Weather Info –All information provided by the National Weather Service ( and the Storm Prediction Center (

This information was gathered from data on the Storm Prediction Center’s website ( I wanted to put as much information as possible in one easy to find location, as it is pretty much scattered throughout the site. All outlook information is from May 22, 2004 – the day of the Hallam, NE tornado. The data was found at: Each product from the SPC and NWS are in Zulu or Grenwich Mean Time. The next slide provides a table on converting the times.

Now that we understand the time conversion, let’s start things off with the Hazardous Weather Outlook

Hazardous Weather Outlook This product is issued between two and three times a day depending on the time of year. Before 6am, before 12pm, and again at 6pm CST is Omaha’s frequency of updates. Issued by your local NWS forecast office. Provides information for the next seven to ten days. On the next slide you will find a sample HWO from Dec. 13, 2006.

Sample HWO 000 FLUS43 KOAX HWOOAX HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 452 PM CST WED DEC IAZ NEZ > > > > > > MONONA-HARRISON-SHELBY-POTTAWATTAMIE-MILLS-MONTGOMERY-FREMONT- PAGE-KNOX-CEDAR-THURSTON- ANTELOPE-PIERCE-WAYNE-BOONE-MADISON- STANTON-CUMING-BURT-PLATTE-COLFAX-DODGE-WASHINGTON-BUTLER- SAUNDERS-DOUGLAS-SARPY-SEWARD-LANCASTER-CASS-OTOE-SALINE- JEFFERSON-GAGE-JOHNSON-NEMAHA-PAWNEE- RICHARDSON- 452 PM CST WED DEC THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EASTERN NEBRASKA AND SOUTHWEST IOWA..DAY ONE...TONIGHT AND THURSDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME..DAYS TWO THROUGH SEVEN...THURSDAY NIGHT THROUGH WEDNESDAY A WINTRY MIX OF PRECIPITATION COULD SPREAD ACROSS SECTIONS OF THE OUTLOOK AREA NEXT TUESDAY AND WEDNESDAY. A LARGE UPPER LEVEL SYSTEM IS FORECAST TO LIFT NORTHEAST ONTO THE PLAINS LATE IN THAT PERIOD. HOWEVER...THERE IS A LOT OF UNCERTAINTY AS TO THE TRACK AND TIMING OF THIS SYSTEM...SO STAY TUNED TO LATER HAZARDOUS WEATHER OUTLOOKS FOR THE LATEST INFORMATION ON THIS DEVELOPING STORM..SPOTTER INFORMATION STATEMENT... STORM SPOTTER ACTIVATION WILL NOT BE NEEDED TONIGHT OR THURSDAY. $$ CHERMOK

000 FLUS43 KOAX HWOOAX HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 452 PM CST WED DEC IAZ NEZ > > > > > > MONONA-HARRISON-SHELBY-POTTAWATTAMIE-MILLS-MONTGOMERY-FREMONT- PAGE-KNOX-CEDAR-THURSTON- ANTELOPE-PIERCE-WAYNE-BOONE-MADISON- STANTON-CUMING-BURT-PLATTE-COLFAX-DODGE-WASHINGTON-BUTLER- SAUNDERS-DOUGLAS-SARPY-SEWARD-LANCASTER-CASS-OTOE-SALINE- JEFFERSON-GAGE-JOHNSON-NEMAHA-PAWNEE- RICHARDSON- 452 PM CST WED DEC THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EASTERN NEBRASKA AND SOUTHWEST IOWA..DAY ONE...TONIGHT AND THURSDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME..DAYS TWO THROUGH SEVEN...THURSDAY NIGHT THROUGH WEDNESDAY A WINTRY MIX OF PRECIPITATION COULD SPREAD ACROSS SECTIONS OF THE OUTLOOK AREA NEXT TUESDAY AND WEDNESDAY. A LARGE UPPER LEVEL SYSTEM IS FORECAST TO LIFT NORTHEAST ONTO THE PLAINS LATE IN THAT PERIOD. HOWEVER...THERE IS A LOT OF UNCERTAINTY AS TO THE TRACK AND TIMING OF THIS SYSTEM...SO STAY TUNED TO LATER HAZARDOUS WEATHER OUTLOOKS FOR THE LATEST INFORMATION ON THIS DEVELOPING STORM..SPOTTER INFORMATION STATEMENT... STORM SPOTTER ACTIVATION WILL NOT BE NEEDED TONIGHT OR THURSDAY. $$ CHERMOK –Pay special attention to the last highlighted line – “Storm Spotter Activation.” Sample HWO (Con’t)

Ok, we’ve looked at the Hazardous Weather Outlook. Let’s say that storm spotter activation may be required later on in the day. If that’s the case, we need to go to the Storm Prediction Center’s website and get the latest information from them. We’ll start by looking at the probability and categorical outlooks. There are three probability outlooks that cover tornadoes, wind, and hail.

Probability Outlooks Details the threat within 25 miles of any point in the area Tornadoes Large hail Severe convective winds Provide the threat of significant severe activity

Probability/Categorical Outlooks Tornadoes –2%, 5%, 15%, 25%, 35%, 45% Hail –5%, 15%, 25%, 35%, 45% Convective Wind –5%, 15%, 25%, 35%, 45% –This graphic is the Day One Categorical Outlook. The next page has the tornado and wind outlooks (also from Day One). –See slide 15 for more details on the probability breakdown.

–Day One Tornado Outlook (Left) –Day One Wind Outlook (Bottom) –See slide 13 for the Day One Hail Outlook

Outlook Issuance Times The Day 1 Outlooks are issued at 0600z (Midnight CST), 1300z (8 am CST), 1630z (11:30 am), 2000z (3 pm) and 0100z (8 pm). The Day 2 Outlooks are issued by 100 am (CST and CDT) and 1730z (12:30 pm) The Day 3 Outlook are issued daily by 230 am Central Time (0830 UTC on standard time and 0730z on daylight time)

Accompanying Text Product –Click above to open the Word document and see the actual Day One Outlook text from the day of the Hallam Tornado.

Significant Event Forecast Hatched Area –10% or greater probability Tornadoes producing F2 damage or worse Large Hail 2 inches in diameter or larger Convective Winds 65 kt or stronger –May 22, 2004 Hail Outlook 11:30AM CDT

Probabilities Breakdown Precipitation Severe Tornado Extreme Event 0% - 100% 0% - 50% 0% - 25% 0% - 10%

Converting to Categorical Descriptions Day One Last Modified: Feb. 14, 2006 Note: A 5% probability for only a tornado threat (mainly associated with tropical systems) can be issued as a SLGT RISK.

Converting to Categorical Descriptions Days Two And Three Last Modified: Feb. 24, 2006

Mesoscale Discussions MESOSCALE DISCUSSION 0823 NWS STORM PREDICTION CENTER NORMAN OK 0302 PM CDT SAT MAY AREAS AFFECTED...SRN/SERN NEB...SRN IA...NRN MO CONCERNING...SEVERE THUNDERSTORM POTENTIAL VALID Z Z...TORNADIC SUPERCELLS SHOULD DEVELOP BY EARLY EVENING FROM SRN NEB INTO SRN IA. TORNADO WATCH WILL BE ISSUED BY 21Z... RAPID AIRMASS DESTABILIZATION IS EXPECTED TO CONTINUE ACROSS THE LOWER MO VALLEY INTO SOUTH CENTRAL NEB OVER THE NEXT FEW HOURS. LATEST DIAGNOSTIC FIELDS INDICATE AN AXIS OF J/KG SBCAPE CURRENTLY EXTENDS NWWD ALONG THE NEB/KS BORDER AHEAD OF INCREASING THUNDERSTORM ACTIVITY SPREADING EWD OFF THE HIGH PLAINS. A SIGNIFICANT INCREASE IN CONVECTION IS OCCURRING AHEAD OF SHORTWAVE TROUGH...INDICATIVE OF LARGE SCALE ASCENT WHICH WILL SPREAD EWD THIS EVENING. IN ADDITION...A RAPID INCREASE IN LLJ WILL IMPINGE ON E-W BOUNDARY ALONG THE KS/NEB...IA/MO BORDERS OVER THE NEXT 3-6 HOURS. SUPERCELL THUNDERSTORM DEVELOPMENT IS EXPECTED WITHIN THE WARM ADVECTION ZONE WHERE SHEAR/INSTABILITY STRONGLY SUPPORTS TORNADIC DEVELOPMENT. A FEW TORNADOES MAY BE STRONG...IN ADDITION TO VERY LARGE HAIL. TORNADO WATCH WILL BE ISSUED BY 21Z...DARROW.. 05/22/2004 ATTN...WFO...DVN...DMX...EAX...OAX...GID –A mesoscale discussion is usually issued before a watch and gives the NWS forecast offices a heads up that a watch may or may not be issued in the coming hours. –Notice the line “ATTN: WFO” – This notifies each weather office affected. OAX is the code for the Valley, NE Weather Office

Watch Information The SPC is responsible for issuing a thunderstorm or tornado watch. Follow this link for more information on how they go about issuing a watch, as well as more information on Mesoscale Discussions:

Tornado Watch Issued when Strong/Violent Tornadoes (F2 – F5) damage is possible 2 or More Tornadoes are Expected Not all tornadoes will occur in a watch!!!

Severe Thunderstorm Watch Organized widespread severe –Supercells –Squall lines –Multicell complexes Organized significant severe –Wind gusts > 64 kt (73 mph) –Damage to permanent structures –Hail > 2.0 inches diameter

“ Particularly Dangerous Situation” Watches Placed in Tornado Watches –Multiple strong or violent (F2 – F5 damage) events Placed in Severe Thunderstorm Watches –Long lived wind events (derechoes)

Tornado Watch Issued May 22, 2004 SEL1 URGENT - IMMEDIATE BROADCAST REQUESTED TORNADO WATCH NUMBER 251 NWS STORM PREDICTION CENTER NORMAN OK 345 PM CDT SAT MAY THE NWS STORM PREDICTION CENTER HAS ISSUED A TORNADO WATCH FOR PORTIONS OF SOUTHWEST IOWA EXTREME NORTH CENTRAL KANSAS CENTRAL AND EASTERN NEBRASKA EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 345 PM UNTIL 1100 PM CDT....THIS IS A PARTICULARLY DANGEROUS SITUATION... DESTRUCTIVE TORNADOES...LARGE HAIL TO 4 INCHES IN DIAMETER... THUNDERSTORM WIND GUSTS TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS. THE TORNADO WATCH AREA IS ALONG AND 65 STATUTE MILES NORTH AND SOUTH OF A LINE FROM 65 MILES SOUTHWEST OF BROKEN BOW NEBRASKA TO 35 MILES EAST SOUTHEAST OF OMAHA NEBRASKA. REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR TORNADOES AND 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 WW WW WW 250WW 247WW 248WW 249WW DISCUSSION...VERY POTENT SITUATION EXPECTED TO DEVELOP ACROSS PARTS OF NEB/IA THIS AFTERNOON/EVENING AS LOW LEVEL WINDS STRENGTHEN. EXTREME INSTABILITY IS IN PLACE OVER WATCH AREA...AND SHOULD LEAD TO EXPLOSIVE THUNDERSTORM DEVELOPMENT IN THE NEXT FEW HOURS. SUPERCELLS CAPABLE OF VERY LARGE HAIL APPEAR LIKELY...WITH THE POTENTIAL FOR SIGNIFICANT TORNADOES AS WELL. AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT TO 4 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM MOTION VECTOR HART –As you can see, this was a PDS Tornado Watch.

Important Note Remember, the SPC is only responsible for issuing watches. All warnings come DIRECTLY from your local NWS Forecast Office. Now let’s move on to some basic Doppler Radar information.

Doppler Radar Information The next two slides show a close-up view from local doppler radar. A great radar tutorial can be found here: tutorial.html or tutorial.html I use a program from Storm Alert, Inc. called StormLab. A 14-day free trial can be found at It is somewhat pricey, but when you see what it can do, it’s well worth the cost. Just about everything you see on your local television station, you can see with this program.

Hallam Daykin Beatrice Lincoln

Wind Chill Index / Heat Index –Double-Click on the worksheet above in order to view a wind chill chart and heat index chart.