Alert archive / Arizona / Severe Thunderstorm Warnings in 1998

Severe Thunderstorm Warning 20, NWS Tucson, AZ

July 18, 1998Pima County, Arizona

NWS Tucson, AZ issued this severe thunderstorm warning at Jul 18, 1998, 12:15 AM MST for Pima County, Arizona. It was in force for 90 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Jul 18, 1998, 12:15 AM MST (07:15 UTC)
Expired: Jul 18, 1998, 1:45 AM MST
In force: 90 min
Issued by: NWS Tucson, AZ
Area: Whole counties

County Pima County, AZ

The radar

The Tucson radar (KEMX), 112 km from the middle of the area, began a volume at 07:17 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

Tuscon, AZ (KTUS), launched 00:00Z, 7.3 hours before the alert went out and 84 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: 979 J/kg
Mixed-layer CIN: -1 J/kg
Mixed-layer LCL: 3214 m above ground
0-6 km bulk shear: 19 kt
0-1 km storm-relative helicity: 15 m²/s²
0-3 km storm-relative helicity: 38 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.8

Open this sounding in Storm Lab

The text

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

789 
WUUS1 KTUS 180716 RRA
SVRTUS
AZC019-180845-

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE TUCSON AZ
1215 AM MST SAT JUL 18 1998

THE NATIONAL WEATHER SERVICE IN TUCSON HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  WESTERN PIMA COUNTY IN SOUTHERN ARIZONA

* UNTIL 145 AM MST

* AT 1213 AM MST... DOPPLER RADAR INDICATED A LINE OF SEVERE
THUNDERSTORMS FROM GILA BEND TO 15 MILES WEST OF SELLS MOVING
SOUTHWEST AT 25 MPH. THESE THUNDERSTORMS HAVE HAD A HISTORY OF
PRODUCING WIND GUSTS OVER 60 MPH.

* THE SEVERE THUNDERSTORMS WILL BE NEAR...
  AJO BY 1245 PM MST
  ORGAN PIPE CACTUS NATIONAL MONUMENT BY 100 AM MST

VPH

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Tucson, AZ wrote its last area forecast discussion before this severe thunderstorm warning went out at Jul 17, 9:30 PM MST, 2 hours 45 minutes earlier.

Area forecast discussion, Jul 17, 9:30 PM MST, 2 hours 45 minutes before

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
930 PM MST FRI JUL 17 1998

SYNOPSIS...AN EASTERLY AIRFLOW AROUND AN UPPER HIGH CENTERED OVER
SOUTHERN NEVADA AND SOUTHWEST UTAH WILL CONTINUE TO INCREASE THE
MOISTURE OVER SOUTHEAST ARIZONA FOR AN UPSWING IN THUNDERSTORM
ACTIVITY THROUGH THE WEEKEND.

DISCUSSION...AN ACTIVE EVENING ACROSS SOUTHEAST ARIZONA. THE 5 PM
TUCSON UPPER AIR SOUNDING SHOWED A CLASSIC "INVERTED V" SIGNATURE.
THIS TYPE OF SOUNDING IS INDICATIVE OF SEVERE DOWNBURST WINDS AND
WAS VERIFIED AT RYAN FIELD AROUND 6 PM WITH A 94 MPH WIND GUST. THE
AIRFIELD HAD 3 MINUTES OF 60 MPH OR GREATER SUSTAINED WINDS! THIS
AREA OF SEVERE THUNDERSTORMS HAD MOVED INTO MEXICO.

THE NEXT AREA OF SHOWERS AND THUNDERSTORMS WAS MOVING ACROSS CENTRAL
GRAHAM COUNTY. THIS AREA WAS MOVING TO THE SOUTHWEST AT 20 TO 25
MPH. THE RATHER QUICK FORWARD SPEED OF THESE STORMS WERE AIDING THE
STRENGTH OF THE DOWNBURST WINDS. THIS NEXT AREA SHOULD HOLD TOGETHER
AND MAKE A RUN TOWARD EASTERN PIMA...NORTHWEST COCHISE AND SANTA
CRUZ COUNTIES DURING THE NEXT 3 TO 6 HOURS. AN UPPER LEVEL LOW
PRESSURE SYSTEM OVER FAR WESTERN NEW MEXICO WAS MOVING INTO EASTERN
ARIZONA AND SHOULD PROVIDE THE FORCING NECESSARY TO KEEP THESE
STORMS GOING PAST MIDNIGHT.

ANOTHER AREA OF THUNDERSTORMS OVER GILA COUNTY WILL HAVE TO WATCHED
FOR ITS IMPACT ON PINAL COUNTY. WITH THIS IN MIND...WILL UPDATE TO
EXTEND THE DURATION OF THE THUNDNERSTORM THREAT IN THE AFFECTED
AREAS. TUS 4343. OKULSKI

.TWC...NONE.

In the hours before

Local storm report, Jul 17, 7:00 PM MST, 5 hours 15 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TUCSON ARIZONA
610 PM MST FRI JUL 17 1998

TIME(MST)  .....CITY LOCATION..... STATE  ...EVENT/REMARKS...
           ....COUNTY LOCATION....

605  ZPM    RYAN FIELD                AZ   WIND DAMAGE
07/17/98   PIMA                           94 MPH WIND GUST

600  PM    TUCSON                    AZ   WIND DAMAGE
07/17/98   PIMA                           MOBILE HOME ROOF DESTROYED

The office that day

Everything else NWS Tucson, AZ issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 17, 5:41 PM MST	Severe Thunderstorm Warning	TWC	Pima	49 min
Jul 17, 6:25 PM MST	Severe Thunderstorm Warning	TWC	Pima	60 min
Jul 17, 7:25 PM MST	Severe Thunderstorm Warning	TWC	Pima	45 min
Jul 17, 7:33 PM MST	Severe Thunderstorm Warning	TWC	Greenlee	47 min
Jul 17, 8:09 PM MST	Severe Thunderstorm Warning	TWC	Pima	61 min
Jul 17, 8:17 PM MST	Severe Thunderstorm Warning	TWC	Graham	48 min
Jul 17, 11:14 PM MST	Severe Thunderstorm Warning	TWC	Pinal	46 min
Jul 18, 1:44 AM MST	Severe Thunderstorm Warning	TWC	Pima	46 min
Jul 18, 1:37 PM MST	Severe Thunderstorm Warning	TWC	Santa Cruz	48 min
Jul 18, 2:08 PM MST	Severe Thunderstorm Warning	TWC	Pima, Santa Cruz	62 min
Jul 18, 2:44 PM MST	Severe Thunderstorm Warning	TWC	Pima	46 min
Jul 18, 3:25 PM MST	Severe Thunderstorm Warning	TWC	Pima	45 min

Nearby

Severe Thunderstorm Warnings in Arizona, 1998 Every severe thunderstorm warning in 1998

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.