SITES
INDICATE...HOWEVER...THAT THE WIND FIELD HAS CONTINUED TO EXPAND.
HURRICANE-FORCE WINDS NOW EXTEND OUT TO ABOUT 150 N MI TO THE
SOUTHWEST...AND THE 50-KT WIND RADII HAVE ALSO INCREASED TO ABOUT
200 N MI IN THAT SAME QUADRANT. BASED ON THE FLIGHT-LEVEL AND
SFMR-ADJUSTED SURFACE WINDS...THE INITIAL INTENSITY IS BEING
MAINTAINED AT 65 KT.

THERE HAVE BEEN SOME TRACK WOBBLES BUT THE INITIAL MOTION ESTIMATE
IS 045/12 KT. THERE REMAINS NO SIGNIFICANT CHANGE TO THE PREVIOUS
FORECAST TRACK OR REASONING. SANDY WILL CONTINUE TO INTERACT WITH A
STRONG NEGATIVELY TILTED SHORTWAVE TROUGH LOCATED OVER THE
TENNESSEE VALLEY THAT WILL CONTINUE TO MOVED EASTWARD TOWARD THE
U.S. EAST COAST OVER THE NEXT 48 HOURS. AS THE TROUGH UNDERCUTS
SANDY TO ITS SOUTH...THE HURRICANE IS EXPECTED TO LIFT
NORTHEASTWARD AND THEN NORTHWARD OVER THE NEXT 24 HOURS...FOLLOWED
BY A TURN TO THE NORTHWEST AND POSSIBLY WEST-NORTHWEST UNTIL
LANDFALL OCCURS WITHIN 48 HOURS OR SO. THE OFFICIAL FORECAST TRACK
IS SIMILAR TO THE PREVIOUS ADVISORY TRACK AND LIES DOWN THE MIDDLE
OF THE TIGHTLY PACKED GLOBAL AND REGIONAL MODEL GUIDANCE.

THE VERTICAL SHEAR IS FORECAST TO DECREASE IN THE 12 TO 36-HOUR
PERIOD AND SANDY IS EXPECTED MAINTAIN A SMALL AREA OF DEEP
CONVECTION NEAR THE CENTER WHILE THE HURRICANE REMAINS OVER SSTS
GREATER THAN 25C. AS A RESULT...THERE IS STILL SOME POTENTIAL FOR
SANDY TO INTENSIFY SLIGHTLY AS A TROPICAL CYCLONE...ESPECIALLY WHEN
IT WILL BE TRAVERSING THE WARM GULFSTREAM TONIGHT. BY 36 HOURS...
THE GLOBAL MODELS SHOW SOME DEEPENING OF THE CYCLONE...WHICH IS
UNDOUBTEDLY DUE TO STRONG BAROCLINIC FORCING...AND A TRANSITION TO
AN EXTRATROPICAL CYCLONE IS EXPECTED PRIOR TO LANDFALL. IT IS
IMPORTANT TO NOTE THAT THIS TRANSITION WILL NOT DIMINISH THE
OVERALL IMPACTS OF THIS DANGEROUS WEATHER SYSTEM. AFTER LANDFALL...
THE GLOBAL MODELS...AND THE OFFICIAL INTENSITY FORECAST...INDICATE
RAPID WEAKENING IS EXPECTED.

AS NOTED IN PREVIOUS ADVISORIES...TO AVOID A HIGHLY DISRUPTIVE
CHANGE FROM TROPICAL TO NON-TROPICAL WARNINGS WHEN SANDY BECOMES
POST-TROPICAL...THE WIND HAZARD NORTH OF THE TROPICAL STORM WARNING
AREA WILL CONTINUE TO BE CONVEYED THROUGH HIGH WIND WATCHES AND
WARNINGS ISSUED BY LOCAL NATIONAL WEATHER SERVICE OFFICES.

FORECAST POSITIONS AND MAX WINDS

INIT 28/1500Z 32.5N 72.6W 65 KT 75 MPH
12H 29/0000Z 34.0N 71.3W 65 KT 75 MPH
24H 29/1200Z 36.4N 70.7W 70 KT 80 MPH
36H 30/0000Z 38.7N 72.9W 70 KT 80 MPH
48H 30/1200Z 40.1N 76.3W 60 KT 70 MPH...POST-TROP/EXTRATROP
72H 31/1200Z 41.3N 77.2W 40 KT 45 MPH...POST-TROP/EXTRATROP
96H 01/1200Z 44.5N 76.8W 30 KT 35 MPH...POST-TROP/EXTRATROP
120H 02/1200Z 46.6N 73.4W 25 KT 30 MPH...POST-TROP/EXTRATROP

$$
FORECASTER STEWART