SANDY BECOMES POST-TROPICAL

HURRICANE SANDY DISCUSSION NUMBER  30...

CORRECTED NWS NATIONAL HURRICANE

CENTER MIAMI FL

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 ANTICIPATES 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

For all graphics see bottom of post

From Dr Jeff Masters Weather Underground

WunderBlog 10:40 GMT Oct 29

Hurricane Sandy is making its final approach, and will be ashore near the Delaware/new Jersey border early this evening. The scale of this massive storm truly earns Sandy the title of “superstorm”, and no storm since at least 1988 has struck the U.S. with a wider area of tropical storm-force winds. High wind warnings are posted from Northern Michigan to Lake Okeechobee, Florida, and from Chicago to Maine. All-time low pressure records have been set at Atlantic City, NJ, Philadelphia, PA, and Wilmington Delaware. The rain is coming down in sheets along the east coast, where heavy rain stretches from Virginia to Pennsylvania and New York. Virginia Beach, VA has seen 9.26″, Dover, DE has seen 6.36″ and Ocean City, MD has seen 6.31″. Some of the heaviest rain, apart from close to the center, is actually on the far western side, where a strong band of precipitation has set up running north to south from Erie, PA south to Pittsburgh, PA. This strong band of rain is moving west into Ohio. Wind gusts have been peaking above 80 mph in New York, Rhode Island, and Massachusetts this afternoon. The strongest gusts we’ve seen today include 86 mph at Westerly, RI, 84 mph on Plum Island, NY, and 83 mph on Cuttyhunk Island, MA. Sustained winds speeds of 40+ mph stretch from Delaware to Rhode island, with the strongest sustained wind closest to the center of circulation in Lewes, DE. All of this strong, onshore wind has been pushing huge amounts of water toward the shore, where it has nothing to do but pile up over land. As of 5pm EDT, here are the highest storm surges seen:

Kings Point, NY: 7.85 ft
Sandy Hook, NJ: 7.55 ft
Bridgeport, CT: 7.3 ft
New Haven, CT: 6.82 ft
The Battery, NY: 6.7 ft
New London, CT: 5.76 ft
Atlantic City, NJ: 5.69 ft
Lewes, DE: 4.46 ft

Sandy bringing high winds all the way to Chicago
The scope of this storm is truly astonishing. As Sandy combines with the fall low pressure system over the Northeast U.S., its circulation will intensify, and winds over the Great Lakes will increase. Storm warnings are posted for Tuesday on Lake Michigan near Chicago, where sustained 55 – 60 mph winds and waves of 20 – 25 feet are expected. Storm warnings are posted on Lake Erie and Lake Ontario, and high winds from Sandy blowing off of Lake Erie caused damage to signs in Port Clinton, Ohio this afternoon. Check out this webcam view of a very angry Lake Erie. High wind warnings extend from northern Michigan to Central Florida.

Sandy’s storm tide peaking early this evening
Storm surge should peak between 7 – 8 pm, and high tide will peak a little later, 8 – 9 pm, depending upon location. The storm tide–how high the water gets above some reference point, commonly chosen to be the average of the daily lowest low tide of the month (Mean Lower Low Water, MLLW) is what we use to discuss how bad storm surge flooding is. The storm tide is the combination of the storm surge and the tide. At Sandy Hook, NJ, the storm tide has reached 10.11′, and is still rising. This breaks the old record set by Hurricane Donna in 1960, and the Nor’easter of Dec 11th, 1992. As of 6 pm EDT, the storm tide at The Battery in New York City was 10.1′. The record is 10.5′, set during Hurricane Donna of 1960. That also happens to be the level the Lower Manhattan subway system will flood, unless the defenses have been improved since last year’s Hurricane Irene. High tide is at 8:53 pm. The rise in surge has slowed down, but the surge may not be slowing down fast enough to avoid record flooding in New York City.

Links for Sandy
An impressive 1-minute resolution satellite loop of Sandy today is at the CSU RAMMB website.

Hurricane Sandy info from NASA.

Joe Romm at climateprogress.org has a thoughtful piece called, How Does Global Warming Make Hurricanes Like Irene More Destructive?

Storm Surge prediction model from the Stevens Institute of Technology, which use a highly detailed 3D ocean model and even includes rainfall and tributary inflows.

Research storm surge model run by SUNY Stonybrook for New York City.

For more on this story go to:

http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2281