TROPICAL STORM SANDY DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL AL182012 500 PM EDT TUE OCT 23 2012 SATELLITE IMAGES CONTINUE TO SHOW FAIRLY
WELL-DEFINED CONVECTIVE BANDING FEATURES
...MAINLY OVER THE EASTERN PORTION OF THE CIRCULATION OF THE STORM. THE CENTER OF
SANDY IS ESTIMATED TO BE LOCATED NEAR THE WESTERN EDGE OF A DEVELOPING CENTRAL
DENSE OVERCAST FEATURE...WHICH IS INDICATIVE OF A BIT OF WESTERLY SHEAR OVER THE SYSTEM. HOWEVER...THE ATMOSPHERIC AND OCEANIC ENVIRONMENT IS EXPECTED TO FAVOR STRENGTHENING DURING THE NEXT DAY OR TWO WITH LAND INTERACTION BEING THE PRIMARY IMPEDIMENT. BY 72 HOURS... SOUTH-SOUTHWESTERLY SHEAR IS EXPECTED TO INCREASE TO MORE THAN 30 KT AND THIS SHOULD LIMIT STRENGTHENING. THE OFFICIAL INTENSITY FORECAST IS A BLEND OF THE LATEST STATISTICAL-DYNAMICAL SHIPS AND LGEM GUIDANCE. BY THE END OF THE PERIOD...GLOBAL MODEL FORECASTS SUGGEST THAT THE CYCLONE WILL BE DERIVING SOME ENERGY FROM BAROCLINIC SOURCES AND THE OFFICIAL FORECAST SHOWS POST-TROPICAL STATUS AT DAY 5. THE INITIAL MOTION IS ESTIMATED TO BE SLOWLY NORTH-NORTHEASTWARD... OR 020/5. NO SIGNIFICANT CHANGES HAVE BEEN MADE TO THE PREVIOUS TRACK FORECAST. AS A MID-TROPOSPHERIC RIDGE TO THE NORTH OF SANDY CONTINUES TO WEAKEN...THE TROPICAL CYCLONE SHOULD MOVE ON A NORTH-NORTHEASTWARD TO NORTHWARD HEADING WITH SOME INCREASE IN FORWARD SPEED OVER THE NEXT COUPLE OF DAYS. IN 2-3 DAYS...A SHARP UPPER-LEVEL TROUGH JUST TO WEST OF SANDY IS EXPECTED TO KEEP THE STORM ON A NORTHWARD TRACK...NEAR THE NORTHWEST BAHAMAS. LATER IN THE FORECAST PERIOD...INCREASING MID-LEVEL WESTERLY FLOW IS EXPECTED TO CAUSE A TURN TOWARD THE NORTHEAST. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE LATEST GFS AND ECMWF SOLUTIONS THROUGH 72 HOURS...AND CLOSE TO THE DYNAMICAL MODEL CONSENSUS. THE FORECAST TRACK AND EXPANDING WIND RADII SUGGEST THAT A TROPICAL STORM WATCH COULD BE REQUIRED FOR PORTIONS OF SOUTHEASTERN FLORIDA AND THE KEYS AS EARLY AS TONIGHT. FORECAST POSITIONS AND MAX WINDS INIT 23/2100Z 14.3N 77.6W 45 KT 50 MPH 12H 24/0600Z 15.7N 77.3W 55 KT 65 MPH 24H 24/1800Z 17.9N 77.1W 65 KT 75 MPH 36H 25/0600Z 20.3N 76.9W 70 KT 80 MPH...INLAND 48H 25/1800Z 22.8N 76.9W 60 KT 70 MPH...OVER WATER 72H 26/1800Z 26.3N 76.7W 60 KT 70 MPH 96H 27/1800Z 29.5N 73.5W 60 KT 70 MPH 120H 28/1800Z 32.0N 69.0W 60 KT 70 MPH...POST-TROPICAL
See updated 5PM graphics below
Tuesday, October 23, 2012 5:45 am -¬†Rob Lightbown of Crown Weather says:
Sandy Is Expected To Impact Jamaica As A Hurricane On Wednesday; Forecast Guidance Trending Towards European Model Idea Of A Major Headache In The Mid-Atlantic States & New England Late This Weekend Into Early Next Week.
Satellite imagery early this morning showed some very deep thunderstorm activity developing on the eastern side of the storm. Even with this, satellite intensity analysis shows that the storm still has 45 to perhaps 50 mph maximum winds this morning. As expected, Sandy has begun its slow northward trek towards Jamaica and it is expected to impact the island on Wednesday with hurricane force winds. I do think that we will see significant strengthening today and tonight to a point that Sandy is a 80 to 85 mph hurricane when it tracks over Jamaica during the day on Wednesday.
From there, Sandy is expected to track over the eastern part of Cuba as potentially a 85 mph Category 1 hurricane late Wednesday night and then track across the central and possibly northwestern Bahamas on Thursday night as a 75 mph hurricane.
Beyond Friday, the model guidance continues to vary quite a bit on the track of Sandy and whether or not it will significantly impact the Mid-Atlantic states and New England. One troubling signal is that the GFS model seems to be slowly trending towards the idea of the European and Canadian models of a significant impact on the Mid-Atlantic states by Sunday and New England as we get into Monday and Tuesday. I am still very skeptical on the Canadian and European model guidance idea of a historic major storm from North Carolina to New England. I am just having a very difficult time wrapping my mind around the European model forecast of a 951 millibar storm bringing hurricane force winds from eastern Massachusetts to coastal sections of Maine on Monday and I especially am having major skepticism with the Canadian model forecast of a 939 millibar storm tracking right across Long Island and New York City on Monday evening.
So, my thinking for a forecast track this coming weekend into early next week is that I think the European and Canadian model guidance are too aggressive and intense with their 939 to 951 millibar central pressures. For those of you with barometers, that would be a pressure of between 27.73 and 28.08 inches. So, I think we will have a storm tracking north-northeastward just offshore of the coast of North Carolina by Sunday and the expected upper level pattern may be such to turn Sandy north-northwestward towards New England as we get into Monday and Tuesday. Residents and vacationers from North Carolina and the Mid-Atlantic states to New England need to monitor this storm closely. Storm force winds of 50 to 60 mph are a possibility along the Mid-Atlantic coast late this coming weekend and across coastal sections of New England by Monday and Tuesday.
Finally, to add credence to the idea of a storm impact on the Mid-Atlantic and New England is that the latest European ensemble guidance supports the operational model of a storm tracking to a position about 200 miles east of Cape Hatteras on Sunday with a central pressure of 988 millibars which I think is much more realistic. From there, the European ensemble guidance forecasts this storm to track to near Cape Cod by next Tuesday and then to near the Bay of Fundy by next Thursday. This sort of track could bring heavy rain and strong winds with gusts to 60 mph to the Mid-Atlantic states from late Saturday to late Sunday, then to much of New England on Monday.
Now, back to the expected impacts for Jamaica: Tropical storm force winds will begin to impact Jamaica late tonight with hurricane conditions expected on the island of Jamaica during the day Wednesday along with rainfall amounts of up to 12 inches which is likely to cause flash floods and mudslides.
Heavy rainfall with totals of 12 to 16 inches are also expected across Haiti and the Dominican Republic from Wednesday to Thursday and thus flash flooding and mudslides are expected.
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