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Archive for the ‘MODIS’ Category

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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VIIRS True Color RGB imagery produced by NASA/SPoRT.  Southwest region domain at 1836UTC, 11 March 2014.

VIIRS True Color RGB imagery produced by NASA/SPoRT. Southwest region domain at 1836UTC, 11 March 2014.

In the southwest CONUS region, severe to extreme drought conditions exist in many areas.  In particular southwest Colorado, northeast New Mexico and the Texas and Oklahoma panhandle areas are very dry according to the U.S. Drought Monitor.  A building high pressure area developed a strong pressure gradient across these areas during the afternoon of 11 March 2014, resulting in 20-30 kt sustained northerly winds with gusts over 40 kt. Combined with the dry conditions, WFOs in the southwest have been anticipating blow dust events to be large and more frequent with strong Spring cyclones. VIIRS True Color RGB imagery (above) shows the blowing dust in Colorado and Texas, but the clouds in Colorado and Kansas have a similar color and the dry ground characteristics in Texas also look similar in color to the dust.  To provide a more efficient analysis of the blowing dust, VIIRS and MODIS can be used to create an RGB imagery product that shows blowing dust in shades of magenta to differentiate it from clouds and ground features.  This is done using the EUMETSAT recipe for the “Dust RGB” per their “Best Practices” after years of experience with the MeteoSat Second Generation SEVIRI instrument.  This geostationary instrument has similar capabilities to that of the future GOES-R ABI instrument.  Hence VIIRS and MODIS provide operational utility now and demonstrate future capabilities that all U.S. forecasters can use to be ready for the next generation of satellite products.  The VIIRS and MODIS passes show three times from this afternoon to aid forecasters with tracking the dust event.

20140311_1836_sport_viirs_swregion_dust_annotated

MODIS Dust RGB Imagery for 1941UTC 11 March 2014

MODIS Dust RGB Imagery for 1941UTC 11 March 2014

VIIRS Dust RGB Imagery for 2019UTC 11 March 2014

VIIRS Dust RGB Imagery for 2019UTC 11 March 2014

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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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The Huntsville County Warning Area received widespread 3-5 inch snowfalls Wednesday night, with a few sites reporting as high as 10 inches!  While it’s melting quickly today with temperatures in the mid and upper 30s, the snow cover did hang around long enough to be captured by the mid-morning MODIS pass (though we are on the very edge of the pass, so the bowtie distortions are noticeable).  That might be nothing new, but this is the first time we’ve been able to view such imagery in AWIPS II.

MODIS Snow/Cloud RGB Image valid 1546 UTC 13 February 2014

MODIS Snow/Cloud RGB Image valid 1546 UTC 13 February 2014

MODIS True Color Image valid 1546 UTC 13 February 2014, viewed in AWIPS II CAVE

MODIS True Color Image valid 1546 UTC 13 February 2014, viewed in AWIPS II CAVE

The Snow-Cloud RGB is particularly illuminating, as it effectively illustrates the downslope-induced cloud breaks over northern Georgia.

Great job to the SPoRT AWIPS II team on helping us get these data back into AWIPS!  There are still some kinks to work out, but this essentially restores the SPoRT data feed that was in place before our A2 upgrade in June 2012.

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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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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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Late yesterday evening (Dec 17th) fog began forming along coastal areas of Lousiana and Texas.  By 10 pm CST, visibilities at some locations along the coast had already dropped to less than 1 SM.  The fog continued to intensify, with visibilities falling to around 1/4 SM or less at many locations during the early morning hours this morning (Dec 18th).   By 2 am CST (0800 UTC), the visibility had fallen to near 0 SM in portions of SW Louisiana as noted by the observation at Jennings (3R7, near Fenton in the image, image 1).

GOES 11-3.9 Spectral Difference Image, with Ceiling (AGL) and Visibility (SM) observations 18 Dec 2013 0800/0815 UTC

Image 1.  GOES 11-3.9 Spectral Difference Image, with Ceiling (AGL) and Visibility (SM) observations 18 Dec 2013 0800/0815 UTC

In this standard GOES spectral difference imagery however, the fog is very diffcult to visually discern, likely due to it’s very shallow depth.   There is some indication of the fog, with slightly brighter pixels in areas of southern LA and SE Texas.  However, notice the better (albeit slightly) detection of the fog in the Nighttime Microphysics RGB products from the VIIRS and MODIS instruments below (images 2 and 3, respectively).  The fog in these images appears as a pinkish-gray color.

Image 2.  Suomi NPP VIIRS Nighttime Microphysics RGB 18 Dec 2013 0808 UTC

Image 2. Suomi NPP VIIRS Nighttime Microphysics RGB 18 Dec 2013 0808 UTC

Image 3.  Aqua MODIS Nighttime Microphysics RGB 18 Dec 2013 0804 UTC

Image 3. Aqua MODIS Nighttime Microphysics RGB 18 Dec 2013 0804 UTC

I think the fog is a little easier to see in the MODIS image, which may be due to higher resolution and small differences in channel wavelengths between the VIIRS and MODIS instruments.  Nevertheless, the fog in all of the imagery is rather subtle and will require development of pattern recognition by forecasters.  Sampling the color contributions, I found that the primary changes between areas of fog and areas without occurred in the green color (assigned the ~10.8-3.9/3.7 channel difference), which would be expected.  For example, when taking a color sample from the pinkish-gray band of fog in SW Louisiana (near Jennings) from the MODIS image, I came up with: Red-180, Green-137, Blue-165.  Meanwhile, sampling of a pixel in central Louisiana without fog: Red-167, Green-99, Blue-150.

So, how did the fog appear in the Day-Night Band RGBs?  Not very well at all, as you can see in the next couple of images…

Image 4.  Suomi NPP VIIRS Day-Night Band Radiance RGB 18 Dec 2013 0808 UTC

Image 4. Suomi NPP VIIRS Day-Night Band Radiance RGB 18 Dec 2013 0808 UTC

Image 5.  Suomi NPP Day-Night Band Reflectance RGB 18 Dec 2013 0808 UTC

Image 5. Suomi NPP Day-Night Band Reflectance RGB 18 Dec 2013 0808 UTC

I wasn’t able to detect any fog at all in the Day-Night Band RGB imagery.  However, there is still potentially important information to glean from all of this.  If the fog is evident (even slightly) in the NT Microphysics RGB imagery mainly due to the 10.8-3.7/3.9 channel difference, but is essentially translucent in the visible spectrum (Day-Night Band), then it is likely very shallow.  This could be helpful for determining the duration of the fog during a change of conditions, such as the development of mixing after sunrise (i.e. shallow fog dissipation will be quicker than thick fog dissipation).

Notice in the GOES visible loop below (images at 0445 UTC and 0601 UTC) that the fog dissipated very quickly after sunrise (click the expanded image to obtain the loop).

Loop of GOES visible images at 1445 and 1601 UTC with observations of

Loop of GOES visible images at 1445 and 1601 UTC with ceiling (AGL) and visibility (SM) observations  oat 1500 and 1600 UTC

The Corpus Christi, Houston and Slidell offices all issued Dense Fog Advisories or Special Weather Statements concerning the fog in their respective County Warning/Forecast Areas during the early morning hours.

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It’s always challenging to determine how rapidly clearing will occur in the winter season, but some snow cover added to the difficulty on Sunday.  It looked like there might be some clearing on GOES visible imagery over the Ohio Valley, but even when looping, it was tough to tell for sure.

GOES Visible Imagery valid 1815 UTC 15 December

GOES Visible Imagery valid 1815 UTC 15 December

To validate this, we leveraged the MODIS snow/cloud RGB image (formerly known as “false color”) from SPoRT’s website, which nicely illustrated the clearing.

Snow/Cloud RGB valid 1658 UTC 15 December

Snow/Cloud RGB valid 1658 UTC 15 December

While those specific breaks did not affect northern Alabama and southern middle Tennessee, it helped to validate a mental model of where clearing was occurring (along with an upper trough axis), improving the sky cover forecast for Sunday evening.

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The RGB Imagery for Aviation and Cloud Analysis got underway on December 1st with SPoRT’s collaborative coastal NWS offices in Southern Region.  These offices include Corpus Christi, Houston, Slidell, Mobile, Melbourne, and Miami.  A separate evaluation with AK offices and CA/OR coastal offices has also begun recently.  The SR coastal office evaluation will run through the end of January, where offices will be evaluating the VIIRS and MODIS Nighttime Microsphysics RGB imagery, VIIRS Day-Night Band Reflectance and Radiance RGBs, in addition to the hybrid GOES/MODIS/VIIRS 11-3.9 um looped product.  SPoRT personnel have conducted training for the offices and will be helping during the evaluation with questions and/or technical issues.  Although RGBs have been used in the European forecast community for years, they are quite new to most U.S. forecasters.  However, and importantly, the imagery available from the Aqua/Terra satellites (MODIS imager) and the Suomi NPP satellite (VIIRS imager) are a part of GOES-R and JPSS Proving Ground activities and will serve as educational tools for forecasters before the GOES-R and JPSS eras.  As a part of the evaluation, forecasters will answer a short survey about the operational impact of these imagery on aviation forecasts in particular, but may of course include impacts for other operational products (i.e. advisories, fire weather, public, hydrologic, etc).

While many potential positive impacts to various forecast products have been related on this blog, I’ll be watching and posting those which forecasters at these offices (and myself) observe during the evaluation period (time permitting of course).  Take the following case from yesterday, December 9th, for example…

Image 1.  SUOMI NPP VIIRS Nighttime Microphysics RGB valid 9 DEC 2013 0736 UTC.

Image 1. SUOMI NPP VIIRS Nighttime Microphysics RGB valid 9 Dec 2013 0736 UTC.

In the image above, notice the swath of light purple colors that extend across a good portion of the TX Gulf Coast.  Further north, in north central and northeastern TX extending to include portions of Oklahoma, Missouri and Arkansas, an area of low clouds with colors closer to dull reds to greenish-white are apparent.  In Image 1, a small area near Corpus Christi, TX has been sampled, with the contributions from Red (183), Green (132) and Blue (209) included in the image (This was sampled in Microsoft Paint).  At about the same time, observations across this region of coastal TX were nearly uniform.  Ceilings were around 300-400 ft from Houston, to Port Lavaca and Corpus Christi, with visibilities ranging from 1.5 to 2.5 SM.

Image 2.  GEOES IR image (730 UTC) with Ceiling (AGL) and Visibility observations (0800 UTC) 9 Dec 2013.

Image 2. GEOES IR image (730 UTC) with Ceiling (AGL) and Visibility observations (0800 UTC) 9 Dec 2013.

Thus, the colors represented by the shades of light purple represented an extensive low stratus/fog deck encompassing the area.  Notice that a swath of this color/cloud type also extended into northern Louisiana and Mississippi.  Low visibilities ranging from 2.5 to 3 SM and low ceilings around 400 ft were observed in both areas.

Herein lies the power of the RGB imagery.  Since the combination of colors are related to several physical characteristics (i.e. red – optical depth, green – particle phase and size, blue – temperature), then it is easier to make assessments about cloud homogeneity or inhomogeneity.   While other satellite observations generally just relate one physical characteristic (usually temperature), or in the case of the standard 11-3.9 channel (particle phase/size), they don’t have the ability to tie together several physical characteristics together in one image like the RGBs can.  It is thus much easier, with RGB imagery, to assess locations where cloud characteristics are the same and make inferences about the similarity of ceilings and visibility in areas without direct observations.

This next image shows a sample of the color taken from the Texarkana site in NE Texas at the same time, underneath the area of low stratus containing more dull red colors.

Image 3.  Suomi NPP VIIRS Nighttime Microphysics RGB valid Dec 9 2013 0736 UTC.

Image 3. Suomi NPP VIIRS Nighttime Microphysics RGB valid 9 Dec 2013 0736 UTC.

As the difference in colors suggests, the cloud characteristics are different here than in SE coastal TX.  Referring to image 2, the ceiling and visibility at Texarkana were 1100 ft and 6 SM, respectively.  Ceilings were still relatively low, but were higher than in coastal TX, as was the visibility.  Essentially, this was a slightly higher stratus deck.  The red color contibutions were very similar in each location, suggesting clouds of similar depth.  However, differences in green and blue are clearly discernible.  The cloud deck near the coast certainly contained more blue, indicating warmer temperatures, which makes physical sense.  The clouds in NE TX contained more green however, which would suggest smaller water particle size. But, emssions in the 3.9 channel from the surface beneath the low/thin cloud deck near the coast may also be contributing to less green color there.  Taking a look at proximity soundings in this area of clouds from Forth Worth (FWD) and Little Rock (LZK), cloud tops decreased during the 00-12 UTC period, but contained super-cooled water droplets by the 12 UTC sounding.

As an aside, forecasters have expressed the desire (including myself) to have the specific values from the red, green, blue color contributions available in AWIPS when sampling the imagery.  This is a valuable part of the feedback and evaluation process.  Unfortunately, this is not possible in AWIPS I, but will be in AWIPS II.

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Brian Bernard runs a website in Southern Canada called Golden Horseshoe Weather.  Brian obtains near real-time sea surface temperature (SST) and green vegetation fraction (GVF) products from SPoRT for ingest into a version of the Environmental Modeling System (EMS) that he runs.  This model is a 4-km Advanced Research Weather and Research Forecasting (WRF-ARM) model that encompasses Southern/Central and part of Northern Ontario.  It uses 40 vertical layers, with most of the layers between 1013 to 650 mb in order to better resolve lake-breeze boundaries and lake effect areas.  As a result, use of the high-resolution SPoRT SST data is critical for resolving some of these boundaries.

Southern and Central Ontario is bounded by water on three-sides and one of the forecasting challenges for the meteorologist is the interaction of the marine layer and the land area. Most of our severe thunderstorm events occur during interactions with lake-breeze boundaries.  In winter, parts of Southern/Central and Northern Ontario are downwind in cyclonic flow events and are susceptible to lake-effect snows.  Areas downwind of Lake Huron can also be affected by multi-lake effect snows.

Brian posts numerous output fields from his real-time WRF runs to a modeling subsection of his website, which is frequented by Canadian, provincial, and U.S. government meteorologists, private sector and media meteorologists, as well as weather enthusiasts and storm chasers. The model is initialized daily at 00Z and run for 36 hours; output is generally available by 1:00 A.M. local time.

A recent lake-effect snowfall event in Southern Ontario was captured well by WRF with the inclusion of the SPoRT SST.  The 24 November 1200 UTC radar image from the King City radar in Ontario shows two distinct lake-effect snow bands (one southwest of Barrie and Midland; one near London).  The corresponding 36-hr WRF forecast (initialized at 0000 UTC on 23 November; valid at 1200 UTC on 24 November) of 900 mb omega shows that the strongest vertical motions associated with snow bands occurred almost exactly in the location of the two snow bands observed in the radar.

Radar reflectivity (dBZ) from the King City radar from 1200 UTC (left) and Exeter radar from 1210 UTC (right) on 24 November 2013 showing two distinct lake-effect snow bands over Southern Ontario.

Radar reflectivity (dBZ) from the King City radar from 1200 UTC (left) and Exeter radar from 1210 UTC (right) on 24 November 2013 showing two distinct lake-effect snow bands over Southern Ontario.

36-hr WRF forecast of low-level vertical velocities valid at 1200 UTC on 24 November 2013.  The larger magnitude vertical velocities are snow bands.

36-hr WRF forecast of low-level vertical velocities valid at 1200 UTC on 24 November 2013. The larger magnitude vertical velocities are snow bands.

In addition to his use of the SPoRT data for modeling applications, Brian also obtains satellite imagery products from SPoRT’s publically-accessible FTP server and generates relevant imagery over Southern Canada for his website users.  As an additional verification of this snow event, Brian used SPoRT’s MODIS false color snow cover product to compare with forecasted snow depth output from WRF.  In the false color image below, the red areas outline where there is snow on the ground, and the outline of the fallen snow matches very closely with the areas where snow was forecasted to fall in the 36-hr forecast.  While the MODIS false color product is unable to provide any quantitative information about snow depth, the MODIS image is annotated with reports from the two areas where the heaviest snowfall occurred.  The heaviest snowfalls in the 36-hr WRF forecast also match nicely with the bull’s eyes of where the heaviest snowfall was reported.

MODIS false color imagery from 1640 UTC on 24 November 2013 showing the extent of the snowfall that occurred during this lake-effect snowfall event over southern Ontario.  The red areas indicate snow on the ground.  The circled areas with annotations show the areas of the heaviest reported snowfall.

MODIS false color imagery from 1640 UTC on 24 November 2013 showing the extent of the snowfall that occurred during this lake-effect snowfall event over southern Ontario. The red areas indicate snow on the ground. The circled areas with annotations show the areas of the heaviest reported snowfall.

36-hr WRF forecast of model snow depth valid at 1200 UTC on 24 November 2013.  The spatial extent of the snow on the ground and largest snowfall areas over southern Ontario coincide with what is seen in the MODIS false color image and snowfall reports.

36-hr WRF forecast of model snow depth valid at 1200 UTC on 24 November 2013. The spatial extent of the snow on the ground and largest snowfall areas over southern Ontario coincide with what is seen in the MODIS false color image and snowfall reports.

 

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