2012-10-30: Discussion of Sandy as a hurricane has now concluded.

2012-10-29: Update: [from the 5 PM NHC discussion] THERE HAS BEEN NO SIGNIFICANT CHANGE TO THE POST-LANDFALL TRACK OR INTENSITY FORECAST. DESPITE THE RAPID FORWARD MOTION TODAY…SANDY
IS EXPECTED TO STALL INLAND TOMORROW. THIS…COUPLED WITH THE VERY
LARGE SIZE OF THE SYSTEM…WILL MEAN THAT CONDITIONS WILL BE SLOW
TO IMPROVE IN THE AFFECTED AREAS. STRONG WINDS WILL PERSIST ALONG
THE COAST AND SPREAD FARTHER INLAND THROUGH AT LEAST TUESDAY. OF
PARTICULAR CONCERN ARE THE UPPER FLOORS OF HIGH-RISE BUILDINGS…AS
RECONNAISSANCE DATA INDICATE THAT WINDS JUST A FEW HUNDRED FEET IN
ALTITUDE ARE VERY MUCH STRONGER THAN THOSE NEAR THE SURFACE. EVEN
AS SANDY WEAKENS…HEAVY RAINS WILL PERSIST OVER A LARGE
AREA…POSING A VERY SIGNIFICANT INLAND FLOOD RISK.

2012-10-29: [from the 5 AM NHC discussion] CENTER FIXES INDICATE THAT SANDY IS NOW MOVING NORTHWARD OR ABOUT 360/13…AS IT BEGINS TO ROTATE AROUND A MID- TO UPPER-LEVEL CYCLONE OVER THE SOUTHEASTERN UNITED STATES. AS IT MOVES BETWEEN THE CYCLONE AND A HIGHLY ANOMALOUS MID-TROPOSPHERIC RIDGE NEAR ATLANTIC CANADA…SANDY SHOULD TURN NORTHWESTWARD AND WEST-NORTHWESTWARD WITH SOME FURTHER INCREASE IN FORWARD SPEED.
THIS TRACK SHOULD RESULT IN THE CENTER MAKING LANDFALL IN THE MID-ATLANTIC STATES THIS EVENING OR TONIGHT. AFTER LANDFALL…THE DYNAMICAL GUIDANCE SHOWS A SIGNIFICANT SLOWING OF FORWARD SPEED AS THE SYSTEM MERGES WITH THE MID- TO UPPER-LEVEL CYCLONE.

2012-10-28: Update: Sandy is expected to make landfall over the upper Delmarva Penisula by Tuesday morning as a winter-characteristic extra-tropical cyclone. Conversion to a an extra-tropical storm just before landfall is not expected to diminish the intensity, and in fact, increase it some. Weakening is expected once on land. High elevations in the Appalachia and Great Smokey Mountains may see precipitation as snow with amounts measured in feet. Hurricane-force wind radius from centre is currently measured at 175 miles and tropical storm winds out beyond 500 miles.

2012-10-28: Sandy is expected to continue to hover around the bottom end of the category one boundary over the next two days until it reaches landfall, projected to be over the Delmarva Peninsula, just north of Chesapeake. The hurricane strength wind radius remains very large, +/-165km from the storm cemtre. Potential still exists for transformation to a tropical cyclone, but the forecast expectation is for transformation to an extra-tropical cyclone within 48 hours, with rapid weakening over landfall. This weakening was beginning to be evident in some of the longer range forecast models last night. It remains important to note, however, while overall intensity may fall, the extremely large area of the storm, coupled with a strong low pressure trough over the US northwest and south central and eastern Canada, and a blocking high over extreme eastern Canada may increase the storm duration over the lower Great Lakes Basin and St. Lawrence Valley. This may result in greater than average rainfall over the duration of the storm. The pressure gradient of Sandy remains deep, 960 mb (28.35 in), which will hold wind speeds high until significant pressure infill occurs.

[Ed. note: Daily entries prior to the 28th have been moved to the 2012 archive in Atlantic and Eastern Pacific Hurricane Activity 2012 post.]

[For general monitoring of the Western Atlantic and Eastern Pacific hurricane season, follow our post at Atlantic and eastern Pacific Hurricane activity 2012)]

Please note, the charts are dynamic, and will change as the forecast models run.

Animation of the future path of Sandy to 2AM EDT Tuesday. Weatherbell Models

Click the chart image below to go to the most recent advisory.

Fronts/Pressure forecast from NOAA, forecast 48 hours out from now. The tight pressure rings of Sandy are the concern – the more and closer they are, the stronger the wind. Sandy’s gradient is indicative of very strong winds.

Model Guidance for Hurricane Sandy, from Weatherbell Models

20-memeber ensemble guidance for Hurricane Sandy, Weatherbell Models. The ensemble forecast is a “best fit” aggregate of several models combined.

Visible GOES East Satellite Image. Click for loop.

AVN colour enhanced satellite image. Click for loop.

WTNT33 KNHC 300251
TCPAT3

BULLETIN
POST-TROPICAL CYCLONE SANDY ADVISORY NUMBER 31
NWS NATIONAL HURRICANE CENTER MIAMI FL AL182012
1100 PM EDT MON OCT 29 2012

…SANDY STILL PACKING HURRICANE-FORCE WINDS…
…NEXT PUBLIC ADVISORY TO BE ISSUED BY THE HYDROMETEOROLOGICAL
PREDICTION CENTER…

SUMMARY OF 1100 PM EDT…0300 UTC…INFORMATION
———————————————–
LOCATION…39.8N 75.4W
ABOUT 10 MI…15 KM SW OF PHILADELPHIA PENSYLVANIA
MAXIMUM SUSTAINED WINDS…75 MPH…120 KM/H
PRESENT MOVEMENT…NW OR 305 DEGREES AT 18 MPH…30 KM/H
MINIMUM CENTRAL PRESSURE…952 MB…28.11 INCHES

WATCHES AND WARNINGS
——————–
CHANGES WITH THIS ADVISORY…

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT…

THERE ARE NO COASTAL TROPICAL CYCLONE WARNINGS IN EFFECT.

HOWEVER…THERE ARE NON-TROPICAL HIGH-WIND WARNINGS IN EFFECT FOR
PORTIONS OF THE MID-ATLANTIC AND NEW ENGLAND STATES. PLEASE SEE
STATEMENTS FROM LOCAL NATIONAL WEATHER SERVICE FORECAST OFFICES.

HURRICANE-FORCE WIND GUSTS ARE POSSIBLE ALONG PORTIONS OF THE COAST
BETWEEN CHINCOTEAGUE VIRGINIA AND CHATHAM MASSACHUSETTS DURING THE
NEXT FEW HOURS. THIS INCLUDES THE TIDAL POTOMAC FROM COBB ISLAND
TO SMITH POINT…THE MIDDLE AND UPPER CHESAPEAKE BAY…DELAWARE
BAY…AND THE COASTS OF THE NORTHERN DELMARVA PENINSULA…NEW
JERSEY…THE NEW YORK CITY AREA…LONG ISLAND…CONNECTICUT…AND
RHODE ISLAND.

TROPICAL-STORM-FORCE WINDS ARE EXPECTED TO CONTINUE NORTH OF CHATHAM
THROUGH MUCH OF NEW ENGLAND…AND OVER THE LOWER CHESAPEAKE BAY…
AND SOUTH OF CHINCOTEAGUE TO EXTREME NORTHEASTERN NORTH CAROLINA.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA…INCLUDING POSSIBLE
INLAND WATCHES AND WARNINGS…PLEASE MONITOR PRODUCTS ISSUED BY
YOUR LOCAL NATIONAL WEATHER SERVICE FORECAST OFFICE.

DISCUSSION AND 48-HOUR OUTLOOK
——————————
AT 1100 PM EDT…0300 UTC…THE CENTER OF POST-TROPICAL CYCLONE
SANDY WAS LOCATED NEAR LATITUDE 39.8 NORTH…LONGITUDE 75.4 WEST.
THE POST-TROPICAL CYCLONE IS MOVING TOWARD THE NORTHWEST AT 18
MPH…30 KM/H. A WEST-NORTHWEST TO NORTHWEST MOTION WITH SOME
REDUCTION IN FORWARD SPEED IS EXPECTED THROUGH TUESDAY. A TURN
TOWARD THE NORTH AND NORTHEAST IS FORECAST TUESDAY NIGHT. ON THE
FORECAST TRACK…THE CENTER OF SANDY IS EXPECTED TO MOVE ACROSS
PENNSYLVANIA DURING THE NEXT DAY OR SO…THEN MOVE INTO WESTERN NEW
YORK TUESDAY NIGHT.

MAXIMUM SUSTAINED WINDS ARE NEAR 75 MPH…120 KM/H…WITH HIGHER
GUSTS. THE STRONGEST WINDS ARE OCCURRING OVER WATER TO THE EAST OF
THE CENTER. STEADY WEAKENING IS FORECAST DURING THE NEXT 48 HOURS.

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 90 MILES…150 KM…TO
THE EAST OF THE CENTER. TROPICAL STORM FORCE WINDS EXTEND OUTWARD
UP TO 485 MILES…780 KM FROM THE CENTER. A SUSTAINED WIND OF 56
MPH…WITH A GUST TO 71 MPH WAS RECENTLY REPORTED AT LAGUARDIA
AIRPORT IN NEW YORK. A TEXAS TECH UNIVERSITY AUTOMATED OBSERVING
SITE HAS REPORTED SUSTAINED WINDS OF 50 MPH…WITH A GUST TO 67
MPH…ALONG THE COAST OF NORTHERN NEW JERSEY WITHIN THE PAST HOUR.

THE ESTIMATED MINIMUM CENTRAL PRESSURE BASED ON SURFACE DATA IS 952
MB…28.11 INCHES.

HAZARDS AFFECTING LAND
———————-
WIND…TROPICAL-STORM-FORCE WINDS WILL CONTINUE OVER PORTIONS OF THE
MID-ATLANTIC STATES FROM VIRGINIA NORTHWARD THROUGH NEW ENGLAND.
HURRICANE-FORCE WIND GUSTS ARE POSSIBLE ALONG THE COAST OF NEW
JERSEY…NEW YORK…SOUTHERN MASSACHUSETTS AND RHODE ISLAND DURING
THE NEXT FEW HOURS.

IT IS IMPORTANT TO NOTE THAT WINDS AFFECTING THE UPPER FLOORS OF
HIGH-RISE BUILDINGS WILL BE SIGNIFICANTLY STRONGER THAN THOSE NEAR
GROUND LEVEL.

STORM SURGE…THE COMBINATION OF AN EXTREMELY DANGEROUS STORM SURGE
AND THE TIDE WILL CAUSE NORMALLY DRY AREAS NEAR THE COAST TO BE
FLOODED BY RISING WATERS. THE WATER COULD REACH THE FOLLOWING
DEPTHS ABOVE GROUND IF THE PEAK SURGE OCCURS AT THE TIME OF HIGH
TIDE…

NC NORTH OF SURF CITY INCLUDING PAMLICO/ALBEMARLE SOUNDS…2 TO 4 FT
SE VA AND DELMARVA INCLUDING LOWER CHESAPEAKE BAY…2 TO 4 FT
UPPER AND MIDDLE CHESAPEAKE BAY…1 TO 3 FT
LONG ISLAND SOUND…RARITAN BAY…AND NEW YORK HARBOR…6 TO 11 FT
ELSEWHERE FROM OCEAN CITY MD TO THE CT/RI BORDER…4 TO 8 FT
CT/RI BORDER TO THE SOUTH SHORE OF CAPE COD INCLUDING BUZZARDS
BAY AND NARRAGANSETT BAY…3 TO 6 FT
CAPE COD TO THE MA/NH BORDER INCLUDING CAPE COD BAY…2 TO 4 FT
MA/NH BORDER TO THE U.S./CANADA BORDER…1 TO 3 FT

SURGE-RELATED FLOODING DEPENDS ON THE RELATIVE TIMING OF THE SURGE
AND THE TIDAL CYCLE…AND CAN VARY GREATLY OVER SHORT DISTANCES.
GIVEN THE LARGE WIND FIELD ASSOCIATED WITH SANDY…ELEVATED WATER
LEVELS COULD SPAN MULTIPLE TIDE CYCLES RESULTING IN REPEATED AND
EXTENDED PERIODS OF COASTAL AND BAYSIDE FLOODING. IN ADDITION…
ELEVATED WATERS COULD OCCUR FAR REMOVED FROM THE CENTER OF SANDY.
FOR INFORMATION SPECIFIC TO YOUR AREA…PLEASE SEE PRODUCTS ISSUED
BY YOUR LOCAL NATIONAL WEATHER SERVICE OFFICE.

RAINFALL…RAINFALL TOTALS OF 3 TO 6 INCHES ARE EXPECTED OVER FAR
NORTHEASTERN NORTH CAROLINA WITH ISOLATED MAXIMUM TOTALS OF 8
INCHES POSSIBLE. RAINFALL AMOUNTS OF 4 TO 8 INCHES ARE EXPECTED
OVER PORTIONS OF THE MID ATLANTIC STATES…INCLUDING THE DELMARVA
PENINSULA…WITH ISOLATED MAXIMUM AMOUNTS OF 12 INCHES POSSIBLE.
RAINFALL AMOUNTS OF 1 TO 3 INCHES WITH ISOLATED MAXIMUM AMOUNTS OF
5 INCHES ARE POSSIBLE FROM THE SOUTHERN TIER OF NEW YORK STATE
NORTHEASTWARD THROUGH NEW ENGLAND.

SNOWFALL..SNOW ACCUMULATIONS OF 2 TO 3 FEET ARE EXPECTED IN THE
MOUNTAINS OF WEST VIRGINIA WITH LOCALLY HIGHER TOTALS TODAY THROUGH
WEDNESDAY. SNOWFALL OF 1 TO 2 FEET IS EXPECTED IN THE MOUNTAINS OF
SOUTHWESTERN VIRGINIA TO THE KENTUCKY BORDER…WITH 12 TO 18 INCHES
OF SNOW EXPECTED IN THE MOUNTAINS NEAR THE NORTH CAROLINA/TENNESSEE
BORDER AND IN THE MOUNTAINS OF WESTERN MARYLAND.

SURF…DANGEROUS SURF CONDITIONS WILL CONTINUE FROM FLORIDA THROUGH
NEW ENGLAND FOR THE NEXT COUPLE OF DAYS.

NEXT ADVISORY
————-
THIS IS THE LAST PUBLIC ADVISORY ISSUED BY THE NATIONAL HURRICANE CENTER ON SANDY. FUTURE INFORMATION ON THIS SYSTEM CAN BE FOUND IN PUBLIC ADVISORIES ISSUED BY THE HYDROMETEOROLOGICAL PREDICTION CENTER…UNDER AWIPS HEADER TCPAT3 AND WMO HEADER WTNT33 KWNH…BEGINNING AT 500 AM EDT. THESE PUBLIC ADVISORIES WILL ALSO BE AVAILABLE ON THE NHC WEBSITE.

[last public discussion]
WTNT43 KNHC 292157
TCDAT3

HURRICANE SANDY DISCUSSION NUMBER 30…CORRECTED
NWS NATIONAL HURRICANE CENTER MIAMI FL AL182012
500 PM EDT MON OCT 29 2012

THE CONVECTIVE STRUCTURE OF SANDY HAS DETERIORATED TODAY…EVEN AS
THE CENTRAL PRESSURE HAS CONTINUED TO SLOWLY FALL…SUGGESTING THAT
THE CONVECTION IS NO LONGER DRIVING THE BUS. THE INTENSIFICATION
OBSERVED THIS MORNING WAS ASSOCIATED WITH STRONG WINDS OCCURRING TO
THE SOUTHWEST OF THE CENTER…OUTSIDE OF THE CENTRAL CORE…AND WAS
ALMOST CERTAINLY DUE TO BAROCLINIC FORCING. IN ADDITION…AIRCRAFT
DATA INDICATE THAT THERE ARE STRONG TEMPERATURE CONTRASTS VERY NEAR
A MODEST RESIDUAL WARM CORE. WATER VAPOR IMAGERY INDICATES THAT
SANDY IS BECOMING ABSORBED WITHIN A LARGE MID-LATITUDE CYCLONIC
CIRCULATION. ALL OF THESE CONSIDERATIONS LEAD US TO CONCLUDE THAT
THE MOST APPROPRIATE CLASSIFICATION AT ADVISORY TIME IS
EXTRATROPICAL. HOWEVER…FOR CONTINUITY OF SERVICE NHC WILL
CONTINUE TO ISSUE ADVISORIES THROUGH LANDFALL. A POST-STORM
ANALYSIS WILL RE-EXAMINE THE TIMING OF EXTRATROPICAL TRANSITION.

WE ANTICIPATE THAT THE LAST NHC ADVISORY ON SANDY WILL BE ISSUED AT
11 PM EDT TONIGHT. SINCE ALL COASTAL TROPICAL CYCLONE WARNINGS HAVE
BEEN DISCONTINUED…THERE WILL BE NO INTERMEDIATE PUBLIC ADVISORIES
ISSUED BETWEEN NOW AND THE 11 PM NHC ADVISORY. TO PROVIDE A
CONTINUOUS FLOW OF INFORMATION…NHC WILL ISSUE TROPICAL CYCLONE
UPDATES AT 7 PM AND 9 PM EDT…AND AT THE TIME OF LANDFALL. THESE
UPDATES ARE ISSUED UNDER WMO HEADER WTNT63…AND AWIPS HEADER
TCUAT3…AND WILL ALSO BE AVAILABLE ON THE NHC WEBSITE. BEGINNING
AT 5 AM EDT TUESDAY…PUBLIC ADVISORIES WILL BE ISSUED BY THE
HYDROMETEOROLOGICAL PREDICTION CENTER…HPC…UNDER THE SAME WMO
AND AWIPS HEADERS AS THE NHC PUBLIC ADVISORIES…WHICH WILL ALSO BE
AVAILABLE VIA THE NHC WEBSITE.

THERE HAS BEEN NO SIGNIFICANT CHANGE TO THE POST-LANDFALL TRACK OR
INTENSITY FORECAST. DESPITE THE RAPID FORWARD MOTION TODAY…SANDY
IS EXPECTED TO STALL INLAND TOMORROW. THIS…COUPLED WITH THE VERY
LARGE SIZE OF THE SYSTEM…WILL MEAN THAT CONDITIONS WILL BE SLOW
TO IMPROVE IN THE AFFECTED AREAS. STRONG WINDS WILL PERSIST ALONG
THE COAST AND SPREAD FARTHER INLAND THROUGH AT LEAST TUESDAY. OF
PARTICULAR CONCERN ARE THE UPPER FLOORS OF HIGH-RISE BUILDINGS…AS
RECONNAISSANCE DATA INDICATE THAT WINDS JUST A FEW HUNDRED FEET IN
ALTITUDE ARE VERY MUCH STRONGER THAN THOSE NEAR THE SURFACE. EVEN
AS SANDY WEAKENS…HEAVY RAINS WILL PERSIST OVER A LARGE
AREA…POSING A VERY SIGNIFICANT INLAND FLOOD RISK.

TO AVOID A HIGHLY DISRUPTIVE CHANGE FROM TROPICAL TO NON-TROPICAL
WARNINGS AS SANDY BECOMES POST-TROPICAL…THE WIND AND OTHER
HAZARDS WILL CONTINUE TO BE CONVEYED THROUGH HIGH WIND WARNINGS
ISSUED BY LOCAL NATIONAL WEATHER SERVICE OFFICES.

FORECAST POSITIONS AND MAX WINDS

INIT 29/2100Z 38.8N 74.4W 80 KT 90 MPH
12H 30/0600Z 39.8N 76.6W 65 KT 75 MPH…POST-TROP/EXTRATROP
24H 30/1800Z 40.4N 78.3W 50 KT 60 MPH…POST-TROP/EXTRATROP
36H 31/0600Z 41.3N 78.2W 40 KT 45 MPH…POST-TROP/EXTRATROP
48H 31/1800Z 42.8N 77.5W 30 KT 35 MPH…POST-TROP/EXTRATROP
72H 01/1800Z 45.1N 75.5W 30 KT 35 MPH…POST-TROP/EXTRATROP
96H 02/1800Z 46.3N 72.2W 25 KT 30 MPH…POST-TROP/EXTRATROP
120H 03/1800Z 47.5N 65.5W 20 KT 25 MPH…POST-TROP/EXTRATROP