GOES-R AWG Fog/Low Cloud Products

Conditions across the middle of the U.S. were ideal for assessing this product. Strong low pressure was forming over the High Plains while high pressure was situated along the Atlantic Coast of the southeast U.S.  Warm air and copious moisture were flowing north up the Mississippi Valley. This morning we focused on the southern coast of Louisiana.  The Louisiana case looked almost completely radiation induced.

When I was introduced to this product during the GOES-R proving ground activities of 2011, I was, to be honest, rather underwhelmed.  Back then, this product used satellite interrogation coupled with boundary layer RH from the GFS.  No observations were included in the assessment and therefore it didn't seem to perform any better than my simply using available satellite imagery and surface obs (and experience.) This year, it appears there has been significant improvement to the inputs of this product.  The boundary layer RH now comes from the Rapid Refresh Model.  Not only is the RH data resolution improved both spatially and temporally, but the Rapid Refresh incorporates the latest surface observations into its output fields.  From the few examples I saw, it is apparent this product will sometimes highlight an area, showing increased probabilities of IFR/LIFR, before these conditions appear in the observations.  This appears to be the strength of using the high resolution Rapid Refresh output.

Anyway, here is the example down along the southern coast of Louisana:

The forecaster working on the 06z TAFs would have used the GFS and NAM MOS (MET/MAV) as part of the decision aid on ceiling and visibility.  In this example, we'll look at the observation in far southeast TX, MTRJAS. See location in image below:

 Here are the METJAS and the MAVJAS products respectively at 00z Oct 23rd, 2012:

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Note the ceiling prediction shows VFR conditions dropping to MVFR from 06z-12z Oct 23rd.  No real hint of IFR, though the temp/dewpoint spread does get pretty tight in the morning.

Below are a series of 4-panel images running from 04:02Z-09:15Z Oct 23, 2012 showing a combination of GOES-R and heritage products.  See caption on first image for details. Note the GOES-R IFR probability is beginning to highlight far southeast TX with increasing probabilities of IFR at 04:02Z. MTRJAS at this point is indicating clear skies and 10 mile visibility.


GOES-R IFR Probability upper left, LIFR probability upper right, heritage brightness temperature difference product lower left, visibible image lower right

 The following image is an hour later at 05:02Z:  MTRJAS is still clear and 10 miles, but note the increasing probabilities of IFR.

At 06:15Z:  MTRJAS is now indicating Clear and 5 miles in fog...probabilities continue to show a trend toward IFR

At 07:15Z:  MTRJAS is Clear and 7 miles visibility.

At 08:15z:  MTRJAS has now gone down to a 200ft broken ceiling and 7 miles visibility. 

And finally at 09:15Z: MTRJAS dropped to as low as 200ft overcast and 2 miles, before seeing improving conditions after about 09:30Z.

In summary, it is clear that, in this case, the GOES-R IFR probability products can give the forecaster an early heads-up that conditions are on their way down to IFR conditions, despite the traditional MOS products from the GFS and the NAM indicating no IFR conditions for that METAR site. 

Steve Davis
CIMSS-MKX