Download 03Apr2014

Severe Event of 3 April 2014
comparison to the two larger events of the winter of 2013-2014
by
Richard Grumm
National Weather Service
State College, PA 16803
1. Overview
A significant spring time severe weather
event brought convectively driven high
winds, hail and 13 confirmed tornadoes to
the Mid-Mississippi Valley (MMV) on 3
April 2014 (Table 1 & Fig. 1). The severe
weather was associated with a plume of
deep moisture (Fig. 2) and a surge of high
precipitable water air into the Mississippi
and Ohio Valleys. The plume of deep
moisture (Fig 2) likely contributed to the
severe weather (Fig. 1) and the heavy
rainfall (Fig. 3) over the MMV and Ohio
Valley.
Ahead of the implied cold front, the GFS
diagnosed Convective Available Potential
Figure 1. Storm reports from the Storm Prediction Center (SPC) for 3 April 2014.
Month
Tornado
Wind
Hail
Total
21-Dec-13
11-Jan-14
20-Feb-14
15
4
37
401
210
435
1
1
28
417
215
500
Region
Ohio Valley and Mid-Mississippi
Valleys
Southeast US
Ohio Valley
Mid-Atlantic Day 2 of 20 Feb
21-Feb-14
7
175
6
188
event. Mainly VA-MD
28-Mar-14
0
100
133
233
West Gulf States mainly TX-LA
2-Apr-14
3
9
137
149
KS to IL
3-Apr
13
184
185
382
Mid-Mississippi Valley
Table 1. Winter 2014 and early Spring 2014 Severe weather events from the Storm Prediction Center (SPC)
Storm Reports. Data include the date, type of severe weather and total reports, and the general
geographic region affected by the severe weather event. Events with fewer than 100 reports not shown.
Energy (CAPE) in the 3600 JKG-1 range at 0000 UTC 3 April (Fig. 4a) and in the 1200 to 2400
range on 3 April from eastern Oklahoma into the MMV as the frontal system moved eastward
(Figs. 4d-f). The surge of high CAPE was well aligned with the high PW air and the strong lowlevel 850 hPa jet (Fig. 5).
The 500 hPa pattern showed a transient short-wave approaching the MMV from the west and a
modest 500 hPa ridge with +1s above normal 500 hPa heights over the southeastern United
States (Fig. 6).
The modestly deep short-wave at 500 hPa and the ridge to the east are features often associated
with intrusions of warm moist air into the central United States. The gradient between the trough
and ridge produced a strong 250 hPa jet over the ridge (Fig. 7) and implied jet entrance region
over the central United States on 3 April 2014. At lower levels, the return flow was relatively
modest in this event producing a modest severe weather event and moderate rainfall event with
areas of 2-3 inches of total rainfall in the Mid-Mississippi and Ohio River Valleys.
2. Earlier Big events of the winter
The data in Table 1 showed several large severe weather outbreaks during the winter of 20132014. The early winter event of 21 December produced severe weather from western
Pennsylvania southward into eastern Texas (Fig.8a). The 21 December event was not associated
with high surface based CAPE (Fig. 9) but had extremely high PW values with PW anomalies in
the +4 to +5 above normal range (Fig. 10) and strong low-level south-southwesterly flow with
+4 to +5 v-wind and total wind (Fig. 11) anomalies at 850 hPa. Similar to the 3 April 2014
event, there was a highly amplified trough to the west with a strong ridge to the east (Fig. 12).
The 21 December event had the similar strong trough-ridge pattern, extremely high PW with
large PW anomalies, and a strong low-level jet. Dissimilar to the 3 April 2014 event, it lacked
significant low-level CAPE. Cold season severe events often require deep moisture and strong
shear to produce significant severe weather.
The 20-21 February 2014 event (Table 1 & Fig. 9) had the similar trough-ridge pattern at 500
hPa (not shown), the surge of high PW air with +3 to +4PW anomalies (Fig. 13), and as strong
low-level 850 hPa jet with +3 to +4 v-wind (Fig. 14) and total wind anomalies (not shown).
The February event did show some CAPE with CAPE values in the 600-1200 JKg-1 range at
1800 UTC 20 February in the MMV and an expansive area of 600 to 1200 JKg-1 CAPE in the
Ohio Valley at 0000 UTC 21 February and some areas of 1800 JKg-1 embedded with the plume
of high PW air and high CAPE.
3. Summary
The first significant high-CAPE severe event of the 2014 struck the MMV and Ohio Valleys on 3
April. Similar to the larger severe events of the winter of 2013-2014 this event had a deep trough
to the west and a strong ridge to the east. This pattern produces strong southerly flow and
provides surges of high PW air. All three significant events, with over 300 reports of severe
weather had these common characteristics.
The 3 April event had significantly large CAPE relative to the February and December events.
The December event lacked any significant CAPE and was driven by strong dynamics and
potentially by elevated instability. The February event had CAPE in the 1200-1800 JKg-1 range
which supported deep convective updrafts.
These data show the common characteristics in terms of the basic pattern for widespread severe
events and the critical role high PW air and shear play in these events. This same basic pattern
can also produce heavy rainfall. High CAPE is often not as significant factor in the winter events
where moisture and strong dynamics appear to be critical factors.
Figure 2. GFS 00-hour forecasts of precipitable water (mm) and precipitable water anomalies (sigma) in 6-hour period from a) 0000 UTC 3 April through f)
0600 UTC 4 April 2014. Isopleths very 5 mm. Return to tex.t
Figure 3. Estimated rainfall for the periods of a) 0000 UTC 2-3 April and b) 0000 UTC 3-4 April 2014. Data from Stage-IV gridded QPE values shaded as in color
bars to right of images. Return to text.
Figure 4. As in Figure 3 except for GFS CAPE showing CAPE in 600JKG-1 intervals. Return to text.
Figure 5. As in Figure 3 except for GFS 850 hPa winds and v-wind anomalies. Return to text.
Figure 6. As in Figure 3 except for 500 hPa heights and height anomalies. Return to text.
Figure 7. As in Figure 6 except for 250 hPa winds and total wind anomalies. Return to text.
Figure 8. As in Figure 1 except for the severe weather reports by type for 21
December 2013 and 20 February 2014. Return to text.
Figure 9. GFS CAPE in 6-hour increments from a) 0000 UTC 21 December through f) 0600 UTC 22 December 2013. Return to text.
Figure 10. As in Figure 9 except for PW and PW anomalies. Return to text.
Figure 11. As in Figure 9 except for 850 hPa winds and total wind anomalies. Return to text.
Figure 12. As in Figure 9 except for 500 hPa heights and height anomalies. Return to text.
Figure 13. As in Figure 10 except for GFS valid at a) 0600 UTC 20 February through f) 1200 UTC 21 February 2014. Return to text.
Figure 14. As in Figure 13 except for GFS 850 hPa winds and v-wind anomalies valid at a) 0600 UTC 20 February through f) 1200 UTC 21 February 2014. Return
to text.
Figure 15. As in Figure 13 except for GFS CAPE. Return to text.