Download The Big Chill of January 2013

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The Big Chill of January 2013
By
Richard H. Grumm
And
Elyse Colbert
National Weather Service State College, PA
1. Overview
The period of 15-27 January saw the incursion of arctic air into eastern North America and much
of the north-central and northeastern United States. During the peak of the cold episode (Fig. 1) a
deep trough with -2 to -3s height anomalies (Fig. 1a) and a pool of deep cold air (Figs. 1b&1c)
were present over much of eastern Canada and the northern tier of the United States. Much of the
North America was dry with large areas where the precipitable water (Fig. 1d) was near or below
normal. The strong and persistent ridge over the southwestern Atlantic limited the penetration of
the cold air into the southern and southeastern United States.
A sudden stratospheric warming (SSWE:Smith and Kushner 2012; Baldwin et al. 2012) event
was observed in long range forecasts in late December 2012 and early January 2013. SSWE
events are typically monitored above 50 km and temperatures on model pressure surfaces of 70
to 10 hPa are often examined to monitor these events. Baldwin and Dunkerton (2001 hereafter
BD2001) noted that stratospheric events often follow the arctic oscillation (AO). Observational
studies suggest that SSWE events be used to predict changes in weather regimes. Large warm
ups over the Polar Regions often lead to arctic outbreaks over North America. BD2001 entitled
their paper “Stratospheric Harbingers of Anomalous weather Regimes” due to the apparent
observational predictability component of such events. During most winters, in the January to
February time frame there is typically 1 major stratospheric warming event (Kuttippuarth and
Nikulin 2012). It will be shown that during early January 2013 there was a northern hemispheric
SSWE.
During the onset of the SSWE event, conditions had been relatively warm over most the eastern
United States. Through December through about 6 January a cold pocket was present over the
pole at 10 hPa which was replaced by a ridge and above normal temperatures after 6 January
2013 (not shown). The strong ridge over the southwestern Atlantic (Fig. 1a) was dominant
feature through first half of January 2013, producing generally warm weather over most the
eastern United States. High temperature records were tied or broken during a prolonged period in
the southeastern United States (Table 1) through 18 January 2013. A surge of warm air ahead of
the first blast of cold air tied or broke over 100 daily maximum temperatures records from 12-13
January 2013 in the eastern United States. The warmth then emerged over the southwestern
United States (Table 1). A second surge of record warmth would affect most of the eastern
United States as the cold air slowly retreated on 27-28 January.
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This paper examines the pattern of January 2013 with a focus on the evolution of the big chill of
mid-January 2013. The persistent ridge over the southwestern Atlantic precluded the intrusion of
the cold air into the citrus growing regions of the southern United States. Forecasts of the event
are presented showing that the event and pattern change were relatively well predicted. Finally,
this event and its associated pattern are compared to the arctic outbreaks of January 1985 and
1994.
2. Data and Methods
The large scale pattern was reconstructed using the Climate Forecasts System (CFS) as the first
guess at the verifying pattern. The standardized anomalies were computed in Hart and Grumm
(2001). All data were displayed using GrADS (Doty and Kinter 1995).
The daily record temperature data were obtained from the National Climate Data Center (NCDC)
website using the interface on this site. Data retrieved included the date, number of records set or
tied and the spatial context was estimated from these data. The record high, lows and record low
highs and record low highs were all tabulated and examined.
The precipitation was estimated using the Stage-IV precipitation data in 6-hour increments to
produce estimates of precipitation during the month of January 2013. Daily records are based on
the NCDC data set similar to that used to compute the daily number of record highs and lows
used in Tables 1 & 2.
The NCEP global ensemble forecast system (GEFS) data were used to show the larger scale
forecasts of the pattern and the peak intrusion of the cold air into the eastern United States.
Overall, large scale models did not indicated a high probability of a transition to a colder pattern
in the eastern United States.
3. Observations
The high and low temperature records tied or set during January 2013 (Tables 1 & 2) and plots of
these data (Fig. 2) show the impact of the change in the pattern over the United States during the
middle of January 2013. There was a distinct shift from cold to warm in the western United
States and a gradual erosion of the warm conditions in the southeastern United States. Despite
the change in the pattern, the cold air mass that affected the eastern United States did not set
many low temperature records.
These data show a decrease (Table 1 and Figure 2b) in the number of record high temperatures
tied or exceeded after 13 January as the cold air pushed most of the warm air out of North
America and the United States. The warm air did not return until the cold air retreated on 27-28
January. The extreme warmth of 27-29 January is a topic for potential farther research.
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As the cold air and pattern change took hold, there was an increase in the number of record low
temperatures tied or exceed. However, the axis of Figure 2 shows that the warm events
outnumbered cold events by nearly 2:1 when comparing the warmest to coldest days. The record
low maximum temperatures to show the influx of the cold air but they too are generally limited
to fewer than 200 records tied or broken per day during the peak of the cold episode. The 2:1
ratio can also be obtained comparing the total number of records tied or broken which shows that
January 2013 had nearly twice as many warm records set or tied relative to cold records set or
tied.
4. Pattern-Tropospheric
The pattern over North America from 01-15 January 2013 (Fig. 3) showed the persistence and the
strength of the ridge over the southwest Atlantic where for 500 hPa height anomalies were +1s
above normal during the period. A strong ridge was present over the eastern Pacific basin. A
weak 500 hPa low was located over extreme northern North America. The ridge over the western
Atlantic extended over most of the eastern United States and Great lakes. Beneath the ridge the
700 and 850 hPa temperatures were above normal. The only cold air of note was over the West
Coast of North America.
The pattern from 15-23 January 2013 (Fig. 4) is a stark contrast to the data in Figure 3. The
eastern Pacific ridge was replaced by a sharp ridge along the West Coast of North America and a
strong vortex was present at 500 hPa over central Canada. Cold dry air was present over most of
central and northern North America. The strong ridge over the southwestern Atlantic was still
present though suppressed to the south and east. This ridge limited the southward extent of the
surge of cold air into the Gulf States and Florida.
The evolution of the cold in the United States is shown in Figures 5 & 6. These data show the
surge of above normal 850 hPa temperatures over most of the United States East of the Rocky
Mountains from 12-14 January 2013. This encompassed the period of above normal warmth in
Table 1 and Figure 2. The arctic air, with 850 hPa temperatures around -34C in its core began to
enter the northern United States at 17/0000 UTC (Fig. 5f). Figure 6 shows the intrusion of cold
air across the northern tier of the United States with a -30C contour at 850 hPa over Great Lakes
at 22/0000 UTC.
The core of the cold air over the Great Lakes and eastern United States at 22/1200 UTC is shown
in Figure 7. The -20C contour was well into the Ohio Valley with -28C air at 850 hPa over the
Great Lakes (Fig. 7b). The cold air was also in a tight gradient between the cyclone off the East
Coast and the anticyclone over the western plains (Fig. 7d).
The lack of a significant number of low temperature records being broken or tied may relate to
how cold the air mass was relative to other mid-January air masses. Table 3 lists cold days from
the COOP station in State College, PA. The dates show many record lows or record high lows
associated with cold days over the region. The pattern associated with the cold episodes of
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January 1994 and January 1985 is shown in Figure 8 & 9. The 1985 event had a pocket of -32C
air at 850 hPa over the Ohio and it was the second coldest 24 hour period in State College. The
January 1994 event had a stronger surface anticyclone over the eastern United States, the coldest
temperatures at 850 hPa were observed at 19/1200 UTC, prior to the arrival of the massive
anticyclone, along with deep snow cover produced the extreme low temperatures on 21 January
1994 (Table 3).
5. Stratosphere
Figure 10 shows the 50 hPa temperature for 15 December 2012, 20 January 2013, the change of
the 50 hPa temperatures from 31 January through 31 December and for the period covered by the
first two periods. These data showed a cold pocket over the pole and northern Europe on 15
January which was replaced by a warm pocket by 20 January 2013. A change of over +30K is
clearly visible over and near the poles. The largest changes occurred from 31 December through
20 January (Fig 10c) thought there was large change in the longer period of 15 December 2012
through 20 January 2013.
These data show that there was an impressive SSWE from late December 2012 through midJanuary 2013 and this SSWE event was related to an arctic outbreak over much of eastern North
America. Though not shown, this warm-up was predicted in the GFS and ECMWF in late
December (not shown).
6. Forecasts
The 500 hPa pattern valid at 1200 UTC 17 January from the NCEP bias corrected GEFS is
shown in Figure 11. Forecasts for 0600 UTC 10 January and 15 January are presented. These
forecasts were somewhat randomly selected though any forecast from the period of 5 to 15
January would illustrate the point as these data cover 16 days and the general cold trend was
present 16 days in advance.
These forecasts show the deep trough over eastern North America with below normal heights
and the below normal 850 hPa temperatures, which correspond well with the surge of low
temperature records in Table 2 and Figure 2. These to comparative forecasts show that the
ensemble mean under predicted the depth of the trough and the intensity of the cold air 7 days
out, likely due to the large spread between the members, relative to the shorter 2-day forecasts.
This impacted the standardized anomalies. But the big differences included the -32C contour and
4800 m contour in the sharper, shorter range forecasts.
The salient point here is the cold episode was generally well predicted.
7. Summary
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A deep trough brought a surge of cold air into eastern North America in mid-January 2013. The
surge of cold air and the deep trough were relatively well predicted by the NCEP GEFS, though
only GEFS bias corrected data are shown here. The SSWE event of late December and early
January 2013 also appeared to be a useful tool to add confidence in anticipating the surge of cold
air into eastern North America. Despite the cold air, the daily number of record lows set during
the period was rather paltry this may be related to the large ridge over the southwestern Atlantic
and other factors.
As the long wave pattern shifted over North America in January, cold air moved into the United
States and the number of tied or broken low temperature records began to rise (Table 2) around
12 January, though most of the records were broken in the western United States. The larger
impact was to reduce the number of high temperature records set during January. There was a
peak in high temperature records being tied or set as the cold air moved southward and the warm
air associated with persistent western Atlantic subtropical ridge pushed warm air northward
ahead of the frontal system.
The surge of cold air into the central and eastern United States from 15 to 24 January 2013 did
not set a significant number of low record temperatures. The data in Tables 1 & 2 and Figure 2
imply that despite the cold, the number of high temperatures broken during the month of January
2013 was far larger than the number of record lows and record low high temperatures. This could
be the result of the a) the lack of deep snow cover over a large portion of the region affected by
the cold air, b) the general lack of extreme cold air over North America due to climate change
or c) the cold episode occurred during a time where historically there have been intrusions of
extreme arctic air masses. The arrival of the arctic air in this event was well timed to coincide
closely with a record cold episode in January 1994. The colder air mass of 1994 relative to 2013
may imply that point b) may have some merit. This is further supported by the fact that the
month of January, despite the intrusion of cold air, had more record warm events than cold
events. An argument often presented by climate change research showing the tendency for more
warm episodes and records relative to cold episodes and records being set.
The large scale pattern during the first 3 weeks of January 2012 showed a ridge off the
southwestern Atlantic (Fig. 1) which support return flow on its flanks. This return flow produced
over 150 mm of rainfall from eastern Texas to southern Virginia (Fig. 12). There was over 300
mm of precipitation along the Gulf Coast during the first 24 days of January. The flow about this
ridge and the cold air to the north limited the precipitation in the southern and central plains and
kept most of the northern tier of the United States relatively dry. The Pacific Northwest too
experienced relatively wet conditions.
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The large scale ridge over the southwestern Atlantic may have limited how deep into the
southeastern United States the cold air penetrated. This too may have limited the number of
record low temperatures set or tied in January 2013.
This event appears to show that SSWEs may be useful “harbingers” of arctic outbreaks into
eastern North America. This event may also suggest that the cold air mass of 2013 may have
lacked the deep cold of similar air masses of 15 to 50 years ago. Or quite simply put, arctic air
over North America appears to lack the punch of arctic air from 20+ years ago.
8. Acknowledgements
Data access to daily highs, lows, and precipitation courtesy of NCDC.
9. References
Baldwin, M.P. and T.J. Dunkerton, 2001: Stratospheric harbingers of anomalous weather regimes,
Science, 244, 581-584.
Baldwin, M.P., and T.J. Dunkerton, 1999: Downward propagation of the Arctic Oscillation from the
stratosphere to the troposphere, J. Geophys. Res., 104, 30,937-30,946.
Doty, B.E. and J.L. Kinter III, 1995: Geophysical Data Analysis and Visualization using GrADS.
Visualization Techniques in Space and Atmospheric Sciences, eds. E.P. Szuszczewicz and J.H.
Bredekamp, NASA, Washington, D.C., 209-219.
J. Kuttippurath and G. Nikulin, 2012: A comparative study of the major sudden stratospheric warming’s
in the Arctic winters 2003/2004–2009/2010. Atm. Chem. Phys,12,8115-8129.
Miller, J.E. 1946: Cyclogenesis in the Atlantic coastal region of the United States. J. Meteor.,3,31-44.
Smith, K. L., and P. J. Kushner (2012), Linear interference and the initiation of extratropical stratospheretroposphere interactions, J. Geophys. Res.
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Figure 1. Composite pattern from the CFSV2 data for the period of 0000 UTC 15-23 January 2013 showing a) 500 hPa heights and height
anomalies , b) 700 hPa temperatures and temperature anomalies, c) 850 hPa temperatures and temperature anomalies, and d) precipitable
water and precipitable water anomalies. Return to text.
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Figure 2. Number of record highs, record lows, and record low high temperatures set or tied during January 2013. Return to text.
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MAX TEMPS
Date
1/1/2013
1/2/2013
1/3/2013
1/4/2013
1/5/2013
1/6/2013
1/7/2013
1/8/2013
1/9/2013
1/10/2013
1/11/2013
1/12/2013
1/13/2013
1/14/2013
1/15/2013
1/16/2013
1/17/2013
1/18/2013
1/19/2013
1/20/2013
1/21/2013
1/22/2013
1/23/2013
1/24/2013
1/25/2013
1/26/2013
1/27/2013
1/28/2013
1/29/2013
1/30/2013
1/31/2013
Total:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
New
Records
1
1
1
1
2
0
1
2
14
15
48
200
159
77
49
25
27
11
37
25
11
23
27
28
27
13
19
56
270
345
147
1662
Ties
1
3
5
0
2
1
1
8
16
9
19
69
78
46
16
17
12
5
14
15
10
10
11
12
15
9
13
21
71
91
28
628
Sum
2
4
6
1
4
1
2
10
30
24
67
269
237
123
65
42
39
16
51
40
21
33
38
40
42
22
32
77
341
436
175
2290
Locations
Alaska
SE, West Coast
NW Coast
Florida
NW Coast
NW Coast
West Coast
Florida, Michigan
Florida (majority), Upper Mississippi Valley
Florida, Upper Mississippi Valley
Mississippi Valley, Florida
Southeast, Midwest
Alaska, Southeast, Midwest
Alaska, Southeast
Southeast
Southeast
Southeast
Southeast
Midwest
Midwest
Southwest
Southwest
Southwest
Colorado, Texas
Colorado, Texas
Texas, Montana
Texas, West
Texas, Southern Plains
Midwest
Midwest to Ohio Valley
Mid Atlantic, Northeast
Table 1. List of Daily high temperatures set and the region or regions of the United States affected.
Data from NCDC including the date, day of month, new records, tied records, total records and
region or regions with most records set or tied. Return to text.
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Date
1/1/2013
1/2/2013
1/3/2013
1/4/2013
1/5/2013
1/6/2013
1/7/2013
1/8/2013
1/9/2013
1/10/2013
1/11/2013
1/12/2013
1/13/2013
1/14/2013
1/15/2013
1/16/2013
1/17/2013
1/18/2013
1/19/2013
1/20/2013
1/21/2013
1/22/2013
1/23/2013
1/24/2013
1/25/2013
1/26/2013
1/27/2013
1/28/2013
1/29/2013
1/30/2013
1/31/2013
Total:
Day of
Month
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
New
Records
6
11
23
9
19
15
5
2
1
2
8
44
69
115
90
45
11
6
4
9
10
22
7
4
2
4
0
2
3
0
1
549
Ties
4
4
11
2
3
2
0
0
0
0
3
15
16
26
14
15
7
2
5
2
7
6
4
1
1
3
0
0
2
0
0
155
Sum
10
15
34
11
22
17
5
2
1
2
11
59
85
141
104
60
18
8
9
11
17
28
11
5
3
7
0
2
5
0
1
704
Locations
West
West
West
West
West/Southwest
Southwest
West
West
West
Gulf Coast
Southwest
West
West
West
West
West
West
Southwest
West
West
West
West, Midwest
West
West, Minnesota
Mid Atlantic
Southwest
Southwest
Arizona
Table 2. As in Table 1 except for the number of low temperature records set. Return to text.
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Figure 3. As in Figure 1 except for 0000 UTC 1-15 January 2013. Return to text.
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Figure 4. As in Figure 1 except for the time period of 0000 UTC 15-23 January 2013. Return to text.
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Figure 1. As in Figure 1 except for 850 hPa temperatures and temperature anomalies at 0000 UTC from a) 12 to b) 17 January 2013. Return to text.
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Figure 6. As in Figure 5 except for 850 hPa temperatures and temperature anomalies at 0000 UTC from a) 17 to b) 22 January 2013. Return to text.
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Figure 2. CFSV2 data showing the pattern at 1200 UTC 22 January 2013 including a) 500 hPa heights and height anomalies, b) 850 hPa temperatures
and temperature anomalies, c) precipitable water and precipitable water anomalies, and d) mean sea-level pressure and pressure anomalies.
Return to text.
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Date
Min
Max
2 Feb 1899
-20
-5
1/21/1985
-17
-3
1/18/1982
-17
-2
1/20/1994
-18
-1
1/18/1977
-11
-11
1/23/1936
-14
7
1/30/1977
-10
9
1/17/2009
-2
8
1/16/1994
-6
3
1/1/1963
-3
10
1/13/1977
-1
11
1/19/1976
-1
15
1/11/1978
-2
12
2/12/2008
2
16
1/22/1966
4
11
1/24/2003
4
12
1/21/2008
7
14
Table 3. List of dates and 24 hour
maximum and minimum temperatures
at State College, PA. Return to text.
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Figure 8. As in Figure 7 except for 0000 UTC 20 January 1994. Return to text.
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Figure 9. As in Figure 7 except for 0000 UTC 21 January 1985. Return to text.
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Figure 10. CFSRV2 50 hPa data showing stratospheric temperatures ( C) over the northern hemisphere at a) 0000 UTC 15 December 2012, b) 20
January 2013, and the 50 hPa temperature changes from c)20 January 2013 and 31 December 2012 and d) 20 January 2013 and 15 December
2012. Time differences are at 0000 UTC for the specified times only. Return to text.
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Figure 12. Stage-IV summed precipitation from 0000 UTC 1 January through 0000 UTC 24 January 2013. Values in mm and values
less than 8 mm not shown. Return to text.
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Figure 11. GEFS bias corrected forecasts of 500 hPa heights and 850 hPa temperatures and standardized anomalies showing the forecasts
valid at 1200 UTC 17 January 2013 from forecasts initialized at a) 06 UTC 10 January 2013 and right) 0600 UTC 15 January 2013. Upper panels
are the 500 hPa forecasts and lower panels the 850 hPa temperatures forecasts from each day. Return to text.
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