Alert archive

Mesoscale Discussion 129

January 23, 2017

The Storm Prediction Center issued this mesoscale discussion at Jan 23, 2017, 3:37 AM CST. It was in force for 53 min.

The area

The outline as issued.

The facts

Issued
Jan 23, 2017, 3:37 AM CST (09:37 UTC)
Expired
Jan 23, 2017, 4:30 AM CST
In force
53 min
Issued by
the Storm Prediction Center

The radar

The Miami radar (KAMX), 56 km from the middle of the area, began a volume at 09:36 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

Miami, FL (KMFL), launched 00:00Z, 9.6 hours before the alert went out and 66 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.

Skew-T log-pSkew-T log-p diagram, Miami, FL at 00:00Z on 2017-01-23Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 635 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Miami, FL at 00:00Z on 2017-01-23The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 204 square meters per square second.1939587897Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
635 J/kg
Mixed-layer CIN
-15 J/kg
Mixed-layer LCL
1027 m above ground
0-6 km bulk shear
52 kt
0-1 km storm-relative helicity
204 m²/s²
0-3 km storm-relative helicity
203 m²/s²
Significant tornado parameter
0.6
Supercell composite
4.7

Open this sounding in Storm Lab

The text

As transmitted.

848 
ACUS11 KWNS 230937
SWOMCD
SPC MCD 230937 
FLZ000-231030-

Mesoscale Discussion 0129
NWS Storm Prediction Center Norman OK
0337 AM CST Mon Jan 23 2017

Areas affected...Extreme South Florida including the upper portion
of the Keys

Concerning...Tornado Watch 24...

Valid 230937Z - 231030Z

The severe weather threat for Tornado Watch 24 continues.

SUMMARY...A band of strong to occasionally severe storms, currently
moving through the coastal areas of Miami-Dade and Monroe Counties,
and the upper portion of the Florida Keys will move offshore by 10Z
(5 AM EST) ending the severe-weather threat across South Florida.

DISCUSSION...Satellite imagery and lightning data showed a 650-700
mile long band of thunderstorms extending from 160- to 200-nm off
the NC and SC coasts, respectively, to the coast of extreme South FL
and into the Florida Straits (south of Key West, FL).  Cape/shear
parameter space along and south of the ongoing band of storms
continues to support locally strong winds gusts and/or a tornado as
the line advances to the east/southeast at 25-30 kt.  Overall
severe-weather threat is expected to end for South FL by 10Z.

..Peters.. 01/23/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MFL...KEY...

LAT...LON   24788090 25378035 26237962 26877891 26187909 25467917
            24597947 24368033 24428098 24788090

Nearby

Every 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.