Alert archive / Maine / Severe Thunderstorm Watches in 1997

Severe Thunderstorm Watch 621

July 17, 19978 counties in Maine; Essex County, Middlesex County, Massachusetts; 6 counties in New Hampshire

The Storm Prediction Center issued this severe thunderstorm watch at Jul 17, 1997, 7:00 PM EDT for 8 counties in Maine; Essex County, Middlesex County, Massachusetts; 6 counties in New Hampshire. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued: Jul 17, 1997, 7:00 PM EDT (23:00 UTC)
Expired: Jul 17, 1997, 11:00 PM EDT
In force: 4 hr
Issued by: the Storm Prediction Center

Counties Essex County, MA, Middlesex County, MA, Androscoggin County, ME, Cumberland County, ME, Kennebec County, ME, Lincoln County, ME, Oxford County, ME, Sagadahoc County, ME, Waldo County, ME, York County, ME, Belknap County, NH, Carroll County, NH, Hillsborough County, NH, Merrimack County, NH, Rockingham County, NH, Strafford County, NH

The radar

The Portland,ME radar (KGYX), 100 km from the middle of the area, began a volume at 23:03 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.

Warnings issued inside it

4 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
Jul 17, 7:21 PM EDT	Severe Thunderstorm Warning	GYX	Belknap	69 min
Jul 17, 7:45 PM EDT	Severe Thunderstorm Warning	GYX	Strafford	60 min
Jul 17, 7:55 PM EDT	Severe Thunderstorm Warning	GYX	York	85 min
Jul 17, 8:17 PM EDT	Severe Thunderstorm Warning	GYX	Cumberland	58 min

The nearest sounding before it

Gray, ME (KGYX), launched 12:00Z, 11.0 hours before the alert went out and 100 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: 1 J/kg
Mixed-layer CIN: -191 J/kg
Mixed-layer LCL: 1430 m above ground
0-6 km bulk shear: 38 kt
0-1 km storm-relative helicity: -4 m²/s²
0-3 km storm-relative helicity: 59 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

862 
WWUS9 KMKC 172223
SEL1  
MKC WW 172223
NHZ000-MEZ000-MAZ000-180300-

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 621
STORM PREDICTION CENTER NORMAN OK
623 PM EDT THU JUL 17 1997

THE STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

   NEW HAMPSHIRE                      
   SOUTHERN MAINE                              
   NORTHEAST MASSACHUSETTS                      
   AND ADJACENT COASTAL WATERS

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 700 PM UNTIL
1100 PM EDT.

HAIL TO 1 1/2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 75
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS ALONG AND 50 STATUTE MILES
EAST AND WEST OF A LINE FROM 55 MILES SOUTH OF CONCORD NEW
HAMPSHIRE TO 20 MILES NORTHWEST OF AUGUSTA MAINE.

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH AREA. 
PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR THREATENING
WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS AND POSSIBLE
WARNINGS.

OTHER WATCH INFORMATION...  CONTINUE...WW 618...WW 619...WW 620...

DISCUSSION...LINE OF SEVERE THUNDERSTORMS MOVING ACRS SOUTHERN NH. 
AIRMASS IS MODERATELY UNSTABLE EASTWARD TO THE COAST. STORMS
EXPECTED TO REMAIN POTENTIALLY SEVERE TO THE COAST WITH ADEQUATE
SHEAR WIND SHEAR PROFILES.


AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 1 1/2 INCHES.  EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 65
KNOTS.  A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 520.  MEAN STORM
MOTION VECTOR 25030.


...HALES

422,0722 443,0710 443,0690 422,0703

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 17, 4:00 PM EDT	Severe Thunderstorm Watch	SPC	Berkshire, Franklin, Hampshire	6 hr

Nearby

Severe Thunderstorm Watches in Maine, 1997 Severe Thunderstorm Watches in New Hampshire, 1997 Severe Thunderstorm Watches in Massachusetts, 1997 Every severe thunderstorm watch in 1997

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.