AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1055 AM EDT FRI AUG 26 2011
.SYNOPSIS...
A FRONTAL BOUNDARY WILL BE STALLED NEAR THE COAST TODAY AND
SATURDAY. MEANWHILE, HURRICANE IRENE WILL MOVE NORTHWARD AND UP
THE EAST COAST SATURDAY AND SUNDAY, HOWEVER EXACTLY WHERE THE
CENTER TRACKS STILL CARRIES SOME UNCERTAINTY. THE STORM IS THEN
FORECAST TO EXIT TO OUR NORTH AND NORTHEAST LATER SUNDAY. HIGH
PRESSURE WILL BUILD IN TUESDAY AND WEDNESDAY BEFORE BEGINNING TO
SHIFT OFF THE COAST THURSDAY.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --THERE WAS LINGERING MOISTURE AROUND THE AREA IN THE FORM OF STRATUS, AND IT WAS SLOWLY MIXING OUT. WE ANTICIPATE THAT IT WILL
TRANSFORM INTO CUMULUS BY EARLY AFTERNOON.
MOST LOCATIONS SHOULD ULTIMATELY RECEIVE A FAIR AMOUNT OF
SUNSHINE. WITH THE REMNANT BOUNDARY STALLING AND PERHAPS
BEGINNING TO DRIFT BACK TO THE NORTHWEST THERE WILL BE A FOCUS FOR
THE DEVELOPMENT OF SHOWERS AND THUNDERSTORMS FROM LATE THIS
MORNING ONWARD. WE HAVE INCLUDED THE MENTION OF SCATTERED SHOWERS
AND THUNDERSTORMS, MAINLY IN OUR CENTRAL AND SOUTHERN COUNTIES.
WITH ABUNDANT LOW LEVEL MOISTURE, THERE COULD BE A BIT OF HEAVY
RAIN IN SPOTS.
AFTERNOON TEMPERATURES ARE ANTICIPATED TO RISE INTO THE 80S IN
MUCH OF OUR REGION WITH A LIGHT SOUTHERLY WIND.-- End Changed Discussion --
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
SCATTERED SHOWERS AND THUNDERSTORMS MAY LINGER INTO THE EVENING
HOURS. A LULL IS POSSIBLE BEFORE WE SEE PRECIPITATION DIRECTLY
ASSOCIATED WITH HURRICANE IRENE`S OUTER BANDS BEGIN TO APPROACH
FROM THE SOUTH LATE TONIGHT.
THE WIND TONIGHT SHOULD BECOME LIGHT AND VARIABLE. BEING THAT THE
AIR WILL REMAIN HUMID, TEMPERATURES SHOULD DROP ONLY INTO THE 60S
AND LOWER 70S IN OUR REGION.
.LONG TERM /SATURDAY THROUGH THURSDAY/...
**DAMAGING AFFECTS FROM HURRICANE IRENE SATURDAY AND SUNDAY ACROSS
THE REGION.** EVERYONE SHOULD BE PREPARING FOR THIS LARGE STORM AS
NOW IS THE TIME. HAVE A PLAN IN PLACE, LISTEN TO LOCAL OFFICIALS
REGARDING ANY EVACUATIONS AND KEEP UPDATED ON THE WEATHER
FORECASTS. SOME EVACUATIONS HAVE ALREADY STARTED ALONG THE NEW
JERSEY COAST. THE 5 AM NHC ADVISORY HAS BEEN INCORPORATED INTO OUR
WIND GRIDS. IN ADDITION, THE EARLIER WATCHES WERE UPGRADED TO
WARNINGS WITH SOME NEW WATCHES ADDED ACROSS THE NORTHERN PART OF
THE CWA. PLEASE NOTE THAT HUNTERDON COUNTY, NEW JERSEY IS UNDER
A TROPICAL STORM WATCH, HOWEVER DUE A SOFTWARE GLITCH IT IS NOT
SHOWING UP IN THE HLS PRODUCT. WE HOPE TO GET THIS CORRECT AS
SOON AS POSSIBLE.
THE MAIN FOCUS FOR THIS PERIOD IS THE TRACK AND IMPACTS OF
HURRICANE IRENE. WE WANT TO STRESS THAT IT IS IMPORTANT TO NOT
FOCUS ON THE EXACT CENTER OF THE STORM, AS IT IS FORECAST TO BE A
LARGE SYSTEM AS IT MOVES THROUGH. WE EXPECT EXTENSIVE IMPACTS FROM
THIS HURRICANE ACROSS THE ENTIRE CWA REGARDLESS OF THE TRACK JUST
INLAND, ON THE COAST OR ABOUT 50 MILES OFFSHORE. THE PEAK OF THE
STORM LOOKS TO GENERALLY OCCUR SATURDAY NIGHT THROUGH ABOUT MIDDAY
SUNDAY. WE WANT TO STRESS THAT THERE IS A RATHER HIGH RISK OF
DAMAGING WINDS AND HEAVY AND POSSIBLY RECORD SETTING RAINFALL
LATER SATURDAY AND SUNDAY.
DESPITE THE FORECAST TRACK OF THE HURRICANE AMONG THE MODELS
WAFFLING BACK AND FORTH SOME DURING THE LAST FEW DAYS, WE WILL
HAVE IMPACTS FROM THIS SYSTEM. THE FINER DETAILS WILL ULTIMATELY
DEPEND ON WHERE THE CENTER TRACKS, WHICH INCLUDES THE SWATH OF
STRONGEST WINDS AND STORM SURGE. THE FIRST UPPER-LEVEL TROUGH IS
FORECAST TO SHIFT NORTHEAST OF THE AREA TODAY LEAVING A WEAKNESS
BETWEEN THE RIDGE IN THE WESTERN ATLANTIC AND ANOTHER UPPER-LEVEL
TROUGH WELL TO THE WEST. THIS WILL SERVE AS A CONDUIT FOR A
NORTHWARD MOTION FOR THE HURRICANE, ALTHOUGH SOME TURN TO THE
NORTH-NORTHEAST IS EXPECTED WITH TIME. ANY LAND INTERACTION PRIOR
TO THE HURRICANE ARRIVING INTO OUR AREA WILL SERVE TO WEAKEN IT,
HOWEVER WE ARE ANTICIPATING RAIN AND INCREASING WIND TO ARRIVE
WELL BEFORE THE CENTER. THIS WILL BE COURTEOUS OF A COASTAL TYPE
FRONT IN PLACE AND A WEALTH OF MOISTURE SURGING INLAND FROM A
STRENGTHENING ONSHORE FLOW.
THE FORWARD SPEED OF HURRICANE IRENE IN CONJUNCTION WITH THE
TIMING AND AMPLIFICATION OF THE INCOMING TROUGH IS CRUCIAL IN
DETERMINING THE WESTERN EXTENT OF THE HURRICANES TRACK. THIS IS
DANGEROUS AS A LATER TIMING IN THE TROUGH AMPLIFYING SOME MORE
WILL TEND TO ALLOW THE HURRICANE TO TRACK FARTHER WEST. OUR WIND
FORECAST IS BASED OFF OF THE GRIDDED WIND FIELD FROM THE OFFICIAL
NHC FORECAST AND THIS WILL BE UPDATED WITH SUBSEQUENT ADVISORY
ISSUANCES. WE GENERALLY BASED OUR POPS MORE TOWARD A BLEND WHICH
ENDS UP SIMILAR TO THE GFS. IF THE CENTER TRACKS FARTHER OFF THE
COAST, THEN THERE MAY BE A RATHER TIGHT GRADIENT IN THE RAIN
SHIELD ACROSS THE CWA FROM EAST TO WEST. IF THE STORM SHIFTS TO AN
INLAND TRACK, THEN THE AXIS OF HEAVIEST RAIN WILL SHIFT AND THE
THREAT OF TORNADOES WILL INCREASE. THERE CONTINUES TO BE A HIGH
RISK OF IMPACTS WITH THIS HURRICANE, WHICH INCLUDES WIDESPREAD
DAMAGING WINDS, TORRENTIAL RAIN, COASTAL FLOODING, DANGEROUS RIP
CURRENTS, AND BATTERING WAVES AND BEACH EROSION. FOR THE HEAVY
RAIN ASPECT, SEE THE HYDROLOGY SECTION BELOW.
INTERESTING TO NOTE THAT MUCH OF THE MODEL GUIDANCE DEVELOPS A
STRONG 250 MB JET NORTH OF THE HURRICANE SATURDAY INTO SUNDAY,
GENERALLY FROM THE EASTERN GREAT LAKES TO NORTHERN NEW ENGLAND.
THIS UPPER-LEVEL JET EVEN HAS SOME ANTICYCLONIC CURVATURE TO IT
AND GIVEN THE ORIENTATION OF THIS JET IT IS SUCH THAT IRENE IS
WITHIN THE RIGHT ENTRANCE REGION AS SHE TRACKS NORTHWARD. THIS
SCENARIO MAY TEND TO HELP WITH A POLEWARD UPPER-LEVEL OUTFLOW
CHANNEL AND ASSIST IN THE INTENSITY OF THE SYSTEM AS A WHOLE.
THEREFORE, DESPITE SOME INCREASING SHEAR AS THE HURRICANE GAINES
LATITUDE ALONG WITH COOLER WATERS AND LAND INTERACTIONS, PERHAPS
THIS IS WHY MUCH OF THE MODEL GUIDANCE NEARLY INSISTS THIS SYSTEM
REMAINS A POWERFUL ONE ALL THE WAY INTO SOUTHERN NEW ENGLAND. IT
BECOMES EVEN MORE OF AN INTENSITY FORECAST CHALLENGE AS TROPICAL
CYCLONES GET THIS FAR NORTH AND INTERACT WITH BAROCLINIC ZONES AND
LARGE SCALE SYNOPTIC FEATURES. AN EXAMINATION OF THE WIND FIELD AT
925 MB IS CONCERNING WITH A LARGE AREA OF 60 TO NEARLY 85 KNOTS
RACKING ACROSS THE CWA SATURDAY EVENING THROUGH SUNDAY MORNING.
WHILE THE FRICTIONAL EFFECTS WILL TEND TO SLOW THE WIND DOWN SOME
AND ALSO ALLOW FOR SOME DECOUPLING BETWEEN THE SURFACE AND ABOVE,
THE PRESSURE GRADIENT COMBINED WITH ENHANCED MIXING WITHIN HEAVIER
RAIN/CONVECTION SHOULD PRODUCE SIGNIFICANT/DAMAGING GUSTS. WE
CONTINUE TO USE A 125 PERCENT OF THE SUSTAINED WINDS TO DERIVE OUR
GUSTS BUT CAPPED THEM AT 90 KNOTS /20 PERCENT REDUCTION OF THE
SUSTAINED WINDS OVER LAND/. THE WIND GUST TOOL THAT INCLUDES
MIXING MAY BE TO HIGH ESPECIALLY OVER AREAS FARTHER INLAND. THERE
SEEMS TO BE A GROWING MODEL CONSENSUS EARLY THIS MORNING THAT THE
HURRICANE MAY END UP MOVING A BIT FASTER THAN EARLIER ADVERTISED
AS IT GETS TO OUR CWA. WE THEREFORE STARTED TO TAPER THE POPS DOWN
A BIT FASTER FROM SOUTH TO NORTH SUNDAY.
ONCE THE STORM MOVES OFF TO THE NORTH AND NORTHEAST LATER SUNDAY,
THE CONDITIONS WILL QUICKLY IMPROVE. OVERALL A MUCH CALMER TIME
FRAME MONDAY THROUGH THURSDAY AS THE WIND WILL QUICKLY DIMINISH
MONDAY AS HIGH PRESSURE BEGINS TO BUILD IN. A WEAK TROUGH WILL
SKIRT OUR REGION TUESDAY, WHICH MAY INCREASE CLOUDS A BIT. HIGH
PRESSURE THEN BUILDS ACROSS ON WEDNESDAY BEFORE SLIPPING TO THE
EAST THURSDAY.
George Wright is a Certified Consulting Meteorologist for Wright Weather Consulting, LLC. George is also a meteorologist with ABC News and Cablevision News 12. Our website is WrightWeather.com.
