Ingredients came together across Northeast Florida and extreme Southeast Georgia to produce widespread severe weather on the afternoon and evening of Thursday, January 21, 2010. Numerous reports of wind damage and flooding were received along with reports of two tornadoes and large hail.
A strong low pressure system tracked across the deep South and Tennessee Valley area on Thursday which pushed a squall line across the Jacksonville County Warning Area (CWA). Dynamics were impressive with a low level jet at about 5,000 feet with speeds upwards of 70 mph moving across the CWA. This produced strong low level turning in the wind field that was favorable for tornadic thunderstorms along the squall line. The squall line strengthened by late morning and early afternoon across extreme Southeast Georgia and Northeast Florida (Fig. 1) with 2 tornadoes confirmed.
The potential for thunderstorm development on January 21, 2010, was first highlighted on Saturday, January 16th by NWS Jacksonville in the local Hazardous Weather Outlook (HWO) and Area Forecast Discussion (AFD). The next day, on the 17th, the potential for strong to severe storms was highlighted in the NWS Jacksonville HWO. The Storm Prediction Center (SPC) began to highlight the Jacksonville CWA under a slight risk of severe storms on January 19th (SPC Day 3 Outlook). SPC continued the slight risk for our area in the Day 2 Convective Outlook that was issued on the 20th (SPC Day 2 Outlook). By noon on January 21st, the HWO described the potentail hazards associated with discrete storms preceding a squall line across our area during the afternoon and evening of January 21st, then hazards associated with the squall line as it moved through north Florida during the evening and overnight. This HWO requested that the public, emergency responders, and NWS Skywarn spotters monitor the evolving weather situation.
Around 4:00 AM on January 21st, spotter activation was requested in the HWO if warnings were issued later in the day for the Jacksonville CWA. The first product issued for strong convection was a Special Weather Statement (SPS) at 4:15 AM on the morning of January 21st. Additional SPS products were issued during the morning of the 21st for strong storms which were capable of producing some damage, then warnings were issued after noon. The Day 1 SPC Convective Outlook issued around noon on the 21st not only continued to highlight our area in a slight risk, but it also detailed probabilties for the most specific weather threats from resultant severe storms, including wind damage probabilities, tornado probabilties, and large hail (> 2 inches) probabilities.
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Watches & Warnings
Tornado watch number 5 was issued by the SPC shortly before 8:30 AM on Thursday morning. This watch was initially valid until 4:00 PM all of southeast Georgia and most of northeast Florida. The watch was later expanded south by NWS Jacksonville to include the remaining Northeast Florida counties and extended through 6:00 PM. The watch was allowed to expire at 6:00 PM.
A total of 12 severe thunderstorm warnings and 8 tornado warnings were issued by NWS Jacksonville. The first severe thunderstorm warning was issued at 12:04 PM for northwest Baker and northeast Columbia counties. The first tornado warning was issued at 12:39 PM for southern Charlton and northwest Nassau counties and covered the Charlton county tornado. Another tornado warning, issued at 1:27 PM, covered the Bradford county tornado. The last tornado warning was issued for northern St. Johns county at 2:30 PM, and the last severe thunderstorm warning was issued for southern Marion county at 6:44 PM.
One tornado was confirmed in Charlton county in Southeast Georgia and another one in Bradford county (storm survey pictures and map) in Northeast Florida. Fortunately, there were no fatalaties but a few minor injuries were reported.
Wind & Hail
Ten of the twelve severe thunderstorm warnings were verified, meaning that the NWS received damage reports from most of the warned storms. Most of the damage reports were from severe strength thunderstorm winds, and the most common type of wind damage was downed trees and power lines. Wind damage reports began just after noon in Suwannee county and progressed east and south across the Jacksonville CWA through the afternoon and evening as storms moved across the area. The last wind damage report was around 7:15 PM in Marion county. A few locations experienced significant wind damage to structures, including a mobile home near Columbia City that was flipped due to severe strength thunderstorm winds. Thunderstorms winds also overturned 6 tractor trailers near Callahan.
There were only a handful of hail reports that were received around 2:00 PM. The hail was produced by a supercell that moved from Bradford county, across Clay county, and then St. Johns county. The largest hail report was that of golfball size hail (1.75 inches in diameter) which fell north-northwest of Green Cove Springs.
In addition, heavy rainfall fell across the CWA especially across Northeast Florida with a strip of 4 to 5 inches with local amounts along this strip near 6 inches measured by doppler radar from southern Suwannee county to northern Putnam and southern Clay counties (Fig. 2).
Below are area co-operative and CoCoRaHS rainfall observations of over 2 inches for the 24 hours ending on Friday morning. The highest values are highlighted in yellow.
HIGH SPRINGS 3.2 SW 3.28
KEYSTONE HEIGHTS 6.9 ENE 5.38
KEYSTONE HEIGHTS 7.6 ENE 5.54
ORANGE PARK 4.7 SW 2.11
GREEN COVE SPRINGS 6.8 SSE 2.93
PALM COAST 1.7 W 4.28
JENNINGS 5.8 WSW 3.70
OCALA 2.8 SSE 2.20
THE VILLAGES 2.7 NNW 2.01
INTERLACHEN 10.4 NNE 5.22
SATSUMA 4.0 NE 2.69
EAST PALATKA 3.5 NNW 4.25
ST. AUGUSTINE SOUTH 2.1 SSW 2.74
LIVE OAK 9.1 NW 2.75
HASTINGS 4 NE 4.00
HIGH SPRINGS 2.30
LAKE CITY 2 E 2.00
PALM COAST 6 NE 4.60
PRIDGEN 1.5 NE 2.12
BAXLEY 5 NNW 2.85
FARGO 17 NE 2.17
This article will be updated as more information becomes available.
Written by Andrew Shashy, Scott Carroll, Angie Enyedi, & David Shuler
Storm Survey Pictures by Pete Wolf & Steve Letro
Article Updated 1/24/10