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Archive for the ‘JPSS Proving Ground’ Category

It is said that a picture says a thousand words…well in this case let’s just say 434 words, as are contained in this post. Anyway, I’d like to point out six features in this morning’s Nighttime Microphysics RGB.  The image below (MODIS Nighttime Microphysics RGB) showed several features of varying degrees of operational relevance.

MODIS Nighttime Microphysics RGB with annotations valid 0755 UTC 16 July 2014

MODIS Nighttime Microphysics RGB with annotations valid 0755 UTC 16 July 2014

 

A myriad of cloud features can be observed, including fog in the valleys of central Appalachia, deep convective clouds along the Florida coast, patches of thin and thick cirrus over north-central Alabama, and low stratus clouds in Missouri…to name just a few.  Sure, this isn’t an exhaustive list of the potential cloud features to observe, but showcases the ability to contrast effectively between different cloud types.  Of perhaps significant interest is the ability to see the contrasting airmasses displayed across the Southeast region.  Notice the  pinkish colors north and west of the yellow curved line that stretches from central Louisiana to southern Virginia.  This represents a lower relative contribution of blue color, or lesser longwave radiation at the 10.8 µm wavelength, which is indicative of cooler temperatures.  To the south and east of this line, much more blue is apparent, which is thus indicative of warmer temperatures.   Surface observations valid at about the same time have been overlaid with the RGB image to provide temperature data context.  Air and dew point temperatures are around 10 degrees F cooler behind the line/front, but notice that the northerly wind shift is still on the south/east side of the line at such locations as Montgomery, AL and Columbus, GA.  At those locations, dew point temperatures were still 70 and 71 F, respectively, with air temperatures at 72 F.  So, the gradient in temperatures still lingered behind the surface front and is well depicted in the RGB imagery.  This type of information can be valuable to forecasters, as temperature, moisture, and wind characteristics are often complex in the vicinity of surface fronts.  Thus, while wind shifts may be observed initially, as in this case, the imagery shows the location of the temperature gradient much better.

The importance of this type of imagery is that it offers a much more effective assessment of meteorological phenomena than existing GOES imagery.  The only problem currently is the limitation of available imagery to forecasters, since these are from polar-orbiting platforms (Terra, Aqua, Suomi NPP), and thus provide just a few snapshots per night over a given location.  Nevertheless, the imagery form the VIIRS and MODIS instruments offer added value to existing GOES imagery and serve as valuable teaching and preparatory aids for future GOES-R and JPSS missions.

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I didn’t have a chance to make this post last week when the imagery were more time-relevant.  Nevertheless, I wanted to point out another example of the usefulness of MODIS and VIIRS imagery over current GOES imagery and show the usefulness of exciting products and imagery to come!  First, let’s take a look at the color-enhanced GOES-IR image below from the morning (0715 UTC) of June 20th.

Color-enhanced GOES-IR (11um) image valid 0715 UTC 20 June 2014

Image 1.  Color-enhanced GOES-IR (11 µm) image valid 0715 UTC 20 June 2014

 

I’ve placed the yellow circles in the image for a reason, which you’ll see below.  Further down, I’m going to show areas of fog displayed in the MODIS and VIIRS imagery, and granted, this is not the standard GOES channel difference (11-3.9 µm) typically used for making fog assessments.   However, this post is meant to show current (MODIS / VIIRS) and future capabilities (GOES-R / JPSS) that will make fog detection and cloud differentiation much more easy for the operational forecaster.  So, in the image above, fog is nearly unidentifiable as it was in the 11-3.9 µm channel difference image that morning (not shown).  Mainly high cirrus clouds can be observed scattered across the region.  Now, let’s take a look at the MODIS “fog” product, or channel difference (11-3.9 um) product valid at about the same time (Image 2).

Color-enhanced MODIS 11-3.9 u m product valid 0718 UTC 20 June 2014

Image 2.  Color-enhanced MODIS 11-3.9 µm image valid 0718 UTC 20 June 2014

Notice that in the same areas we can now begin to see low clouds (indicated by yellow colors) scattered around the valleys of the southern Appalachian region.  While the GOES-East imager is capable of detecting larger scale fog often in the valleys in the eastern circle, fog in the valleys in the western circle present challenges for the current GOES-East instrument, and is often not shown very well (even in the standard 11-3.9 µm channel difference).    Next, let’s take a look at a VIIRS Nighttime Microphysics RGB valid at about the same time.

VIIRS Nighttime Microphysics RGB valid 0723 UTC 20 June 2014

Image 3.  VIIRS Nighttime Microphysics RGB valid 0723 UTC 20 June 2014

In the RGB imagery it is much easier to detect the extent of the fog, making the operational forecast process much more effective.  Notice also that it is possible to see the fog through the higher clouds around the TN/GA/NC border region.  Not only does the resolution of the VIIRS and MODIS instruments allow for superior fog detection, but the RGBs in particular offer tremendous operational advantages.  As a user of RGBs for about 2 years now, I am convinced that this type of imagery has a relevant and needed place in future operational forecasting.  Of course, it will take time for forecasters to become accustomed and adjust to the new imagery, but it will happen.

 

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Author: Emily Berndt

This week NASA SPoRT began producing and disseminating real-time Cross-track Infrared and Microwave Sounding Suite (CrIMSS) ozone products to the Ocean Prediction Center, Weather Prediction Center, and Satellite Analysis Branch. CrIMSS retrievals are a combination of retrievals from the Cross-track Infrared Sounder (CrIS) and Advanced Technology Microwave Sounder (ATMS) instruments aboard the NOAA/NASA Suomi NPP satellite which is our Nation’s next generation polar-orbiting operational environmental satellite system. Since CrIS is an infrared sounder its ability to detect atmospheric variables through cloudy regions is limited, therefore the retrievals are combined with ATMS retrievals to view atmospheric variables in partly cloudy regions. Despite the use of microwave retrievals, retrievals are still degraded or blocked by thick clouds, similar to AIRS. Recall AIRS infrared retrievals are also combined with microwave retrievals from the Advanced Microwave Sounding Unit (AMSU) to overcome this limitation of the infrared sounder.

Expanding the ozone products to included CrIMSS retrievals will provide National Center forecasters with additional retrievals to evaluate for identifying stratospheric air related to forecasting rapid cyclogenesis and high-wind events.

While the CrIMSS algortihm differs from AIRS, the creation of ozone products using CrIMSS is the first step to expanding SPoRT’s ozone products to the next generation instrumentation aboard the Suomi NPP satellite. There are slight variations in the retrievals, but decent agreement in ozone concentration is observed between AIRS and CrIMSS retrievals. Retrievals processed via The NOAA Unique CrIS/ATMS processing System (NUCAPS) are planned for release this summer. NUCAPS is a version of the AIRS Science Team Algorithm. Once SPoRT has access to the NUCAPS retrievals the CrIS ozone product will be updated. The advantage of the NUCAPS retrievals will be the the ability to directly compare the AIRS and CrIS/ATMS ozone retrievals across satellite platforms/instruments and provide forecasters with greater spatial and temporal coverage.

The four images below are an example of consecutive AIRS and CrIMSS ozone retrievals now available to forecasters in N-AWIPS format.

1400 UTC 14 May 2014 AIRS Total Column Ozone

1400 UTC 14 May 2014 AIRS Total Column Ozone

1500 UTC 14 May 2014 CrIMSS Total Column Ozone

1500 UTC 14 May 2014 CrIMSS Total Column Ozone

1600 UTC 14 May 2014 AIRS Total Column Ozone

1600 UTC 14 May 2014 AIRS Total Column Ozone

1700 UTC 14 May 2014 CrIMSS Total Column Ozone

1700 UTC 14 May 2014 CrIMSS Total Column Ozone

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A strong cold frontal boundary that surged south across the high plains of Colorado, New Mexico, Oklahoma and Texas April 29, 2014 was forecast to produce widespread strong winds and blowing dust.   The presence of cloud cover is a key limitation of observing important surface features from satellite imagery.  The following series of imagery illustrates how the availability of the Dust RGB composite product can improve analysis of dust through clouds even when compared with other high resolution satellite imagery.  The 500-meter Visible valid at 2026 UTC over west Texas shows exceptional detail of the cloud field over the area however based on surface observations it is difficult to see verify any dust.  The 1-km True Color image valid at the same time also shows various cloud structures as well as the background appearance of the land surface.  Again, it is still difficult to discern any dust in the imagery.  Finally, the Dust RGB at 2026 UTC details precisely where the location of the main dust field exists beneath the cloud cover.  Source regions are even visible over southeastern Colorado.  A sharp boundary along the southern extent is also evident over the Permian Basin.  This area of dust surged west into eastern NM through the morning of the 30th and even produced visibility reductions in the Rio Grande Valley around Albuquerque.

MODIS-VIIRS 500-meter visible image valid at 2026 UTC April 29, 2014.

MODIS-VIIRS 500-meter visible image valid at 2026 UTC April 29, 2014.

MODIS-VIIRS 1-km True Color image valid 2026UTC April 29, 2014.

MODIS-VIIRS 1-km True Color image valid 2026UTC April 29, 2014.

MODIS-VIIRS 1-km Dust RGB image valid 2026UTC April 29, 2014.

MODIS-VIIRS 1-km Dust RGB image valid 2026UTC April 29, 2014.

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This was one of those storms that people will talk about for years, especially those that were directly affected by it.  It all started with three separate shortwaves that all phased together once off the Mid-Atlantic coast, far enough offshore to limit any direct effects save for some unusual late season snow and gusty winds the next day.  The highest impact area included Cape Cod, Nantucket, Nova Scotia, and New Foundland.  I’m sure any ships that were in the vicinity were not happy with this situation!

GOES-Sounder RGB Air Mass animation valid 03/24/14-03/26/14.

GOES-Sounder RGB Air Mass animation valid 03/24/14-03/26/14.

The evolution of the nor’easter can be seen in the GOES Sounder RGB Air Mass animation above.  A southern stream system originating in the Gulf of Mexico moved east of Florida while two other shortwaves dropped southeast out of Canada.  All of the pieces combined near the North Carolina coastline, but the explosive deepening took place as the combined system moved northeast away from the Mid-Atlantic.  There appears to be a few stratospheric intrusions, but the most impressive intrusion occurs with the final shortwave as noted by the dark oranges and reds that appear at the end of the day on 03/25.  When models are forecasting a phasing situation, this product can be quite useful in identifying the features and observing the stratospheric drying seemingly “bleed” from one shortwave to the other.

MODIS RGB Air Mass product valid at 1540 UTC on 03/26/14.

MODIS RGB Air Mass product valid at 1540 UTC on 03/26/14.

MODIS RGB Air Mass product with ASCAT winds overlaid valid at 1540 UTC on 03/26/14.

MODIS RGB Air Mass product with ASCAT winds overlaid valid at 1540 UTC on 03/26/14.

The two MODIS RGB Air Mass products above show the nor’easter near peak intensity.  Notice how distinct the gradient between oranges and greens is in this image, almost as though you can see the upper portion of the frontogenesis, well behind the actual front.  The intensity of the stratospheric intrusion is quite evident by the dark pinks near the center of the cyclone.  The second image shows the wind field overlaid from ASCATB.  Notice the large area of hurricane force winds (red wind barbs) near the bent-back front, in the comma-head of the cyclone.  This area of wind affected parts of Southeast Massachusetts, including Nantucket where winds gusted from 60-85 mph.  Nantucket recorded a wind gust of 82 mph and about 10″ of snow.  Meanwhile, Nova Scotia bore the brunt of this beast with wind gusts of 129 mph at the Bay of Fundy and 115 mph in Wreckhouse.  Waves were equally impressive with altimeter readings between 40-50 ft and a buoy report of 52.5 ft.

GOES-13 Infrared imagery with the GLD-360 30-minute lightning density product overlaid.

GOES-13 Infrared imagery with the GLD-360 30-minute lightning density product overlaid.

Another interesting aspect of this storm was the two distinct areas of thunderstorms that erupted.  I overlaid the OPC and TAFB offshore zones for reference.  Notice well east of the Bahamas there are possible supercell thunderstorms associated with the southern shortwave energy.  Meanwhile, as the strong northern stream shortwaves exit the NC coastline, two areas of thunderstorms developed with the easternmost storm exhibiting supercell characteristics.  Although the lightning was not as intense with this northern area, I would speculate that the storms were associated with very strong wind gusts due to the dry air associated with the stratospheric intrusion.

VIIRS Visible image valid at 1719 UTC on 03/26/14.

VIIRS Visible image valid at 1719 UTC on 03/26/14.

VIIRS Visible image with the 18 UTC OPC surface analysis overlaid.

VIIRS Visible image with the 18 UTC OPC surface analysis overlaid.

I’ll finish this entry with two VIIRS Visible images above showing the majestic beauty of this nor’easter.  The 18 UTC OPC surface analysis depicts the storm at a maximum intensity of 955 mb, after a 45 mb drop in 24 hours!  This qualifies as one of the most explosive cyclones on record.  Another tidbit. . .this was the strongest storm in this part of the Atlantic since Hurricane Sandy (2012).

Thanks for reading!

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Well, it’s February and it’s the East Pacific off of California, so the short answer is no.  But. . .what an amazing structure, right?  We haven’t seen anything this good looking in the tropical Atlantic in years!  But I digress. . .

MODIS RGB Air Mass product valid at 0621 UTC on 02/28/14.  The blue lines are the boundaries of OPC (north), TAFB (south), and Hawaii (west)

MODIS RGB Air Mass product valid at 0621 UTC on 02/28/14. The blue lines are the boundaries of OPC (north), TAFB (south), and Hawaii (west)

MODIS RGB Air Mass product valid at 1032 UTC on 02/28/14.

MODIS RGB Air Mass product valid at 1032 UTC on 02/28/14.

The first image was collected four hours before the second image and you can see how the center of the intense storm developed an “eye-like” feature (images courtesy of NASA SPoRT).  Notice the distribution of the pinks and reds in both images as well.  That is dry, stratospheric air filling the center of the strong upper-level low (~300-500 mb).  The second area shows an additional area of pink approaching the southern California coast.  This area is associated with strong instability that has led to rare California thunderstorms.

So, how do we know if there is stratospheric air?

AIRS Total Column Ozone product valid at 2200 UTC on 02/27/14.

AIRS Total Column Ozone product valid at 2200 UTC on 02/27/14.

AIRS Ozone Anomaly Product valid at 2200 UTC on 02/27/14.

AIRS Ozone Anomaly Product valid at 2200 UTC on 02/27/14.

The first image above is the AIRS Total Column Ozone product developed at NASA SPoRT.  The color bar on the left is not correct.  The main idea is that the warmer (cooler) the colors, the more (less) ozone is in the atmospheric column.  The green colors indicate ozone levels above 200 Dobson Units (ozone unit of measurement) with the magenta areas indicating ~500 Dobson Units.  The second image shows the AIRS Ozone Anomaly product with the first level of blue indicating 125% of normal, while the yellow region indicates >200% of normal ozone at that latitude and geographic location.  Stratospheric air is associated with high levels of ozone and potential vorticity which can help identify the strength of the upper-level low.  These images show the connection of this ozone pocket with the “reservoir” of ozone located in the northern latitudes at this time of year.

AIRS Total Column Ozone Product valid at 1000 UTC on 02/28/14.

AIRS Total Column Ozone Product valid at 1000 UTC on 02/28/14.

AIRS Ozone Anomaly valid at 1000 UTC on 02/28/14.

AIRS Ozone Anomaly valid at 1000 UTC on 02/28/14.

As the upper-low cut off and became stacked over the surface low (~971 mb), you can see how the high concentration of ozone becomes more focused over the storm.  Once again, the magenta coloring indicates ozone levels >500 Dobson Units.  The anomalies are more incredible with a large area of >200% of normal directly west of southern California.

I will continue to work with forecasters at OPC, TAFB, SAB, and WPC on discovering ways to use these products in conjunction with the RGB Air Mass products to gauge storm strength and look for signals upstream of developing tropopause folds and stratospheric intrusions.

GOES-15 Visible imagery with the GLD-360 30-minute lightning density product overlaid.

GOES-15 Visible imagery with the GLD-360 30-minute lightning density product overlaid.

The ozone isn’t the only impressive part of this storm.  Notice the occasional bursts of lightning within the spiral bands of the parent storm.  Although not completely unusual, this is a great indicator of how much energy is available to this storm.

GOES-Sounder RGB Air Mass product with GLD-360 lightning strikes overlaid.

GOES-Sounder RGB Air Mass product with GLD-360 lightning strikes overlaid.

I put together a longer animation of the GOES-Sounder RGB Air Mass product with the GLD-360 lightning strikes overlaid.  Note the first system that came ashore in California earlier this week, then moved over the four-corners regions with plenty of lightning, especially for this time of year.  The current storm is seen lurking offshore with more lightning developing in a band of thunderstorms that moved from Los Angeles to just north of San Diego.  This system will be responsible for the next bought of winter weather for the Midwest to the Mid-Atlantic next week.

Thanks for reading and as always, feel free to contact me with questions and feedback!

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SPoRT is conducting an assessment of RGB imagery for Aviation and Cloud Analysis with Alaska WFO partners.  A 17 minute training module for high-latitude application of nighttime RGBs with an Alaska example was created by SPoRT to support this assessment (see SPoRT training page to download or launch module). The Juneau WFO provided feedback for 1/24/14.  Here is a part of their feedback regarding the value of the Nighttime Microphysics RGB imagery from MODIS and VIIRS and an example image from AWIPS/D2d.

WFO Juneau feedback:
“… the microphysics image was very helpful in picking out where the fog and low clouds were in the complex terrain that is the SE panhandle. most of the fog this morning was confined to the narrower valleys and channels while the wider channels were mostly clear. This is possibly due to higher winds still present in the wider channels limiting fog formation there. It also showed little or no fog and low clouds out in the gulf. The microphysics image was very helpful with figuring out fog for zone and marine forecasts. It also helped out with the TAFs with seeing if there were any higher clouds layers above the fog layer.”

AJK_Ntmicro_assess_feedback_for_blog_20140124_0736_annotated

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Just thought I’d make a short post to mention a myriad of features observed in the early morning hours of the 12th from the VIIRS instrument aboard the Suomi NPP satellite.  In image 1 below, a faint surface snow field can be seen stretching across parts of northwestern Missouri into Iowa, deep convective clouds and even a couple of flashes of lightning were present in the western Atlantic off the North Carolina coast, and rippling wave clouds can be seen in the lee of the Appalachians.  These were among several features I wanted to showcase, and importantly, the surface snow field and lightning are two features observable only in the Day-Night Band.  However, I also wanted to point out an unusual and rather sharp reflectance that appeared in the near coastal waters of Louisiana.  In fact, it’s probably the most prominent feature in the image.  In image 1 below, notice the bright yellow colors that appear in the Gulf waters just south of Louisiana.

Image 1.  Soumi NPP VIIRS Day-Night Band Radiance RGB, valid 12 Jan 2014 0700 UTC

Image 1. Soumi NPP VIIRS Day-Night Band Radiance RGB, valid 12 Jan 2014 0700 UTC

This image is the Radiance RGB produced from the raw image of emitted and reflected light.  There is likely no source emitting that much light south of Louisiana, so this is largely reflected light.  But, what is doing the reflecting?  Also, why was there such a sharp gradient in the reflected light?  At the time of the Suomi NPP passage, the moon was at an elevation of about 35.5 degrees above the western horizon (at New Orleans, courtesy of the U.S. Naval Observatory).  So, the moon wasn’t behind the satellite during its passage, resulting in some glare from directly reflected light, but was relatively low on the horizon to its left (from the point of view facing Earth).  I don’t really have any answers, but wanted to point out this odd feature in case someone else had any good ideas.

For the previous day, I noticed that winds in the region had been southwesterly, but then shifted from the west to northwest by the aftenoon as a cold front crossed the area.  Offshore winds dominated for the rest of the day and were gusty at times before calm winds prevailed late that night.  Perhaps some material of a more reflective property upwelled during the afternoon and evening?  Or perhaps there was something about the thermal properties of the water that resulted in refraction of light into the sensor?  Without a more thorough analysis I can’t be sure.  I don’t recall seeing anything like this in the Day-Night Band imagery before.  Notice the area of brightness appears in the Day-Night Band Reflectance product quite well too (image 2).

12Jan2014_VIIRS_DNBReflectance_GulfReflectance

Image 2. Soumi NPP VIIRS Day-Night Band Reflectance image, valid 12 Jan 2014 0700 UTC

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A well defined TROWAL feature that set up over the high plains from eastern NM into western TX and KS on December 21, 2013 was captured very well by the NESDIS snowfall rate product.   A composite radar reflectivity loop in the first image below summarizes the overall evolution of this feature between 12 UTC on December 21st and 00 UTC on the 22nd (click image to loop and enlarge).  Initially temperatures were too warm for snow across much of the area however as a potent cold front shifted south over the region rain changed over to snow.  In the area of greatest instability the snow became heavy at times from near Tucumcari, NM (KTCC) to Dalhart, TX (KDHT).

Composite Radar Reflectivity Loop December 21, 2013.  Click to enlarge.

Composite Radar Reflectivity Loop December 21, 2013. Click to loop and enlarge.

The following series of images compare hourly precipitation reports at several sites across western TX and KS with the NESDIS snowfall rate product.  The first image was captured at 2040UTC and the AWIPS cursor readout at KDUX (Dumas, TX) is shown.  Note the observation is reporting an hourly precipitation accumulation of 0.05 (P0005) with moderate snowfall and a visibility of 1/2SM.  The cursor readout comparison with the QPE product is 0.0544 in/hr.  The following sample point valid for KPYX (Perryton, TX)  is reporting a visibility of 1/4SM however no weather or precipitation is available since it is only an AWOS.  However, the QPE product is sampling a precipitation rate of 0.1064 in/hr which converting with a simple 10:1 snow ratio would equate to heavy snow at 1″ per hour.  The next image was captured at 2236UTC and the cursor readout at KDDC (Dodge City, KS) is shown.  Note the observation is reporting an hourly precipitation accumulation of 0.07 (P0007) with moderate snowfall and a visibility of 1/2SM.  The QPE comparison in the readout shows a rate of 0.092 in/hr.  These values are exceptionally representative of the current conditions and the latency is less than 30 minutes.

NESDIS QPE valid 2040 UTC December 21, 2013.  Note the sample point comparison for the observation at KDUX (Dumas, TX).

NESDIS QPE valid 2040 UTC December 21, 2013. Note the sample point comparison for the observation at KDUX (Dumas, TX).

NESDIS QPE valid 2040 UTC December 21, 2013. Note the sample point comparison for the observation at KPYX (Perryton, TX).

NESDIS QPE valid 2040 UTC December 21, 2013. Note the sample point comparison for the observation at KPYX (Perryton, TX).

NESDIS QPE valid 2236 UTC December 21, 2013. Note the sample point comparison for the observation at KDDC (Dodge City, KS).

NESDIS QPE valid 2236 UTC December 21, 2013. Note the sample point comparison for the observation at KDDC (Dodge City, KS).

After the storm system pulled out of the region the Snow-Cloud RGB product provided a stellar view of this mesoscale band of snowfall.  Modifying temperatures over the following days significantly eroded snowpack in most areas except where the heaviest snow fell.  Local storm reports obtained from the Iowa State website indicated between 6 and 11 inches of snow impacted the area within the central axis of the TROWAL feature.

Snow-Cloud RGB valid at 1704 UTC December 22, 2013.

Snow-Cloud RGB valid at 1704 UTC December 22, 2013.

Snow-Cloud RGB valid at 2014 UTC December 24, 2013.

Snow-Cloud RGB valid at 2014 UTC December 24, 2013.

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I’ve posted about this a few times, but this morning offered another good example of the ability of the Suomi NPP VIIRS Day-Night Band RGB imagery to show low clouds beneath thin cirrus.  First, take a look at the 11-3.9 µm imagery (with the standard color curve) from the VIIRS instrument, valid this morning at approx 0749 UTC.  Focus your attention mainly over southern Texas.

Suomi NPP VIIRS 11-3.9 µm image valid 19 Dec 2013 0749 UTC

Image 1.  Suomi NPP VIIRS 11-3.9 µm image valid 19 Dec 2013 0749 UTC

In the image above, high, cirrus clouds will appear as blue colors, while lower clouds appear yellow.  Notice the bank of low clouds in the northern Gulf extending into portions of extreme SE Texas and southern Louisiana.  Notice that some low clouds can also be observed in and around the thin cirrus to the southwest in southern Texas.  These cloud features show up arguably better in the VIIRS Day-Night Band image from the same time (image 2).

Image 2.  Soumi NPP VIIRS Nighttime Microphysics RGB 19 Dec 0749 UTC

Image 2. Soumi NPP VIIRS Nighttime Microphysics RGB 19 Dec 0749 UTC

With the Nighttime Microphysics RGB, the low clouds appear as an off-white, while the high thin cirrus are the deep reds and blues spreading across much of the CONUS in the image.  Notice the low clouds in southern Texas still cannot be observed very well beneath the cirrus canopy, as the cirrus are mostly opaque to the longer IR wavelengths.  Now, let’s take a look at the VIIRS Day-Night Band imagery.  I like the Day-Night Band Radiance RGB best for this particular situation (image 3).

Image 3.  Suomi NPP VIIRS Day-Night Band Radiance RGB 19 Dec 2013 0749 UTC

Image 3. Suomi NPP VIIRS Day-Night Band Radiance RGB 19 Dec 2013 0749 UTC

Since the cirrus are mostly translucent in the visible portion of the spectrum, the low clouds can be seen beneath.  Also, given that the Day-Night Band Radiance RGB has an IR component, this results in better delineation between high and low clouds.  In this situation, forecasters would have a much better idea of the extent of the low cloud deck.  Observations from 0800Z indicated the cloud bases were around 1-2 kft in that area of southern Texas, which could have significant impacts on sensible weather and forecasts, especially for aviation.

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