Notes on Mid Week Nor’easter

Believe it or not we could use the precipitation in southern New England. The last measurable snow in Boston was 2.5" on February 18th. We have not had to plow snow since the 3.6" on February 15th. So far in March only 2.2" of snow have fallen, with .82" rain (and combined melted snow) so far this month. For the year 8.19" of precipitation has fallen at Boston Logan Airport, about a 15 percent deficit of the climatological average of 9.61" for this far into 2014. It's not a huge deal, but we like to have plenty of moisture when the warm winds of April and May can spark high fire danger.
How did I get on this subject? I guess it's a surprising statistic because it seems we have had so many storms this winter. And also because I have spent most of the month in Vermont where the snow is deeper and softer than anyone can remember in late March.
Here at Jay Peak Resort 64" of snow has fallen in just the last two weeks.

JayStaircaseMarch212014.jpglarge.jpg

Hate to leave you hanging, but our web host just wiped out 60 minutes of writing and editing, that's why I leave this apparent dead end.

It was genius, now it's gone. Very disappointing.

I will cut and paste a great discussion from Benjamin Sipprell and all at the National Weather Service in Taunton MA, along with a video I did for my surfing friends.

Also a link to Tidal Threat in Southern New England.

*/ HIGHLIGHTS...

  - STRONG OFFSHORE STORM TUESDAY INTO WEDNESDAY WITH SNOW/WIND
  - SEASONABLE AND DRY FOR THURSDAY WITH HIGH PRESSURE
  - MILDER WITH RAIN SOMETIME FRIDAY THROUGH SATURDAY
  - BRIEFLY COLD BEFORE TURNING MILDER SUNDAY INTO NEXT WEEK

*/ OVERVIEW AND MODEL PREFERENCE...

MAIN FOCUS IS ON THE TUESDAY NIGHT INTO WEDNESDAY SIGNIFICANT AND
POTENTIALLY DANGEROUS OCEAN STORM. THOUGH 12Z GUIDANCE HAS COME
INTO BETTER AGREEMENT...VARIANCE CONTINUES SO MUCH SO THAT THE
WOBBLE OF SOLUTIONS YIELDS SIGNIFICANT OUTCOMES FOR SE NEW ENGLAND.
JUST A 50 MILE CHANGE IN TRACK CAN MAKE ALL THE DIFFERENCE.

A VERY DIFFICULT AND CHALLENGING FORECAST...AND JUST TRYING TO
CONVEY BOTH THOUGHTS AND UNCERTAINTY IS IN AND OF ITSELF A
CHALLENGE. HAVE DONE THE BEST TO CONVEY THINKING BASED ON SIGNALS
AND MODEL CONSENSUS WHILE WEIGHTING WITH CIPS ANALOGS. BROKE DOWN
THE DISCUSSION TO CLEARLY CONVEY THE MESSAGE OF POTENTIAL THREATS
AND IMPACTS. IT MAY BE A BIT TOO LONG BUT FEEL ITS IMPORTANT TO
DELIVER THE MESSAGE WITH SUCH AND IMPRESSIVE STORM.

MODERATE CONFIDENCE ALL-AROUND CONTINUES WITH THE HIGHEST OVER SE
NEW ENGLAND INCLUDING CAPE COD AND THE ISLANDS WHERE THE GREATEST OF
IMPACTS IS EXPECTED. DID GIVE SOME HIGHER WEIGHTING TO THE 12Z
GFS/CANADIAN/ECMWF AS THEY FELL CLOSER TO THE GFS/ECMWF ENSEMBLES.
AGAIN...NO ONE SOLUTION IS PREFERRED.

*/ OFFSHORE STORM...

TUESDAY INTO WEDNESDAY...

E-CONUS BROAD-SCALE TROUGHING IS AMPLIFIED BY A ROBUST SHORTWAVE
CYCLONICALLY DIGGING S OUT OF CANADA TUESDAY INVOKING A NEGATIVE-
TILT THAT CLOSES OFF OVER THE GULF OF MAINE WEDNESDAY. INTERACTING
WITH A SURFACE FRONTAL-ZONE ACROSS THE GULF OF MEXICO...AN AREA OF
LOW PRES DEVELOPS OFF THE CAROLINAS ON TUESDAY...DEEPENING NE AND
PASSING SE OF THE 40N/70W BENCHMARK AROUND MIDNIGHT WEDNESDAY...
BOMBING OUT AND UNDERGOING OCCLUSION ACROSS THE GULF OF MAINE INTO
HALIFAX DOWN TO A CENTRAL PRES OF 960-970 MB WEDNESDAY NIGHT. SUCH A
STORM OF 3-4 STANDARD DEVIATIONS IN TERMS OF STRENGTH AND MAGNITUDE
POSES A SERIOUS THREAT TO SOUTHERN NEW ENGLAND.

ABSOLUTELY NO CERTAINTY WITH THIS FORECAST AS TO EXACT SPECIFICS.
CONTINUED SPREAD OF OUTCOMES PER 12Z FORECAST GUIDANCE IN BOTH LOW
TRACK...STRENGTH...AND POSITION LIKELY DUE TO DIFFERENCES IN TIMING
AND AMPLITUDE OF UPSTREAM ENERGY TOWARDS THE EVOLUTION OF THE MID-
TO UPPER-LEVEL NEGATIVE-TILT OF THE TROUGH...DESPITE BETTER
AGREEMENT BETWEEN THE ECMWF/GFS/CANADIAN. WOBBLES-VARIANCE ARE
ALSO APPARENT WITHIN INDIVIDUAL FORECAST GUIDANCE. SUCH SLIGHT
DIFFERENCES CAN EQUATE TO ROUGHLY A 50 MILE SHIFT IN THE LOW TRACK
MAKING ALL THE DIFFERENCE BETWEEN SIGNIFICANT IMPACTS AND NEARLY
NEXT TO NOTHING.

FEEL WE CAN MAKE EDUCATED-GUESSES PER CONSISTENT SIGNAL OF BOTH
DETERMINISTIC AND ENSEMBLE SOLUTIONS WITH REGARDS TO THE ANTICIPATED
OFFSHORE STORM. PER SYNOPSIS DISCUSSION ABOVE...BELIEVE THE LOW WILL
PASS SE OF THE 40N/70W BENCHMARK AROUND MIDNIGHT WEDNESDAY...BOMBING
OUT OVER THE GULF OF MAINE INTO EASTERN HALIFAX WEDNESDAY. THUS HAVE
HIGHEST CONFIDENCE OF IMPACTS ACROSS THE CAPE AND ISLANDS INCLUDING
ADJACENT WATERS...WITH LESSER CONFIDENCE N AND W.

WILL CONTINUE YESTERDAYS FORECAST THEME FOCUSING ON THE POTENTIAL
WHAT/WHERE/WHEN OF IMPACTS BASED ON COLLABORATION BETWEEN THOUGHTS
ABOVE...LATEST FORECAST GUIDANCE AND SIGNALS...AND FINALLY CIPS
ANALOGS.

*/HEAVY SNOW...

SYNOPSIS...COMBINATION OF SW-NE SNOW-BANDING TO THE NW-QUADRANT OF
THE SURFACE LOW /PER TROWALING AND DEFORMATION/ WITH AN ISALLOBARIC/
AGEOSTROPHIC COMPONENT FROM THE INTERIOR WILL LIKELY MAKE FOR A
SHARP NW-SE GRADIENT OF SNOWFALL.

TIMING: TUESDAY NIGHT TOWARDS MIDDAY WEDNESDAY.

IMPACTS:

- SNOW WILL BE HEAVY AT TIMES RESULTING IN HAZARDOUS TRAVELING
CONDITIONS AS WELL AS VISIBILITIES DOWN TO A QUARTER MILE OR LESS
FOR FAR E/SE CAPE COD AND NANTUCKET. BLOWING AND DRIFTING OF SNOW
MAY BE AN ISSUE AS WELL.

CONFIDENCE:

- WINTER STORM WARNINGS POSSIBLE FOR CAPE COD AND THE ISLANDS...
PERHAPS INTO SOUTHEAST PLYMOUTH COUNTY. WINTER WEATHER ADVISORIES
FOR E/SE MA AND E/SE RI. MODERATE CONFIDENCE.

- BLIZZARD CONDITIONS POSSIBLE...ESPECIALLY FOR BETWEEN HYANNIS AND
CHATHAM ON THE EASTERN CAPE...AND NANTUCKET. LOW CONFIDENCE.

- CIPS ANALOGS IN GOOD AGREEMENT WITH LATEST SNOWFALL PROBABILITIES
WITH THE HIGHEST PROBABILITY OF MEETING/EXCEEDING WARNING CRITERIA
OVER FAR SE NEW ENGLAND.

*/STRONG TO DAMAGING WINDS...

SYNOPSIS...BOMBING LOW AND STRONG PRESSURE FALLS LENDS TO A SURFACE
LOW PRESSURE CENTER OF 960-970 MB OVER THE GULF OF MAINE TOWARDS
HALIFAX AROUND WHICH NORTHERLY WINDS WILL AMPLIFY ROUGHLY 3-4
STANDARD DEVIATIONS /ANOMALOUS/ THROUGH A WELL-MIXED BOUNDARY LAYER.

TIMING: TUESDAY NIGHT INTO WEDNESDAY NIGHT.

IMPACTS:

- NORTHERLY WIND GUSTS OF 45 TO 60 MPH WILL RESULT IN DOWNED TREE
LIMBS AND POWER LINES. STRUCTURAL DAMAGE WILL ALSO BE POSSIBLE.
ISOLATED TO SCATTERED POWER OUTAGES.

- WINDS WILL ALSO AID IN THE BLOWING AND DRIFTING OF SNOW AND
POSSIBLY MAKE FOR BLIZZARD CONDITIONS OUT ON THE FAR EASTERN CAPE AS
WELL AS NANTUCKET..

- WORST OF THE WINDS WILL BE ALONG NORTH-FACING EXPOSED SHORELINES
SUCH AS CAPE ANN...CAPE COD...AND NANTUCKET.

CONFIDENCE:

- HIGH WIND WARNINGS MAY BE NEEDED FOR FAR EASTERN CAPE COD AND
NANTUCKET WITH WIND GUSTS OF AT LEAST 58 MPH. MODERATE CONFIDENCE.

- WIND ADVISORIES MAY BE NEEDED FOR LOCATIONS ALONG THE E-SHORE SUCH
AS CAPE ANN AND DOWN THROUGH SE MA WITH GUSTS OF AT LEAST 45 MPH.
MODERATE CONFIDENCE.

- GALE WARNINGS LIKELY FOR ALL WATERS WITH WINDS IN EXCESS OF 34 KTS
WITH THE POSSIBILITY OF STORM WARNINGS FOR THE E/SE OUTER WATERS AND
BOTH CAPE COD BAY AND NANTUCKET SOUND WITH WINDS IN EXCESS OF 48 KTS.

- CIPS ANALOGS HIGHLIGHT THE GREATEST PROBABILITY OF WINDS GREATER
THAN 45 MPH OVER SE NEW ENGLAND. LOCAL IN-HOUSE CLIMATOLOGY AFTER
EVALUATING UPPER-LEVEL WINDS SUPPORTS POTENTIAL HAZARDS AND HEAD-
LINES OUTLINED ABOVE.

*/COASTAL IMPACTS...

TIMING: WEDNESDAY MORNING HIGH TIDE NEAR 8 AM.

IMPACTS:

- COMBINED WITH WINDS AND PERHAPS A 1-2 FOOT SURGE...THERE IS THE
POTENTIAL FOR SPLASHOVER AND MINOR COASTAL FLOODING...ESPECIALLY FOR
EXPOSED NORTH-FACING SHORELINES.

CONFIDENCE:

- COASTAL FLOOD HEADLINES MAY BE NEED FOR THE NORTH-FACING
SHORELINES SUCH AS CAPE ANN...WITHIN CAPE COD BAY...AND NANTUCKET.
MODERATE CONFIDENCE.

- WAVE HEIGHTS OF 15 TO 20 FEET POSSIBLE ON THE E/SE WATERS.
MODERATE CONFIDENCE.

*/ REMAINING DAY-TO-DAY DETAILS...

WEDNESDAY NIGHT...

HIGH PRES BUILDS INTO THE RGN. COLDER-DRIER AIR WORKING IN. EXPECT
LINGERING SNOW TO QUICKLY CONCLUDE OVER THE E-SHORE AND ADJACENT
WATERS. MAIN CONCERN IS BLUSTERY NW WINDS STRONGEST IN THE EVENING
WITH THE POTENTIAL FOR 50 MPH GUSTS OVER THE E/SE SHORELINE. WINDS
RELAXING OVERNIGHT WITH A SURGE OF WARMER AIR ALOFT AND COLD-AIR
ADVECTION AT THE SURFACE ALLOWING A MORE STABLE BOUNDARY-LAYER
PROFILE. GRADUAL CLEARING TOWARDS MORNING. LOWS DOWN INTO THE TEENS.

THURSDAY INTO THURSDAY NIGHT...

HIGH PRES. NW WINDS RELAXING VEERING SW. WILL SEE TEMPS RETURN TO
SEASONABLE LEVELS. MOSTLY CLEAR AND ABUNDANT SUNSHINE WILL LIKELY
MAKE IT CONSIDERABLY WARMER. LOW- TO MID-40S HIGHS EXPECTED WITH A
NON-DIURNAL LOW-TREND OVERNIGHT /UPPER-20S TOWARDS MIDNIGHT/ WITH
INCREASING SW WINDS.

IF THE STORM COMPLETELY MISSES THE REGION WITH SIGNIFICANT PRECIP...
AM CONCERNED ABOUT FIRE WEATHER POTENTIAL AS MIN RELATIVE HUMIDITIES
ARE POSTULATED TO FALL BELOW THE 25 PERCENT THRESHOLD...IN ADDITION
TO WARMER CONDITIONS AND BREEZY SW FLOW.

FRIDAY INTO SATURDAY...

A COLD FRONT SLIDES ACROSS THE NE CONUS. SOME TIMING DISCREPANCIES
WHICH AS ALLUDED TO BY THE PRIOR FORECAST WILL HAVE AN IMPACT ON
TEMPS. NEVERTHELESS...EVALUATING SIGNALS...A PRONOUNCED S-STREAM OF
GULF MOISTURE AIDED BY AN OFFSHORE HIGH /BLUSTERY SW WINDS EXPECTED
WITH THE ENHANCING PRES-GRADIENT/ EXPECT A RAIN-BAND WITH EMBEDDED
HEAVIER SHOWERS TO DELIVER DECENT RAINS ACROSS THE REGION /PWATS IN
EXCESS OF AN INCH/. CONTINUED LOW CONFIDENCE CONCERNING THUNDER.

COMBINATION OF MILDER CONDITIONS...DECENT RAINS...AND REMNANT SNOW-
PACK NETS THE CONSIDERATION OF POTENTIAL NUISANCE  FLOODING AND
PERHAPS ICE ISSUES ON THE RIVERS. LOW CONFIDENCE ON SUCH OUTCOMES
FOR NOW.

SUNDAY INTO MONDAY /INCLUDING AN OUTLOOK/...

PERHAPS A REPEAT OF THURSDAYS WEATHER? BLUSTERY NW FLOW IN WAKE OF
THE LATE-WEEK SYSTEM BRINGS A SHOT OF COLDER CONDITIONS. BUT THIS IS
QUICKLY REPLACED BY MILDER WEATHER WITH HIGH PRES BUILDING OUT OF
THE CENTRAL CONUS SETTLING EAST ACROSS BERMUDA RESULTING IN A MODEST
SOUTHERLY FETCH OF WARMER AIR.

PER ENSEMBLE MEMBERS...THE AO-INDEX EXHIBITS A TREND BACK TO A NEAR-
NEUTRAL STATE BY THE BEGINNING OF APRIL. THE 8-DAY CANADIAN ENSEMBLE
MEAN SHOWS A STRONG POSITIVE ANOMALY ACROSS THE CENTRAL CONUS WITH A
NEGATIVE ANOMALY LOCKED UP OVER CANADA. THE 192- AND 264-HOUR CIPS
ANALOG GUIDANCE CONVEYS SUPPORT TOWARDS SUCH OUTCOMES. THE CPC 8-14
DAY OUTLOOK /UNCHANGED AS OF YESTERDAY/ HAS HIGHER PROBABILITIES OF
A WARMER-TREND CREEPING INTO THE NE CONUS. ARCTIC-AIR LOCKED AWAY...
PACIFIC AIR LOOKS TO STAY.

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