Detection of Low Clouds and Fog on January 6-7, 2010

Low clouds and fog during the winter months are generally more widespread across New Mexico’s eastern plains and more limited to valleys across northern and western locations.  At four of our seven TAF sites, visibility restrictions peak during the month of January.  The western sites can certainly be a forecast challenge.

During the first week of January, conditions were ripe for the formation of low clouds and fog on a number of occasions.  In the morning AFD on January 4th and 5th, the possibility of patchy fog was mentioned for Farmington, in the extreme northwest corner of the state.  On the morning of the 6th, focus was on the approaching arctic front, conditions seemed less favorable for fog at Farmington and there was no suggestion of low clouds or fog in the AFD or TAF.  Low clouds and eventually some fog did develop in the early morning hours and were not detected in advance using conventional imagery.

GOES Imager Combined Fog Product 06 January 2010

The GOES Imager Combined fog product at 12 and 13Z is shown above.  The 12Z images hints at some low clouds west of Farmington (KFMN) and in the 13Z image they are closer to the site as scattered low clouds and then a ceiling are reported.

KFMN 061238Z 03003KT 10SM BKN005 M14/M15 A3018 RMK AO2 CIG 003V006
KFMN 061231Z AUTO 03005KT 10SM BKN003 M14/M16 A3018 RMK AO2 CIG 003V006 FZRANO TSNO
KFMN 061203Z AUTO 00000KT 10SM FEW007 M13/M15 A3018 RMK AO2 FZRANO TSNO
KFMN 061153Z AUTO 00000KT 9SM CLR M13/M15 A3018 RMK AO2 SLP271 T11281150 11106 21139 58003 FZRANO TSNO

Unfortunately, these were not anticipated in the TAF and amendments were necessary.

Later in the day, a strong front moved into the northeast corner of the state and by midnight the front was through New Mexico’s eastern plains and to the central mountains.

In these instances, low clouds and fog are common across the eastern plains.  The challenge can be whether or not they will work past the central mountains and into the Rio Grande Valley.  This next image depicts the topography of north central New Mexico.  I added a crude cyan line marking a common westward extent of the low clouds.

Terrain depiction of Northern NM with Sangre de Cristo moutains (not labeled) most evident and the mountains just to the east of Albuquerque (Sandia/Mazanos) and north of Albuquerque (Jemez) highlighted.

During the morning briefing on the 7th of January, the forecaster mentioned how useful the GOES low cloud base imagery was.  Low clouds, some fog and even snow made it west of the central mountains to Santa Fe and to the Jemez Mountains (including Los Alamos).  These are not TAF sites, but still it is important to be able to track fog and snow during these events.

I’ve tried to capture the detail in a three panel image of the GOES low cloud base overlaying topography – it may be difficult for those unfamiliar with the area to see the details.

GOES Low Cloud Base Imagery on the morning of 7 January 2010. Westward expansion of low clouds, fog and even some snow is evident in the imagery and the observations.

Finally, the sharp edge of the boundary was evident on the MODIS product at 0903Z.

MODIS 1km 11-3.9um Product at 0903Z on the morning of 7 January 2010

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