F0 tornado, San Marcos, Texas, December 30, 2002

1. F040 to 72 mphthis tornado

   Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

2. F173 to 112 mph

   Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

3. F2113 to 157 mph

   Considerable damage. Roofs torn off well-built houses, frame homes shifted on their foundations, mobile homes destroyed, large trees snapped or uprooted, cars lifted off the ground.

4. F3158 to 206 mph

   Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

5. F4207 to 260 mph

   Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

6. F5261 to 318 mph

   Incredible damage. Strong frame houses swept off their foundations, car-sized missiles thrown more than 100 meters, steel-reinforced concrete badly damaged, high-rise buildings deformed.

7. Unrated

   The survey recorded a tornado but could not put a number on it, most often because it crossed open country and damaged nothing a rating can be read from.

Rating

F0

Date

December 30, 2002

Touchdown

3:25 PM CST (21:25 UTC)

Path length

1.2 miles (1.9 km)

Path width

50 yards (46 m)

Deaths

0

Injuries

0

County

Hays County

Touchdown point

29.900, -97.850

Lift-off point

29.950, -97.830

Record number

821

A small tornado was spotted by a member of the Austin Police Department 3 miles east of San Marcos. The tornado was on the ground around five minutes as it moved northeastward to near the Caldwell County lin e before dissipating. No damage was reported.

From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.

7 minutes of warning. NWS EWX issued a tornado warning for this county at 21:18 UTC, 7 minutes before the tornado touched down, in force until 22:15 UTC.

Every warning and watch covering the touchdown point that day, from the Iowa Environmental Mesonet's archive of National Weather Service products. Lead time is measured from the issue of the warning in force to the touchdown time in the database, both of which were recorded to the minute by different people.

The Storm Prediction Center had this point in a Moderate Risk, with a 0.15 chance of a tornado within 25 miles. The outlook in force was issued at 20:00 UTC.

SPC's Day 1 convective outlook as it stood when the tornado began, read at the touchdown point. The same archive is on the radar archive.

NWS Austin/San Antonio, TX wrote its last area forecast discussion before the tornado touched down at Dec 30, 3:25 PM CST, 0 minutes earlier.

SOUTH CENTRAL TEXAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
325 PM CST MON DEC 30 2002

NO CHANGES FROM EARLIER THINKING BEYOND FIRST 12 HOURS.  PREFRONTAL
TROF WORKING ACROSS CWA AT THIS TIME.  TRUE COLD FRONT SHOULD ARRIVE
HILL COUNTRY ZONES AFTER 02Z...CENTRAL ZONES AROUND MIDNIGHT.  WITH
LOW STILL DIGGING SOUTHWARD AM HESITANT TO REMOVE POPS CENTRAL ZONES
BEFORE MORNING.
10/18/VL/KW

PRELIMS...
AUS 042 062/032 068 5000
DRT 039 069/039 070 0000
SAT 045 065/034 070 4000

.EWX...TORNADO WATCH UNTIL 6 PM.

TXZ171>173-183>194-202>209-217>225-228-311200-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
550 AM CST MON DEC 30 2002

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH CENTRAL TEXAS.

.DAY ONE...
A POTENT UPPER LEVEL LOW AND ASSOCIATED COLD FRONT NEAR EL PASO WILL
PROGRESS SOUTHEAST TODAY AND INTERACT WITH MOISTURE FROM THE GULF OF
MEXICO TO PRODUCE NUMEROUS THUNDERSTORMS OVER SOUTH CENTRAL TEXAS.
CHANCES FOR THUNDERSTORMS WILL BE GREATEST ALONG AND EAST OF
INTERSTATE 35 BETWEEN SAN ANTONIO AND AUSTIN. THESE STORMS WILL
LIKELY BECOME SEVERE...PRODUCING LARGE HAIL AND DAMAGING WINDS.
ISOLATED TORNADOES WILL BE POSSIBLE AS WELL. THE GREATEST THREAT FOR
SEVERE THUNDERSTORMS WILL BE ALONG THE COLD FRONT THIS AFTERNOON.

.DAYS TWO THROUGH SEVEN...
NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION WILL LIKELY BE NEEDED ACROSS THE EASTERN HALF OF
SOUTH CENTRAL TEXAS TODAY.

In the hours before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO, TX
319 PM CST MON DEC 30 2002

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

0225 PM    HELOTES                   TX   TORNADO
12/30/02   BEXAR                          UNCONFIRMED TORNADO
                                          REPORTED BY BEXAR COUNTY
                                          FIRE ALARM BETWEEN HELOTES
                                          AND LEON SPRINGS.

KW

The radiosonde launches on either side of the tornado, from the nearest station that was launching then, drawn and analyzed the way Storm Lab does: the same diagram, the same parcel and shear definitions SPC's mesoanalysis uses.

San Marcos (Awos) (HYI), 4 km from the path, in the two hours either side.

From the Iowa Environmental Mesonet's archive of airport observations.

The Austin/San Antonio radar (KEWX), 31 km away, was scanning. The volume nearest the touchdown began at 21:23 UTC.

Open the radar archive at this moment, over the track

Reflectivity and velocity, decoded from the Level II archive in the browser. Volumes take a few seconds to open the first time.

The live radar over the trackEvery 2002 tornado in TexasEvery tornado in Texas since 1950Warnings in force in Texas nowThe forecast where you are

10 more were confirmed in the United States that day.

Ratings are the survey's, read off the damage rather than measured; the rating scale is above. Tornado counts rise through the record as reporting improved, so a year in the 1950s is not comparable with one today except for the strongest tornadoes, which were always noticed.

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.