NWS State College Case Examples
The quick warm up of 14-15 May 2013
By
Richard H. Grumm
National Weather Service State College, PA
Contributions by the Albany Map and Ron Holmes
Abstract:
A retreating late season cold front and an advancing early season warm air mass led to rapid
temperature changes in the Midwest on 14 May and in the Mid-Atlantic region on 15 May 2013.
The elevated mixed layer of very warm air mixed down as the cool air mass retreated producing
283 near or tied record high temperatures in the afternoon hours of 14 May 2013 after a
relatively chilly period for early May.
High temperatures in the Midwest reached well into the 80s and 90s on 14 May. Several dozen
station reached high temperatures of 100F or greater to include locations in the State of
Minnesota.
In the Mid-Atlantic region, the rapid erosion of the low-level cold air during the later morning
and afternoon hours of 15 May 2013 led to many rapid temperature rises in the Mid-Atlantic
region. Despite the rapid temperature rises, few high temperature records were set in the MidAtlantic region.
This meteorologically curious event was also relatively well predicted.
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1. Overview
A period of rapid warming affected much of the central and eastern United States on 14-15 May
2013. A rapidly retreating cold air mass (Fig. 1) with 850 hPa temperatures running -1 to -2
below normal was rapidly replaced by an 850 hPa air mass with temperatures over +3 above
normal in the upper Midwest and about +2 above normal in the Mid-Atlantic region (Figs. 1cf). The rapid warm up produced temperatures in the 80s, 90s, and lower 100s across the Midwest
on 14 May leading to rapid snow and ice melt in some locations and new record high
temperatures. Sioux City Iowa recorded a high temperature of 106F on 14 May beating the
previous record of 97F set in 2001 and set a new monthly record high displacing the 105F
reading set on 30 May 1934.
Several sites in Minnesota broke 100F on 14 May 2013 though most locations recorded high
temperatures in the 80s and 90s except near frozen lakes where temperatures were considerably
colder. The Twin cities reached 98F breaking the record high of 95 set in 1932 and setting a new
early season high temperature record. Shelborne and Winnebago MN recorded high temperatures
of 103F and 102F respectively. The high temperatures and record high temperatures were
attributed to the warm dry air mass which moved over the region. In many locations the delayed
start to spring and minimal green-up may have played a role in the temperature extremes.
As the warm air mass moved eastward it produced warm conditions in the Mid-Atlantic region
which included a rapid warm-up in portions of central Pennsylvania in 15 May. The retreating
cold air mass and surface anticyclone (Fig. 2) kept low-level cold air in place through around
1200 to 1500 UTC on 15 May 2013 (Fig.3). Temperature rises of 20 to 30F were experienced at
nearly all ASOS and AWOS sites in central Pennsylvania during the early afternoon hours of 15
May 2013 as the low-level cold air was rapidly mixed out. In the Mid-Atlantic region the rapid
temperature increases were more impressive than the high temperatures achieved.
This paper the meteorological conditions associated with the rapid warm up and record warmth
in the central United States and the rapid warm-up in the Mid-Atlantic region. The focus is on
the pattern and the anomalies of key fields associated with temperature extremes.
2. Data and Methods
The large scale pattern was reconstructed using the Climate Forecast System as 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).
Temperature data were retrieved from NCDC. The record high high-temperature data during the
event and record low-temperature data data leading up to the event were examined. A summary
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of record highs set from 14-17 May is summarized in Table 1. A daily summary of temperatures
above 100F on 14 May, recorded on the morning of 15 May is show in Table 1. Similar data
were produced for low temperature data but are not shown here.
Day
New Records
Ties
Total
14 May
84
41
125
15 May
62
221
283
16 May
20
19
39
17 May
10
8
18
Table 1. Record Highs tied or broken and total number of records for the
dates shown. Data based on NCDC data site.
3. Pattern over the region
Table 1 shows the number of daily high temperature records set or tied during the period from
14-17 May 2013 and Table 2 lists the data for stations which reached a high of 100F or greater
on 15 May 2013. Listing sites that achieved 90F or greater would require around 180 more rows
of data. Despite the rapid warm up in the Mid-Atlantic region on 15 May 2013 few record high
temperatures were set, thus there were few records recorded on 16 May 2013.
The larger scale pattern from 11-16 May 2013 (Fig. 5) shows a deep trough over the central
United States at 11/1200 UTC. This deep trough progressed eastward bringing cold air and some
record lows to the central and eastern United States 81, 168, and 181 record lows were set or tied
respectively on12, 13 and 14 May 2013. As the 500 hPa trough moved eastward, the large ridge
along the West Coast moved into the central United States (Figs. 5b-d). The surge of warm air
was accompanied by a models surge in the precipitable water (PW:Fig 6.). The PW data imply
that some of the regions where the rapid warm up was observed in the Midwest on 14 May, such
as Minnesota and Iowa had relatively moisture columns, perhaps outside the boundary layer, as
the PW values were in the 25 to 30mm range as analyzed by the CFS1 and were 1 to 2 above
normal. The sounding from Omaha (Fig. 7) showed a PW value near 20mm at 14/1200 UTC
which was within 5mm of the CFS value at that point and time.
4. RAP
The RAP analysis of hourly of 2m temperatures in increments showed the warm up over
Pennsylvania (Fig. 8) as temperatures nearly -1 below normal were replaced by temperatures
over 2above normal in the span of under 6 hours. Many locations had 5-hour temperature
changes of 4-8C. The RAP forecasts (Fig. 9) from 1500 UTC showed the rapid warm-up and the
RAP forecasts tended to be warmer than the RAP analysis. The salient point was that short-term
high resolution models predicted the relatively rapid warm-up quite well.
1
There were some clear dew point errors in the NCEP GFS this day with low-level dew points running over 5C
above observed values. It is unclear if this impacted the CFS analyzed moisture fields.
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Though not shown, part of the success in these forecasts was the presence in model sounding of
the elevated well mixed layer just above the remnant cold air in the boundary layer. Once the
cold air mixed out the potential for temperatures to increase rapidly were present in the model
forecasts.
The rapid temperature rise was generally well predicted in most forecast guidance. The 15/0900
UTC SREF (Fig. 10) showed a rise at a point near State College from 40F to about 76F. The
high temperature was relatively low relative to observations which peaked out at about 80F (Fig.
3).
5. Summary
A retreating late season cold front and an advancing early season warm air mass led to rapid
temperature changes in the Midwest on 14 May and in the Mid-Atlantic region on 15 May 2013.
The elevated mixed layer which mixed down the warm air as the cool air retreated produced 283
near or tied record high temperatures in the afternoon hours of 14 May 2013 (Table 1) and there
were 10s of Stations which reached high temperatures of 100F or greater (Table 1). Few high
temperature records were set in the Mid-Atlantic region though there were locations which had
remarkable temperature increases on 15 May.
The cold spring and cold air mass which impacted the eastern United States on mother’s Day
weekend 2013 likely contributed to the large temperature swings. This air mass had several days
of low temperature records in the central United States before the warm air mass moved into the
region. The observed high and low data for Minneapolis-St Paul (Fig. 11) show the cold period
from March through late April. The warm surge and record high on 14 May came after a cold
period which was proceeded by two weaker warm surges.
The event was meteorologically interesting, but not necessarily meteorologically significant like
a tornado or hurricane. The event was also relatively well predicted by the NCEP models. It was
a rare chance for forecasters to improve upon guidance as guidance typically does not perform
well predicting record high temperatures. But the case also demonstrates the value of high
resolution models in predicting rapid changes as synoptic scale patterns evolve.
6. Acknowledgements
Albany Map for data and comments related to the rapid warm up of 14-15 May 2013.
7. References
Coniglio, Michael C., Harold E. Brooks, Steven J. Weiss, Stephen F. Corfidi, 2007: Forecasting the
Maintenance of Quasi-Linear Mesoscale Convective Systems. Wea. Forecasting, 22, 556–570. doi:
http://dx.doi.org/10.1175/WAF1006.1
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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.
Gallus, W.A., N.A. Snook, and E.V. Johnson, 2008: Spring and Summer Severe Weather Reports
over the Midwest as a Function of Convective Mode: A Preliminary Study. Wea. Forecasting, 23,
101–113.
Johns, R. H., and W. D. Hirt, 1987: Derechos: widespread convectively induced windstorms.
WeatherForecasting, 2, 32-49.
Klimowski, B.A., M.R. Hjelmfelt, and M.J. Bunkers, 2004: Radar Observations of the Early
Evolution of Bow Echoes. Wea. Forecasting, 19, 727–734.
Rasmussen, E.N. and S. A. Rutledge, 1993: Evolution of Quasi-Two Dimensional Squall
Lines. Part 1: Kinematic and Reflectivity Structure. J. Atmos. Sci. ,50, 2584-2606.
Schmocker, G.K., R.W. Przybylinski, and Y.J. Lin, 1996: Forecasting the initial onset of
damaging downburst winds associated with a Mesoscale Convective System (MCS) using the
Mid-Altitude Radial Convergence (MARC) signature. Preprints, 15th Conf. on Weather
Analysis and Forecasting, Norfolk VA, Amer. Meteor. Soc., 306-311.
Weisman, M. L., and R. Rotunno, 2004:“A theory for strong long-lived squall lines” revisited. J.
Atmos. Sci.,61,361–382.
——, J. B. Klemp, and R. Rotunno, 1988: Structure and evolution of numerically simulated squall
lines. J. Atmos. Sci., 45, 1990–2013
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Weaver, S. C., and S. Nigam, 2008: Variability of the Great Plains low level jet: Large scale circulation
context and hydroclimate impacts. J. Climate,21,1532–1551.
RECORD EVENT REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
205 PM CDT TUE MAY 14 2013
...RECORD DAILY AND MONTHLY MAXIMUM TEMPERATURE SMASHED AT
SIOUX CITY IA...
AT 135 PM THE TEMPERATURE REACHED 106 DEGREES AT THE SIOUX CITY
GATEWAY AIRPORT ESTABLISHING A NEW RECORD DAILY MAXIMUM TEMPERATURE
FOR THIS DATE AND A NEW RECORD FOR THE HIGHEST TEMPERATURE FOR THE
MONTH OF MAY.
THE PREVIOUS RECORD DAILY MAXIMUM TEMPERATURE WAS 97 DEGREES SET IN
2001 AND THE PREVIOUS RECORD MONTHLY MAXIMUM TEMPERATURE FOR MAY WAS
105 DEGREES SET ON MAY 30, 1934.
THE TOP TEN HIGHEST TEMPERATURES FOR MONTH OF MAY FROM 1889 TO 2013
DEGREES
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
105
103
102
102
101
100
99
99
98
98
DATE
5/30/1934
5/29/1934
5/25/1967
5/31/1934
5/15/2001
5/06/1934
5/19/1934
5/18/1934
5/28/2006
5/24/1939
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Figure 1. CFS plots of 850 hPa temperatures and temperature anomalies in 12 hour increments from a) 1200 UTC 13 May 2013 through f) 000
UTC 16 May 2013. Return to text.
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Figure 2. As in Figure 2 except for CFS mean sea-level pressure (hPa) and pressure anomalies. Return to text.
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Figure 3. Hourly plots of surface temperatures and dew points at (upper) University Park Airport and (lower)
Clearfield. Data courtesy of Ron Holmes. Return to text.
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Figure 4. NCDC number and location of record highs set or tied on 14 May 2013. Due to data collection times dates are
scored as the following morning and appear as 15 May 2013 records. Return to text.
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Figure 5. As in Figure 1 except for 500 hPa heights and height anomalies in 24 hour intervals from a) 1200 UTC 11 May through f) 1200 UTC 16
May 2013. Return to text.
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DATE
REC
PREV
PREV DATE
POR
ST
NAME
5/15/2013
107.1
107.1
5/15/1988
32
CA
BAKER
5/15/2013
106
106
5/15/2006
44
AZ
BEAVER DAM
5/15/2013
102.9
91.9
5/15/2007
115
IA
ALGONA 3 W
5/15/2013
102.9
93
5/15/2001
110
MN
WINNEBAGO
5/15/2013
102.9
91.9
5/15/1991
115
NE
TEKAMAH
5/15/2013
102.9
96.1
5/15/2001
96
NE
WALTHILL 1E
5/15/2013
102.9
93.9
5/15/2001
113
NE
DAVID CITY
5/15/2013
102
93.9
5/15/1988
104
IA
POCAHONTAS
5/15/2013
102
91
5/15/2001
110
IA
FORT DODGE 5NNW
5/15/2013
102
96.1
5/15/2001
98
MN
WASECA EXP STATION
5/15/2013
102
91.9
5/15/2001
115
NE
FREMONT
5/15/2013
102
90
5/15/2001
62
NE
TRENTON DAM
5/15/2013
100.9
93
5/15/1988
109
IA
BRITT
5/15/2013
100.9
90
5/15/2001
105
IA
JEFFERSON
5/15/2013
100.9
91
5/15/2001
120
IA
LOGAN
5/15/2013
100.9
90
5/15/2001
114
IA
ROCKWELL CITY
5/15/2013
100.9
98.1
5/15/2001
115
IA
LE MARS
5/15/2013
100.9
89.1
5/15/2001
64
IA
CASTANA EXP FARM
5/15/2013
100.9
95
5/15/2007
47
KS
NORTON DAM
5/15/2013
100.9
91.9
5/15/2007
117
MN
ALBERT LEA 3 SE
5/15/2013
100.9
93.9
5/15/1941
117
NE
RAVENNA
5/15/2013
100.9
93
5/15/2001
48
NE
CANADAY STEAM PLANT
5/15/2013
100.9
96.1
5/15/1931
111
NE
CURTIS 3NNE
5/15/2013
100.9
89.1
5/15/1962
58
NE
MEDICINE CREEK DAM
5/15/2013
100.9
91.9
5/15/2001
97
NE
OSCEOLA
5/15/2013
100.9
96.1
5/15/2001
115
NE
WAKEFIELD
5/15/2013
100
89.1
5/15/2007
70
IA
MAPLETON NO.2
5/15/2013
100
93.9
5/15/2001
91
IA
CHEROKEE
5/15/2013
100
91.9
5/15/2001
66
IA
EMMETSBURG
5/15/2013
100
93
5/15/2001
102
IA
SIBLEY 3 NE
5/15/2013
100
91.9
5/15/2001
116
IA
CARROLL
5/15/2013
100
97
5/15/1931
86
KS
ATWOOD
5/15/2013
100
91
5/15/2007
72
MN
AUSTIN WASTE WATER TREATMENT
5/15/2013
100
90
5/15/2007
54
NE
SUPERIOR 4E
5/15/2013
100
97
5/15/1915
72
NE
GREELEY
5/15/2013
100
93
5/15/1944
114
NE
WEST POINT
5/15/2013
100
97
5/15/1941
114
SD
VERMILLION 2 SE
Table 2. List of NCDC data where temperatures exceed 100F on 15 May 2013. Data includes the date, record for the date,
previous record and the date of that record, the period of record for the station, the State and the town or Station name or
ID. Return to text.
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Figure 6. As in Figure 6 except for precipitable water (mm) and precipitable water anomalies in 12 hour increments from a) 1200 UTC 13 May through
f) 0000 UTC 16 May 2013. Return to text.
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Figure 7. Sounding from Omaha, Nebraska at 1200 UTC 14 May 2013. Sounding courtesy of Lance Bosart and the Albany map.
Return to text.
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Figure 8. NCEP RAP analysis of 2m temperatures in 1-hourly increments from a) 1500 UTC through f) 2000 UTC 15 May 2013. Values in C. Return to text.
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Figure 9. As in Figure 8 except for RAP forecasts initialized at 1500 UTC 15 May 2013. Return to text.
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Figure 10. NCEP SREF initialized at 0900 UTC 15 May 2013 showing a) 2m temperatures ( F), b) 850 hPa temperatures (C ) and, c)
7700 hPa temperatures. Thick yellow line is the median black is the mean and each member is color coded. Return to text.
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Figure 11. Climate range showing mean high and low with daily highs for Minneapolis, Minnesota. Cold colors are ranges for low and hot colors
show ranges for high temperatures. XMACIS data plot provide by Charles Ross. Return to text.