LONG RANGE – SEASONAL OUTLOOK UPDATE

October 26, 2009     

NOVEMBER OUTLOOK & WINTER UPDATE

ONE LOOK AT THE CURRENT OCTOBER TEMPERATURE ANOMALY MAP (page 2), WILL CONVINCE ANY DOUBTERS THAT VERY COLD AIR MASS INTRUSIONS HAVE DOMINATED THE COUNTRY FOR MUCH OF THE MONTH!

EVEN THOUGH THE ATTACK POINT OF THE COLD AIR WAS FAR TO THE WEST OF THE NORTHEASTERN U.S., AS EXPECTED, THE OVER-POWERING NATURE OF THE COLD INTRUSIONS EASILY OVERWHELMED ANY ATTEMPT AT SUSTAINED WARMING ACROSS THE NORTHEAST / NEW ENGLAND REGIONS…  EVEN IN A MODIFIED FORM THE COLD AIR WAS STILL ABLE TO FORCE THE NORTHEASTERN STATES TO RUN COLDER THAN AVERAGE…

LIKE SEPTEMBER & OCTOBER, THERE IS ANALOG SUPPORT FOR AN ATTEMPT AT MODERATING NORTHEASTERN TEMPS DURING NOVEMBER!

BUT GIVEN THE CONTINUING STRONG SIGNAL FOR POWERFUL COLD AIR PRODUCTION ACROSS NORTHWEST CANADA AND THE FACT THAT I HAVE BEEN BURNED TWICE NOW BY NOT GIVING ENOUGH WEIGHT TO THE ABILITY OF THE COLD AIR TO HAVE A MORE SIGNIFICANT IMPACT FURTHER EAST, MEANS I MAY NEED TO ADJUST THE MY THINKING ABOUT NOVEMBER…

I LIKE THE NORTHWEST, THE WEST-CENTRAL AND NORTH-CENTRAL PORTIONS OF THE U.S. SEEING THE GREATEST COLD ANOMALIES EARLY IN THE MONTH… 

THE BEST POTENTIAL FOR A MILDER THAN NORMAL PERIOD ACROSS THE NORTHEAST / NEW ENGLAND REGIONS SHOULD COME DURING THE MIDMONTH PERIOD, NOVEMBER 10^th TO NOVEMBER 20^th, AS HEMISPHERIC TRENDS SUPPORT AT LEAST MODEST, IF NOT BRIEFLY STRONG, SOUTHEASTERN U.S. RIDGING!!!

COOL, NOT UNUSUALLY COLD, SIGNAL WILL BE IN PLAY DURING THE FIRST WEEK OF NOVEMBER, PRIOR TO ANY SHIFT TOWARD MIDMONTH MILD TREND!  LATE MONTH COLD SIGNAL MIGHT BE THE ONE TO WATCH AND COULD BE THE TRUE WINTER TREND SETTER!

SOME ADJUSTMENTS, MOSTLY MINOR, BEING MADE TO THE WINTER OUTLOOK…

OVERALL A VERY COLD MIDWEST PATTERN THAT BLEEDS INTO MUCH OF THE NORTHEAST STILL LOOKS LIKE THE BEST CALL… 

MAINE AND FAR NORTHERN NEW ENGLAND CONTINUE TO BE ENIGMAS, SINCE THE DIRECT DISCHARGE OF THE COLDEST AIR INTO THE CENTRAL U.S. & THE MIDWEST ARGUES FOR THESE AREAS AVERAGING CLOSER TO NORMAL…

November 2009 DISCUSSION

Overview… Please note, a November 2009 Outlook Map has been included with this update and should be viewed to better understand my narrative points. 

That is one very impressive coast to coast cold anomaly pattern depicted in the map below (current October anomaly map).  The black arrows show the average position of what has been a very persistent and highly amplified west-central / central U.S. upper air trough.  If you go back and view my October forecast anomaly map, you will find I had the coldest anomaly centered just about where the actual anomaly map shown below has it (violet & purple areas).  The problem was the intensity of the cold anomaly.  I thought I was being bold calling for a large -2.0 to -3.5 degree anomaly from the High Plains eastward into the Midwest!  In reality, as shown below, the cold anomaly became an incredible -11 to -8 degree departure.  This was a testament to not only a large reservoir of cold air across Northwest Canada, but also to a very amplified jet stream trough the provided the cold air delivery into the central U.S.

My call, as you know, for the Northeast / New England regions, as well as for much of the eastern U.S., was for a general +0.5 to +2.0 across New England & NY, a bit milder southward and an enhanced +2 to +4 anomaly just to the north.  It was believed that a central / Midwest cold anomaly of about -2.0 to -3.5 would not be able to overwhelm the eastern states given some modest mild signals.

Well what a -2 to -3.5 degree anomaly could not do, the -8 to -11 degree anomaly had no problem doing.  And that was overwhelming the East enough to prevent any mild period from getting traction.  We will likely see the Northeastern U.S. finish the month with widespread -2 to -5 degree anomalies, or about half of the Midwest anomaly.

Other than one impressive direct discharge into the Northeast, most of the cold anomaly that built across the Northeast came with a west to southwest jet stream flow across the eastern U.S.  Note the mean jet flow on the map on page 2.  The jet flow drilled the cold air into the central U.S. and then it swept east/northeast toward the NY/New England and Middle Atlantic regions.  Many times a flow like this forces the Northeast region of the country to average above normal, or possibly close to normal, unless it is unusually cold across the midsection of the country.  This time without strong Southeast or East Coast ridging there was nothing to block the eastward advancing Midwest cold.

Now on to November!  Before the start of the summer season I discussed the fact that even though there was a strong cool signal for the summer it is awfully tough to get a 3-month period with each month averaging colder than normal.  Also, many of the analogs opened the door for a warm August.  Thus I was not shocked that August flipped to warmer than normal, after both June and July averaged colder than normal.  In some regards, I think this fall also has some of the same issues.  There had been quite a bit of analog support for a milder than normal fall, regardless of the cold winter signal for the country.  We have already seen 2 Northeastern fall months (Sept. & Oct.) run colder than the analog data suggested.  Late in the summer I ran away from the analog package and went with the summer trend of coolness.  This ended up being a mistake, as August broke the summer trend and went the way of the analog package.  Given the Sept. /Oct. trend it would be easy to abandon the fall analogs and call for another month where the cold intrusions out-duel the mild periods.  But given the large-scale hemispheric trends and the recent arrival of a Southeast ridge, I think the fall analogs should be given more weight.

With all this in mind, I will call for the best cold anomaly to setup further west that the past 2 months and also call for occasional Southeast / East Coast ridging, especially during the 2^nd and/or 3^rd week(s) of November, to blunt the eastward progression of the western and central cold intrusions.

The following sections discuss the regional breakdown of the expected November Temperature Anomaly pattern.  Again, a November Outlook map has been issued along with this discussion.

GENERAL NORTHERN MIDDLE ATLANTIC REGION, NEW YORK AND NEW ENGLAND NOVEMBER 2009 OUTLOOK…

The ridge development discussed in the paragraph above has already started to flex its muscles and will do strongly at the end of this week.  This will allow temps across the Northeast & New England regions to spike well above normal at the end of this week on into the first day of the weekend.  It is possible the ridge induced warming will stick around in the first day of November, but cooling will be following shortly thereafter.

Right now I favor the first week of November averaging modestly cooler than normal, generally -2 to -4 degrees.  After the first week, the potential for East Coast ridging should be increasing on into the midmonth period.  This is an absolute must if my November forecast is going to verify. 

If the ridging does indeed verify, strong moderation occurs as we move into or through the second full week of November and then continue into the midmonth period.  This period of warming is expect to be able to wipe away the early month cool anomaly and should leave much of the area by the time we get to about November 20^th with a modest plus anomaly of +2 to +4 degrees.

Very often we see the first signs of the true winter pattern as we move through November, especially late November.  I expect this to be the case again this year.  After a fairly bland midmonth period, I think we will see an energized winter pattern finish out the month.  Where the first attack of the winter pattern develops will be key to how much cold air can into the Northeast prior to the close of the month. 

I think the favored intrusion point for cold air mass intrusions during the first half of the winter will be into the central U.S. and Midwest.  For that reason, I do not think the Northeast feels the full affect of the late November cold shots, but like October has to deal with somewhat modified late month cold air intrusions, as the cold air masses round the base of a Midwest trough and spread eastward.

The question will be; can the late month cold reverse any midmonth warm anomaly?  For now, I will call for the cold to return to the Northeast strongly by month’s end, but since there is uncertainty about when the midmonth ridge induced warming will totally collapse I am not going to wipe away the expected midmonth warm anomaly.  I am also going to let the fall analog package have one more shot at verifying a milder than normal month, even if it is not a terribly significant end of the month warm anomaly.

There will continue to be a very favorable high latitude pattern for cold air production.  If this monthly outlook fails and ends up running colder than normal, it will once again by under-estimating the power of the expected cold air intrusions into the central U.S. and over-estimating the potential for East Coast or Southeast ridging!

SUMMARY POINTS

- First full week of November averages modestly cooler than normal, generally -2 to -4 degrees.

- Trend toward moderation expected prior to or during the midmonth period due to East Coast or Southeast ridging.

- Late month cold pattern expected, but it is uncertain if it will be early enough to reverse a midmonth warm anomaly.

- Northeast regional temperature anomaly is expected to be +1 to +2.

OTHER REGIONS…

November should open with the best cold air delivery making itself felt across the Pacific Northwest on into the Northern High Plains and then the Northern Plains.  I expect these areas, especially the interior Pacific Northwest, to bear the brunt of the very early month cold.  It is not unusual or unexpected to see very significant pattern realignments during November.  I would not be surprised, in fact there is decent model and analog support for early month cold to shift eastward during the month with the Northern & Central Plains becoming the focus point for cold air mass attacks.  The question is when would any such shift occur?  Some analog supports a total reversal of the early month pattern with the some of the areas I am indicating will average colder than normal flipping above normal by month’s end.  I have not bought into that idea yet, but it is interesting to see it being proposed. 

My current assessment calls for a significant cold anomaly to run from the Pacific Northwest east-southeast into the Plains, western Midwest and western Great Lakes.  I have labeled this area as ZONE B with an inner core of enhanced cold, ZONE A.

I favor the overall north to south trough amplitude to be a bit less during early/mid November compared to October.  I also, as indicated earlier in the discussion, favor at least some significant periods of East Coast or Southeast ridging, especially after the first week on through the midmonth period. These 2 ideas favor a warm anomaly running across the southern tier of the country from the Southwest eastward along the Gulf Coast then on northeastward up the East Coast into NY & New England. 

This is depicted on the map as ZONE C.  It has general positive anomaly of +1.5 to +3.0 degrees that decreases once into the Northeast to +1 to +2 degrees.  The decrease across the Northeast states is due to the expected late month cold trend, which might be able to really eat into or destroy the expected midmonth warming.

2009-10 UPDATED WINTER THOUGHTS…

I will be issuing an updated Winter Map prior to the end of the week and then a full winter forecast update will be issued prior to or on November 20^th.

For now, just some general thoughts about current trends since I see nothing that makes me want to make major changes in my current outlook.

The El Nino pattern is now clearly moving into a moderate category.  Most data supports the El Nino peaking between now and mid December.  It should then start a slow steady decline on through the remainder of the winter season.

The pattern continues to look very supportive for powerful cold air production across the North American polar regions this winter.  It is possible, in fact likely, that we will see the first dump of true winter cold during the second half of November.  As has been discussed several times already, the main forecast issue revolves around the location of the best and most consistent cold air delivery.

I favor, as do a host of other forecasters, the Central U.S. on into the Midwest for at least the early part of the winter; late November through December.  The second question then becomes how easily will the Midwest cold be able to flow eastward? 

My earlier Winter Map releases have clearly shown the core of the coldest air setting up across the Midwest.  I have no reason to change that idea at this point in time.  In fact, if anything, I may need to pull the coldest anomaly a bit further north in the Midwest and ease up just a bit on the cold expected across the Deep South.  Both of these items are considered minor adjustments.

Overall there is more data than not supporting a very cold winter, on average, for the eastern half of the country, with the coldest anomaly centered on the Midwest, especially for the first half of the winter.  I still think the Northeastern States, including much of New England, will average colder than normal but not to the degree areas to the west will.

There is some potential for the best cold air delivery to migrate eastward closer to the Northeast, as the winter progresses, and it should be noted that even though the average cold air delivery point may be across the Midwest, there will be short-term shifts that allow it to move toward or into New England.

What does this all mean?  It means I still favor a cold eastern U.S. winter with the coldest of the cold centered west of NY/New England.  Also, it means the option for an extremely cold winter is still on the table for the central and eastern U.S.

There continues to be a nagging question about Maine and far northern New England.  There has been and continues to be some analog data the keeps the colder than normal anomalies during the winter season out of these areas.  That does not necessarily mean an above normal winter anomaly, but at least one that is near normal.

Again, a new winter outlook map will issued this week and a full winter forecast update will be released on or prior to November 20^th.