April 27, 2016 Southwest Iowa Tornadoes

Tornadoes:

Tornado #1 - 6.0 mi ESE of Bedford Taylor County Date April 27, 2016 Time (CDT) 4:40pm - 4:47pm EF Rating EF-0 Est. Peak Winds 65 mph Path Length 2.37 miles Max Width 200 yards Injuries/Deaths 0/0 Summary: This was a broad and weak tornado that caused no reported damage and was recorded by a storm chaser. Track Map

Reflectivity image during the tornado from the Des Moines WSR-88D radar. showing a weak hook echo. Storm-relative velocity radar data shows a tight circulation at the location of the tornado. A video capture of tornado by Simon Brewer. View Full Video Additional screen capture of the tornado on the right with the second satellite tornado to the left by Simon Brewer. View Full Video

Tornado #2 - 6.1 mi E of Bedford Taylor County Date April 27, 2016 Time (CDT) 4:44pm - 4:46pm EF Rating EF-0 Est. Peak Winds 60 mph Path Length 0.91 miles Max Width 40 yards Injuries/Deaths 0/0 Summary: This small satellite tornado formed south of Tornado #1 and moved to the ENE. It was photographed from multiple angles and caused no reported damage. Track Map

A MESO-SAILS reflectivity radar scan from the Des Moines radar during the time of the tornado. A MESO-SAILS storm-relative velocity radar scan from the Des Moines radar during the time of the tornado. Video screen capture of the satellite tornado on the left and the main tornado on the right by Simon Brewer. View Full Video Another video screen capture of the tornado by Matt Churchill. View Full Video

Tornado #3 - 2.1 mi NW of Clearfield Taylor County Date April 27, 2016 Time (CDT) 5:12pm - 5:13pm EF Rating EF-0 Est. Peak Winds 85 mph Path Length 0.63 miles Max Width 50 yards Injuries/Deaths 0/0 Summary: This brief tornado damaged one farmstead where damage was high EF-0. One outbuilding collapsed, several trees were damaged, and a camper was flipped. Track Map

The previously discrete cells were starting to merge together on reflectivity imagery. Storm relative velocity data showed a very tight couplet near the area of farm damage. An outbuidling was destroyed on a farm NW of Clearfield. Photo by Taylor County EM. A camper was flipped on a farm NW of Clearfield. Photo by Taylor County EM.

Tornado #4 - 4.6 mi S of Creston Union County Date April 27, 2016 Time (CDT) 5:40pm - 5:47pm EF Rating EF-0 Est. Peak Winds 70 mph Path Length 4.01 miles Max Width 250 yards Injuries/Deaths 0/0 Summary: This broad and weak tornado formed south of Creston and tracked east of the Creston Airport, damaging an outbuilding south of town, some trees at a cemetery, and some tree limbs on the SE side of Creston. Track Map

By the time the storms reached Creston, they had merged into a squall line. While reflectivity data was unrevealing, storm-relative velocity data still showed a tight circulation. Video still of the low, rain-wrapped tornado just south of Creston by Simon Brewer. View Full Video Trees were damaged in the cemetery south of town. Photo provided to KCCI.

The Enhanced Fujita (EF) Scale classifies tornadoes into the following categories:

EF0 Weak 65-85 mph	EF1 Moderate 86-110 mph	EF2 Significant 111-135 mph	EF3 Severe 136-165 mph	EF4 Extreme 166-200 mph	EF5 Catastrophic 200+ mph

Storm Reports

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0434 PM     HAIL             5 SE BEDFORD            40.63N 94.64W
04/27/2016  E0.88 INCH       TAYLOR             IA   TRAINED SPOTTER  

             
0435 PM     HAIL             5 SE BEDFORD            40.62N 94.66W
04/27/2016  E1.00 INCH       TAYLOR             IA   TRAINED SPOTTER  

0452 PM     TORNADO          3 SE CONWAY             40.71N 94.58W
04/27/2016                   TAYLOR             IA   PUBLIC           

            VIDEO EVIDENCE OF A BRIEF TORNADO TOUCHDOWN 
            NEAR THE INTERSECTION OF HIGHWAY 2 AND 
            ROCKWOOD ROAD. NO DAMAGE REPORTED AT THIS 
            TIME. 

0500 PM     FUNNEL CLOUD     4 E CONWAY              40.75N 94.55W
04/27/2016                   TAYLOR             IA   TRAINED SPOTTER  

            SPOTTER ON HW25 OBSERVING A WEAK ROPE FUNNEL 
            CLOUD AND RAPID ROTATION TO THE WEST. 

0514 PM     TSTM WND DMG     2 NNW CLEARFIELD        40.83N 94.50W
04/27/2016                   TAYLOR             IA   EMERGENCY MNGR   

            DAMAGE TO A BARN. TIME ESTIMATED FROM RADAR. 

0543 PM     TORNADO          3 SSW CRESTON           41.02N 94.38W
04/27/2016                   UNION              IA   TRAINED SPOTTER  

            TORNADO 1 MILE WEST OF THE CRESTON AIRPORT 
            HEADING TOWARDS CRESTON. 

0547 PM     TORNADO          1 SSW CRESTON           41.04N 94.37W
04/27/2016                   UNION              IA   PUBLIC           

            TORNADO JUST SOUTH OF CRESTON BUT HAS BECOME 
            RAIN WRAPPED. 

0551 PM     TORNADO          3 NNE CRESTON           41.09N 94.35W
04/27/2016                   UNION              IA   LAW ENFORCEMENT  

            RELAYED REPORT OF A TORNADO NORTH OF CRESTON 

0618 PM     HAIL             LEON                    40.74N 93.75W
04/27/2016  E0.88 INCH       DECATUR            IA   EMERGENCY MNGR  

Environment

After sparking widespread severe thunderstorms across the central and southern U.S. on April 26, a seasonably strong vertically-stacked low pressure system and upper level shortwave trough pivoted up across eastern Nebraska during the afternoon of April 27. This 300mb wave provided the focus for thunderstorm development during the early afternoon hours near the Missouri River between Kansas City and Omaha. A warm front branching southeastward from the surface cyclone lifted northward into southwest Iowa during this timeframe.

Figure 1: Surface observations at 3:00pm CDT showing the warm front lifting into SW Iowa.	Figure 2: 925mb analysis at 3:00pm CDT depicting good moisture transport into SW Iowa.	Figure 3: 500mb analysis at 3:00pm showing how the developing storms align with the upper trough.

A narrow ribbon of surface-based instability developed along and south of the warm front with MLCAPE values of 500 to 1000 J/kg being reached by 2:00-3:00pm. Strong easterly flow to the immediate north of the warm front combined with southerly flow south of the boundary led to a favorable low-level shear environment for tornadoes. The lifted condensation levels (LCLs) were also very low, meaning that the base of the storms would be very low and tornadogenesis was more likely, but the tornadoes could be harder to spot.

Figure 4: MLCAPE plot at 4:00pm showing the region of surface instability with no inhibition.	Figure 5: Effective SRH plot showing values of over 200 m2/s2 over southern Iowa.	Figure 6: LCL plot showing values well below 1000m over Iowa.

Additional Information

The Forecast

SPC Day 3 Categorical Outlook	SPC Day 3 Probabilistic Outlook	SPC Day 2 Categorical Outlook	SPC Day 2 Probabilistic Outlook
SPC Day 1 Categorical Outlook	SPC Day 1 Tornado Outlook	SPC Day 1 Hail Outlook	SPC Day 1 Wind Outlook

Warning Lead Time

Summaries from other NWS Offices

• NWS Omaha, Nebraska (3 Tornadoes)