Alert archive / Maine / Mesoscale Discussions in 2021

Mesoscale Discussion 1297

July 16, 202110 counties in Maine

The Storm Prediction Center issued this mesoscale discussion at Jul 16, 2021, 11:34 AM EDT for 10 counties in Maine. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Jul 16, 2021, 11:34 AM EDT (15:34 UTC)
Expired: Jul 16, 2021, 2:00 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 20%

Counties Androscoggin County, ME, Cumberland County, ME, Hancock County, ME, Kennebec County, ME, Knox County, ME, Lincoln County, ME, Penobscot County, ME, Sagadahoc County, ME, Waldo County, ME, Washington County, ME

The radar

The Caribou radar (KCBW), 154 km from the middle of the area, began a volume at 15:38 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

Gray, ME (KGYX), launched 12:00Z, 3.6 hours before the alert went out and 159 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 153 J/kg
Mixed-layer CIN: -98 J/kg
Mixed-layer LCL: 1157 m above ground
0-6 km bulk shear: 36 kt
0-1 km storm-relative helicity: 103 m²/s²
0-3 km storm-relative helicity: 146 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted.

582 
ACUS11 KWNS 161535
SWOMCD
SPC MCD 161534 
MEZ000-161800-

Mesoscale Discussion 1297
NWS Storm Prediction Center Norman OK
1034 AM CDT Fri Jul 16 2021

Areas affected...Maine

Concerning...Severe potential...Watch unlikely 

Valid 161534Z - 161800Z

Probability of Watch Issuance...20 percent

SUMMARY...Storms may increase in intensity within the surface trough
over the next several hours. Marginally severe hail or wind is most
likely, but a brief/weak tornado cannot be ruled out where surface
winds remain backed.

DISCUSSION...Visible satellite shows strong heating across southern
NH and ME with a thicker band of cloud and PWAT ahead of the cold
front. A few storms were already ongoing near the zone of
differential heating.

As the surface low continues to pull away from the region, low-level
winds will continue to veer, in part due to boundary-layer mixing.
While this will reduce low-level shear, hodographs may be
sufficiently long to support a few strong to severe cells or small
lines capable of hail or localized strong gusts. 

As of 1530Z, objective analysis indicates around 100 m2/s2 0-1km SRH
over eastern ME where surface winds are more southerly than farther
west. As ongoing storms over central ME continue east, some
strengthening is anticipated due to heating and destabilization. Any
tornado threat is highly conditional on low-level shear remaining
strong enough through the afternoon.

..Jewell/Dial.. 07/16/2021

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

ATTN...WFO...CAR...GYX...

LAT...LON   45656894 46006813 45926776 45626733 45316732 44986744
            44626764 44366796 44046850 43926913 43367038 43777080
            44217080 44867007 45656894

Nearby

Mesoscale Discussions in Maine, 2021 Every mesoscale discussion in 2021

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.