1-minute imagery of warm conveyor belt on 1-2 February 2016 winter storm


A winter storm that passed through Colorado on 1-2 February 2016 resulted in significant snowfall over northern / northeast Colorado:


One of the key aspects of this extra-tropical cyclone was the development of a warm conveyor belt (Harrold 1973).  The 4-km NSSL WRF-ARW synthetic water vapor imagery from the 0000 UTC 1 February run valid 1800 UTC 1 Feb to 0600 UTC 2 Feb:


forecasts what appears to be a warm conveyor belt (WCB) by around 0100 UTC 2 Feb, highlighted here:



Keep in mind, one the of the limitations of the synthetic water vapor imagery from the NSSL WRF is that that areal coverage of cold cloud tops tends to be underdone due to the microphysics scheme of this model run.  Interpretation should focus on the feature of interest (the WCB) rather than the specific cloud top temperatures to compare with GOES.

For this event, GOES-14 Super Rapid Scan Operations for GOES-R (SRSOR) was in effect, meaning that 1-minute imagery was collected (Schmit et al. 2015).  This is in preparation for GOES-R (scheduled for launch in October 2016) since 1-minute imagery will be available much more frequently for significant weather events.

In the 1-minute GOES-14 water vapor imagery between 1800 UTC 1 Feb to 0100 UTC 2 Feb:


We can see the development of the WCB over eastern Colorado and western Kansas, consolidating by the end of the loop:


Next, lets consider the perspective of the GOES-IR (10.7 um) 1-minute imagery:


Note the rapid expansion in areal coverage of colder cloud tops from the Texas panhandle / western Oklahoma into western Kansas then curving cyclonically westward into Colorado.  This is the WCB of interest.  Where is the surface low in this loop?  Note the highlighted region below:



In the animation near this time, we observe a circulation with colder brightness temperatures just after 2300 UTC followed by what appears to be a deformation zone that is quasi-stationary.  The surface low is slightly southeast of this zone that is quasi-stationary.

Later, between 0100 and 0600 UTC 2 Feb:


We see the continued expansion of colder cloud tops associated with the WCB that is impacting Colorado.  During this period, snowfall rates increased as a result of this WCB as heavy snow impacted much of northern / northeast Colorado.

We observe a number of interesting features in the 1-minute imagery that we normally would not see under routine GOES scanning at 15 minute intervals.  For example, note the highlighted region in the following two images at 0300 and 0418 UTC:




Closer inspection of the animated imagery during the time period shows the development of transverse bands along the western edge of the WCB (which has a well defined limiting streamline).

Moving on to the next time period of IR imagery:


We see a number of gravity waves along the edge of the WCB that appear and disappear over short-time scales, for example, note the highlighted region at 0645 UTC:


1-minute imagery from this winter storm illustrates one of the reasons why GOES-R will be a “game changer”.  The high temporal resolution imagery will show features that were not sampled adequately to be observable under current/past temporal resolution.  Since some of these features have not been seen before, there will be an opportunity for research into these new features to understand what we are observing, and more importantly, potential applications for use in operational meteorology.  Another consideration is the 1-minute imagery latency on AWIPS will be approximately 1-minute, much greater than currently available for GOES RSO (Rapid Scan Operations), this impacts how much more effectively the data could be used operationally.

For completeness, analyze the 1-minute water vapor imagery for the remainder of the event.  What additional features do you see?



How does the development of the WCB relate to the increase in snowfall rates as observed from the NESDIS Snowfall rate product retrieved from polar orbiting satellites?




Harrold, T.W. 1973: Mechanisms influencing the distribution of precipitation within baoclinic disturbances. Q.J.R. Meteorol. Soc., 99, 232-251.

Schmit, T.J., and Coauthors, 2015: Rapid Refresh Information of Significant Events: Preparing Users for the Next Generation of Geostationary Operational Satellites. Bull. Amer. Meteor. Soc.96, 561–576.

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Himawari imagery of 924 mb low in the Pacific

At 0600 UTC 13 December 2015, the NOAA Ocean Prediction Center analyzed a 924 mb surface low in the north Pacific in the vicinity of the western Aleutian islands:


The analyzed minimum central pressure of 924 mb ties the record for lowest pressure in the north Pacific during the period of record (since the winter of 1969-1970).

Satellite imagery from the new Japanese satellite (Himawari-8) provided a spectacular perspective of this cyclogenesis event.  First, we will look at the larger scale by analyzing the RGB airmass product (please allow sufficient time for this loop to load):


Warmer air is displayed in green and red where the green regions have higher moisture content than the red regions. Mid-latitude air has a bluish color and areas of dark red show areas of subsidence and high ozone and potential vorticity.   Click here for more detailed information.

The first feature that catches your attention is typhoon Melor east of the Philippines.  As you may suspect for an intensifying tropical cyclone, green colors in the vicinity of the storm indicate higher moisture.

Focusing our attention to the extra-tropical cyclone further north.  Early in the loop, we see the system over Japan moving northeast with a trailing deformation zone on the northwest flank of the cyclone.  In time, this feature dissipates as we see the system intensify, it develops a comma cloud followed by a strong surge of high ozone air (orange/red colors) associated with the dry slot.  This corresponds to a stratospheric intrusion deep into the troposphere.  Soon after this feature we see a cusp that develops and eventually wraps cyclonically around the upper low until becoming vertically stacked by the end of the loop.  Note the red/orange colors during this process as well, corresponding to high potential vorticity that is tracked by the high ozone air caused by the stratospheric intrusion.

Next we’ll look at the longwave infrared (11 um) loop zoomed in over the north Pacific:


In this channel, we can see low-level cumulus clouds which correspond to low-level cold advection over the relatively warm sea surface.  The position of the cold front can readily be tracked by following the low-level cumulus.  When the cold front wraps around the low and intersects the warm front, the occlusion process begins.  The leading edge of the relatively colder clouds that wrap around the system appear to be associated with a sting jet.  Wind gusts over 100 knots were observed with this storm.

Finally, we analyze a zoomed in perspective of Himawari True Color / Geocolor imagery:

Alternately, you may view this loop:


True color imagery is shown during daylight hours, and Geocolor imagery is shown during nighttime hours.  The CIRA Hybrid Atmospherically Corrected (HAC) method is applied to produce this “true color” imagery.

The Hybrid Atmospherically Corrected (HAC) true color method uses the red, green, and blue Himawari bands, in addition to some information from bands 4 (0.86 micrometers) and 13 (10.4 micrometers).  A Rayleigh correction is performed at each band in order to correct for the effects of Rayleigh scattering.  The result is an image that is significantly more crisp and clear, and less milky, than without the correction.

Once the imagery transitions over to nighttime the CIRA Geocolor algorithm is applied to the imagery.  White colors are high level ice clouds, reddish colors represent lower level liquid water cloud and city lights (static) are shown in yellow.

For more detailed information on analyzing spiral rings around extra-tropical cyclones, see this article.

Real-time Himawari-8 imagery may be viewed at:



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Himawari-8 True Color / Geocolor product

CIRA now provides Himawari-8 daytime true color imagery and nighttime geocolor imagery:


The example above begins at 0230 UTC 12 November 2015 with most of the scene in daylight, therefore true color imagery is shown.  The CIRA Hybrid Atmospherically Corrected (HAC) method is applied to produce this “true color” imagery.

The Hybrid Atmospherically Corrected (HAC) true color method uses the red, green, and blue Himawari bands, in addition to some information from bands 4 (0.86 micrometers) and 13 (10.4 micrometers).  A Rayleigh correction is performed at each band in order to correct for the effects of Rayleigh scattering.  The result is an image that is significantly more crisp and clear, and less milky, than without the correction.

Once the imagery transitions over to nighttime the CIRA Geocolor algorithm is applied to the imagery.  White colors are high level ice clouds, reddish colors represent lower level liquid water cloud and city lights (static) are shown in yellow.  More information on the Geocolor imagery may be found here:


Real-time Himawari-8 imagery may be viewed at this page:


See the “Full Disk AHI True Color” for the imagery in the example illustrated above.

A similar product is planned for GOES-R so you may familiarize yourself with this imagery from the Himawari-8 satellite presently.

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GOES-14 SRSOR 1-minute visible imagery for 19 May 2015 over Texas

GOES-14 will be in Super Rapid Scan Operations for GOES-R (SRSOR) mode between 18 May – 12 June, 2015.  This special mode allows for 1-minute temporal imagery for GOES, similar to what will be available when GOES-R becomes available in 2016.

We will discuss the 1-minute imagery over Texas on 19 May, 2015.

First, we will look at the early period between 1730 to 1940 UTC:


Regions of convection at this time include:

1) southeast Texas (moving southeast), which leaves behind a stable air mass (clear area to its northwest)

2) central Oklahoma

3) eastern Texas panhandle moving into western Oklahoma

Next, we turn our attention on southwest Texas.  We see indications of developing cumulus along a dryline (clear to the west).  The northern portion of the developing cumulus has multiple failed attempts at convective initiation since the anvils get detached (commonly called orphan anvils) from the main updraft base.  By the end of the loop we begin to see more robust looking cumulus slightly further south down the dryline.

Next, we’ll look a the period between 1941 to 2136 UTC:


We keep our attention in southwest Texas along the dryline and note that convective initiation occurs in two areas (a northern area and southern area), along the dryline.  The northern area continues to show the earlier trend, which is soon after development the storms dissipate (perhaps moving into more stable air?) then another storm develops and follows the same fate.  Meanwhile the storm to the south quickly expands and intensifies with multiple reports of tornadoes associated with it. We see cumulus streets just southeast of this storm indicating an unstable air mass that is feeding into this storm.  We also see a nearly east-west oriented line of cumulus on the western flank of the storm.  This appears to be a pre-existing convergence line that is augmented by the flanking line of the storm itself.  Note the northern storm eventually dies off by the end of this loop, storms had struggled to persist in this region earlier, and now with the larger storm to the south it may have completely cutoff the inflow into the northern storm.

Look at convection developing in other parts of Texas and Oklahoma, notice how much more clear features appear in 1-minute imagery relative to what you are used to analyzing.  A cold front exists in the northern Texas panhandle extending northwest into northeast New Mexico, stratus clouds and/or stable wave clouds exist behind the cold front.  Any convection that crosses the cold front briefly are enhanced along the cold front but quickly dissipate as they move to the cold side of the front where CAPE goes away.  The convection in western Oklahoma leaves behind an outflow boundary that may play a role later in the day.

Now we will consider our final loop between 2137 to 2349 UTC:


Our storm in southwest Texas continues to exhibit numerous characteristics of a severe storm – overshooting top, back-sheared anvil, crisp edge to the anvil cirrus, flanking line with enhanced cumulus and unstable air (cumulus streets) feeding into the storm.  Note the weaker storm that developed near the Mexican border and moved north, the pulsing updraft with that storm can be followed underneath the anvil cirrus of the dominant storm for a while.  It looks like it moves just east of the main updraft of the more intense storm.

In the Texas panhandle, we see an MCS outflow boundary that originated from the MCS in western Oklahoma oriented ESE to WNW with an area of convection riding along that boundary that seems to enhance the intensity of the convection.  Further north and west, we see the cold front with its stratus clouds behind it, and any convection that crosses it towards the cold air quickly dissipates.

Further east, just west of the Dallas metroplex and south of the Oklahoma-Texas border we see a number of new thunderstorms developing.  A number of these were severe including tornadoes.  Note the anvil orientation is towards the southeast, different than some of the other anvil orientations we were looking at for other storms.  Remember that anvil orientation is a function of the vector difference between the mid-level steering flow (in this case west-southwest) and storm motion.  The storm motion varies across Texas, accounting for the different anvil cirrus orientations that we observe.

Real-time 1-minute imagery may be viewed here:


Also, be sure to check out the CIMSS Satellite blog entry on this same event:


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Synthetic imagery from the 4-km NSSL WRF-ARW model for the 22 April 2015 severe weather event

This blog entry consists of a youtube video:



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10 November 2014 Colorado Dust Storm Matched to Aircraft Photo

By Steve Miller (CIRA)

This blog entry is in Powerpoint show format, click on the link below to view the Powerpoint show:

Powerpoint show file

Posted in Blowing Dust (Blue-light absorption technique), Blowing Dust Detection (Split-window technique) | Leave a comment

Leeside cold front of 10 November 2014: Blowing dust and deep-tropospheric gravity waves

A strong cold front pushed southward across the Plains during the day on November 10, 2014.  The temperature gradient across the front was quite dramatic, as seen by the surface observations at 23:00 UTC:


Visible imagery from GOES-East during the afternoon hours centered over Colorado clearly showed the southward progress of the cold front as dust was being lofted at the edge of the cold front where surface winds are strongest:


Note the rapid movement of the cold front as it moves from southeast Colorado towards northeast New Mexico as you can easily trace it by the blowing dust.

The GOES-West shortwave albedo product also clearly shows the blowing dust:


Confirming the existence of the dust is this webcam along I-25 at Raton Pass (along the New Mexico / Colorado border):


Another interesting aspect of this event are the deep-tropospheric gravity waves created by the leeside cold front.  The GOES water vapor imagery shows narrow bands coincident with the cold front as it moves southward immediately to the lee of the Rockies:


Relatively strong vertical motion exists along these narrow bands in a broad zone through the upper troposphere and into the lower stratosphere.  The resulting vertical displacements are up to 1 km, making them appear in the water vapor imagery.

Interestingly enough, the synthetic water vapor imagery from the 4-km NSSL WRF-ARW model also depicts these narrow bands associated with the leeside cold front:


The model was too slow with the leeside cold front, and this is a known model bias due to sharp inversions that exist with shallow arctic fronts.

For more information on leeside cold fronts and their appearance in water vapor imagery see:

Ralph, F.M., P.J. Neiman, and T.L. Keller, 1999:  Deep-Tropospheric Gravity Waves Created by Leeside Cold Fronts. J. Atmos. Sci., 56, 2986-3009.

Posted in Synthetic NSSL WRF-ARW Imagery | Leave a comment

Convective Initiation Application via the Split Window Difference product

One of the exciting new products that will be available on GOES-R is the split window difference (SWD) which is simply the difference between the 10.35 micron and 12.3 micrometer channels.  This channel difference has been shown to provide information about atmospheric column water vapor.  Higher SWD values (larger positive difference) can correspond to deepener low-level moisture in a cloud-free environment.  This signature can be utilized to anticipate where and when convective initiation will occur in cloud-free conditions away from complex terrain (such as the Great Plains).  Although similar bands were available on some previous GOES instruments, their coarse resolution and poor signal-to-noise ratio made them less useful for identifying subtle small-scale features in the low level moisture field.

In order to demonstrate this product (since the 12.3 micron channel is not available on the current GOES imager), we use synthetic imagery from the 4-km NSSL WRF-ARW model.  Here is an example of the SWD on a day with a dryline across Texas:

The larger (positive difference) values of SWD are shown in warm colors, while the location of the cross section (shown below) is illustrated by the east-west oriented black line.  Next, we will look at output from the NSSL WRF-ARW model along the cross section line:

The white line indicates SWD values (scale on the right) while the colors are specific humidity.  SWD values are greatest along the dryline where the depth of the moisture is greatest.  The low-level temperature lapse rate also plays a role in the SWD, but as can be seen in the cross section, the depth of the moisture is the dominating factor.

A loop of the synthetic SWD from the NSSL WRF-ARW:


shows the animation from 1500 – 0000 UTC at hourly intervals from the model.  On the left is the synthetic IR (10.35 micron) band and on the right is the synthetic SWD product (larger SWD values are shown in warmer colors).

The first thing to note is the skies are clear before convective initiation across Texas which is necessary to make use of the product in this way.  The larger SWD values develop along the dryline prior to convective initiation.  Keep in mind this synthetic data is at hourly intervals, but once GOES-R becomes available, the data will be displayed at 5 (or even 1) minute intervals.

We can preview how this data may appear on GOES-R by looking at an example from the MSG (Meteosat Second Generation) SEVERI instrument over Europe.  An event occurred on 6 July 2012 where convection developed along a convergence boundary under clear skies prior to initiation.  Also, this event occurred over flat terrain (Poland) which is important since complex terrain complicates this signature.

Here is the zoomed in visible imagery (over Poland) from the MSG satellite from 0845 – 1500 UTC 6 July 2012:


The key to note is the clear skies prior to convective initiation.

Here is the zoomed in SWD imagery (over Poland) from the MSG satellite over the same time period:


Focus on the clear area (that was shown in the visible image) from the center of the scene southeastward.  SWD values gradually increase (going toward warmer colors) indicating deepening moisture along this convergence boundary, followed by convective initiation (expanding regions of blue/purple later in the loop).

A local maximum in SWD developed over a convergence boundary (under clear skies) about 2 hours prior to convective initiation.  Forecasters can make use of this information when attempting to predict where / when convective initiation will occur.  As looking at this imagery becomes routine with GOES-R for diagnosing convective initiation (under clear skies beforehand), experience with this product will lead to greater forecaster confidence in timing and location of convective initiation.

For more detailed information on this product, see this article:

Lindsey, D.T., Grasso, L., Dostalek, J.F., and J. Kerkmann, 2014: Use of the GOES-R Split-Window Difference to Diagnose Deepening Low-Level Water Vapor. J. Appl. Meteor. Climatol., 53, 2005–2016.  http://dx.doi.org/10.1175/JAMC-D-14-0010.1

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GOES-14 SRSO for 11 May 2014 Severe Weather Event

GOES-14 was operating on super rapid scan operations schedule for May 11, 2014, meaning that images were being taken every 1 minute.  This high temporal resolution data will be routinely available for severe weather events with GOES-R, therefore it is beneficial to learn how to maximize the value added by this dataset.  SPC issued a moderate risk for portions of Nebraska and Kansas which will be the focus here.  The GOES visible imagery from 1838 to 2011 UTC is shown here:


To aid in interpretation of this loop, an annotated image is shown:

Around this time, a southwest-northeast oriented cold front was surging southward in western Kansas while a dryline was positioned just east of this cold front where convective initiation occurs in southwest Kansas.  An east-west oriented warm front is annotated above, which was slowly moving northward.  Moderate instability and high shear existed along the warm front in southeast Nebraska.  The warm sector is characterized by cloud streets, parallel to the low-level (southerly) flow while north of the warm front a much more stable air mass exists characterized by stable wave clouds oriented perpendicular to the winds at inversion top level.

Earlier convective initiation occurs in southwest Kansas along the dryline.  The high temporal resolution allows one to see multiple updrafts attempting to penetrate the capping inversion and eventually lead to thunderstorm development.  The first sign of convective initiation are shadows projected by anvil cirrus.

Further north, in the region delineated with an oval in the annotated image above, we can see attempts at convective initiation along the western portion of the warm front, near the intersecting cold front.  Multiple updrafts merge into one dominant updraft region where the supercell develops.  Initial motion of these updrafts is towards the northeast, but by the end of the loop as we see one dominant updraft we can already see indications of this storm turning towards the right (east) along the warm front.

For access to real-time GOES SRSO (when available) click here:


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More dust – this time amidst the clouds – 29 April 2014 case

A recent post took a look at the CIRA dust products for the widespread blowing dust event across the Southern Plains behind a strong cold front on 27 April.  The associated upper-level trough moved into the middle of the nation and became a giant closed low that stalled for days.  Figure 1 shows the position of the closed 500 mb low along with an analysis of sea level pressure and NOWRAD radar reflectivity for midweek (0000 UTC on 30 April).  The giant upper-level low affected the weather across much of the nation; here we focus on the strong northerly winds on its backside across the plains of eastern Colorado and the Texas and Oklahoma Panhandles.

Figure 1. 500 mb and MSLP analysis with NOWRAD radar reflectivity for 0000 UTC/30 April.

We will take a closer look at the 2000 UTC time, which is when the Suomi/NPP satellite passed over the area of interest.  The surface plot near this time is shown in Figure 2.

Figure 2. Surface METAR plot at 1943 UTC on 29 April.

The very strong northerly winds, with gusts as high as 70 mph in eastern Colorado, produced intense areas of blowing dust that created very hazardous driving conditions, forcing a number of roads to close during the day (including for a time Interstate 70 in eastern Colorado).  A picture taken in the late morning near the intersection of Highway 40 and 287, in eastern Colorado south of I-70, shows the near zero visibility (Figure 3).

Figure 3. Photo from eastern Colorado in the late morning showing the near zero visibility in blowing dust.

What was particularly interesting about this case, and challenging for forecasters, was the blowing dust being present amidst lots of clouds and even rain (and some snow) showers, as seen in the next two figures showing conditions near 2000 UTC.

Figure 4. NOWRAD radar reflectivity image at 2000 UTC on 29 April.

Figure 5. GOES visible satellite image at 1945 UTC.

Often blowing dust events occur without many clouds present, since the associated airmass is often quite dry (see for example the blog from 27 April).  In this case it is certainly difficult to see dust plumes across the eastern Plains of Colorado amidst all the cloudiness, or farther to the south, given all the cloudiness.  Did the CIRA dust products help in this regard?  First we will focus on eastern Colorado, then shift farther to the south centering on the Texas Panhandle, all for the 2000 UTC Suomi/NPP pass.  As noted in previous blogs, Polar orbiting satellites have higher spatial resolution but limited time resolution, but are useful to replicate products that will be available at both high spatial and time resolution in the GOES-R era.  In Figure 6 a True Color visible image is shown, followed by the CIRA Pink Dust product in Figure 7.

Figure 6. Suomi/NPP True Color visible satellite image at 2000 UTC centered on Colorado.

Figure 7. CIRA Suomi/NPP Pink Dust satellite image at 2000 UTC centered on Colorado. Dust appears as pink colors.

The True Color visible image is striking, but the dust is difficult to see, whereas it is much more obvious in the CIRA Pink Dust product in Figure 7.  The same is true for the blowing dust farther to the south at this time across the Texas Panhandle, with the dust not so easy to see in the visible True Color image in Figure 8 but very obvious with the CIRA Pink Dust product in Figure 9.

Figure 8. True Color visible image at 2000 UTC centered over the Texas Panhandle.

Figure 9. CIRA Pink Dust product at 2000 UTC centered over the Texas Panhandle.

CIRA also has a dust discrimination product using GOES, which allows for much better time resolution than from the Polar satellites, but considerably lower spatial resolution (10 km using a split window technique from GOES sounder data).  This type of image for this case at 1945 UTC is shown in Figure 10.

FIgure 10. CIRA dust discrimination product from the GOES sounder data, for 1945 UTC on 29 April. Dust appears as yellow, or red for thicker dust.

With the lower resolution it is not so easy to see the dust amidst the clouds in Figure 10, but the technique does a nice job of showing the dust farther to the south.

You can find more information on this (and other CIRA GOES-R Proving Ground products) product at http://rammb.cira.colostate.edu/research/goes-r/proving_ground/cira_product_list/ The products are available for display in AWIPS I or II; contact CIRA if interested in receiving them.

Posted in Blowing Dust (Blue-light absorption technique), Blowing Dust Detection (Split-window technique) | Leave a comment