Feeds:
Posts
Comments

Archive for the ‘Uncategorized’ Category

A cooler, drier continental airmass was moving into the Tennessee Valley on the evening of Sunday, September 21st.  Showers and a few thunderstorms developed along the associated frontal boundary as it crossed into the Huntsville County Warning and Forecast Area late in the afternoon and through much of the evening.  One thunderstorm began to strengthen as it crossed from the Lynchburg, TN area into northwestern portions of Franklin County, TN (Image 1).  The total lightning data, in fact, provided the first indication that this cell was undergoing strengthening.  Notice the “spike” in data, particularly beginning at 2153Z, when values jumped from a moving average of around 50-100 to over 200.

 

Image 1.  KHTX 0.5 Reflectivity loop 2132-2221Z 21st Sep 2014. Radar data overlaid with North Alabama LMA data (source density) and NLDN 15-min lightning data (cyan lines). Observations displayed were valid at 2200Z.

Image 1. KHTX 0.5 Reflectivity loop 2132-2221Z 21st Sep 2014. Radar data overlaid with North Alabama LMA data (source density) and NLDN 15-min lightning data (cyan lines). Observations displayed were valid at ~2215Z.  Notice the 39 kt gust at Winchester, TN. 

 

Severe weather was not expected this evening, with somewhat unfavorable environmental conditions.  Nevertheless, cells during the late afternoon were being watched for incidences of strong winds (up to about 40 mph), small hail and frequent lightning.  The “spike” in the lightning data was the first indicator that this cell was undergoing strengthening and prompted heightened situational awareness and thus closer inspection of radar data.  A special weather statement was issued for this cell at 2204Z.  Had it not been for the total lightning data running and viewable in the AWIPS II window, a closer inspection of this cell may not have been prompted until later.  These data have proven beneficial to operations for over a decade now at the Huntsville NWS office, and will continue to be a integral part of operations here for some time to come.

 

Read Full Post »

Kevin Fuell:

Here is an excellent satellite imagery interpretation by Paul Nutter of the Great Falls WFO regarding the Nighttime Microphysics RGB. As Paul demonstrates with his ability to describe this image and support its value based on current imagery, training and continued experience can lead to efficient use of RGB-type imagery.

Originally posted on TFX-shoptalk:

A strong early season cold front pushed through Montana from Alberta on 9 September 2014. The front produced several layers of cloud cover that appeared richly on the Nighttime Microphysics RGB imagery. This provides an excellent case for a study of capabilities we expect to have available on the GOES-R platform.

WPC Daily Weather Map valid 12 UTC 9 Sept 2014

WPC Daily Weather Map valid 12 UTC 9 Sept 2014

SPoRT VIIRS Night-time Microphysics RGB valid 0844 UTC 09-Sep-2014.

SPoRT VIIRS Night-time Microphysics RGB valid 0844 UTC 09-Sep-2014.

Table 1. Wavelength Band or band difference contributions to the RGB triplets and their physical interpretation used within the Nighttime Microphysics RGB composite imagery.

Color Band / Band Diff. Physically Relates to: Little contribution to composite indicates: Large contribution to composite indicates:
Red 12.0 – 10.8 Optical Depth Thin clouds Thick clouds
Green 10.8 – 3.9 Particle Phase and Size Ice particles;
Surface (i.e. cloud free)
Water clouds with
small particles
Blue 10.8 Temperature of surface Cold surface Warm surface

Violet colored…

View original 587 more words

Read Full Post »

Kevin Fuell:

Here is a posted application of the VIIRS Day-Night Band by the NWS Forecast Office in Great Falls. It was posted on their local blog.

Originally posted on TFX-shoptalk:

Clear skies and a bright moon in the early morning hours on September 12th 2014 allowed for good view of the extent of recent snowfall on the VIIRS Day-Night Band Reflectance imagery. At 1km resolution it’s about as detailed as a GOES visible image during daylight.

-Bob

VIIRS_DNB_ref_201409120930z_state_snow


Image1: Note Calgary’s location (bright city lights) on the eastern flank of the snowfield. east of the Canadian Rockies.

Viirs_snow_tfx

Image 2: Closer look at the TFX CWA

VIIRS_snow_RMF

Image3: Good detail of the extend of snowfall along the Rocky Mtn Front.

View original

Read Full Post »

MODIS Air Mass RGB Imagery with limb correction applied to the water vapor and ozone channels.  1859 UTC, 13 May 2014

MODIS Air Mass RGB Imagery with limb correction applied to the water vapor and ozone channels. 1859 UTC, 13 May 2014

The Air Mass RGB imagery product via MODIS has often appeared to lack “green” coloring near the edge of the swath and there have been noticeable differences between the channels from Aqua and Terra used within the RGB.  Forecasters from the Great Falls, MT and Albuquerque, NM WFOs applying this experimental data noted these issues.  The above image is a limb and bias corrected version of the Air Mass RGB.  The water vapor and ozone channels tend to “cool” near the swath edge as they pass through more atmosphere and the differences in satellite instrument quality result in physical characteristics between the images having different coloring.  SPoRT has worked to develop a non-linear function to correct much of the limb cooling as well as a bias correction, both through comparison of the MODIS instruments to the EUMETSAT SEVIRI instrument.  Annotations to the image attempt to classify the various features indicated by the resulting composite color during a MODIS pass from 1859 UTC on 13 May 2014 when a cold air mass was moving into the upper Midwest.  Simple interpretation guides can be found via SPoRT’s Training page or EUMETSAT. For comparison, additional plots of GOES Water Vapor,  and NAM 500mb Temperature, Humidity, and Height 0-hour analysis and 6-hour forecasts are provided below for reference. There is also a single image of the Hybrid GEO/LEO Water Vapor / Air Mass RGB product that loops GOES Water Vapor imagery and inserts the MODIS Air Mass RGB swath as it is available because the RGB is largely made up of water vapor channels.  Both the Hybrid and single-swath MODIS files are available in netCDF format for use in AWIPS I or II as well as KML format.

This new limb/bias corrected Air Mass RGB product is credited in large part to graduate student work being done at the University of Alabama Huntsville in conjunction with NASA/SPoRT. Primary contributors are:
Nicolas Elmer (UAH graduate student)
Dr. Emily Berndt (NASA/SPoRT Post-Doctoral Scientist)
Dr. Gary Jedlovec (NASA/SPoRT PI)

Additional contributors include:
Frank LaFontaine (Raytheon, Data processing and analysis)
Kevin McGrath (Jacobs, Product code development and real-time processing)
Matthew Smith (UAH, Data processing and product code development)
Dr. Andrew Molthan (NASA/SPoRT, RGB code development and research science)

g13.2014133.1845_US_wv

GOES Water Vapor Imagery at 1845 UTC, for 13 May 2014

 

 

 

 

NAM 500mb, 0-hour forecast valid 1200 UTC, 12 May 2014 of Temperature, Humidity, and Height via

NAM 500mb, 0-hour forecast valid 1200 UTC, 13 May 2014 of Temperature, Humidity, and Height via NCAR RAL website

NAM 500mb, 0-hour forecast valid 1200 UTC, 13 May 2014 of Temperature, Humidity, and Height via NCAR RAL website

N

NAM 500mb, 6-hour forecast valid 1800 UTC, 13 May 2014 of Temperature, Humidity, and Height via NCAR RAL website

NAM 500mb, 6-hour forecast valid 1800 UTC, 13 May 2014 of Temperature, Humidity, and Height via NCAR RAL website

CAR RAL website

Example: SPoRT Hybrid GEO/LEO Water Vapor and Air Mass RGBimagery

Example: SPoRT Hybrid GEO/LEO Water Vapor and Air Mass RGBimagery

Read Full Post »

Despite the hours of darkness becoming rare over Alaska as the northern hemisphere approaches its summer solstice, the RGB Night-Time Microphysics product still has some utility in Alaska south of the Arctic Circle right around midnight. Just before midnight Alaska Time on May 6, 2014 (0743 UTC, May 7) an RGB NT Micro image derived from the SNPP VIIRS instrument depicted a deck of moderately low marine stratus clouds over the northeastern Bering Sea, as outlined in the black box in Figure 1.

Image

Figure 1: RGB NT Micro product derived from VIIRS data, 1143pm Alaska Daylight Time May 6, 2014. Area of interest noted in the black box.

A closer view of this area is shown in Figure 2, along with the ceiling and visibility data from surface observing sites. In this scenario, ceilings, rather than visibility, are the problematic weather element, with the exception of Nome where the imagery shows a localized area of higher conditions. It can be challenging to discern ceilings and visibilities from satellite imagery, and in this respect the RGB NT Micro product has an advantage over conventional satellite imagery. Per the Quick Guide available at http://weather.msfc.nasa.gov/sport/training/rgb_ntmicro/RGB%20Night-time%20Microphysics%20Reference%20Guide%20AK%20by%20SPoRT.pdf and as demonstrated in the Alaskan training module http://weather.msfc.nasa.gov/sport/training/aviationForecasting_Alaska/launcher.html a tan to light green appearance indicates low clouds, but not necessarily fog, in colder climate regions such as Alaska. Surface observations on Saint Lawrence Island and in the Yukon Delta area indicate MVFR ceilings of between one and three thousand feet, but no reduction to visibility due to fog.

Image

Figure2 : the same RGB NT Micro product as in Figure 1, zoomed into the northeastern Bering Sea. Ceiling and visibility data from surface observation sites are also shown in green.

Read Full Post »

On April 28, 2014 a tornado outbreak occurred across the Southeast, with the states of Mississippi, Alabama and Tennessee being hit the hardest. Several EF-3 and EF-4 tornadoes occurred across these states. As skies cleared over the area from west to eas, the International Space Station (ISS) orbit tracked across the city of Louisville, MS on Sunday May 4. This town was hard hit by an EF-4 tornado.  True color imagery from the ISS SERVIR Environmental Research and Visualization System (ISERV) captured the track of this tornado in its entirely.

 

The above ISERV image shows the tornado track on the southeastern portion of the town with the EF Scale Damage Indicators overlaid on top.

The above ISERV image shows the tornado track on the southeastern portion of the town with the EF Scale Damage Indicators overlaid on top.

 

SPoRT uploaded all the ISERV images to an online viewer where one can explore for more detail. That viewer can be found here.

For a comparison between pre-storm Landsat imagery and post-storm ISERV imagery, see the SERVIR team link and story here.

 

Read Full Post »

Here at the Huntsville National Weather Service Forecast Office (NWSFO), we’ve been using various SPoRT LIS parameters, namely absolute and relative soil moisture and skin and soil temperatures, for situational awareness purposes for some time now.  Specifically, I’ve been using soil moisture data to help with drought monitoring application and subsequent feedback to the U.S. Drought Monitor for a few years.  But, we’ll leave that particular use for another post.  Today, I wanted to post about the relevance of these data on the far other end of the hydrologic spectrum, that is, flooding.  Let’s take the most recent example here in Alabama and adjacent areas of Mississippi and Florida.  I’m going to start with a graphic of precipitation over the region during the 24 hour period ending at 12UTC 7 April 2014.

Stage-IV Precipitation (NWS RFCs) for the 24 Hour period ending 12 UTC 7 April 2014

Stage-IV Precipitation (NWS RFCs) for the 24 Hour period ending 12 UTC 7 April 2014

 

As shown in the graphic above, some locations on the south side of the Birmingham metro received around five to six inches of rain in about a 12 hour period.  This lead to significant flash flooding across parts of the metro where some water rescues were even necessary.  Rainfall amounts here in northern Alabama ranged from around one inch in the far northwestern part of the state to about 3.5-4 inches in parts of north central and northeastern Alabama.

Now, let’s investigate the antecedent soil moisture conditions before heavy rainfall moved across the region.  Let’s begin by taking a look at the shallow layer (0-10 cm) relative soil moisture produced by the SPoRT LIS.

SPoRT LIS 0-10 cm Relative Soil Moisture (%) 12 UTC 6 April 2014

SPoRT LIS 0-10 cm Relative Soil Moisture (%) 12 UTC 6 April 2014

Relative soil moisture values generally south of Birmingham, and in particular in the “black belt” region of Alabama, a region characterized by rich, black topsoil, but underlying less permeable chalks and clay soils, were around 75% to 90%.  So, even before widespread heavy rains of three or more inches moved across the region, soil moisture values were relatively high.  Note here in northern Alabama however, that values were lower, at around 50%.  The combination of lower antecedent soil moisture conditions and similar to lower rainfall led to less incidence of flash flooding in northern Alabama.  In fact, only two flash flood warnings were issued for the event and were for the same location: encompassing parts of DeKalb, Jackson and Marshall Counties in northeastern Alabama.  Incidentally, soil moisture values were higher in the Big Wills Valley in DeKalb County where most of the flash flooding occurred.  Although, other factors should be considered there such as the narrow and steep-walled drainage basin characteristics.

Now, let’s take a look at the deep layer (0-200 cm) antecedent relative soil moisture conditions across the region (below).

SPoRT LIS 0-200 cm Relative Soil Moisture (%) 12 UTC 6 April 2014

SPoRT LIS 0-200 cm Relative Soil Moisture (%) 12 UTC 6 April 2014

 

In this image, the solid darker green indicates relative soil moisture values around 60% or higher, while blue shades indicate values in the 70s-90s%.  Notice that values were this high or higher across much of Mississippi and central and southern portions of Mississippi.  Next is a map of flooding locations as of this morning (April 11th…unfortunately, I don’t have one from earlier).

River Flood Summary courtesy of the SERFC valid as of ~14 UTC 11 April 2014

River Flood Summary courtesy of the SERFC valid as of ~14 UTC 11 April 2014

 

Streams and rivers with orange and red boxes indicate locations of minor and moderate flooding, respectively.  Notice that many of these are located where rains were heaviest, but also where antecedent soil moisture values were highest.  The main take away item here is that while rainfall values of this magnitude can occur in this part of the country, importantly, soil moisture values must be included to make a more complete assessment of the threat for flooding.  We certainly have had higher rainfall amounts in the region with much less flooding.  Such was the case with the passage of Tropical Storm Lee in September 2011, especially here in northern Alabama.

Here at the Huntsville NWSFO it has taken some time, but we have noticed that when deep layer (0-200 cm) relative soil moisture values exceed about 60%, we are at a greater risk for longer term flooding on local stream and river basins when we receive a “typical” synoptic rainfall event totaling around 2-3 or more inches.  Values in northern Alabama before this event were generally under 60%, with the exception of the Big Wills Valley in DeKalb County and in some small portions of the Paint Rock Valley in Jackson County.  Incidentally, in addition to the flooding along the Big Wills Creek in Fort Payne, minor flooding occurred along the Paint Rock River in Jackson County here in northern Alabama.  This was one of the locations with some indication of relatively wet antecedent soils (relative soil moisture values ~60%).  Thus, once again, we received further confirmation in these rough thresholds.  These two locations contain streams that are particularly prone to flooding, but it has been difficult to gauge what rainfall amounts are necessary.  This is because an important component of that assessment was lacking until the advent of LIS soil moisture data into our operations beginning over a year ago.

Thanks to the SPoRT team, we now have these data back in AWIPS (II) and can overlay other important data, such as QPF from the Weather Prediction Center.  Although these flooding threat analyses are mostly qualitative and subjective at this point, the plan is to undertake a more objective study of soil moisture and rainfall thresholds in our more problematic drainage basins to have a better understanding of threats for flooding in the future.

 

 

Read Full Post »

Older Posts »

Follow

Get every new post delivered to your Inbox.

Join 586 other followers