Alert archive / South Carolina / Mesoscale Discussions in 2017
Mesoscale Discussion 649
The Storm Prediction Center issued this mesoscale discussion at May 4, 2017, 7:16 PM EDT for 6 counties in South Carolina. It was in force for 89 min.
The area
The outline as issued.
The facts
- Issued
- May 4, 2017, 7:16 PM EDT (23:16 UTC)
- Expired
- May 4, 2017, 8:45 PM EDT
- In force
- 89 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 20%
Counties Beaufort County, SC, Berkeley County, SC, Charleston County, SC, Colleton County, SC, Dorchester County, SC, Jasper County, SC
The radar
The Charleston,SC radar (KCLX), 70 km from the middle of the area, began a volume at 23:19 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
Charleston AFB, SC (KCHS), launched 12:00Z, 11.3 hours before the alert went out and 32 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
- 10 J/kg
- Mixed-layer CIN
- -155 J/kg
- Mixed-layer LCL
- 1414 m above ground
- 0-6 km bulk shear
- 34 kt
- 0-1 km storm-relative helicity
- 10 m²/s²
- 0-3 km storm-relative helicity
- 88 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.1
The text
As transmitted.
758 ACUS11 KWNS 042316 SWOMCD SPC MCD 042316 SCZ000-050045- Mesoscale Discussion 0649 NWS Storm Prediction Center Norman OK 0616 PM CDT Thu May 04 2017 Areas affected...Coastal SC Concerning...Severe potential...Watch unlikely Valid 042316Z - 050045Z Probability of Watch Issuance...20 percent SUMMARY...Isolated damaging winds, or perhaps a brief weak tornado, remain possible across coastal SC this evening. DISCUSSION...A narrow band of deep convection has translated across eastern GA into western SC...trailing south-southwest along the FL Atlantic Coast. While this activity is mostly sub-severe in nature, low 70s surface dew points have advanced inland along the SC coast. This increase in low-level moisture appears to be partly responsible for possible tornado with long-lived supercell as it tracked from southeast GA into Chatham County SC. Over the next few hours models suggest 850mb flow will increase across the Carolinas and shear profiles should remain supportive of sustained deep rotating updrafts. Given the modest lapse rates/buoyancy observed within this warm advection regime, greatest risk for a brief/weak tornado should be across the coastal plain where 70s surface dew points have returned. Otherwise, isolated wind gusts can not be ruled out with the strongest activity. Even so, the expected isolated nature warrants the probability for a tornado watch around 20 percent. ..Darrow/Edwards.. 05/04/2017 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ILM...CHS...CAE... LAT...LON 32578119 33398043 33617958 33107909 31968053 32578119
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 4, 12:48 PM EDT | Mesoscale Discussion | SPC | Allendale, Hampton, Jasper | 2 hr |
Nearby
Mesoscale Discussions in South Carolina, 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.