Satellite Liaison Blog

Irma was named a Tropical Storm on 30 August in the far eastern tropical Atlantic. Irma strengthened rapidly on 31 August to a Category 3, Major Hurricane. The NHC Day 4-5 forecast cone on 1 September put Irma just east of the Lesser Antilles as a Major Hurricane. With Irma outside of the GOES-16 5-min CONUS sector and no mesoscale sectors yet positioned over the storm, 15-min imagery was the highest temporal resolution available on the 1st. It is also important to remember that given the distance the storm was from GOES-16 nadir, the perceived spatial resolution was degraded as well.

Figure 1. 01 September 2017 GOES-16 15-min Full Disk VIS of Hurricane Irma. Full res: https://satelliteliaisonblog.files.wordpress.com/2017/09/20170901_vis_irma_sunrise4.gif

1-min meso sectors from GOES-16 began tracking Irma on the 3rd. By the 4th, Irma continued to track west as a strong, category 3 major hurricane. 1-min satellite imagery from GOES-16 captured the eye of the storm during the morning of the 4th (Fig 2).

Figure 2: 04 September 2017 GOES-16 1-min VIS zoomed in on eye of Hurricane Irma. Full res: https://satelliteliaisonblog.files.wordpress.com/2017/09/20170904_vis_irma_1min_morning_big.gif

By the morning of 5 September, Irma had strengthened to a category 5 major hurricane with 175 mph sustained winds! 1-min imagery continued to be available over the hurricane, providing striking views. The sandwich product, an image combination discussed in previous blog posts, combines visible and IR window imagery into one image. This visualization provides temperature information about the clouds in the storm while maintaining the high spatial resolution (Fig 3).

Figure 3: 5 September 2017 GOES-16 VIS/IR sandwich combo over Hurricane Irma. Full res: https://satelliteliaisonblog.files.wordpress.com/2017/09/20170905_irma_sw_zoom_anno2.gif

Tuesday evening, Irma remained a strong category 5 hurricane packing sustained winds to 185 mph with a minimum central pressure of 926 mb. The NHC forecast had Irma near the southern Florida Peninsula on Sunday (Fig 4).

Figure 4: 5 September 2017 GOES-16 15-min IR and 5 PM NHC Forecast. Full res: https://satelliteliaisonblog.files.wordpress.com/2017/09/20170905_15min_ir_irma_track_small_label.gif

Hurricane Irma passed over Antigua and Barbuda early on September 6, producing a measured wind gust of 155 mph before the anemometer broke. The 5 AM update from NHC kept Irma as a strong category 5 hurricane, with 185 mph sustained winds and a minimum central pressure of 914 mb. The previous day, GOES-16 began collecting 30-sec imagery over Irma by overlaying the two 1-min mesoscale sectors. 30-sec imagery over Irma continued into the 6th (Fig 5).

Figure 5: 06 September 2017 GOES-16 30-sec VIS/IR Sandwich combo of Hurricane Irma. Full resolution: https://satelliteliaisonblog.files.wordpress.com/2017/09/20170906_irma_sw_anno.gif

Two additional storms were named on Tuesday: Katia and Jose. Katia in the Gulf of Mexico is expected to impact Mexico, while Jose is currently forecast to remain in the Atlantic. A zoomed out view of GOES-16 Water Vapor Imagery from Tuesday night to Wednesday morning reveals these three tropical cyclones. Additionally, the upper-level trough over the eastern US is easily identified. This large-scale feature will continue to move east as a ridge builds behind it. Another smaller-scale trough will then move southeast, weakening the ridge, and helping to determine the eventual track of Irma.

Figure 6: 05 – 06 September 2017 GOES-16 6.19 um upper-level water vapor imagery. Full resolution: https://satelliteliaisonblog.files.wordpress.com/2017/09/20170906_ulwv.gif

By Thursday early evening, Irma remained a strong category 5 major hurricane, packing sustained winds of 175 mph with a minimum central pressure of 922 mb. Today, we take a look at Irma in all 16 GOES-16 ABI spectral bands (Fig 7). As a reminder, the first two bands are in the visible, the next four are near-IR, and final ten are IR. Bands 8, 9, and 10 are the three water vapor bands. Aside from bands 7 (SWIR) and 12 (Ozone), all of the IR bands have almost the same temperature at the top of Irma since those clouds are at the top of the troposphere, above tropospheric moisture and CO2. The hurricane appears warmer in band 7 due to reflectance of solar radiation off of the cloud tops and Band 12 is warmer due to emission from ozone in the stratosphere where there is a temperature inversion.

Figure 7: 07 September 2017 GOES-16 ABI 16 spectral bands. Bands 1-16 from left to right, top to bottom. Full res: https://satelliteliaisonblog.files.wordpress.com/2017/09/20170907_irma_16p_anno.gif

The two-day IR loop below shows the category 5 hurricane maintaining strength as it advances toward the US. Use the feature-following zoom tool in AWIPS to create animations such as the one below (Fig 8).

Figure 8: 07 September 2017 GOES-16 half-hourly IR from Tuesday evening t0 Thursday evening. Full res: https://satelliteliaisonblog.files.wordpress.com/2017/09/20170907_irma_ir_2day_anno_2.gif

On Friday the 8th, Irma remained a category 4 major hurricane packing 155 mph winds and a minimum central pressure of 924 mb.  Irma was expected to turn more north late Saturday and head for the Florida Keys hitting the Keys early Sunday. A seamless transition of GOES-16 imagery from VIS (day) to IR (night) can be accomplished in AWIPS (Fig 9). Simply overlay VIS on IR, and make the lowest portion of the VIS color-table (0 – 0.5) transparent.

Figure 9: 08 September 2017 GOES-16 VIS-to-IR transition of Hurricane Irma. Full resolution: https://satelliteliaisonblog.files.wordpress.com/2017/09/20170909_irma_daynight4.gif

The interaction of Irma with Cuba Friday night into Saturday morning caused it to weaken slightly to a category 3 hurricane with 125 mph max sustained winds and a minimum central pressure of 941 mb at the 11 AM Saturday update. Today we compare visible (Fig 10) imagery from GOES-16 (at 89.5 W) with that from GOES-13 (at 75 W, GOES-East). From GOES-16 today, one mesoscale sector is available over Irma providing imagery every minute. Meanwhile, GOES-13 is operating in Rapid Scan Mode, which provides imagery every 5, 7, 8, and 10 minutes (and 30-minutes every 3 hours for full disk). Spatially, the visible (IR) imagery from  GOES-16 is 0.5 km (2 km), while that from GOES-13 is 1 km (4 km).

Figure 10: 09 September 2017 GOES-16 (left) and GOES-13 (right) VIS. Full res: https://satelliteliaisonblog.files.wordpress.com/2017/09/20170909_vis_compare.gif

Early Friday evening, Irma maintained category 3 strength as continued its west-northwest trajectory. Showers, thunderstorms, and strong winds were beginning to impact Florida and the Florida Keys. GOES-16 1-min VIS/IR sandwich combo imagery shows the impressive structure of Irma and thunderstorm activity over Florida.

Figure 10: 09 September 2017 GOES-16 1-min VIS/IR sandwich combo. Full resolution: https://satelliteliaisonblog.files.wordpress.com/2017/09/20170909_irma_sw_anno.gif

A few hours later, Irma began the turn north towards the Florida Keys as depicted in GOES-16 IR (Fig 11). Also included in the animation are NLDN cloud-to-ground lightning. There has been quite a bit of lightning activity, as expected, with the outer convective bands  in the front right quadrant moving into southeast Florida. Several tornado warnings have been issued with at least two confirmed tornadoes in south Florida.

Figure 11: 09 September 2017 GOES-16 5-min IR and NLDN CG lightning. Full res: https://satelliteliaisonblog.files.wordpress.com/2017/09/20170909_irma_ir_ltng3.gif

Hurricane Irma made landfall over the Florida Keys Sunday morning as a category 4 major hurricane. A 20 hour loop ending at 1415 UTC this morning, or just after landfall, shows the sharp turn north Irma took last night and its acceleration to and over the Keys (Fig 12).

Figure 12: 9 – 10 September 2017 15-min GOES-16 10.3 um IR. Full res: https://satelliteliaisonblog.files.wordpress.com/2017/09/20170910_ir.gif

Irma again made landfall at 3:35 PM at Marco Island, Florida where a 130 mph wind gust was reported. Irma then advanced to Naples. 30-sec imagery was available from GOES-16 over the hurricane during landfall by overlapping the two mesoscale sectors. In the 30-sec VIS/IR sandwich combo, the eye is apparent along with bubbling convection in the front right quadrant.

-Bill Line, NWS

“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”

Hurricane (now Tropical Storm) Harvey’s journey started rather arduous, then it entered a very favorable environment and the rest is ongoing history.  After making landfall as a Category 4 (130 mph) hurricane on Friday, Harvey has moved in a tight cyclonic loop and is now just about to re-enter the Gulf of Mexico.  After unleashing stunning rainfall totals in the Houston metro, the most intense bands of thunderstorms have been drifting east toward Beaumont and southwest Louisiana this morning.  The break in Houston is likely temporary as additional rain bands will develop today, while Harvey may attempt some mild re-intensification prior to a second landfall near the Sabine River.

In the meantime, the tropical storm has taken on a rather hybrid, comma-shape in the last 24 hours, so what are the chances of Harvey making a comeback before a second landfall?  What may impede it?  How much more rain will fall in the Houston to Lake Charles area?

GOES-16 Air Mass RGB showing the evolution of Hurricane Harvey valid from 0000 UTC 08/25/17 – 2357 UTC 08/27/17.  *Preliminary, Non-Operational Data* (Click here to open in a new window)

The GOES-16 Air Mass RGB animation above shows Hurricane Harvey rapidly intensifying prior to landfall, then changing shape as the cyclone weakens over eastern Texas.  Note how the environment changes around the cyclone as more oranges appear in the animation due to an upstream shortwave (upper-level disturbance) drifting south-southeast into western Texas.  This shortwave introduces some dry air into the western and southern portions of the tropical cyclone leading to a re-orientation of the strongest thunderstorms to the eastern quadrant (responsible for the Houston flooding).

IASI Ozone Anomaly valid at 0302 UTC on 08/28/17.  (Click here to open in a new window)

Will Harvey now transition to an extratropical cyclone or will it remain tropical?  The answer may lie in the Infrared Atmospheric Sounding Interferometer (IASI) Ozone Anomaly product as it shows little in the way of anomalous ozone surrounding Harvey (Blue coloring indicates 125%+ of normal ozone, indicative of a stratospheric intrusion).  The normal (white) to slight below normal (brown) shading would indicate that there is no tropopause fold nearby and the shortwave responsible for the drying on the western flank of Harvey may be more transient, rather then directly leading to a full baroclinic transition.  This would suggest the possibility that Harvey could intensify once back over the Gulf of Mexico.

But. . .As NHC Hurricane Specialist Pasch stated in the 4 a.m. CDT update, “Significant strengthening is not anticipated, however, due to the system’s lack of an inner core and strong southwesterly shear associated with an upper-level trough over Texas.”  This makes sense as the system would need to detach from the aforementioned shortwave, spend more time over water, and rebuild the inner core to significantly intensify.  The main threat will continue to be the heavy rain and significant flooding.

WPC Mesoscale Precipitation Discussion valid at 0500 UTC 08/28/17.  (Click here to open in a new window)

GOES-16 7.3um water vapor animation valid from 0000 UTC to 0600 UTC on 08/28/17.  *Preliminary, Non-Operational Data* (Click here to open in a new window)

WPC Forecaster Otto mentioned the 7.3 µm water vapor imagery in the 0500 UTC Mesoscale Precipitation Discussion (MPD) that focused on the continuing heavy rain threat in southeast TX into southwest LA”:

“EXPERIMENTAL GOES 16 7.3 MICRON LOW LEVEL WATER VAPOR
IMAGERY SHOWED RELATIVELY DRIER AIR WRAPPING AROUND TROPICAL STORM
HARVEY TO THE SOUTH INTO THE HOUSTON METRO REGION AS OF 06Z. THE
DRYING IS REFLECTED WITH A MLCAPE GRADIENT NOTED IN THE SPC
MESOANALYSIS AND THE RAP. ON THE WRN EDGE OF THE INSTABILITY POOL
WAS A SOUTH TO NORTH BAND OF HEAVY RAIN WITH RAINFALL RATES OF 2-3
IN/HR OVER CHAMBERS COUNTY…JUST EAST OF GALVESTON BAY.
REFLECTIVITY FROM KHGX WAS RELATIVELY QUIET FOR COASTAL COUNTIES
ALONG AND WEST OF GALVESTON BAY WITH ONLY LIGHT SHOWERS APPEARING
DESPITE TOTAL PRECIPITABLE WATER VALUES OF 2.3 TO 2.5 INCHES AS OF
06Z.”

CIRA Total Precipitable Water (microwave) product showing the greater than 2.3″ PW values at 0600 UTC 08/28/17. (Click here to open in a new window)

By using this particular water vapor channel, the forecaster is able to analyze the low-level water vapor gradients to determine where the best convergence will occur.  To further emphasize the amount of moisture available to the east of Tropical Storm Harvey, the CIRA Total Precipitable Water product shows the 2.3″-2.5″ PWs that Forecaster Otto referenced in the MPD streaming onshore from the western Gulf of Mexico.

These tools are proving to be valuable to forecasters as they continue to assess the current and future threats posed by Tropical Storm Harvey.

For additional blog posts on Harvey, please visit our Proving Ground partner’s blogs:

https://nasasport.wordpress.com/

http://cimss.ssec.wisc.edu/goes/blog/

Thanks for reading!

A strengthening Tropical Storm Harvey  approached Texas Gulf coast on 24 August 2017. Harvey initially developed and was named on 17 August in the Atlantic just east of the Lesser Antilles. A couple days later, Harvey weakened to a wave before crossing over the Yucatan Peninsula . After advancing into the Gulf of Mexico on 22 Aug, Harvey strengthened again to a Tropical Storm. On 24 Aug, Harvey is forecast to become a Major Hurricane before making landfall early 26 Aug. Widespread rainfall of 15+” is forecast with this storm as it is not expected to move much after making landfall.

A GOES-16 1-min mesoscale sector was consistently available over Harvey during its life cycle. For tropical cyclones, 1-min imagery has proven to aid in identifying a center of circulation and in tracking thunderstorm evolution.

On 24 August, 30-second imagery (two overlapping 1-min sectors) was requested to track Harvey, providing a rare look at a strengthening tropical system. In Figure 1, a linear, compressed color map is used to capture storm top features.

Figure 1: 24 August 2017 GOES-16 30-sec VIS. Full res: https://satelliteliaisonblog.files.wordpress.com/2017/08/20170824_30sec_harvey2.gif

30-sec imagery continued over Harvey during the morning of the 25th as the storm continued to strengthen nearing the Texas Gulf Coast.

Figure 2: 25 August 2017 GOES-16 30-sec VIS of Harvey. Full res: https://satelliteliaisonblog.files.wordpress.com/2017/08/20170825_30sec_harvey_am.gif

Harvey made landfall Friday night as a category 4 hurricane.

Saturday morning, Harvey had weakened to a category 1 hurricane, continuing to produce strong winds and heavy rain across a large swath of Texas.

Figure 4: 26 August 2017 IR to VIS transition of Hurricane Harvey. Full res:

By Monday morning, Harvey had not moved much, still dropping heavy rainfall over southeast Texas and now western Louisiana. The GOES-16 IR animation in Figure 5 depicts the hourly evolution of Harvey from 8/22 when it redeveloped in the Gulf to 8/28.

Figure 5: 8/22 – 8/28 GOES-16 10.3 um IR 1-hr imagery. Full resolution: https://satelliteliaisonblog.files.wordpress.com/2017/08/20170828_1hr_harvey_long_ir2_small3_anno.gif

On Tuesday, the storm had shifted east, producing heavy rain over the Louisiana/Texas border.

By Thursday, Harvey had weakened to a depression, and continued to slowly shift east into the ArkLaMiss region. The storm maintained its heavy rain threat (WPC high risk) and a tornado risk (SPC slight risk). By early afternoon, a tornado watch and several tornado warnings were in effect from N MS to SW TN. GOES-16 1-min sectors continued to follow the threats associated with Harvey (Fig 6).

Figure 6: 31 August 2017 GOES-16 1-min VIS. Full res: https://satelliteliaisonblog.files.wordpress.com/2017/08/20170831_vis_zoom2.gif

-Bill Line, NWS

“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”

During the late morning to early afternoon hours of 21 August 2017, a much anticipated solar eclipse occurred across the United States. GOES-16 provided an incredible view of the eclipse shadow as it moved across the CONUS from Oregon to South Carolina. To observe the event in unprecedented manner, GOES-16 meso-1 (1-min imagery) followed the path of totality from 1645-2000 UTC, shifting its position every 10-15 minutes. Figure 1 is GOES-16 1-min visible imagery view of the eclipse shadow crossing the US, while figure 2 is the 5-min view.

Figure 1: 21 August 2017 GOES-16 1-min VIS for western US. Full resolution: https://satelliteliaisonblog.files.wordpress.com/2017/08/20170821_1min_west2.gif

Figure 2: 21 August 2017 GOES-16 1-min VIS for Eastern US. Full resolution: https://satelliteliaisonblog.files.wordpress.com/2017/08/20170821_1min_east.gif

Figure 2: 21 August 2017 GOES-16 1-min VIS for full US. Full resolution: https://satelliteliaisonblog.files.wordpress.com/2017/08/20170821_1min_conus_big.gif

Figure 3: 21 August 2017 GOES-16 5-min VIS for CONUS. Full resolution: https://satelliteliaisonblog.files.wordpress.com/2017/08/20170821_1min_conus4.gif

-Bill Line, NWS

“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”

GOES-16 was put into Mode 4 (Continuous Full Disk Mode) the afternoon of 19 August through the evening of the 20th. Mode 4 includes 5-min imagery across the full disk (no 1-min sectors) as opposed to 15-min imagery. This provides a great opportunity to observe the evolution of features outside of the CONUS (which benefits from 5-min imagery regardless of mode). Figure 1 depicts a developing low in the far south Pacific Ocean.

Figure 1: 20 August 2017 GOES-16 VIS. Full res: https://satelliteliaisonblog.files.wordpress.com/2017/08/20170820_south2_overlay.gif

-Bill Line, NWS

“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”

During the early evening hours of 18 August 2017, a potent severe storm with a history of producing very large hail and damaging wind gusts crossed from southwest MN into northwest IA. This activity was within a SPC slight risk for severe and a SPC severe thunderstorm watch. With the Iowa State Fair ongoing in Des Moines, WFO Des Moines requested a GOES-16 Meso Sector for DSS, beginning at 00z. The 1-min sector captured the tornado warned storm just as the sun set, providing a great depiction of the overshooting tops and anvil-top gravity waves. Further, smoke from Canadian fires is seen being drawn into the storm.

Figure 1: 18 August 2017 GOES-16 1-min VIS. Full res: https://satelliteliaisonblog.files.wordpress.com/2017/08/20170818_1min_vis_iowa.gif

-Bill Line, NWS

“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”