REVISED: WINTER 2011 FORECAST

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– There have been some factors which require a major revision of the winter forecast, this will end the streak of several very accurate winter forecasts and the accurate call last summer for hot and dry. Last winter was correct more due to a fact the stronger than expected el-nino balanced the strongly negative AO.  Once again this winter so far we have been dominated by a strong – AO. This promotes a trough in the eastern portion of the United states this was coupled with a typical la-nina signal for a colder than normal december and the result was a cold and snowy december for the region.

Lexington, KY climate report Louisville NWS

PRELIMINARY LOCAL CLIMATOLOGICAL DATA (WS FORM: F-6)

                                          STATION:   LEXINGTON KY
                                          MONTH:     DECEMBER
                                          YEAR:      2010
                                          LATITUDE:   38  1 N
                                          LONGITUDE:  84 36 W

  TEMPERATURE IN F:       :PCPN:    SNOW:  WIND      :SUNSHINE: SKY     :PK WND
=======================================================
1   2   3   4   5  6A  6B    7    8   9   10  11  12  13   14  15   16   17  18
                                     12Z  AVG MX 2MIN
DY MAX MIN AVG DEP HDD CDD  WTR  SNW DPTH SPD SPD DIR MIN PSBL

1  33  24  29 -12  36   0    T  0.1    0 11.9 21 260   M    M  10 8      26 250
2  34  22  28 -12  37   0 0.01  0.1    0  6.8 15 240   M    M   4 1      20 250
3  38  26  32  -8  33   0 0.01    T    0  3.4 10 320   M    M   6 128    14 330
4  32  28  30 -10  35   0 0.35  2.7    1  8.1 15  10   M    M  10 168    18 320
5  30  22  26 -13  39   0 0.01    T    2  9.7 18 310   M    M  10 18     24 310
6  22  15  19 -20  46   0    T    T    2 10.7 21 290   M    M   8        26 290
7  24  11  18 -21  47   0    T    T    1  6.8 16 290   M    M   5        20 280
8  25   6  16 -22  49   0 0.00  0.0    T  2.4  8 240   M    M   0        10 250
9  34   8  21 -17  44   0 0.00  0.0    T  5.1  9 150   M    M   1 8      12 140
10  47  31  39   1  26   0 0.00  0.0    0  9.7 18 220   M    M   5        23 220
11  49  33  41   4  24   0 0.27  0.0    0 11.2 25 160   M    M   7 1      32 150
12  41  20  31  -6  34   0 0.40  2.4    T 13.4 24 180   M    M  10 1      31 180
13  23  16  20 -17  45   0 0.07  1.9    4 14.2 22 310   M    M  10 1      29 300
14  20   2  11 -26  54   0    T    T    3  7.1 15 300   M    M   3        20 310
15  26   2  14 -22  51   0 0.05  0.7    2  4.7 10 110   M    M   4 18     14 120
16  32  23  28  -8  37   0 0.66  0.4    3  7.5 14 120   M    M  10 126    17 120
17  27  23  25 -11  40   0    T    T    3  6.9 14 270   M    M  10 18     18 260
18  28  23  26  -9  39   0 0.00  0.0    2  1.9  8 270   M    M  10 8      12 280
19  29  19  24 -11  41   0 0.00  0.0    1  2.6 10 340   M    M   8 18     12 150
20  33  25  29  -6  36   0 0.12  0.7    1  5.2 12 110   M    M   8 18     15 120
21  37  31  34  -1  31   0 0.01  0.2    1  6.5 13 120   M    M  10 128    16 120
22  37  26  32  -3  33   0    T    T    0  9.2 20 330   M    M  10 12     24 330
23  33  23  28  -6  37   0 0.00  0.0    0  5.7 12 350   M    M   9 18     14 360
24  31  27  29  -5  36   0 0.11  1.2    0  6.8 12  70   M    M   9 1      15  80
25  27  24  26  -8  39   0 0.04  0.7    2  7.8 15  10   M    M  10 18     18 360
26  27  21  24 -10  41   0 0.02  1.3    2 11.3 23 350   M    M  10 18     30 360
27  26  14  20 -14  45   0    T    T    2  7.8 20 340   M    M   9        24 330
28  34  14  24  -9  41   0 0.00  0.0    2  6.7 13 210   M    M   2 18     15 220
29  39  28  34   1  31   0 0.01  0.0    1  8.4 15 150   M    M   9        18 140
30  54  37  46  13  19   0 0.35  0.0    0 12.3 23 170   M    M   8 1      29 200
31  63  45  54  21  11   0 0.00  0.0    0 14.8 29 180   M    M   5        36 180

SM 1035  669      1157   0  2.49    12.4 246.6          M      230
AV 33.4 21.6                               8.0 FASTST   M    M   7    MAX(MPH)
                                 MISC —->  # 29 180               # 36  180
thus instead of a few degrees below normal with some light snow more blasts of arctic air came through with more snow since a la-nina usually tends to promote more precipitation in our region.

The primary idea for the winter was for the typical la-nina southeast ridge to develop and dominate leading to a storm track to our north with frequent shots of mild air. This idea is no longer and here are three reasons why.

1. the AO will be still negative through the foreseeable future

2.  the starting collapse of la-nina by winter’s end

3. a stratospheric warming event across the north pole in the next week

– The AO idea makes the pattern colder overall

– Our la-nina right now is around -1.5*C for the SST anomalies this should back off some during late winter, when a strong nino/a dissipates this usually means some action to end winter

– most of the focus will be on #3 today.  Both the GFS and ECMWF weeklies now show a major arctic blast entering northern Canada by week 2 and the natural progression of this by week 3 brings this southeast into the united states. Again stratospheric warming in the north pole promotes a displacement of the polar jet which can send extremely cold air south nad most often is a key factor in a major arctic outbreak.

GFS which also approximates the ECMWF week 2 forecast

the operational run was even more extreme

This stratospheric warming sets-up what should be a largely cold January. We should have several systems track from the northwest into the southern plains and off the east coast during this time frame.

back to point #2 that the la-nina may weaken by late winter.

here is a look at expected SST values ( CPC)

 do any analog winters ring a bell think what the last winter that had SST values go from -1.5 to -1 around the end of winter into spring.

A: 07-08

In fact the expected decrease in SST values are right about the same. The southeast ridge won’t be as prounced but should make an appearance by the end of January.  Also by Feb the amount of cold in Canada should be reduced because of the Jan cold, I’m cancelling these two factors for now. Hopefully 07-08 Feb/Mar rings a bell severe weather and warmth to start the month  and icy mix in the middle then snow to end it with the biggest snow in march with a fight between cold and warm over our region.

here are the Feb 08 climate numbers for Lexington, notice only one degree below normal but plenty of action (accuweather)

FEB-08 FOR LEXINGTON, KY (988′)                     LAT=38.0N LON= 84.6W

                 TEMPERATURE                       PRECIPITATION
          ACTUAL           NORMAL
        HI   LO  AVG     HI   LO  AVG   DEPT     AMNT   SNOW SNCVR   HDD
1      41   27   34     41   25   33     +1     0.14  trace    0     31
2      49   24   37     42   25   33     +4     0.00    0.0    0     28
3      51   32   42     42   25   34     +8     0.00    0.0    0     23
4      60   46   53     42   25   34    +19     0.76    0.0    0     12
5      66   56   61     42   26   34    +27     0.44    0.0    0      4
6      65   34   50     43   26   34    +16     1.39    0.0    0     15
7      36   33   35     43   26   34     +1    trace  trace    0     30
8      47   29   38     43   26   35     +3     0.00    0.0    0     27
9      52   38   45     43   26   35    +10     0.01    0.0    0     20
10      44   13   29     44   27   35     -6     0.00    0.0    0     36
11      26   12   19     44   27   35    -16     0.42    3.0    3     46
12      41   25   33     44   27   36     -3     1.27    0.0    0     32
13      30   19   25     45   27   36    -11     0.06    0.7    2     40
14      40   22   31     45   27   36     -5    trace  trace    0     34
15      47   32   40     45   28   36     +4     0.00    0.0    0     25
16      50   26   38     46   28   37     +1     0.00    0.0    0     27
17      64   46   55     46   28   37    +18     0.19    0.0    0     10
18      46   27   37     46   28   37     +0    trace  trace    0     28
19      31   21   26     46   29   37    -11    trace    0.1    0     39
20      36   17   27     47   29   38    -11    trace  trace    0     38
21      31   15   23     47   29   38    -15     0.28  trace    0     42
22      38   31   35     47   29   38     -3     0.45    0.0    0     30
23      31   28   30     48   30   39     -9     0.00    0.0    0     35
24      34   28   31     48   30   39     -8    trace  trace    0     34
25      43   31   37     49   30   39     -2    trace    0.0    0     28
26      44   25   35     49   31   40     -5     0.17    0.5    0     30
27      27   19   23     49   31   40    -17    trace  trace    0     42
28      38   19   29     50   31   40    -11    trace  trace    0     36
29      46   30   38     50   32   41     -3     0.18  trace    0     27

                     TOTALS FOR LEX  
HIGHEST TEMPERATURE   66         TOTAL PRECIP        5.76
LOWEST TEMPERATURE    12         TOTAL SNOWFALL       4.3
AVERAGE TEMPERATURE 35.5         NORMAL PRECIP       3.41
DEPARTURE FROM NORM -1.0         % OF NORMAL PRECIP   169
HEATING DEGREE DAYS  849
NORMAL DEGREE DAYS   841

This winter ended with a winter storm in the first week of march.

Now onto the forecast. Hopefully you have figured out it’s not going to be 3-5*F above normal the rest of the way.

Jan 1st-6th normal

Jan 7th-15th about 5*F below normal

temperature map

jan 15th-22nd

temperature map notice the WB which is way below come into the Ohio valley. modeling currently shows anywhere from -15 to -25*F below normal from this cold shot that includes the ecmwf weeklies in the middle. This should moderate some but still An extreme cold shot with temperatures for the week from 8-18*F below normal appear possible for this period. Normal for lex is 39/24 during this time I expect a few days that could be toward the upper extreme that’s lows around 5-15 and highs from 20-30 for the week average with some days cooler and some warmer. There is potential still for 2 or 3 days of 25*F below normal ( lows below 0 and highs in the 10’s, not going that far yet.)

storm track for these two weeks

jan 23rd-30th – moderation with a return to normal temperatures

February ideas: overall I like the 07-08 idea with normal being far from normal. A couple of weeks should be above normal with a severe threat with a couple of weeks featuring cold and more snow/ice chances. Kentucky should be in the fight zone between cold and warm

The southeast ridge comes back typical of la-ninas with a back and forth month which should last into march.

For the next two weeks I have updated the 14 day normal till late week then a preview shot of cold by weeks cold before the big blast. Don’t worry still some snow chances as well.

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5 Responses to “REVISED: WINTER 2011 FORECAST”

  1. mitchg Says:

    don’t think I;ve ever seen before from the cpc 8-14 day forecast before.

  2. tornadolarkin Says:

    This is sounding awesome Mitch!!

  3. mitchg Says:

    even more awsome is adding two more accumulating snows to the forecast for this week.
    – the GFS has come on board bringing a 1-3 snow wednesday night for the state
    – snow showers and squalls friday should lay down some accumulations
    – folks this is the normal week of the next four!!!!

  4. mitchg Says:

    make sure to check out the 00z gfs surface maps each day for the next 16 one of the most extreme model runs in terms of cold and snow i have seen in quite some time.

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