Event Summary
     National Weather Service, Raleigh NC


December 15, 2006 Fire Weather Event
Updated 2008/04/18






Event Headlines

...Several forest and wild fires developed on December 15, 2006 across portions of central North Carolina...
...The 3.9 micron channel can be used by forecasters to detect hot spots associated with fires...


Event Overview

The motivation for this case study was the result of an investigation of unexpected weather reports from the Fayetteville Regional Airport (KFAY) on consecutive days in the middle of December. Forecasters at the National Weather Service forecast office in Raleigh noticed the visibility at KFAY inexplicably decreased to 5 miles with haze (HZ) at 500 pm on December 14, 2006.

This case study will demonstrate the utility of surface observations and remote sensing, specifically satellite imagery, in the detection of fires. It will be demonstrated that the properties of the shortwave infrared (3.9 micron) channel, make it valuable for detecting hot spots associated with fires. While visible channel satellite imagery can detect smoke emanating from fires and the longwave (10.7 micron) infrared satellite imagery can detect surface based hot spots from fires, the 3.9 micron channel is better suited for fire detection.


Synoptic Overview

The weather pattern before the fire weather event featured a general west to southwesterly flow at mid and upper levels on Thursday December 14, 2006. At the surface, weak high pressure was centered over the Carolinas and Southeast U.S..

By Friday morning, the short wave trough over the Great Lakes had intensified and extended southward into the Ohio valley. The associated cold front moved into the Ohio Valley and weakened The high pressure center over the Carolinas moved southward and recentered over the northern Gulf of Mexico. Widespread early morning fog during the daybreak hours gave way to mostly sunny skies by the afternoon.

By Friday afternoon, the short wave trough was approaching the central Appalachians. The low level flow at 850 mb was from the northwest which aided in the development of a lee side trough across the Carolina and Virginia Piedmont. Low level thickness values were 20 to 30 meters above normal allowing temperatures to reach the mid to upper 60s with relative humidities in the 35 to 40 percent range.



Reduced Visibilities at the Fayetteville Regional Airport

The motivation for this case study was the result of an investigation of unexpected weather reports from the Fayetteville Regional Airport (KFAY) on consecutive days in the middle of December, 2006. Forecasters at the National Weather Service forecast office in Raleigh noticed the visibility at KFAY inexplicably decreased to 5 miles with haze (HZ) at 500 pm on December 14, 2006 (as shown in the observations below).

Surface observations at KFAY from 200 to 700 pm on December 14, 2006.
METAR KFAY 141853Z 26007KT 10SM CLR 19/08 A3006 RMK AO2 SLP173 T01890078
METAR KFAY 141953Z 24003KT 9SM CLR 19/08 A3005 RMK AO2 SLP170 T01890078
METAR KFAY 142053Z 26007KT 9SM CLR 18/07 A3004 RMK AO2 SLP168 T01830072
METAR KFAY 142153Z 29003KT 5SM HZ CLR 16/07 A3005 RMK AO2 SLP171 T01610072
METAR KFAY 142253Z 23003KT 9SM CLR 14/07 A3005 RMK AO2 SLP171 T01390072
METAR KFAY 142353Z AUTO 20005KT 8SM CLR 12/07 A3004 RMK AO2 SLP169 T01170067 10189 20111 58000

Forecasters have recognized that HZ is reported in surface observations as fog develops or dissipates. Fog was not the issue on this occasion, since the dew point depression was 9 degrees Celsius at the time in question. Since surrounding surface observations (not shown) reported unlimited visibility, and because the visibility at KFAY increased to 9 miles the following hour, it was assumed that the reported 5 miles with haze was simply a visibility irregularity or sensor error.

On the following afternoon, December 15th, the visibility again decreased to between 5 and 6 miles at KFAY. Reduced visibilities persisted at KFAY through the remainder of the afternoon, evening, and overnight hours. During the overnight hours, the reduced visibilities were largely a result of fog formation which forecasters expected. Forecasters were surprised to see the reduced visibilities begin before sunset at 500 pm.

Surface observations at KFAY from 200 to 700 pm on December 15th, and 800 am on the 16th
METAR KFAY 151953Z AUTO 24005KT 10SM CLR 20/07 A2984 RMK AO2 SLP099 T02000072
METAR KFAY 152053Z AUTO 26007KT 10SM CLR 19/06 A2986 RMK AO2 SLP107 T01940061
METAR KFAY 152153Z AUTO 30003KT 10SM CLR 18/05 A2989 RMK AO2 SLP116 T01780050
METAR KFAY 152253Z AUTO 27005KT 6SM HZ CLR 15/06 A2991 RMK AO2 SLP122 T01500056
METAR KFAY 152353Z AUTO 25004KT 5SM HZ CLR 12/05 A2992 RMK AO2 SLP127 T01220050 10200 20106 51019

Forecasters were initially unsure of what was producing the reduced visibilities during the afternoon of the 14th, and again prior to fog formation on the 15th. Forecasters then realized that smoke from a fire burning three counties to the west of Fayetteville was responsible for the reduced visibilities that were incorrectly identified as haze.



Remote Sensing Fires

Remote sensing instruments, specifically satellite and radar, provide imagery which can be quite useful for fire detection. Smoke plumes from fires can be viewed with weather surveillance radars and visible channel satellite imagery while the shortwave infrared (3.9 micron) satellite channel can literally sense heat associated with fires.

Meteorologists most often use longwave (10.7 micron) infrared satellite imagery in weather forecasting. This case study will demonstrate the utility of surface observations and remote sensing, in the detection of fires. While visible channel satellite imagery can detect smoke emanating from fires, the shortwave infrared (3.9 micron) satellite channel can literally sense heat associated with fires. The brightness temperature of the 10.7 micron channel gives more accurate surface or cloud top temperatures than that of the 3.9 micron channel, since the temperature uncertainty of the shorter wavelength channel increases sharply with decreasing temperature. The properties of the 3.9 micron channel, however, make it valuable for detecting hot spots associated with fires. Blackbody radiance in the 3.9 micron channel increases more rapidly with temperature than the radiance in the 10.7 micron channel. Therefore, the 3.9 micron channel is more sensitive to sub pixel hot spots then the 10.7 micron channel, and is resultantly better suited for fire detection.

Visible Satellite Imagery from 1815Z, December 15, 2006
The image below shows a subtle smoke plume emanating from a fire in Richmond County. Also notable are the surface weather observations at Mackall U.S. Army Airfield, which reported smoke (FU) with a visibility of 1 mile in otherwise clear skies during the middle of the afternoon.

A visible satellite loop
shows the smoke plume much more clearly. The loop shows the rapid dissipation of fog, evident as shrinking bright white areas at the beginning of the loop. This smoke plume was referenced in the Satellite Service Division product from 02 UTC 16, December





3.9 Micron Satellite Imagery from 1815 UTC, December 15, 2006
The image below shows prominent hot spots in Richmond County, near the Yadkin River on the Davidson and Rowan County border, and in Chesterfield County, SC.





Web-based image from the Satellite Services Division Fire Product Web Page
A web page has been developed that allows visitors to interactively view data from the trained satellite analysts in the Satellite Analysis Branch (SAB), within the Satellite Services Division (SSD), to manually integrate data from various automated fire detection algorithms with GOES and polar (Advanced Very High Resolution Radiometer (AVHRR), Moderate Resolution Imaging Spectroradiometer Fire Algorithm (MODIS) and Defense Meteorological Satellite Program/Operational Linescan System (DMSP/OLS) satellite images. The result is a quality controlled display of the locations of fires and significant smoke plumes detected by meteorological satellites.

The image below shows the detected hot spots and smoke plumes as analyzed by integrated datasets on the Satellite Services Division Fire Product web page. Real time fire detection and smoke analysis data can be found here.

Satellite Services Division Fire Product



Archived Text Data from the Fire Weather Event

Select the desired product along with the date and click "Get Archive Data."
Date and time should be selected based on issuance time in GMT (Greenwich Mean Time which equals EST time + 5 hours).


Product ID information for the most frequently used products...

RDUAFDRAH - Area Forecast Discussion
RDUZFPRAH - Zone Forecast Products
RDUAFMRAH - Area Forecast Matrices
RDUPFMRAH - Point Forecast Matrices
RDUHWORAH - Hazardous Weather Outlook
RDUNOWRAH - Short Term Forecast
RDULSRRAH - Local Storm Reports
RDUSPSRAH - Special Weather Statement
RDUSPSRAH - Fire Danger Statement
RDUFWFRAH - Fire Weather Forecast
RDUFWMRAH - Fire Weather Forecast


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Lessons Learned

  • Smoke plumes from fires can be viewed with weather surveillance radars and visible channel satellite imagery while the shortwave infrared (3.9 micron) satellite channel can literally sense heat associated with fires.
  • The 3.9 micron channel is more sensitive to sub pixel hot spots than the 10.7 micron channel, and is resultantly better suited for fire detection.



Acknowledgements

Many of the images and graphics used in this review were provided by parties outside of WFO RAH. The surface analysis graphic was obtained from the Hydrometeorological Prediction Center. Upper air analyses were obtained from the Storm Prediction Center and the Penn State NARR data archive. Detected hot spots and smoke plume imagery provided by the SSD Fire Detection Program.


Case Study Team

Michael Strickler
Jonathan Blaes


For questions regarding the web site, please contact Jonathan Blaes.


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