Alert archive / Texas / Mesoscale Discussions in 2017
Mesoscale Discussion 809
The Storm Prediction Center issued this mesoscale discussion at May 21, 2017, 8:02 PM CDT for 9 counties in Texas. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- May 21, 2017, 8:02 PM CDT (01:02 UTC)
- Expired
- May 21, 2017, 10:30 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 40%
Counties Brooks County, TX, Cameron County, TX, Hidalgo County, TX, Jim Hogg County, TX, Kenedy County, TX, Kleberg County, TX, Starr County, TX, Willacy County, TX, Zapata County, TX
The radar
The Brownsville radar (KBRO), 113 km from the middle of the area, began a volume at 01:03 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
The nearest sounding before it
Brownsville Intl, TX (KBRO), launched 00:00Z, 1.0 hours before the alert went out and 115 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 2410 J/kg
- Mixed-layer CIN
- -57 J/kg
- Mixed-layer LCL
- 887 m above ground
- 0-6 km bulk shear
- 36 kt
- 0-1 km storm-relative helicity
- 30 m²/s²
- 0-3 km storm-relative helicity
- 64 m²/s²
- Significant tornado parameter
- 0.3
- Supercell composite
- 1.9
The text
As transmitted.
560
ACUS11 KWNS 220102
SWOMCD
SPC MCD 220102
TXZ000-220330-
Mesoscale Discussion 0809
NWS Storm Prediction Center Norman OK
0802 PM CDT Sun May 21 2017
Areas affected...South Texas
Concerning...Severe potential...Watch possible
Valid 220102Z - 220330Z
Probability of Watch Issuance...40 percent
SUMMARY...A severe threat will be possible this evening across south
Texas. Wind damage and isolated large hail will be the primary
threats. Weather watch issuance could be needed across south Texas
if the current severe threat increases.
DISCUSSION...The latest surface analysis shows a 999 mb low in
northern Mexico with a trough extending eastward from the low to
near the Gulf Coast and then northward into south Texas. Low-level
convergence appears to be maximized along the surface trough which
is supporting thunderstorm development. Surface dewpoints in south
Texas are in the lower to mid 70s F and MLCAPE is estimated to be in
the 1500 to 2500 J/kg range. This combined with moderate deep-layer
shear evident on regional WSR-88D VWPS and steep lapse rates will be
favorable strong updrafts with isolated large hail potential. Backed
surface winds to the east are also contributing to low-level shear
which will could aide the developing of bowing structures with a
wind damage threat. The bowing line segment that is near the Rio
Grande River and is currently moving into south Texas at 25 to 30
kt. This should keep any wind damage threat isolated. Nevertheless,
trends will continue to be monitored and a weather watch is still
being considered.
..Broyles/Hart.. 05/22/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...CRP...BRO...
LAT...LON 27099727 26759723 26309707 25949709 25879754 25929847
26269908 27009962 27369954 27529912 27609778 27389721
27099727SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 22, 2:01 PM CDT | Severe Thunderstorm Watch | SPC | Andrews, Bailey, Castro, Cochran, Deaf Smith, Gaines and 5 more | 7 hr |
Nearby
Mesoscale Discussions in Texas, 2017Every mesoscale discussion in 2017
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.