Severe Weather and Wind Event - April 15, 2007

Severe Weather and Wind Event - April 15, 2007
Write-up by Melissa Hurlbut and Scott Carroll
Baker County survey by Steve Letro, Pete Wolf, and Scott Carroll


Introduction
On April 15, 2007, a deep low pressure center created conditions that led to severe weather including two tornado reports, several damaging wind reports, and very windy conditions ahead of and following the cold front.  The strong winds associated with the strong low produced additional damage and sporadic power outages across much of the area.

Synoptic Situation
In the early morning hours of April 15, 2007, a deepening low pressure center moved across the Southeast United States.  Northeast Florida and Southeast Georgia were located in the warm sector of this system (Image 1).  A pre-frontal squall line developed ahead of a cold front as it moved eastward. Temperatures in the lower 70's and dew points in the upper 60's, along with large scale lift due to the frontal system itself, supported thunderstorm development. A low level jet and strong deep layer shear were conducive for damaging winds, as well as rotating thunderstorms.

The Storm Prediction Center (SPC) had indicated that roughly the northwestern half of the Jacksonville county warning area was under a moderate risk of severe weather, with the remainder of the region under a slight risk (Image 2).

Surface Map
Image 1:  Surface weather map 7am April 15, 2007

Image 2:  SPC Day 1 Convective Outlook 853pm April 14, 2007

Products Issued by NWS Jacksonville
Area Forecast Discussions Hazardous Weather Outlooks Warnings & Statements
4/10/07 at 233pm
4/11/07 at 310am
4/11/07 at 257pm
4/12/07 at 326am
4/12/07 at 253pm
4/13/07 at 315am
4/13/07 at 1001am
4/13/07 at 251pm
4/13/07 at 837pm
4/14/07 at 317am
4/14/07 at 942am
4/14/07 at 258pm
4/14/07 at 854pm
4/15/07 at 349am
4/15/07 at 1139am
4/15/07 at 217pm
4/11/07 at 451am
4/11/07 at 609pm
4/12/07 at 358am
4/13/07 at 344am
4/14/07 at 344am
4/14/07 at 445pm
4/14/07 at 1009pm
4/15/07 at 1200am
4/15/07 at 622am
4/15/07 at 909am
4/15/07 at 1118am
4/15/07 at 1015pm
Severe Thunderstorm Warnings
700am:  N Baker, Charlton, SE Ware, NW Nassau
819am:  SE Bradford, Clay
824am:  Duval
930am:  E Putnam
952am:  S St. Johns
Tornado Warnings
713am:  S Charlton, NW Nassau
752am:  Alachua
1008am:  SE St. Johns

Severe Weather Statements
728am:  N Baker, Charlton, SE Ware, NW Nassau
759am:  S Charlton, NW Nassau
830am:  Alachua
857am:  SE Bradford, Clay
857am:  Duval
1004am:  SE St. Johns
1018am:  S St. Johns
1020am:  SE St. Johns
Event Storm Report Summary Wind/ Lake Wind Advisories
4/14/07 at 245pm
4/14/07 at 756pm
4/15/07 at 1254pm
4/15/07 at 237pm
4/15/07 at 905pm

Radar Imagery - Baker County EF2 Tornado
Reflectivity Loop - Baker County Tornado 0.5 base velocity loop 0.5 deg storm relative velocity
0.5° reflectivity loop with warning polygons overlaid (744 Kb) 0.5° base velocity loop showing strong inbound velocity and initial convergent flow (814 Kb) 0.5° storm relative velocity loop showing tight circulation (869 Kb)
2.4 deg reflectivity loop lightning loop  
2.4° reflectivity loop showing bounded weak echo region (BWER)  (1.03 Mb) 5 minute lightning loop (117 Kb)  

Damage Survey - Baker County EF2 Tornado
damage pathNWS Jacksonville conducted a storm survey of damage in extreme northeastern Baker county about 7 mile north northeast of Taylor (damage path map to left).  We confirmed that the damage was in fact due to an EF2 tornado (Enhanced Fujita Scale). Radar imagery of this event is depicted above in the radar imagery section.  The path started in a dense wooded area about one quarter of a mile southwest of the southern leg of Moccasin Creek Circle, cut a path across farmland off of  Lacy Crews Road, the ended about one quarter of a mile northeast of the northern leg of Moccasin Creek Circle in more dense woods.  The approximate length of the path was 1.5 miles and the approximate width of the path was 300 yards.  

Numerous trees were snapped, both in the wooded areas surrounding the farmland and in several patches of trees on the property.  Several large oak trees were uprooted as well.  Evidence of  the tornado vortex was found along the path. Additionally, bark was partially stripped from several trees.  Two out buildings north northeast of the residence were completely destroyed. This was very weak construction, and the home on the property only suffered minor damage.  However, a large branch was blown into the side of  a screened porch.  A few pieces of metal roofing material from the out buildings was found in the woods on the northeast end of the property wrapped around trees.

Some of the digital photos taken on the survey are linked to the thumbnails below.  Descriptions of the photos will appear once your mouse is placed over the thumbnail.  Pictures range from 133 Kb to 411 Kb in size.

trees snapped and uprooted west southwest of residencelarge branches strewn southwest to northeasttree damagelarge uprooted tree southwest of residencetrees snapped with wood splitsnapped trees in wooded area southwest of propertylarge branch blown from southwest to northeast toward residence
large branch damage to screened porch on west side of houseout building #1out building #2metal roofing material from an outbuilding wrapped around treefallen tree in fork of another treemetal roofing material which was blown into the air and into wooded area northeast of propertysurveying the surveyors

Strong Winds
The deep low pressure center that influenced severe weather across the Southeast also generated very windy conditions due to a tight pressure gradient. The last April event on record with extended sustained winds of greater than 20 mph was April of 2001, making this a somewhat rare event. Numerous downed trees and power outages were reported on the 15th of April. Peak wind speeds at local automated surface observation systems were as follows:

Jacksonville, FL: West at 45 mph
Gainesville, FL: Northwest at 39 mph
Alma, GA: South at 43 mph
Saint Simons Island, GA: West at 46 mph




Return to News Archive

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.