Supercells were expected to initiate along a dryline in west-central Oklahoma during Saturday evening on April 23rd. The Storm Prediction Center had issued a slight risk of severe storms in their 1630 Z (1:30 PM CDT) outlook, with the risk tornadoes (5%), damaging hail (15%), and damaging wind (15%). Thunderstorms initiated around 2200 Z (5:00 PM CDT) as shown from the Day Cloud Phase Distinction RGB animation below. As the sun began to set near the end of the animation, decreasing contributions from the green (Channel 2, visible) and blue (Channel 5, near-IR) bands created a shift to more red colors in the imagery (Channel 13, clean-IR).
As convection matured into supercells after sundown, satellite imagery became confined to the infrared bands (Channels 7-16), with Clean-IR imagery most often used. Additionally, rapidly updating (1 minute) lightning data from the GLM Flash Extent Density product can provide information about thunderstorm trends between NEXRAD full-volume scans (4-5 minute updates). At night, the GOES-16 GLM detection efficiency often exceeds 90% across the south-central United States.
Intensification of two supercells and tightening of their low level mesocyclones, southwest of Oklahoma City and southwest of Stillwater, as indicated by radar prompted the NWS Norman office to issue tornado warnings for both storms. The Tornado Warning for the Stillwater supercell was issued at 2359 Z (6:59 PM CDT), and the Tornado Warning for the Oklahoma City supercell was issued at 0003 Z (7:03 PM CDT).
The animation above is from 2330 Z to 0030 Z (5 minute intervals), and shows how both storms intensified from the perspective of the GLM FED and ABI Clean-IR products. Deep overshooting tops were observed from the ABI along with notable increases in GLM flash rates. In this scenario satellite information may have provided a ‘heads-up’ on which storms to monitor, along with additional confirmation of trends observed from NEXRAD.
One-minute data was observed from the GOES-East Mesoscale Domain for both products (below). In this scenario NWS Norman also had access to the Terminal Doppler Weather Radar at the Oklahoma City Airport (TOKC), providing 1-minute radar reflectivity and doppler velocity data within the vicinity of the airport. For the supercell near Oklahoma City, this may make a forecaster less reliant on one-minute satellite data when making warning decisions. However, for the storm southwest of Stillwater no TDWR data was available. The rapid increase in lightning flash rates identified by the GLM FED product for this storm can provide additional verification for an NWS forecaster that the updraft was intensifying, and tightening of the low level mesocyclone prior to tornadogenesis may be imminent.
During the early morning hours of April 22nd, fog began to form across southern Ohio, West Virginia, and Pennsylvania. In anticipation of the fog, the NWS Weather Forecast Office in Wilmington OH issued a Dense Fog Advisory for a portion of their forecast area.
Latest guidance increases confidence in development of areas of dense fog late tonight. Based on this, have hoisted Dense Fog Advisory south of Interstate 71.
Confirmation of the dense fog can be observed via satellite from the Nighttime Microphysics RGB starting around 0500 Z (1:00 AM EDT), with greater contributions from the Green Band (10.3 um – 3.9 um band difference) and minor contributions from the Blue Band (10.3 um band). The stationary, more faint, and highly localized appearance of the fog stands in contrast to the low level clouds in southwest Pennsylvania and central West Virginia, which often have a similar color due to similarities in their composition. Additionally the movement of cirrus and stratocumulus clouds into the area, from precipitation over Indiana, did obscure the extent of the fog in western Ohio by 1000 Z (6:00 AM EDT). This is one limitation of the product, as skies have to be fairly clear in order to properly identify fog.
Based on surface observations and imagery from the Nighttime Microphysics RGB, it was apparent by 0830 Z (4:30 AM EDT) that the dense fog was expanding north of Interstate 71. This confirms NWS Wilmington expanding the Dense Fog Advisory north into the Cincinnati and Dayton metro areas, prior to the increase of traffic during the morning rush. In this case the combination of surface observations and the Nighttime Microphysics RGB can provide confirmation of developing fog and its spread overnight for the Dense Fog Advisory. Using satellite RGBs in tandem with other observations can help maximize situational awareness, especially when satellite data cannot be relied on exclusively as shown in this example.
The fog is becoming dense in many locations across northern KY, southern Ohio, and southeast Indiana. Have expanded the dense fog advisory north to about I-70.
During the late evening hours on April 12th, 2022, convection initiated along a retreating dryline and advancing cold front in southern Nebraska and central Kansas. Initiation across the line can be observed from the Clean-IR band (Ch 13) from GOES-16 and the NEXRAD mosaic below. The near-uniform initiation of these thunderstorms along the dryline provided a unique example of how GOES imagery can be combined with radar data to monitor rapid thunderstorm development and dissipation.
Additionally, the initiation and subsequent outflow boundary along the leading edge of the front produced an undular bore, which traveled across central Oklahoma from 0600 Z to 1000 Z and initiated convection just after 1030 Z. Tracking the bore/front in this scenario could have been done by the Clean-IR band or radar (as seen below). However, the Nighttime Microphysics RGB can provide additional information not observed from a single ABI band or from radar.
Strong contributions from the Green band (Ch 13 – Ch 7) and moderate contributions from the Red band (Ch 15 – Ch 13) in the RGB recipe make the green-yellow clouds formed along the bore stand out from the magenta surface. Early signs of initiation along from the front can also be observed from strong contributions by both the Red and Green band, with low contributions from the Blue band (Ch 13), and the development of stratus clouds in central and eastern Oklahoma indicate an environment with greater low level moisture. In this scenario, the Nighttime Microphysics can provide an early ‘heads up’ that CI may be coming soon as the front moves into a more favorable environment for severe weather in southeast Oklahoma, southwest Arkansas, and northeast Texas. This coincides with the SPC Mesoscale Discussion issued just after 1200 Z.
During the early morning hours of 14 March 2022, a plume of moisture from the Gulf of Mexico was advected northward prior to a severe weather setup later that day. Along with surface observations and RAP surface analysis data, imagery from the GOES-16 Nighttime Microphysics RGB provided conformation of this moisture advection with stratus clouds developing across eastern Texas and southern Oklahoma (green-yellow) from Figure 1. Strong contributions in the red and green bands signify thick clouds that mostly contain water, helping to determine that these are low level stratus clouds driven by the synoptic scale advection of low level moisture across the region.
The NWS Storm Prediction Center issued a Slight Risk for northeast Texas and the Ark-La-Tex region, with all hazards (tornadoes, large hail, and damaging winds) possible (see slideshow below). Use of the Nighttime Microphysics RGB in this scenario may provide conformation of the moisture advection, along with its current spatial extent in regions where few surface observations exist. Monitoring the extent of these stratus clouds also provides a ‘first look’ at which areas will receive more or less solar heating during the morning, which may impact the initiation time, coverage, and maximum strength of convection later in the day.
A broad trough and embedded shortwaves digging east across the southern US brought severe weather, including tornadoes, to parts of the south and southeast US on 21-22 March 2022. The evolution of the trough across the country is shown well in 6.2 um GOES-East Water Vapor Imagery in Figure 1. GLM FED is also included in the animation as progressively more opaque yellow atop the green cold clouds.
Adding RAP sfc and upper level analysis fields onto the water help one to better understand features in the imagery by associating them with familiar fields, such as 500 mb height and wind speed, and sfc pressure (Figure 2).
Partially overlapped GOES-East 1-min mesoscale sectors resulted in a corridor of 30-second imagery across central Texas. The difference between 30-second imagery and 1-min imagery may not sound like a lot, put processes that are occurring on such small timescales do appear notably smoother to the human eye in the side-by-side comparison. This is exemplified in an animation of visible imagery over a tornado-producing severe thunderstorm on the border of 30-sec and 1-min imagery (Fig 3).
Further south near San Antonio, the evolution of the cu field leading up to eventual convective initiation is captured in 30-second Day Cloud Phase Distinction imagery. The 2.5 hour animation (300 images) reveals a cumulus field becoming increasingly agitated with the growth of cumulus clouds into towering cu, eventual glaciation with the colors changing from blue/cyan to green, to convective initiation diagnosed by vertical growth and transition of colors from green to yellow/red (Fig 4). The growth of the eventual first severe-warned storm occurs under high cirrus (red), but can be followed in the very high temporal resolution imagery.
Post convective initiation, 30-second imagery of storm maturation captured the evolution of storm top features, such as overshooting tops and an above anvil cirrus plume, in much detail (Fig 5). The imagery is extremely fluid, and ensures forecasters are receiving updates about the storm faster than ever. The animation is 240 images, or 2 hours long.
During the same period of 30-second imagery, adding a semitransparent 10.3 um overlay, resulting in the VIS/IR Sandwich, helps to capture the storm top features a little better by including the quantitative brightness temperature information (Fig 6).
After viewing the 30-sec animation a few times, take a peak at the 1-min animation of the same scene. It is fascinating how 1-min imagery appears relatively “choppy” (Fig 7)!
The most impressive storm developing near San Antonio exhibited an exposed updraft in the GOES-East 30-second imagery. Rocking a 30-sec visible imagery animation of this storm over a 25 minute period reveals counterclockwise rotation of the updraft (Fig 8). Extending west of the updraft is the more horizontally oriented flanking line. Inflow feeder clouds are also analyzed southeast of the updraft, as well as an overshooting top and above anvil cirrus plume at the storm top. Given the presence of high clouds, and rapid evolution, some of these features can easily be missed in coarser temporal resolution imagery.
As was shown in Figure 1+2, the convective threat shifted east to the southeast on the 22nd as the broad upper trough shifted east and another shortwave and associated strong jet streak spread across the region. Two strong thunderstorms passed through the New Orleans area just after sundown, and were captured in GOES-East 1-min ABI and GLM imagery. The northern storm produced an EF1 tornado, while the thunderstorm produced an EF3 tornado. The 1-min IR imagery revealed rapidly cooling cloud tops just prior to the initial tornado reports between 0024 UTC and 0029 UTC (Fig 9).
GLM FED associated with the storms included rapid upticks in total lightning activity leading up to tornado development (Fig 10). The FED data highlights the location and movement of the most intense storm updrafts, as well as the presence of lightning flashes and resulting lightning danger well removed of the storm core.
Finally, combining the GLM Flash Extent Density with Minimum Flash Area into a single RGB reveals where an abundance of small flashes (indicative of strengthening updraft) were occurring, as bright shades of yellow (Fig 11). Red represents low FED and small flashes, so a transition from Red to Orange to yellow in this RGB indicates increasing numbers of small flashes. Shades of blue represent long flashes, which are often present with the anvil regions of the thunderstorms, as well as with decaying updrafts.
A hyperactive period of intense, extratropical cyclone development unfolded last month across the North Atlantic. A series of four winter storms, each generating hurricane force winds, developed in rapid succession. No minimum central pressure records were broken, but all four storms underwent rapid cyclogenesis or bombogenesis. One of the storms, Storm Dennis (named by the UK Met Office), attained the second lowest pressure reading behind Storm Braer in 1993. Three of these four cyclones managed to achieve remarkable pressures in the 920-930 mb range.
Below is a table summarizing what we know about each of these four storms.
Next, we describe each system using a combination of satellite and surface analyses.
The first storm, which we are calling the “Greenland Bomb,” deepened explosively to 930 mb by February 8. In the surface analysis below, the storm – designated as a hurricane-force low – is located just east of the tip of Greenland. The extreme cyclonic wind field helped propel the next storm in the series, shown over Newfoundland as a 966 mb low, into Europe.
The low reached the British Isles as a 945 mb storm, causing widespread flooding and wind damage. It was named Storm Ciara by the UK Met Office, and is shown on the synoptic surface chart below.
On 12 February 2020, a third storm was brewing in the North Atlantic Ocean that was forecast to rapidly intensify into an strong extratropical cyclone that would develop hurricane-force winds. The system’s pressure dropped from 1005 mb on 12 February at 00 UTC to 962 mb on 13 February at 00 UTC, a 43 mb decrease in pressure in just 24 hours that classified this system as a bomb cyclone. We are referring to this third cyclone as the “Iceland Bomb.”
Stratospheric air intrusions are a known contributor to rapid intensification of extratropical cyclones via the advection of potential vorticity from the stratosphere into the troposphere. In the case of the Iceland Bomb, there was a strong signal of stratospheric air in the troposphere seen in GOES-16 Airmass RGB imagery, indicated by deep red/magenta in the dry slot of the cyclone.
The wave pattern across the North Atlantic was extremely active, as seen in the Airmass RGB imagery above and Atlantic surface analysis below. A storm force low preceded the Iceland Bomb, and Storm Dennis closely following.
In the image below, the RGB imagery of the Iceland Bomb does a remarkable job of delineating “textbook” conveyor belts, or the basic 3D circulation branches of a wintertime, marine cyclone. The dry conveyor belt descends from the stratosphere into the southwestern quadrant of the storm. The warm conveyor belt – with its moisture-laden, high cloud shield originating in the warm sector – stands out in stark contrast to the cold conveyor belt. The cold conveyor belt undercuts the warm conveyor belt from the east, wrapping into the comma-head of low and middle layer clouds.
The Iceland Bomb deepened further as it moved across the Atlantic and reached its minimum central pressure of 929 mb on 14 February at 06 UTC. Hurricane-force winds were sustained for 48 hours by this extratropical cyclone, slamming Iceland with winds of historic strength and producing phenomenal wave heights up to 64 ft. Although terrain enhanced, the highest wind gust recorded in Iceland was 159 mph in Hafnarfjall.
Almost like dejavu, another cyclone closely followed the Iceland Bomb. The low pressure system, which would eventually receive the name of Storm Dennis, originated in the same location as the Iceland Bomb and took nearly the same path. The system deepened from 996 mb on 13 February at 12 UTC to 956 mb on 14 February at 12 UTC, a 40 mb drop in 24 hours, classifying this system as another bomb cyclone.
Unlike the Iceland Bomb, this cyclone moved a little more to the east, impacting Ireland and the United Kingdom with intense hurricane-force winds. A wind gust of 118 mph was recorded in the Scottish Highlands, and a gust of 107 mph was recorded in Brocken, Germany, the strongest gust recorded outside of the United Kingdom (WNEP).
Other impacts included intense waves with heights up to 52 ft, severe flooding produced by prolonged intense rainfall, and structural damage caused by falling trees. All of this occurred just a week after the region was hit by storm Ciara, which exacerbated the impacts.
Rapid intensification of Storm Dennis was aided by a stratospheric air intrusion that originated in a trough located over the eastern United States that can be seen in the Airmass RGB imagery above. Deep red/majenta coloring indicates dry upper levels and high ozone concentrations associated with stratospheric air in the troposphere. Orange coloring indicates potential vorticity in the Airmass RGB product, and it trails all the way from the trough towards Europe, feeding into storm Dennis. Also pictured above is a massive atmospheric river stretching across the entire North Atlantic that provided ample moisture for the development of Storm Dennis.
The low pressure centers from the Iceland Bomb and Storm Dennis met up just south of Iceland where they did a Fujiwara dance, rotating around each other and then merging into one low pressure center. The dance can be seen in the Atlantic surface analysis above and the Airmass RGB imagery below. The Fujiwara effect is most commonly observed when two tropical cyclones pass close to one another. The combined system continued to move northeastward and dissipated by 18 February at 00 UTC.
Broader Perspectives Of The Hyperactive Storm Period
Having bomb cyclones in February is not unusual, as the peak season for these events in the North Atlantic and North Pacific is September through April, but having FOUR bomb cyclones in rapid succession of this intensity is unique.
This winter has featured a persistent, strongly positive arctic oscillation (AO) index, as shown below. Such a strong, positive index is driven by intense low pressure over the polar North Atlantic and high pressure ridging in the subtropical Atlantic.
The extreme pressure difference or gradient, in turn, has ratcheted up the intensity of the zonally-oriented polar jet stream coursing across the Atlantic Basin – at times reaching 240 mph. The dynamics of such an intense jet are a key reason for the sequence of very intense North Atlantic cyclones.
When one compares this winter’s East Coast snow activity (thus far, one of the least snowiest winters on record for portions of the Mid Atlantic), with the winter of 2009-2010 (record-breaking seasonal snowfall), the contrast in persistent North Atlantic Oscillation phase is striking (image below). Since early December, nor’easters have failed to materialize along the typical breeding ground of Cape Hatteras.
The intensity of the Iceland Bomb and Storm Dennis was aided by a massive atmospheric river spanning the entire width of the Atlantic Ocean. The atmospheric river funneled moisture from the tropical Caribbean all the way to Europe, following along a 5,000 mile long surface cold front and an intense upper air jet, which aided Dennis in producing an impressive 6.2 inches of rain over 48 hours in Cray Reservoir in South Wales as well as high rain totals across the region (WNEP).
Shown below is the integrated water vapor (IVP) product at 12 UTC on 16 February, showing extensive plume of Caribbean moisture entering into the large circulation of Storm Dennis (top panel). Also below, the Atlantic surface analysis the day prior illustrates the lengthy cold front, bisecting the entire Atlantic basin, that helped concentrate this atmospheric river.
This stormy period will be remembered for the incredible low pressures, verified hurricane-force winds (using ASCAT), and significant wave activity. The North Atlantic has remained stormy in early March, but pressures have been higher, though hurricane-force wind events continue.
Thank you for reading!
Deirdre Dolan (U. of MD-College Park), Jeffrey Halverson (U. of MD-Baltimore County), and Michael Folmer (NWS/NCEP/OPC)
The 4 March 2020 FDTD Satellite Applications Webinar was a tag-team discussion of a high profile snow squall event in PA/NY led by Dave Radell (SOO at New York City, NY) and Mike Jurewicz (SOO at State College, PA). In this webinar Mike and Dave shared several tips and tricks for fellow forecasters who may face this type of phenomenon in their own offices in the future. Here is one example of how satellite data was used to give a more complete picture as the event unfolded:
“A product that’s gaining a lot of popularity is the Day Cloud Phase, it’s an RGB product […] I would highly recommend the RGB product not only for these snow squall scenarios but for convection in general. […] although you get some idea in the traditional visible of the cloud enhancements, it really jumps out at you on the RGB loop. As these cloud features are growing taller and you’re getting more glaciation at the higher levels. With the ingredients that go into the RGB loop you can see that red and orange tint so it really jumps out at you nicely what the developing convective features are versus the lighter blue shading which is the flatter more laminar stratocumulus features. Again it could be another clue as to what really are the features of interest.”
“These snow squalls can be pretty robust convection in the winter time but in the grand scheme they’re fairly shallow features so you’re going to have issues with radar overshooting. But if you can combine your radar analysis with satellite you can get a more complete picture of how things are evolving.”
FDTD Satellite Applications Webinars are peer-to-peer learning; staff from WFOs, National Centers, CWSUs, RFCs lead the presentations. The presentations are short (less than 30 minutes) and recorded for on-demand viewing.
A rapidly intensifying low pressure system made its way into the Atlantic on Tuesday, 11 February 2020 and quickly grew into a powerful extratropical cyclone producing hurricane force winds by Thursday, 13 February 2020. By 0600 UTC on 14 February 2020, the low bottomed out with a minimum low pressure of 929mb. This system deepened by more than 40 mb in 24 hours during its rapid intensification phase, classifying it as a “bomb” cyclone. It tracked north towards Iceland where it caused hurricane force wind gusts, the highest gust, although terrain enhanced, reached 159 mph (https://www.severe-weather.eu/recent-events/near-record-wind-gusts-255kmh-hafnarfjall-iceland-mk/). These gusts were recorded on the leading edge of the cyclone where the cold conveyor belt north of the occluded front in the N-NE quadrants played a role.
This intense extratropical cyclone was closely followed by another cyclone (named Dennis by the UKMet office) rapidly intensified during the day on 14 February 2020 deepening by 40 mb in 24 hours, classifying it as another bomb cyclone. This system is following a similar path as the previous cyclone, capitalizing on the favorable baroclinic environment left in the wake of the first cyclone.
In the RGB Airmass imagery (above) from GOES-16, it is clear that there is also a large potential vorticity anomaly (red shading) upstream of the system, originating from a trough over the eastern United States. This inflow of potential vorticity into the storm is aiding the rapid intensification of the system. This system deepened to 920 mb as of the Ocean Prediction Center (OPC) 1800 UTC analysis on 15 February 2020. Hurricane force winds have been sampled by ASCAT scatterometers and by aircraft in the early morning hours of 15 February 2020 with maximum winds of 94 kt!
The above ASCAT and Altimeter images from ~1700-1745 UTC on 15 February 2020 show winds in the primary 920 mb low (south of Iceland) still at hurricane-force (>65 kt) with significant wave heights near 42 ft in the southeast quadrant. Meanwhile the older, lee-side low that was part of the 13 February 2020 storm is still exhibiting winds of 50-60 kt, aided by a barrier jet in eastern Greenland and a tip jet near the southern tip of Greenland. The altimeter readings near this latter storm were 30-42 ft (note that it’s possible higher waves (~50+ ft) were in the vicinity of both storms at this time).
These latest ASCAT and Altimeter passes show the 922 mb low (as of the 0000 UTC 16 February 2020 OPC analysis) has started to fill (weaken slightly) with plenty of storm-force wind barbs and significant waves still over 40+ ft, though higher winds of 65+ kt and waves over 50 ft are most likely not sampled.
We will have a more detailed recap of this past week’s stormy north Atlantic in the coming days, so please stay tuned.
The tropical Atlantic has been putting on quite the show over the last couple of weeks of Hurricane Harvey (Category 4). . .I’m sure you heard of that one, followed by Irma (Category 5), Jose (Category 4), and Katia (Category 2). Katia made landfall last night in Mexico and now we continue our focus on Irma and Jose. Why is it so active? A few reasons: warm ocean (sea surface temperature and high ocean heat content), lack of a true El Nino Southern Oscillation (ENSO) signal, though it looks like a weak La Nina, little to no shear throughout much of the basin, a lack of dust from the Sahara, and a strong Azores high. Oh yeah, on top of that, we have the Madden-Julian Oscillation (MJO) more or less stuck in favorable phases for the Atlantic (8, 1, 2, 3) and forecasts suggest that stays in place for a while.
ECMWF MJO verification and forecast courtesy of the Climate Prediction Center (CPC). Click here to open in a new window.
GEFS MJO verification and forecast courtesy of CPC. Click here to open in a new window.
One product I noticed in use at the Ocean Prediction Center (OPC) on Friday, 09/08/17 was the GOES-16 Daytime Convection RGB, so I thought this would be a nice opportunity to show you all three current Atlantic systems with a comparison to the 10.3 µm “clean” channel.
GOES-16 Daytime Convection RGB of Hurricane Irma valid 1100 UTC to 2300 UTC on 09/08/17. *Preliminary, Non-Operational Data* Click here to open in a new window.
Note the bright yellow coloring that highlights, new convection with smaller ice particles indicating strong overshooting tops in the outer rainbands, while the main central dense overcast (CDO) surrounding the eye also gets brighter. This indicates that after the eyewall replacement cycle ended, the new eyewall started to contract and strengthen (winds at this time were 155 mph, but shortly after this strengthened to 160 mph.
GOES-16 10.3 um “clean” infrared window channel similar to the previous animation of Hurricane Irma. *Preliminary, Non-Operational Data* Click here to open in a new window.
Notice that the 10.3 µm “clean” window shows us the brightness temperature of the coldest cloud tops. Although you can see the new overshooting tops, as those thunderstorms rotate around the CDO, it gets more difficult to identify the newer, important convection.
GOES-16 Daytime Convection RGB for Hurricane Jose valid 1000 UTC to 2045 UTC on 09/08/17. *Preliminary, Non-Operational Data* Click here to open in a new window.
By contrast, notice how compact Hurricane Jose became as it strengthened to a 150 mph Category 4 hurricane on Friday (09/08/17). Again, the beginning of the animation shows plenty of yellows that indicate new convection, wile the older convection fades to oranges, then reds. Also notice how the CDO becomes more yellow as the eye becomes cleaner and the storm takes on a more donut structure, even with the strong outflow channel to the northeast that makes the storm look lopsided. Could this RGB be helpful in identifying CDO changes? Or help with indicating eyewall replacement cycles (ERCs) in conjunction with microwave imagery?
GOES-16 10.3 um “clean” infrared imagery similar to the previous animation of Hurricane Jose. *Preliminary, Non-Operational Data* Click here to open in a new window.
Again, to contrast the Daytime Convection RGB, the above 10.3 µm animation shows very cold cloud tops, but the newer convection starts to blend in with the CDO over time. Do you see other differences?
GOES-16 Daytime Convection RGB of Hurricane Katia valid 1200 UTC to 2357 UTC on 09/08/17. *Preliminary, Non-Operational Data* Click here to open in a new window.
Finally, Hurricane Katia was very small in comparison with the other two hurricanes, but notice there are differences in the intensity of the convection on Friday (09/08/17). What do you see in the imagery? There are less yellows than in Irma or Jose, yet the storm intensified to a Category 2, 90 kt (105 mph) hurricane prior to landfall on Friday evening. The warming clouds and less cold, newer convection may have been due to dry air entrainment due to the close proximity to mountainous land nearby and a weak trough to the north.
GOES-16 10.3 um “clean” infrared imagery similar to the previous animation of Hurricane Katia. *Preliminary, Non-Operational Data* Click here to open in a new window.
How does the 10.3 µm imagery above contrast with the Daytime Convection RGB?
So, what is steering Irma? What about Jose and Katia? Well, I’m glad you asked. . .
GOES-16 Air Mass RGB image valid at 0900 UTC 09/09/17. *Preliminary, Non-Operational Data* Click here to open in a new window.
The GOES-16 Air Mass RGB image (courtesy of NASA SPoRT) above with my crude drawings show a rough idea of the players affecting the steering flow around the three hurricanes. Katia has made landfall as it was pushed southwest due to the old cold frontal boundary (responsible for the cool air in most of the country) along with a disturbance highlighted in the yellow circle. This disturbance will close off over the Tennessee Valley area and help to pull Hurricane Irma north, then northwestward in the next 48 hours. Finally, Jose (east of the Lesser Antilles) will be pulled north through a weakness in the ridge due a weakness created by the Tropical Upper Tropospheric Trough (TUTT in the yellow “T”) to the northeast and Irma’s broad circulation. Since the current trough over the northeast U.S. moves east/northeast and the central Atlantic TUTT remains stationary, Irma gets left behind in the southeast U.S., but weakening after landfall, while Jose gets left behind and may perform a tight anticyclonic loop before “possibly” moving northwest. We’ll deal with Jose later. . .
I have included the GOES-16 Air Mass RGB and 7.3 µm low-level water vapor animations below so you can get a better feel of the overall pattern.
GOES-16 Air Mass RGB animation valid 0800 UTC 09/08/17 to 0900 UTC 09/09/17. *Preliminary, Non-Operational Data* Click here to open in a new window.
GOES-16 7.3 um low-level water vapor animation valid from 0800 UTC 09/08/17 to 0715 UTC 09/09/17. *Preliminary, Non-Operational Data* Click here to open in a new window.
My final thoughts. . .please follow the National Hurricane Center for official track and intensity guidance on Irma and Jose. I have included the track forecasts below.
The 8 am EDT NHC track forecast for Hurricane Irma. Click here to open in a new window.
The 8 am AST NHC track forecast for Hurricane Jose. Click here to open in a new window.
Following on the heels of our post on the early March 2017 eruption of Bogoslof in the Aleutian Islands, the Washington Volcanic Ash Advisory Center (VAAC) located at the NESDIS Satellite Analysis Branch (SAB) noted an interesting SO2 signal following the eruption of Kambalny on the Kamchatka Peninsula in the various Himawari multispectral imagery. The ash plume lasted many hours and was carried hundreds of miles from the Kamchatka Peninsula.
Himawari-8 Nighttime Microphysics RGB with the SO2 plume (bright pink coloring emanating from the Kamchatka Peninsula) valid 03/25/17-03/27/17. Click here to enlarge
From SAB Analyst, Mike Turk (10pm March 25 – 7am March 26): I had to handle the coordination with Tokyo and Anchorage VAACs regarding possible hand off of responsibility from Tokyo to Washington. Anchorage-VAAC called to discuss need for a Significant Meteorological Information (SIGMET) statement for the Oakland Flight Information Region (FIR). the Nighttime Microphysics RGB clearly showed the initial penetration of ash into the Oakland FIR .
Himawari-8 Dust RGB with the ash cloud (orange/salmon) and SO2 plume (light green) emanating from the Kamchatka Peninsula, valid 03/25/17 – 03/27/17. Click here to enlarge
Himawari-8 Air Mass RGB with the ash cloud (white) and SO2 plume (light pink) faintly visible near the southern tip of the Kamchatka Peninsula as they get caught up in the dry, stratospheric air (red shading), valid 03/25/17 – 03/27/17. Click here to enlarge
From SAB Analyst, Ellen Ramirez (10pm March 26th -8am March 27th): At the beginning of my shift it was daylight over Kambalny and I could not discern the ash plume in the Daytime Microphysics RGB. Several hours later after sunset the plume was most distinguishable in Nighttime Microphysics RGB, followed by the Dust RGB, and barely in the Air Mass RGB but only because I knew where to look.
The ash plume is enhanced in the multispectral imagery due to the 12.4 µm – 10.4 µm band difference. The SO2 plumes are enhanced in the multispectral imagery due to the absorption of SO2 at the 8.6 µm (Dust) and 7.3 µm (Air Mass) wavelengths.
For more satellite analysis of this eruption, please see the CIMSS Volcano Blog entry on Kambalny.
All multispectral imagery in this post is courtesy of NASA SPoRT through the GOES-R Proving Ground.