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Archive for the ‘Assessment’ Category

Gridded NUCAPS products developed as part of a multi-organization JPSS PG/RR project are currently being evaluated at the Hazardous Weather Testbed (HWT) Experimental Warning Program (EWP).  The project contains contributions by researchers from UW/CIMSS, CSU/CIRA/ UAF/GINA, and SPoRT.  NUCAPS soundings are retrieved temperature and moisture soundings from the Suomi-NPP CrIS and ATMS sounders.  The evaluation of NUCAPS at HWT is aimed at providing upper air temperature and moisture information in the pre-convection environment to better understand variables that are necessary for convection and severe weather.  The Gridded NUCAPS products allows for isobaric plan views of temperature and moisture that forecasters can use to gain confidence in the model output

Forecasters at the HWT-EWP posted some input on the use of the Gridded NUCAPS products.  On the Satellite Proving Ground at HWT Blog (http://www.goesrhwt.blogspot.com/2016/04/nucaps-planviews.html), a forecaster noted:

“[Gridded NUCAPS] would be beneficial in the forecasting environment as added temperature data would be available in between standard upper-air launches.  This could serve as a good proxy to help judge the strength of a capping inversion, while also possibly serving as an additional information source during winter wx events.

However, the forecaster also noted that the amount of missing data included in the product limits its utility.  Currently, the Gridded NUCAPS contains only the highest quality (i.e., “best”) data that comes from a combination of both microwave and infrared (top image below).  In this image, the dark blue pixels represent the data that are discarded due to QC issues.  However, this quality control can be strict at times and leave out “good” data that can still be useful to the forecasters.  When these “good” data are included, there are much more useful data (bottom image below) without any noticeable discontinuities or oddities in the data.

SPoRT plans to use the feedback from HWT-EWP participants to test pushing the inclusion of the “good” quality data to the Gridded NUCAPS product to provide forecasters with more data for their analysis.

NUCAPS.2016.04.21.1902329.853mbtemp_QCeq1

853 hPa Gridded NUCAPS temperature product from 21 April 2016 at 1902 UTC including only the highest quality flags.  Dark blue pixels denote discarded data that results in data gaps.  Note that a lot of over-land observations are discarded.

NUCAPS.2016.04.21.1902329.853mbtemp_QCle2

853 hPa Gridded NUCAPS temperature product from 21 April 2016 at 1902 UTC including both “best” and “good” quality flags.  Dark blue pixels denote discarded data.  Missing pixels generally correspond to thick cloud features.

 

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Forecaster Jennifer Palucki from Albuquerque, New Mexico submitted a nice case study to our online evaluation form being used during the current 2016 NESDIS Snowfall Rate Evaluation.  Here are some of her discussion and impressions of using the product:

A very well defined band of snow developed along a frontal boundary extending from the southern Sangre de Cristo Mountains, toward Las Vegas, and continued southeastward toward Melrose. Initially the southeast part of the band was rain, but as temps dropped it changed to snow. At 0052z (552pm MST; see image below) the merged SFR likely did very well distinguishing where there was snow and no snow, however, in areas that there was snow, amounts were way underdone. At 545pm, approximately 4″ of snow had fallen in Sapello in the southern Sangre de Cristo Mtns. Snow likely started around 1 or 2pm, which is an average of about 1″/hr compared to the 0.3″/hr the SFR product was showing with an 18:1 ratio. Thus, the amounts via the SFR product were largely underdone. It was still snowing heavily according to the spotter at 545pm. At 645pm, approximately 1.5 inches of snow was reported in Las Vegas. The SFR product was showing around 0.1″/hr for this area.

ABQ_160203_0052Z_annotated_zoom

NESDIS SFR Product at 0052 UTC on 03 February 2016 showing light snow over Las Vegas, NM.

Another pass at 0330z (830pm MST; see image below), the SFR product missed the southeastern extent of the snowfall, and again had amounts that were likely underdone. A report of 0.5 inches of snow in the last hour was reported at 841pm in Taos. The SFR product showed around 0.02 liquid equivalent, or around 0.3″/hr snowfall rate given 18:1 ratio (which should be close to the snow ratios in that area).

ABQ_160203_0330Z_annotated

NESDIS SFR Product at 0330 UTC on 03 February 2016 showing some heavier snow over Taos, NM.

Really like using this product to gather intel on where it is snowing in areas without radar coverage. Do have some concerns about the amounts, especially in these scenarios where the heavier amounts are likely isolated. In this case, the band was very narrow, likely no more than 10 to 15 miles wide.

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Winter Storm Jonas tracked across the eastern United States this past weekend dropping near-record amounts of snowfall in a track from West Virginia through southern New York.  Two things about this storm are particularly interesting:  1) the heavy amounts of snow that fell for long periods of time and 2) the relatively narrow swath of the heaviest snows.  Below is the 48-hour snow accumulations from the National Weather Service ending Sunday, January 24.  It is striking that New York City received on the order of 30 inches of snow, while areas less than 100 miles to the north received little if any snow.

NWS_SnowTotals

48-hour snowfall totals ending Sunday, January 24, 2016 (from NWS Central Region).  Contours are every 3″ with the darkest reds indicating 30″ of snow.

Select Eastern Region WFOs are currently evaluating the NESDIS Snowfall Rate product, which uses passive microwave observations from 5 sensors, to observe total column snowfall rates.  Below is a series of images from this past weekend showing the SFR product displayed as a 10:1 solid/liquid conversion.  The darkest greens indicate snowfall rates at the top of the sensor detection range at approximately 2″/hr.  Depending on the actual solid/liquid ratio in individual areas, rates may have been higher.

SFR_Collage_first4

SFR_Collage_second4

NESDIS SFR Product showing the evolution of Winter Storm Jonas from late on Friday through early Sunday.  The darkest greens indicate solid snowfall rates of around 2″/hr.

In the images, the NESDIS SFR product shows very good agreement with the location and track of the heaviest snows (greens) compared to the heaviest totals in the ground reports.  Additionally, the SFR product does well in picking up the abrupt northern edge of the snowfall (especially across southern New York).

UPDATE:  The Sterling, VA WFO included mention of the SFR product in a forecast discussion to confirm snowfall rates that would cause white out conditions:

Sterling_AFD

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Beginning in the morning hours of 22 January 2016, rain began to change to snow across Mississippi, Tennessee, and Alabama.  The NESDIS Snowfall Rate, which is currently being evaluated by a handful of Weather Forecast Offices, has the ability to differentiate rain from snow.  This ability was particularly important for the large winter storm impacting much of the eastern half of the United States.  The animation below shows the 10:1 Solid SFR Product with METAR station observations indicating temperatures and precipitation.

AL_TN_SFR_Example_20160122_07-19Z_slower

The animation shows the evolution of snow across the area beginning with snow in Western Tennessee and Eastern Mississippi at around 1200 UTC (6:00a local time).  Also of note at that same time is that the SFR Product indicates relatively heavy snow (~1.5 in./hr. solid snow) directly over the Nashville area; however, the METAR site at the airport is still reporting rain.  In the following hour (1300 UTC; not shown in the loop here because there was no SFR product valid near 1300 UTC) Nashville was reporting snow.  Thus, the SFR product was seeing in-cloud snow in that area that began to reach the ground within an hour of the observation.  This is one way forecasters can use the product to view in-cloud snow to determine the potential for snow to reach the ground.

Later in the period, a similar set up appears in the Huntsville area at the Madison County Executive Airport (KMDQ).  The 1853 UTC SFR product shows light snow over Madison County, but the 1900 UTC METAR was not yet reporting any snow.  However, the 2000 UTC METAR showed snow beginning to fall across the Huntsville area.  The change over to snow falling across Western Madison county into Central Madison county was between 1830 and 1900 UTC, verified as I drove home from work.

The NESDIS SFR product will continue to be evaluated as blizzard conditions begin to set up along parts of the East Coast.

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Researchers at the National Environmental Satellite and Information Service (NESDIS) have recently wrapped up development of the latest iteration of their Snowfall Rate (SFR) product to aid WFOs in situational awareness of snowfall events and snowfall forecasting.  The developers within NESDIS have teamed up with SPoRT, utilizing SPoRT’s unique transition, training, and evaluation capabilities to deliver the SFR products to several WFOs in the CONUS and Alaska.  During the evaluation period this winter, I will be evaluating the SFR and merged SFR products for use mainly here in the Tennessee Valley (provided the atmosphere obliges), but I will also be looking at the product CONUS-wide (and perhaps AK too, as the opportunity affords).

The SFR products are being delivered in two main versions: a merged snowfall rate product (merged polar-orbiter and radar data) and a product that contains only data from polar orbiters.  Through collaboration with researchers and forecasters (especially at the Boulder NWS office), SPoRT is including SFR data with liquid to snow ratios of 10:1, 18:1, and 35:1.  These data are being ported in AWIPS II workstations at the NWS offices.  In the merged product, the polar swath data are complimented with NSSL’s Multi-Radar/Multi-Sensor (MRMS) precipitation data, and update much more frequently (every 10 minutes).  Swaths containing polar orbiter data of course come in as associated polar orbiter swaths cross a region, with updates from about every 30 minutes to as long as ~4-5 hours over any location.

A look at the products the past several days has brought the opportunity for some initial evaluation.  So far, the SFR product looks rather promising.  Here’s a quick look at the product as a snowstorm was ongoing yesterday evening (Dec 15th) across the northern/central Rockies and the Northern Plains.  The loop below (Image 1) shows data from 0110Z through 0410Z 16 Dec 2015.

NESDIS Merged Snowfall Rate Product (showing 10:1 liquid to snow ratio) 0110Z to 0410Z 16 Dec 2015

Image 1.  NESDIS Merged Snowfall Rate Product (showing 10:1 liquid to snow ratio) 0110Z to 0410Z 16 Dec 2015

The loop above shows the Merged Snowfall Rate product (displaying 10:1 liquid to snow ratio).  Most of what you see is the MRMS precipitation during the loop.  At the end of the loop however, you will notice a sudden expansion of the apparent snowfall over the region as an insertion of snowfall rate derived from a polar orbiter swath is incorporated into the product.  So, let’s take a closer look at that single image containing the polar orbiter data (Image 2).

 

NESDIS Merged Snowfall Rate product (10:1 ratio) with polar orbiter data insertion, 0410Z 16 Dec 2015

Image 2.  NESDIS Merged Snowfall Rate product (10:1 ratio) with polar orbiter data insertion, 0410Z 16 Dec 2015

In the image above, you will notice that MRMS data remain and replace satellite retrievals where these data are available.  That is, the MRMS data take precedence over the satellite data in the merged SFR product.  However, data are inserted for locations where snowfall is detected by satellite instruments and radar (MRMS) data are not available.  For large areas of Wyoming and Colorado, where radar coverage is certainly more limited, notice that the insertion of polar-orbiter data allowed for a more thorough and proper analysis of locations likely experiencing snowfall.  Many of the surface observations (in yellow) likewise corroborate the snow that was occurring, particularly for locations in Wyoming, where coverage from radar data alone was very lacking.  However, there are some surface observations that do not corroborate where the SFR product is indicating snowfall.  Multiple reasons for this apparent discrepancy may exist, but it’s important to remember that the polar orbiting satellite instruments are detecting snowfall in the clouds.  Some of this snowfall may not be reaching the surface due to sublimation aloft.  Also, the snowfall could be very light and patchy in some instances with detection issues at some of the automated ground observation sites.

Now, let’s take a quick look at the polar orbiting data alone (Image 3).

NESDIS SFR product (liquid to snow ratio 10:1) 0345 UTC 16 Dec 2015

Image 3.  NESDIS SFR product (liquid to snow ratio 10:1) 0345 UTC 16 Dec 2015

The resolution of the polar orbiting data still allowed for the detection of banded structures across parts of the Dakotas that were evident in the MRMS data.

Further evaluations and posts about this product will be forthcoming as we progress through the winter.  Perhaps I’ll have the chance at some point to evaluate the product here in the Tennessee Valley…that is, if the current mild Eastern U.S. pattern changes.

 

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As mentioned in the previous post, we were concerned about the potential of organized thunderstorm outflow creating favorable conditions for blowing dust, as well as previous heavy rain activity increasing the potential for flash flooding in portions of Southeast Arizona yesterday (Sep 2) and today.  We have been trying to use LIS data as part of our process in determining the threat of both of these problems.  Yesterday was a mixed bag as I briefly outline below with less than full cooperation from the atmosphere.

Convective initiation occurred in locations we expected (similar to the WRF output posted previously), however we were unable to get the chain reaction of outflows that we hoped for.  We had problems in many valley locations (especially the Tucson Metro area) with early debris cloud and then anvils from early convection blocking solar insolation. We also underestimated the eastern extent of a modest low level drying trend filtering in from western Pima county.

Below is a loop of velocities with some observation and warning overlays early yesterday afternoon. The initial 45 kt outflow from the SVR southeast of Tucson attenuated rapidly as it approached Tucson.  Readings from Davis-Monthan AFB on the southeast side of Tucson at 2137Z showed a gust out of the SE at 30kts, and shortly later Tucson International Airport (a couple of miles further west) registered 23 kts.  By the time the outflow was west of Tucson it was difficult to detect.  There was no additional activity along this outflow in Pima County and it certainly wasn’t strong enough on it’s own to generate any dust problems by the time it got to areas we were concerned about.  The initial area that it started southeast of Tucson does have dust issues at times, but referring back to the soil moisture imagery from the previous post, things were pretty wet there.

sep2velsvr

It was an active day however.  Below is a composite post of the Severe Thunderstorm (yellow) and Flash Flood (green) products we issued yesterday.  When you compare to the 09z LIS output posted yesterday, the Flash Flood warnings were issued in an area with relative soil moistures above 70 percent (posted again for convenience).

severe and flash sep 2

soilmstrdusttue-20150902_090000

We once again have a favorable atmospheric profile for strong storms today (Sep 3), but with a little more convective inhibition to overcome and continuing issues with cloud cover.  We do have a stronger impulse embedded in the southwesterly flow that will push into our area late today and this evening.  Most standard and mesoscale model output (including latest UofA WRF and national HRRR) show increased coverage and organization of thunderstorm activity by late afternoon, especially west of Tucson.  This seems very reasonable, keeping the aforementioned caveats in mind.

A look at today’s LIS output shows that soil conditions are even more favorable in the areas of concern west and northwest of Tucson.  Especially in eastern Pinal and Maricopa counties with widespread values below 15 percent:

sep3mrnsoil-20150903_090000

Some of the special communications to our partners and the general public yesterday morning extended into mentions of issues for today as well.  We will adjust our weather story and social media posts to reflect the latest information, but our message is similar to yesterday.  We will again coordinate with Phoenix about any possible coordinated dust headline later this morning.  An example of the partner email we sent yesterday below:

BriefingUAPD09022015

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An upper level closed low near Baja and a backdoor front combined to bring considerable precipitation to New Mexico during the day and overnight period of March 19, 2015.  Ample moisture surged northward over New Mexico ahead of the closed low, and precipitable water as measured by the soundings at Albuquerque, NM and El Paso, TX tied for the fourth highest value for March since 1950 (at both locations). Additional support for this event came in the form of a back door cold front which raced through the eastern plains of New Mexico during the day on March 19.  Because of warm temperatures, Winter Storm Warnings (blue) and Advisories (yellow)  were limited to the New Mexico northern high terrain including the Jemez Mountains, San Juan Mountains and Sangre de Cristo mountains, as shown in the figure below.

WSW

Two NESDIS Snowfall Rate (SFR) products were available for review the morning following the event.  The first is from 0353Z on 20 March 2015, or about 10pm MDT on the evening of March 19, and is shown in the figure below with the 04Z surface observations.  The east to northeast flow in the eastern half of the state indicates the progress of the back door front.  Most locations in central and eastern New Mexico are reporting rain, including Raton (KRTN) just to the east of the active snow area in the SFR product. Angel Fire (KAXX) just to the south of the area is reporting snow.  At this time, the SFR product appears to do a good job in distinguishing between rain and snow despite the fact the Angel Fire is just outside the SFR active area.

NESDIS_SFR_20150320_0353Z_obs

The 0.5 reflectivity mosaic at the same time illustrates beam blockage that impacts the area east of Albuquerque, but also the limited radar coverage in northern New Mexico, though there are weak echos associated with the snow report at KAXX as well as the rain at KRTN.  Also note convection in western Texas – earlier in the evening one-inch hail was reported in eastern New Mexico.  This is an example of the interesting regimes that can impact our CWA in that we can have winter weather warnings and severe weather at concurrent times.

0_5reflectivity_20150320_0400Z_obs

Similar graphics are shown for 0855Z, or 3am MDT, on the morning March 20th. Activity has weakened considerably and the WSW is about to be cancelled.  Still, light snowfall rates are depicted by the SFR over the northern high terrain.  The metar observation at Angel Fire, KAXX, is still reporting snow.

NESDIS_SFR_20150320_0855Z_obs

The 0.5 reflectivity mosaic illustrates that the only isolated precipitation continues over western and central New Mexico, with no returns over the northern high terrain.

0_5reflectivity_20150320_0854Z_obs

In the image below, the 0855Z SFR product is combined with the awips hi-res topography map to illustrate the agreement with the SFR and the highest terrain of the southern San Juan and northern Sangre de Cristo Mountains in northern New Mexico.

SFR_0855Z_withTerrain

One of the frustrations with evaluating the NESDIS SFR product is that consecutive products can be separated by long periods of time, in this case by 5 hours. However, substantial snow accumulations were reported in the Sangre de Cristo mountains – from 6 to 19 inches. Thus the area depicted by the SFR product seems to be fairly accurate, but the evaluation is rates is more difficult.

In addition to snow, widespread rainfall reports ranged from one quarter of an inch to one inch. Early this morning, the following DOT report was posted – the combination of rain and snow resulted in rock slides on at least two roads in northern New Mexico.

DOTinfo

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