More details on the record cold and snowy February for Northern & Eastern Maine, updated 3/7

February 2015 was a month to remember across New England and the greater Northeast U.S. in general.   It was one of the coldest Februaries on record with average temperatures 9 to 15 degrees below normal.  Caribou, Maine had its all-time coldest February on record with an average temperature of just 2.8 degrees, which surpassed 1993 when the average temperature was 4.1 degrees.  Even more impressive, Bangor set an all-time coldest month record.   The average temperature of 6.1 degrees smashed the previous record for February of 11.3 degrees in 1993.  It also broke the all-time coldest month record by more than 2 degrees. The old record of 8.4 degrees was established in 1994.

Across New England there were some other impressive monthly temperature records. Portland, Maine observed its coldest February on record, and the 2^nd coldest month of all-time.  Boston, Massachusetts  and Providence, Rhode Island each had their 2^nd coldest February and 2^nd coldest month of all time.  Hartford, Connecticut had its coldest month ever on record.  Below is a map (Fig. 1) of the departure from normal temperatures (F) during the month of February from the Northeast Regional Climate Center.   Fifteen of the 35 airport climate sites had a record cold February (Fig.2)

In addition to the cold, many areas, especially coastal New England had record snowfall, with totals up to 4 ½ feet above normal (Fig.3).  Seventeen of the 35 airport climate sites had a top 10 snowy February.   Two sites (Boston and Worcester) had their all-time snowiest month on record.

The remainder of this article hopes to explore the upper air and surface weather patterns that produced the persistent cold weather across all of the Northeast U.S., and the snowy weather that was observed across much of coastal New England.  In order to do this, a reanalysis of upper air and surface patterns was examined using NOAA’s Earth System Research Laboratory’s reanalysis tool.  In the near future, plans are to examine in more depth the causes of this pattern with an examination of several climate indices.

First, we will examine the composite mean 500 millibar geopotential heights across the northern Hemisphere during the month of February (Fig.7).  One will note the persistence of the low 500 millibar heights across central Siberia, northern Canada, and into the Great Lakes and Northeast U.S.   If one takes a closer look at the 500 millibar composite anomalies (1981-2010 climatology) (Fig.8) negative anomalies on the order of 90 to 120 millibars are noted across the northeast U.S. including all of New England.  At the same time, strong positive height anomalies were noted west of the continental divide.  The persistence of the upper air pattern led to well below normal temperatures at the surface (Fig. 9) that corresponded well with the upper air anomalies.

Next, we will examine the surface pattern during the month of February.   A persistent surface trough was evident just off the Northeast U.S. coast (Fig. 10).  When one compares the composite mean surface sea level pressure to the 1981-2010 climatological mean (Fig.11) it becomes evident that surface pressures were lower than the climatlogical mean just off the Northeast U.S. Coast.   There were a number of surface lows that moved toward the Northeast U.S. coast from the west and intensified across the Canadian Maritimes.  The persistence of this pattern led to favorable conditions for significant snowfall along and near the New England Coast.

In the near future the NWS Caribou hopes to examine in more depth the causes of this pattern with an examination of several climate indices.

Flood Potential Outlook for Northern & Eastern Maine issued on March 5th 2015

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WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE CARIBOU ME
703 PM EST THU MAR 5 2015

...WINTER/SPRING FLOOD POTENTIAL OUTLOOK FOR NORTHERN...
CENTRAL...AND DOWNEAST MAINE...

THIS IS THE FIFTH WINTER/SPRING FLOOD POTENTIAL OUTLOOK FOR
2015...ISSUED BY THE NATIONAL WEATHER SERVICE IN CARIBOU, MAINE.
THE WINTER/SPRING FLOOD POTENTIAL IS FOR NORTHERN, CENTRAL AND
DOWNEAST MAINE FOR THE TWO-WEEK PERIOD FROM MARCH 5 THROUGH MARCH
19, 2015.

THE WINTER/SPRING FLOOD POTENTIAL FOR THE CENTRAL MAINE HIGHLANDS
SOUTH TO THE COAST IS ABOVE NORMAL. FOR NORTHERN MAINE, THE FLOOD
POTENTIAL IS NEAR NORMAL, WITH FAR NORTHERN PORTIONS OF THE
COUNTY LIKELY A BIT BELOW NORMAL FOR EARLY MARCH.

THE POTENTIAL FOR FLOODING DUE TO ICE JAMS IS SLIGHTLY ABOVE
NORMAL FOR ALL OF NORTHERN, CENTRAL, AND DOWNEAST MAINE.

...CLIMATOLOGICAL GUIDANCE...

FEBRUARY WAS A BRUTALLY COLD MONTH ACROSS ALL OF NWS CARIBOU`S
FORECAST AREA. MOST LOCATIONS AVERAGED SOME 10 TO 15 DEGREES
COLDER THAN NORMAL. BANGOR HAD ITS COLDEST MONTH ON RECORD, WHILE
CARIBOU HAD ITS COLDEST FEBRUARY OF ALL TIME.

THANKFULLY, WE`RE FINALLY SEEING SIGNS THAT THIS PROLONGED COLD
PATTERN IS GOING TO CHANGE. MUCH OF THE FORECAST MODEL GUIDANCE IS
SHOWING THAT UPPER LEVEL RIDGING IS GOING TO DEVELOP ACROSS THE
SOUTHEASTERN UNITED STATES, RESULTING IN A WEST-SOUTHWEST OR
WESTERLY FLOW OVER THE NORTHEASTERN UNITED STATES. THIS WILL
FORCE THE POLAR JET STREAM TO LIFT NORTH AND PUSH THE ARCTIC AIR
BACK INTO CANADA. ALTHOUGH IT WILL BE TEMPERED A BIT BY THE DEEP
SNOWPACK, THIS PATTERN CHANGE COMBINED WITH A STRENGTHENING SUN
WILL ALLOW A GRADUAL WARMING TREND IN TEMPERATURES OVER THE NEXT
COUPLE OF WEEKS.

THE OFFICIAL NATIONAL WEATHER SERVICE 8-14 DAY OUTLOOK FOR MID
MARCH SUPPORTS THE ABOVE THINKING AS IT CALLS FOR TEMPERATURES TO
BE ABOVE NORMAL OVER ALL OF MAINE. PRECIPITATION DURING THIS TIME
FRAME IS EXPECTED TO AVERAGE BELOW NORMAL.

...OBSERVED SNOW DEPTH AND WATER EQUIVALENTS...

CONTRARY TO WHAT WE NORMALLY SEE HEADING INTO MARCH, THE DEEPEST
SNOW CURRENTLY LIES ACROSS COASTAL AND DOWNEAST MAINE. THESE AREAS
ARE BLANKETED BY 30 TO 45 INCHES OF SNOW. THIS DECREASES AS ONE
HEADS NORTH INTO THE CENTRAL HIGHLANDS AND SOUTHERN AROOSTOOK
COUNTY. HERE THE SNOW DEPTH IS 20 TO 30 INCHES. FOR THESE AREAS,
THIS AMOUNT OF SNOW IS ABOVE NORMAL AND IS OF COURSE WELL ABOVE
NORMAL DOWNEAST. ACROSS NORTHERN MAINE, WHERE SNOW DEPTHS ARE 12
TO 20 INCHES, SNOW AMOUNTS ARE NEAR NORMAL. PORTIONS OF THE SAINT
JOHN VALLEY ARE PROBABLY EVEN A BIT BELOW NORMAL, WITH FORT KENT
ONLY REPORTING 14 INCHES OF DEPTH AS OF MARCH 4TH.

THE SNOW WATER EQUIVALENT, OR THE AMOUNT OF WATER CONTAINED IN
THE SNOWPACK, IS CLEARLY WELL ABOVE NORMAL OVER DOWNEAST MAINE.
THERE IS 6 TO 9 INCHES OF WATER CONTAINED IN THE SNOW IN THESE
LOCATIONS. THE SWE LESSENS AS ONE HEADS NORTH, WITH THE CENTRAL
HIGHLANDS AND SOUTHERN AROOSTOOK COUNTY REPORTING 5 TO 8 INCHES
OF WATER IN THE PACK, WHICH IS A BIT ABOVE NORMAL. MUCH OF THE
REMAINDER OF THE STATE HAS 4 TO 6 INCHES OF LIQUID EQUIVALENT.
THIS IS FAIRLY CLOSE TO NORMAL. AGAIN, THE EXCEPTION IS ACROSS THE
FAR NORTH WHERE THERE IS 3 TO 5 INCHES OF WATER IN THE SNOWPACK,
WHICH IS A BIT BELOW NORMAL FOR EARLY MARCH.

...SOIL MOISTURE AND WATER SUPPLY CONDITIONS...

NEAR SURFACE SOIL MOISTURE CONDITIONS, WHICH ARE INDICATIVE OF
NEAR TERM MOISTURE TRENDS, HAVE CONTINUED TO DRY OUT AS FEBRUARY`S
BITTERLY COLD TEMPERATURES HAVE GREATLY LIMITED SNOWMELT. FOR THE
MOST PART, THE SOIL MOISTURE IS NEAR NORMAL IN OUR AREA. THE
EXCEPTION IS DOWNEAST, WHERE MOISTURE STATES ARE SLIGHTLY WETTER
THAN NORMAL DUE TO THE COPIOUS AMOUNTS OF SNOW THAT FELL THROUGH
THE PREVIOUS MONTH.

THE LATEST PALMER DROUGHT SEVERITY INDEX, WHICH TAKES A LOOK AT
MOISTURE STATES OVER THE LONGER RANGE OF WEEKS TO MONTHS, SHOWS
NEAR NORMAL ANTECEDENT MOISTURE CONDITIONS OVER MUCH OF THE PINE
TREE STATE. ONCE AGAIN, THE EXCEPTION IS DOWNEAST WHERE VERY MOIST
CONDITIONS ARE BEING MEASURED.

...RIVER AND ICE CONDITIONS...

RIVER FLOWS HAVE CONTINUED TO SUBSIDE OR HOLD FAIRLY STEADY
THROUGH THE MONTH OWING TO THE VERY COLD TEMPERATURES. THEY ARE
GENERALLY NEAR NORMAL ACROSS THE REGION AS WE TYPICALLY DON`T SEE
MUCH SNOWMELT DURING FEBRUARY ANYWAY. DOWNEAST WATERWAYS MAY AGAIN
BE THE EXCEPTION TO THIS RULE.

ICE THICKNESSES ARE GENERALLY 1 TO 2 FEET ACROSS OUR ENTIRE AREA,
WITH THE COASTAL WATERWAYS AVERAGING CLOSE TO A FOOT. THIS IS
FAIRLY CLOSE TO NORMAL. WHAT IS ABNORMAL IS THE STRENGTH OF THE
ICE, ESPECIALLY IN OUR CENTRAL AND MORE SOUTHERN RIVERS. ALL THE
ICE IS STILL EXCEPTIONALLY STRONG, RATHER THAN HAVING STARTED TO
SHOW SIGNS OF WEAKENING AND ROT. THIS IS LIKELY DUE TO THE
ANOMALOUSLY COLD TEMPERATURES THAT WE EXPERIENCED THROUGH
FEBRUARY. ALTHOUGH THE STRENGTHENING SUN AND MILDER TEMPERATURES
WILL BEGIN TO WORK ON THE RIVER ICE, THEY WILL BE HINDERED BY THE
DEEP AMOUNT OF SNOW THAT STILL LIES ATOP THE ICE.

WE CONTINUE TO MONITOR SEVERAL ICE JAMS THAT REMAIN LOCKED IN
PLACE ALONG MANY OF OUR RIVERS. THESE JAMS INCLUDE A 10-15 MILE
LONG JAM ON THE SAINT JOHN THROUGH SAINT FRANCIS, AS WELL AS ONE
IN MADAWASKA AS REPORTED BY NWS STAFF. THERE ARE ALSO SEVERAL
KNOWN JAMS ON THE AROOSTOOK RIVER, INCLUDING ONE IN WASHBURN
THROUGH CROUSEVILLE, ONE BETWEEN PRESQUE ISLE AND CARIBOU, AND
ANOTHER DOWNSTREAM OF FORT FAIRFIELD. FOR THE CENTRAL RIVERS,
WE`VE NOTED ICE JAMS ON THE PISCATAQUIS IN MAXFIELD, AND THE
PENOBSCOT RIVER NEAR ORONO. THESE JAMS ARE WELL FROZEN IN PLACE
AND HAVE NOT MOVED NOR CAUSED ANY FLOODING ISSUES THROUGH THE
LATER WINTER MONTHS. HOWEVER, THEY WILL BEAR WATCHING AS WE HEAD
THROUGH THE SPRING AS THEY WILL LIKELY SERVE AS A FOCUS FOR BREAK
UP JAMS AND/OR WILL PROVIDE AMPLE ICE DEBRIS AVAILABLE TO JAM
DOWNSTREAM.

...IN CONCLUSION...

BASED ON THE AFOREMENTIONED INFORMATION, THE WINTER/SPRING FLOOD
POTENTIAL IS ABOVE NORMAL FOR ALL OF CENTRAL AND DOWNEAST MAINE,
INCLUDING THE PENOBSCOT, PISCATAQUIS, AND SAINT CROIX RIVER
BASINS. ALTHOUGH RIVER FLOWS ARE NEAR TO A BIT BELOW NORMAL IN
THESE AREAS, ANTECEDENT MOISTURE STATES ARE NEAR TO ABOVE NORMAL,
ESPECIALLY DOWNEAST. THE SNOWPACK AND THE LIQUID WATER EQUIVALENT
CONTAINED THEREIN ARE WELL ABOVE NORMAL. NOW THAT WE ARE IN MARCH
AND EXPECT A WARMING TREND, MELTING SNOW WILL BEGIN TO RAISE WATER
LEVELS. THIS MAY BE SLOW AT FIRST AS THE SNOWPACK WILL BE ABLE TO
ABSORB MELT UNTIL THE PACK RIPENS. HOWEVER, WITH SO MUCH WATER
CONTAINED IN THE SNOW, EVEN WITH NO SIGNIFICANT RAIN EVENTS
EXPECTED IN THE NEAR FUTURE, IT IS STILL MORE LIKELY THAN NORMAL
THAT WE WILL SEE FLOODING IN THESE AREAS THIS SPRING.

ACROSS THE REMAINDER OF THE STATE, THE WINTER/SPRING FLOOD
POTENTIAL IS NEAR NORMAL TO A BIT BELOW NORMAL OVER FAR NORTHERN
MAINE. IN THESE AREAS, THE PRIMARY IMPETUS IN THE NEAR NORMAL
DESIGNATION IS THE NEAR NORMAL SNOW DEPTHS AND AMOUNTS OF WATER
IN THAT PACK. GIVEN THIS IN ADDITION TO THE NEAR NORMAL RIVER
FLOWS, NEAR NORMAL GROUNDWATER LEVELS, AND SOMEWHAT DRY ANTECEDENT
CONDITIONS, A NEAR NORMAL FLOOD THREAT SEEMS REASONABLE. FAR
NORTHERN MAINE HAS A BIT LESS SNOW AND LIQUID EQUIVALENT THAN
WHAT WE`D NORMALLY SEE IN EARLY MARCH, SO THIS AREA`S FLOOD
POTENTIAL IS A BIT BELOW NORMAL.

THE POTENTIAL FOR FLOODING DUE TO ICE JAMS IS SLIGHTLY ABOVE
NORMAL ACROSS THE ENTIRE AREA. THE RIVER ICE IS QUITE THICK, AND
ALTHOUGH IT IS NOT ABNORMALLY SO, IT IS STILL VERY STRONG AND
SOLID. THE WARMING SUN AND MILDER TEMPERATURES WILL HAVE A VERY
HARD TIME WORKING ON THE RIVER ICE, ESPECIALLY SINCE THE ICE IS
STILL COVERED BY AS MUCH AS 30 INCHES OF SNOW IN SOME PLACES.
THEREFORE, THE ICE WILL LIKELY STAY STRONG OVER THE NEXT FEW WEEKS,
MEANING THE ICE JAM THREAT WILL ALSO REMAIN THROUGH MARCH AND INTO
APRIL. THIS MEANS THAT ANY LARGE SCALE RUNOFF EVENTS OVER THE NEXT
MONTH TO 6 WEEKS WILL HAVE THE POTENTIAL TO CAUSE ICE JAM
FLOODING. THIS EASILY JUSTIFIES AN ABOVE NORMAL THREAT.

IT IS IMPORTANT TO REMEMBER THAT VERY HEAVY RAINFALL CAN BRING
FLOODING AT ANY TIME OF THE YEAR, EVEN IN AREAS THAT DON`T HAVE A
SIGNIFICANT SNOWPACK.

THE NEXT WINTER/SPRING FLOOD POTENTIAL OUTLOOK WILL BE AN
INTERMEDIATE STATEMENT ISSUED BY NWS CARIBOU ON THURSDAY, MARCH
12, 2015, FOLLOWED BY THE REGULAR ISSUANCE ON MARCH 19, 2015.

$$

HASTINGS