1. Improved water vapor channel (Imager channel 3)
2. Slightly different visible channel (Imager chanel 1)
3. 13.3 µm IR (Imager channel 6) replaces the 12.0 µm  IR (Imager channel 5)
4. Improved Image Navigation and Registration (INR)
5. Shorter image outages during Spring and Fall season “eclipse periods”
6. Less noise on many of the Sounder channels

GOES-11 vs GOES-15 Imager water vapor channel data as the source for GOES-West

The improvement made to the GOES-15 Imager instrument water vapor channel is likely the most important change that operational users will notice. In the sequence of AWIPS images above, the first 3 images are using the 8-km resolution GOES-11 6.7 µm channel as the source for GOES-West water vapor imagery, while the final 3 images use the 4-km resolution GOES-15 6.5 µm channel. Note the change to slightly warmer/drier water vapor brightness temperatures (brighter yellow color enhancement) after the changeover to GOES-15 — this in part due to the fact that the spectral response function of the 4-km resolution water vapor channel on GOES-12 and beyond is much wider than that of the 8-km resolution water vapor channel on GOES-8 through GOES-11. In addition, notice that the north-south “seam” joining the GOES-West and GOES-East water vapor channel images disappears, since the characteristics of the water vapor channels are now identical on those two satellites.

In the sequence of AWIPS images below, the first 2 images are using the GOES-11 Sounder instrument 6.5 µm channel as the source for GOES-West water vapor imagery, while the final 2 images use the GOES-15 Sounder 6.5 µm channel. Note the improvement in noise seen in the Sounder instrument water vapor images after the changeover to GOES-15. Since the 3 GOES Sounder water vapor channels are a component of the GOES Sounder Total Precipitable Water derived product imagery, the quality of that product should also improve.

GOES-11 vs GOES-15 Sounder 6.5 µm water vapor channel data as the source for GOES-West

In terms of the visible imagery, a comparison using GOES-11 (the first 3 images) vs GOES-15 (the final set of 3 images) Imager visible channel data is seen below (during a test on 29 November). Immediately obvious is the fact that the GOES-15 visible channel imagery appears “brighter” than the GOES-11 visible channel imagery — this is due to the fact that the performance of the GOES visible detectors degrades over time. The 0.63 µm visible channel on GOES-15 is also slightly different than the 0.65 µm visible channel on GOES-11, as is discussed in the “GOES-13 is now the operational GOES-East satellite” blog post. GOES-15 is similar to GOES-13, since it is part of the GOES-N/O/P series of spacecraft.

Using GOES-11 vs GOES-15 as the source for GOES-West visible channel images

One of the benefits of GOES-15 is improved Image Navigation and Registration (INR), which leads to less image-to-image “wobble” when viewing an animation. The improved GOES-15 INR is quite evident when compared to GOES-11 for this blowing dust case on 27 November (below; click image to play animation).

GOES-11 0.65 µm and GOES-15 0.63 µm visible images (click image to play animation)

A comparison of the GOES-15 0.63 µm visible channel, the 10.7 µm “IR window” channel, and the 13.3 µm “CO2 absorption” IR channel (below) shows that high cloud features will show up with more clarity on the 13.3 µm images — by examining the weighting function of the 13.3 µm IR channel, it can be seen that this CO2 absorption channel samples radiation from a much deeper, much higher altitude than the standard 10.7 µm IR window channel.

GOES-15 0.63 µm visible channel, 10.7 µm IR channel, and 13.3 µm IR channel images

The 13.3 µm “CO2 absorption” IR channel is also used for the creation of derived products such as Cloud Top Pressure. An example of a combined GOES-15 (GOES-West) + GOES-13 (GOES-East) Cloud Top Pressure product is shown below (courtesy of Tony Schreiner, CIMSS).

GOES-15 + GOES-13 Cloud Top Pressure product

An example of the value of having larger batteries onboard the GOES-13/14/15 spacecraft during eclipse periods can be seen below, as Hurricane Ike was making landfall along the Texas coast in September of 2008. During the approximately 3 hour image outage from GOES-12 during the eclipse period (when the satellite was in the Earth’s shadow, and the solar panels could not generate the power necessary to operate the GOES imager and GOES sounder instrument packages), GOES-13 IR images continued to be available — and these GOES-13 images showed a strong spiral band that was in the process of intensifying and moving inland along the far northeastern Texas and far southwestern Louisiana coastlines.

GOES-12 vs GOES-13 IR images (Hurricane Ike making landfall)

Additional information can be found on the VISIT training lesson “GOES-15 Becomes GOES-West“.

HISTORICAL NOTE: GOES-15 became GOES-West on the 45th anniversary of the launch of ATS-1 on 06 December 1966. ATS-1 was the first meteorological satellite to provide geostationary images — an example of an early ATS-1 visible image is seen below, and QuickTime movies are available which show animations of some of the early ATS-1 images.

ATS-1 visible image (11 December 1966)

Using GOES-11 vs GOES-15 as the source for GOES-West water vapor channel images

GOES-15 is scheduled to replace GOES-11 as the operational GOES-West satellite on 06 December 2011. On 29 November 2011, a test was conducted by NOAA/NESDIS which briefly substituted GOES-15 data for GOES-11 data as the source of GOES-West satellite imagery in AWIPS. In the sequence of AWIPS images shown above, the first 3 images are using GOES-11, while the final set of 3 images are using GOES-15 as the source for GOES-West Imager water vapor channel data. The changes to the GOES-15 Imager water vapor channel are quite obvious — GOES-15 uses a 4-km resolution channel centered at 6.5 µm that has a wider spectral response, compared to the 8-km resolution 6.7 µm channel with a more narrow spectral response on GOES-11. Even at high latitudes (where the large satellite viewing angle shifts the GOES water vapor weighting function to higher altitudes) the improved GOES-15 water vapor channel imagery will do a better job of depicting the moisture gradients and structure associated with mid-tropospheric dynamical features (Gulf of Alaska example | Nunavut, Canada example).

A similar comparison using GOES-11 (the first 3 images) vs GOES-15 (the final set of 3 images) Imager visible channel data is seen below. Immediately obvious is the fact that the GOES-15 visible channel imagery appears “brighter” than the GOES-11 visible channel imagery — this is due to the fact that the performance of the GOES visible detectors degrades over time (GOES-11 was launched in 2000, and became the operational GOES-West satellite in 2006). The 0.63 µm visible channel on GOES-15 is also slightly different than the 0.65 µm visible channel on GOES-11, as is discussed in the “GOES-13 is now the operational GOES-East satellite” blog post. GOES-15 is similar to GOES-13, since it is part of the GOES-N/O/P series of spacecraft.

Using GOES-11 vs GOES-15 as the source for GOES-West visible channel images

Finally, below is a comparison of GOES Sounder data, using GOES-11 as the source of GOES-West 6.5 µm Sounder water vapor channel data (the first 2 images) vs GOES-15 (the final set of 2 images). Note that the GOES-15 Sounder water vapor channel imagery has less noise than that from GOES-11.

Using GOES-11 vs GOES-15 as the source for GOES-West Sounder water vapor channel images

GOES-15 6.5 µm water vapor images (click image to play animation)

McIDAS images of GOES-15 6.5 µm water vapor channel data (above; click image to play animation) showed the changing signature of a persistent upper level cut-off low lingering over the north-central US during the 23 September – 27 September 2011 period. As the system lingered over the region, it produced widespread wind gusts in the 30-40 mph range (with a peak wind gust of 46 mph at Green Bay, Wisconsin), and rainfall totals of 4-5 inches at some locations in northern Illinois.

AWIPS images of the hourly GOES sounder Total Column Ozone product on 25 September - 26 September (below; click image to play animation) revealed a distinct elevated ozone signature (300-400 Dobson Units, green to red color enhancement), which indicated that the height of the tropopause was lower in the vicinity of the cut-off low.

GOES sounder Total Column Ozone product (click image to play animation)

One notable impact associated with this cut-off low included thunderstorms along the Lake Michigan shoreline that produced a number of waterspouts that were seen from Milwaukee to Chicago. A comparison of MODIS 0.65 µm visible channel and 11.0 µm IR window channel image at 17:28 UTC (12:28 pm local time) on 24 September (below) showed one of the storms that exhibited cloud top IR brightness temperatures colder than -40ºC (blue color enhancement), along with a number of cloud to ground lightning strikes as it moved inland.

MODIS 0.65 µm visible channel and 11.0 µm IR window channel images

Another impact of this cut-off low included a number of pilot reports of light to moderate turbulence over the central and southern Great Plains region. A well-defined bloom of cirrus clouds developed within a zone of high 400-200 hPa layer wind shear, as seen on 4-km resolution GOES-13 6.5 µm water vapor channel images with overlays of CRAS model fields (below; click image to play animation).

GOES-13 6.5 µm water vapor images + turbulence reports + CRAS layer winds and shear (click image to play animation)

Better detail of the banded structure of the cirrus cloud features within the high-shear deformation zone can be seen on a 1-km resolution MODIS 6.7 µm water vapor image (below). Note the pilot report of light to moderate turbulence during the entire flight from Denver (DEN) to Kansas City (MCI).

MODIS 6.7 µm water vapor image + pilot reports of turbulence

A sequence of 1-km resolution MODIS 6.7 µm water vapor channel images on 26 September (below) showed some very intricate dry air and moisture structures within the cut-off low during that particular day.

MODIS 6.7 µm water vapor channel images

In a comparison of MODIS 0.65 µm visible channel and MODIS 6.7 µm water vapor channel images (below), note how much more structure is seen in the water vapor image — even in areas that are cloud-free in the visible image. This allows a number of water vapor features and gradients to be tracked using 3 consecutive GOES water vapor images, to produce MADIS high-altitude atmospheric motion vectors (AMVs) that can provide important wind direction and wind speed data. An AMV with a wind speed of 130 knots (at 300 hPa) was seen in the dry slot over southern Missouri.

MODIS 0.65 µm visible image + MODIS 6.7 µm water vapor image + MADIS satellite winds

GOES-11 6.7 µm (left) and GOES-15 6.5 µm (right) water vapor channel images (click image to play animation)

McIDAS images of 8-km resolution GOES-11 6.7 µm and 4-km resolution GOES-15 6.5 µm water vapor channel data (above) demonstrated the advantage of improved spatial resolution for the detection of features and gradients in the water vapor imagery associated with a weak upper level low moving eastward across the southwestern US on 14 September 2010. GOES-15 is scheduled to replace GOES-11 as the operational GOES-West satellite in December 2011.

AWIPS images of the GOES-11 sounder Convective Available Potential Energy (CAPE) product (below) showed that the atmosphere was destabilizing in advance of the upper low, with CAPE values in the 1000-2000 J/kg range.

GOES-11 sounder Convective Available Potential Entegy (CAPE)

With the increasing instability and large scale lift ahead of the upper low, areas of thunderstorms developed over parts of Nevada, Arizona, and Utah, as seen on a MODIS 11.0 µm IR image with an overlay of cloud-to-ground lightning strikes (below). About an hour after the time of the MODIS image, one of these storms produced 1.0-inch diameter hail that covered the ground near Munds in northern Arizona (SPC storm reports).

MODIS 11.0 µm IR image + cloud-to-ground lightning strikes

CIMSS participation in GOES-R Proving Ground activities includes making a variety of MODIS and additional GOES Sounder images and products available for National Weather Service offices to add to their local AWIPS workstations. Currently there are 49 NWS offices receiving MODIS imagery and products from CIMSS.

MODIS Total Precipitable Water product

The National Weather Service forecast office in Salt Lake City, Utah referred to the MODIS Total Precipitable Water (TPW) product (above) in their afternoon forecast discussion on 27 August 2011:

FXUS65 KSLC 272201
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
355 PM MDT SAT AUG 27 2011

.SYNOPSIS...HIGH PRESSURE NEAR THE FOUR CORNERS WILL DRIFT WEST AND
WEAKEN ON SUNDAY. A VERY MOIST AIRMASS WILL REMAIN IN PLACE SUNDAY
BRINGING SCATTERED THUNDERSTORMS TO UTAH. WESTERLY FLOW WITH A
GRADUAL DRYING TREND IS THEN EXPECTED ON MONDAY AND TUESDAY.

.DISCUSSION...UPPER LEVEL AREA OF HIGH PRESSURE REMAINS CENTERED
NEAR THE FOUR CORNERS AREA THIS AFTERNOON...KEEPING A VERY MOIST
AIRMASS IN PLACE ACROSS UTAH. GPS-MET SENSOR CONTINUES TO SHOW THAT
COLUMN PRECIPITABLE WATER IS HOVERING AROUND 1.20 INCHES IN SALT
LAKE CITY.  AFTERNOON MODIS IMAGERY INDICATES THAT PRECIPITABLE
WATER VALUES ARE GENERALLY 1.0 TO 1.25 INCHES STATEWIDE.

The MODIS TPW values were in general agreement with those seen on the GOES sounder TPW product (below), but with finer spatial resolution (4-km MODIS, vs 10-km GOES) the various TPW gradients appear smoother on the MODIS image.

GOES sounder Total Precipitable Water product

The Blended TPW product (below) displayed complete coverage (even in cloudy areas), but lacked the finer scale definition of the MODIS or GOES products due to the use of only Global Positioning System derived TPW data over inland areas.

Blended Total Precipitable Water product

The Percent of Normal TPW product (below) indicated that the TPW values present across the region were generally 150-200% above normal for the date.

Percent of Normal TPW product

Their forecast discussion went on to state:

AIRMASS QUICKLY DESTABILIZED IN THE EARLY AFTERNOON WITH SCATTERED
CONVECTION FORMING IN THE SOUTH AND EAST AND MORE ISOLATED COVERAGE
IN THE NORTHWEST.

The MODIS 0.65 µm visible channel image (below) showed the areas where organized convection had already developed across Utah and the surrounding states.

MODIS 0.65 µm visible chanel image

CIMSS participation in GOES-R Proving Ground activities includes making a variety of MODIS images and products available for National Weather Service offices to add to their local AWIPS workstations. Currently there are 49 NWS offices receiving MODIS imagery and products from CIMSS. In addition, the VISIT training lesson “MODIS Products in AWIPS” is available to help users understand these products and their applications to weather analysis and forecasting.

GOES-13 0.63 µm visible channel images (click image to play animation)

AWIPS images of GOES-13 0.63 µm visible channel data (above; click image to play animation) showed an interesting swirl of smoke aloft which moved eastward across the Upper Midwest region during the late afternoon hours on 25 August 2011.

The curved shape of the smoke feature was due to the cyclonic circulation associated with a transient potential vorticity (PV) anomaly, which was lowering the dynamic tropopause (taken to be the pressure level of the PV1.5 surface) as it moved eastward. A comparison of 1-km resolution MODIS 0.65 µm visible channel, 1-km resolution MODIS 6.7 µm water vapor channel, and 10-km resolution GOES-13 Total Column Ozone product images (below) showed that the PV anomaly was lowering the tropopause to about the 375 hPa pressure level. Upward vertical motion ahead of the PV anomaly was producing a “moist signal” on the MODIS water vapor image (but no clouds were yet seen on the corresponding MODIS visible image). In addition, GOES sounder Total Column Ozone levels were slightly elevated in the vicinity of this PV anomaly (as high as 340 Dobson Units, green color enhancement), compared to the background ozone levels of 100-110 Dobson Units.

MODIS visible and water vapor images + GOES-13 sounder Total Column Ozone product

It is interesting to note that the smoke feature did not exhibit any signal on the 1-km resolution MODIS 3.7 µm shortwave IR or 11.0 µm IR window images (below) — such thin smoke layers are effectively transparent to the warmer thermal radiation reaching the satellite from below. On the other hand, the hot signatures of cities and urban areas (showing up as darker black pixels) were quite obvious on the IR images.

MODIS 0.63 µm visible, MODIS 3.7 µm shortwave IR, and MODIS 11.0 µm IR window channel images

However, the smoke feature did exhibit a well-defined signature on the MODIS 1.4 µm near-IR “cirrus detection channel” image (below) — this channel is sensitive to any airborne particles that are efficient scatters of light (such as ice crystals, smoke, dust, volcanic ash, etc).

MODIS 0.65 µm visible channel and MODIS 1.4 µm "cirrus detection channel" images

As the smoke aloft began to approach Madison (station identifier KMSN on the satellite images) the feature was captured by the west-facing camera on top of the Atmospheric, Oceanic, and Space Sciences building on the University of Wisconsin campus (below; click image to play QuickTime animation). The airborne smoke layer contributed to a colorful yellow/orange sunset.

AOSS building west-facing rooftop camera images (click to play QuickTime animation)

NOAA ARL HYSPLIT model backward trajectories (below) showed that air parcels arriving over Madison (around the time that the leading edge of the smoke aloft moved overhead) had likely originated over Idaho and Wyoming, where several large wildfires had been burning during the previous days. Other fires burning across southeastern Montana may have also contributed to this smoke.

NOAA ARL HYSPLIT model backward trajectories arriving over Madison, Wisconsin

GOES-13 0.63 µm visible channel images

A tornado produced EF1 damage and was responsible for one fatality (NWS Green Bay summary) as it moved though the town of Wausaukee in far northeastern Wisconsin during the late afternoon hours on 19 August 2011. This event brought the number of tornado deaths to 550 so far in 2011, making this the 4th deadliest year on record so far in terms of tornado-related fatalities.

McIDAS images of 1-km resolution GOES-13 0.63 µm visible channel data (above) showed the development of the thunderstorm along the Wisconsin/Michigan border region around 18:00 UTC (1:00 pm local time), which then moved southeastward ahead of an advancing cold frontal boundary. The “W” overlaid on the images indicates the location of Wausaukee. Some features to note on the GOES visible imagery include: (1) the formation of a series of northwest-to-southeast oriented boundary layer horizontal convective roll clouds in the vicinity of Iron Mountain (station identifier KIMT), which marked the location of a residual convective outflow boundary from a squall line which moved eastward across the Upper Peninsula of Michigan during the early morning hours on 19 August, (2) subtle storm top shadowing indicating the presence of vigorous overshooting tops, and (3) the development of a well-defined back-sheared storm top anvil along the western edge of the storm toward the end of the animation. A photo of the back-sheared anvil was taken from the Green Bay, Wisconsin area around 00:40 UTC, looking northeast toward the storm (below, courtesy of Peg Zenko).

Photo of back-sheared anvil (courtesy of Peg Zenko)

AWIPS images of 4-km resolution GOES-13 10.7 µm IR channel data (below) showed that cloud top IR brightness temperatures associated with this storm cooled to about -60ºC (darker red color enhancement), but no distinct “enhanced-v” or other severe storm top signatures were apparent.

GOES-13 10.7 µm IR channel images

However, about an hour and 45 minutes before the tornado moved through Wausaukee, a comparison of a 1-km resolution POES AVHRR 10.8 µm IR image with the corresponding 4-km resolution GOES-13 10.7 µm IR image around 20 UTC (below) illustrated the distinct advantage of higher spatial resolution for detecting the presence of colder overshooting cloud tops (-69ºC on POES AVHRR, compared to -57ºC on GOES) as well as important cold/warm thermal couplets (the POES AVHRR image displayed a well-defined cold/warm thermal couplet of -69ºC/-49ºC).

POES AVHRR 10.8 µm IR image + GOES-13 10.7 µm IR image

The GOES-13 sounder Convective Available Potential Energy (CAPE) derived product image at 19:00 UTC (below) revealed that there were pockets of CAPE in the 2300-2900 J/kg range (brighter yellow color enhancement) just ahead of the developing storm, which at that time was centered just west-northwest of Land O Lakes, Wisconsin (station identifier KLNL).

GOES-13 sounder Convective Available Potential Energy (CAPE)

GOES-13 10.7 µm IR images (click image to play animation)

AWIPS images of GOES-13 10.7 µm IR data (above; click image to play animation) showed the progression of two long-lived Mesoscale Convective Systems (or “derechos”) on 11 July 2011 — one moving southeastward from the Dakotas and Minnesota, and another moving northeastward from Nebraska. These two MCS features were responsible for a large number of severe weather reports (SPC: 10 July reports | 11 July reports).

Note the elongated band of cirrus that developed  behind the departing MCS feature, curving across parts of Iowa, Nebraska, Kansas, and Colorado toward the end of the IR image animation above — this striated cloud band marked the location of a well-defined deformation zone. Areas of light to moderate turbulence aloft are often present in association with such deformation zones, as was seen by the number of pilot reports overlaid on a GOES-13 6.5 µm water vapor channel image at 17:45 UTC (below).

GOES-13 6.5 µm water vapor channel image + pilot reports of turbulence

The GOES-13 sounder Total Precipitable Water (TPW) derived product (below; click image to play animation) showed that abundant moisture (TPW values of 50-60 mm or 2.0 to 2.4 inches, violet color enhancement) was in place ahead of the storms as they moved rapidly eastward.

GOES-13 sounder Total Precipitable Water product (click to play animation)

A closer view of GOES-13 10.7 µm IR images with overlays of the Automated Overshooting Top Detection product (below; click image to play animation) revealed a number of overshooting tops, with the minimum cloud top IR brightness temperature of -81ºC occurring over eastern Iowa at 09:45 UTC. The overshooting tops were very evident after sunrise on GOES 0.63 µm visible channel imagery, as they cast shadows upon the thunderstorm anvil tops below (11:45 UTC visible image + overshooting top detection product comparison).

GOES-13 10.7 µm IR images + Overshooting Top Detection (click to play animation)

A set of three comparisons of 1-km resolution POES AVHRR 10.8 µm IR images with their corresponding 4-km resolution GOES-13 10.7 µm IR images (below) demonstrated the value of improved spatial resolution for more accurate detection of the location and magnitude of the coldest cloud tops on severe thunderstorms. On the 08:22 UTC, 08:47 UTC, and 11:37 UTC POES AVHRR images, the coldest cloud top IR brightness temperatures were -84ºC, -90ºC, and -85ºC, respectively (the coldest GOES-13 IR brightness temperatures were -78ºC for all three of those times). Note that the apparent northwestward displacement of cloud features on the GOES-13 images is a result of parallax error due to the large viewing angle from the geostationary satellite.

1-km resolution POES AVHRR 10.8 µm IR and 4-km resolution GOES-13 10.7 µm IR images

1-km resolution POES AVHRR 10.8 µm IR and 4-km resolution GOES-13 10.7 µm IR images

1-km resolution POES AVHRR 10.8 µm IR and 4-km resolution GOES-13 10.7 µm IR images

Very strong surface winds were observed along and in the wake of the well-defined bow echo seen on radar — peak wind gusts included 74 mph at Dubuque, Iowa, 75 mph at Chicago Midway Airport, and 85 mph at Michigan City, Indiana. These strong winds created a seiche across southern Lake Michigan (Seiche Warning | NWS Chicago event summary), with oscillations in water levels seen at Calumet Harbor, Illinois, Milwaukee, Wisconsin, and Holland, Michigan.

GOES-11 0.65 µm visible and 10.7 µm IR images (click image to play animation)

Strong thunderstorm outflow winds (gusting as high as 69 mph) created a severe dust storm (or “haboob“) in the Phoenix, Arizona area around 02:00 to 03:00 UTC on 06 July 2011 (or 7pm to 8pm local time on 05 July 2011), restricting the surface visibility to near zero with blowing dust and forcing a 45-minute Ground Stop at Phoenix Sky Harbor Airport (an interesting YouTube video of the approaching dust storm is available here). The Phoenix National Weather Service forecast office published a summary of the event, and additional information and 3D radar animations are available on the AccuWeather WeatherMatrix blog. A high-resolution GOES image can be found at the NOAA Environmental Visualization Laboratory.

McIDAS images of GOES-11 0.65 µm visible channel data during the day and GOES-11 10.7 µm IR channel data at night (above; click image to play animation) show how the Mesoscale Convective System over Arizona on 05 July evolved into a Mesoscale Convective Vortex (MCV) on the following morning over the deserts of southern California, as the cirrus canopy of the convective system eroded to reveal the mid-level circulation. The MCV then appeared to play a role in helping to initiate new convective activity over California later in the afternoon on 06 July.

AWIPS image comparison from 18:00 UTC on 06 July

MCVs maintain their structure through the release of latent heat associated with condensation when clouds form and especially when precipitation forms. This release of heat alters the stability of the atmosphere, inducing the formation of a cyclonic potential vorticity anomaly. MCVs erode when they encounter high wind shear.

An AWIPS image comparison (above) shows GOES visible channel data (the seam in the middle of the images demarcates data from GOES-11 or GOES-West and GOES-13 or GOES-East; note that the older GOES-11 data is darker because of the age and degradation of that satellite’s visible sensors), GOES 10.7 µm IR channel data, the Blended Total Precipitable Water (TPW) Percent of Normal product, and 850-300 hPa layer wind shear from the GFS and RUC models. In the present example, the MCV exists in an axis of low values of 850-300 hPa wind shear, as noted by model forecasts from the RUC and from the GFS. Abnormally high values of precipitable water are also present, exceeding 200% of normal according to the ‘Blended Product’ that combines observations from the GOES Sounder and ground-based GPS stations. Rawinsonde reports from Phoenix (00 UTC and 12 UTC on 06 July) and from Yuma (12 UTC and 14 UTC on the 06 July) show abundant moisture and relatively low shear. All of these data show environmental conditions that support MCVs.

GOES-11 Sounder TPW and LI derived product images

In the pre-convective environment across southern Arizona on 05 July, GOES-11 Sounder derived product images (above) showed Total Precipitable Water (TPW) values in the 40-50 mm (1.6 to 2.0 inch) range, and Lifted Index (LI) values as low as -5º to -8º C.

MODIS 11.0 µm IR image + negative and positive cloud-to-ground lightning strikes

As the MCS continued to move westward across Arizona, an AWIPS image of 1-km resolution MODIS 11.0 µm IR data at 05:33 UTC (above) showed cloud top IR brightness temperatures as cold as -72º C (black color enhancement), along with numerous negative and positive cloud-to-ground lightning strikes. At that time, the thunderstorm outflow winds were moving through Blythe, California (station identifier KBLH) producing wind gusts of 46 knots (52 mph) with a reduction in visibility to 1.5 miles, and also through Yuma, Arizona (station identifier KNYL) producing wind gusts of 40 knots (46 mph) with a reduction in visibility to 1.25 miles.

GOES-13 and MODIS water vapor images + RUC model wind speeds at 500 hPa, 400 hPa, 300 hPa, 250 hPa, and MaxWind levels

A major outbreak of severe weather (SPC storm reports) occurred across much of the southern Great Plains region of the US on 24 May 2011. One of the ingredients for this severe weather scenario was the approach of a strong jet stream, which was rounding the base of a broad upper level trough located over the Rocky Mountains. Due to these strong winds, a prominent mountain wave signature was seen on AWIPS images of 4-km resolution GOES-13 6.5 µm and 1-km resolution MODIS 6.7 µm “water vapor channel” data (above). Overlays of the RUC80 model isotachs at the 500 hPa, 400 hPa, 300 hPa, 250 hPa, and Maximum Wind levels showed the magnitude of these jet stream winds.

Strong winds were also found at the surface, and McIDAS images of GOES-13 0.63 µm visible channel data (below; click image to play animation) showed several large plumes of blowing dust (along with some smoke plumes from a few wildfires) which streamed eastward and northeastward behind the dryline that acted as the focus for the development of the severe thunderstorms. The haziness seen across the southeastern half of Texas was due to smoke which had been transported northward from fires burning in the Yucatan Peninsula region of Mexico.

GOES-13 0.63 µm visible channel images (click image to play animation)

GOES-13 sounder Total Precipitable Water (TPW) derived product images (below) revealed that TPW values in excess of 30 mm or 1.2 inches (yellow color enhancement) began to stream northward from Texas into Oklahoma by 18:00 UTC. This moisture helped to fuel the development and maintenance of the deep convection across the region.

GOES-13 sounder Total Precipitable Water derived product images

The 12 UTC rawinsonde report from Norman, Oklahoma revealed a classic “loaded gun” type of profile, which would lead to a very unstable airmass once strong surface heating took place during the morning and early afternoon hours. GOES-13 sounder Lifted Index (LI) derived product images (below) showed LI values of -10 to -13 C (red to violet color enhancement) just ahead of the dryline, where the atmosphere had indeed become very unstable.

GOES-13 sounder Lifted Index derived product images

Once the severe thunderstorms began to form across western Oklahoma after 18:15 UTC, GOES-13 6.5 µm water vapor channel images (below) displayed a pronounced warm/dry signature (orange color enhancement) immediately behind the storms — this could be the signature of a strong and large-scale rear flank downdraft in the wake of the storms.

GOES-13 6.5 µm water vapor channel images

AWIPS images of 1-km resolution POES AVHRR 0.86 µm visible channel and 12.0 µm IR channel data at 20:32 UTC (below) revealed distinct overshooting tops on the visible image, with corresponding cloud top IR brightness temperatures as cold as -85º C (violet color enhancement). Note that large swaths of rain-cooled ground could be seen on the IR image, which exhibited a lighter gray appearance immediately behind the thunderstorms.

POES AVHRR 0.86 µm visible channel and 12.0 µm IR channel images

For more information on this severe weather outbreak, see the National Weather Service websites at Norman OK, Tulsa OK, Dodge City KS,  and Wichita KS.

===== 26 May Update =====

MODIS true color Red/Green/Blue (RGB) image (displayed using Google Earth)

A 250-meter resolution MODIS true color Red/Green/Blue (RGB) image from the SSEC MODIS Today site (above; viewed using Google Earth) revealed one of the 24 May tornado damage tracks (oriented from southwest to northeast) which was located just to the northwest of Oklahoma City. Early in its life cycle, the tornado crossed Interstate 40, overturning a number of vehicles.

A comparison of before (22 May 2011) and after (26 May 2011) MODIS true color images (below) showed that the tornado damage path was not present on the 22 May image,

MODIS true color Red/Green/Blue (RGB) images before (22 May) and after (26 May) the 24 May tornado even