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.

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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.

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April 27 – Severe weather followed by blowing dust across the Plains

The extensive outbreak of severe weather on Sunday 27 April (see SPC plot of reports below in Figure 1) made headlines with many destructive tornadoes.  A strong cold front associated with an intense low lifting out of the Rockies led to the large outbreak (Figure 2 shows the low at 1200 UTC Monday morning 28 April).  Meanwhile very strong winds behind the front produced a large area of blowing dust across the Southern Plains.  In this blog entry we will take a look at this dust area through some satellite products designed to highlight blowing dust.140427_rpts Reports Graphic

Figure 1.  Plot of severe weather reports from the Storm Prediction Center for 27 April.

Click Image For Station Plots

Figure 2.  Surface mslp analysis with fronts at 1200 UTC on Monday 28 April.

First a comparison is made between how the dust storm looked on Sunday afternoon on GOES visible imagery currently on AWIPS and imagery from about the same time from the Suomi/NPP (Polar orbiting) satellite with the VIIRS instrumentation.  The products from the Suomi/NPP satellite represent the type of imagery that will be available at high spatial and temporal resolution when the GOES-R satellite is launched.  For now the spatial resolution is high (1 km) but the temporal resolution is low, with 2 times that can be shown using VIIRS for this case, one at 1859 UTC and the other at 2038 UTC.  Similar looking imagery is also available from the MODIS Aqua and Terra Polar orbiting satellites, but is not shown here as the image swaths are at about the same time.

Images for the first time are shown in Figures 3-5.  Figure 3 shows how the dust appears in AWIPS for a GOES visible image at 1852 UTC, overlaid with METAR observations from 1900 UTC. Gusty (30 mph or greater gusts) southwest winds prevail across much of Kansas and Oklahoma, with even strong winds farther west across the High Plains, lifting plumes of dust.  Visible imagery from VIIRS with a true color background at 1857 UTC is shown in Figure 4.  So much dust is lifted that it looks like we can easily see the plumes in the AWIPS image, and somewhat better in the true color image.  It is not always so easy to see where the dust plumes are, however, so CIRA has developed a product that highlights the dust in a pink color (a similar version uses yellow for the dust), and this image is shown also for 1857 UTC in Figure 5.  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 dust plumes are easily seen in this image, which represents a product that will be available in the GOES-R era.  Notice how the southernmost plume of dust in the Texas Panhandle is easily seen, whereas it is not so obvious in the GOES visible image shown in Figure 3.

Figure 3. GOES visible image at 1852 UTC on 27 April from AWIPS overlaid with 1900 UTC observations.

Figure 4. Suomi/NPP True Color image at 1857 UTC on 27 April.

Figure 5. CIRA Suomi/NPP Pink dust image at 1857 UTC.

The same images are shown for the second available time (2038 UTC).  Strong southwest winds continue to prevail across the Southern Plains, with areas of dust discernible in the visible image (Figure 6) across west-central KS and OK and the TX Panhandle.  The Suomi/NPP images are shown for two areas in Figures 7-10.  For the northern area most of the dust shown in the Pink dust image can also be seen in the two visible images.  Figures 9 and 10 show the area farther to the south, and here the CIRA dust product in Figure 10 highlights dust plumes farther to the south that are not so obvious in the AWIPS visible imagery or even the true color image, showing the potential value of such a product.

Figure 6. GOES visible image from AWIPS at 2038 UTC on 27 April with 2000 UTC observations

Figure 7. Suomi/NPP True Color image at 2038 UTC.

Figure 8. CIRA Suomi/NPP Pink Dust image at 2038 UTC over the same area.

Figure 9. Suomi/NPP True Color image at 2038 UTC but zoomed in on the Texas Panhandle.

Figure 10. CIRA Suomi/NPP Pink Dust image at 2038 UTC also over the Texas Panhandle.

Dust discrimination imagery can also be created from the current GOES satellites through the GOES sounder, with a split window technique that uses the 10.7 um (more-transparent longwave) and 12.0 um (less-transparent longwave) infrared window bands.  The resolution is much lower (10 km) than for images from the Polar satellites (and from what will be available in the GOES-R era), but there is the advantage of hourly time resolution, which means one can loop the imagery.  Further description of the imagery and how it is made can be found on the link to the CIRA products page given earlier.  An example of this GOES-based dust imagery produced by CIRA for this case is shown in Figure 11 for 1846 UTC and in Figure 12 at 2046 UTC on 27 April.  Dust appears as yellow or red (red for thicker dust).

Figure 11. CIRA GOES-based dust product at 1846 UTC on 27 April.

Figure 12. CIRA GOES-based dust product at 2046 UTC on 27 April.

The imagery shown in this example is available now for display in AWIPS I or II; contact CIRA if interested.

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