On the morning early of 04/06/17, TAFB forecasters noted a nice V-pattern to convection at the tail end of a front in the northeast Gulf of Mexico. The increased temporal and spatial resolution of GOES-16 compared to the GOES-13 (east) provided more details on the organization and maintenance of the convective line that would otherwise have been analyzed.
GOES-16 0.64 um “Red” visible animation showing strong convection in the eastern Gulf of Mexico, valid 0900 UTC – 1600 UTC on 04/06/17. *Preliminary, Non-Operational Data* Click to Enlarge
Hugh Cobb (TAFB Branch Chief) noted: “We also looked at the Red VIS Band 2 for this event. The VIS imagery was more striking in that you could see the shadows of the high cirrus cast on the lower cloud deck in the animation and the “beavertail” of of the low clouds feeding into and maintaining the deep convection.”
GOES-16 10.3 um “Clean” infrared animation (same as above), valid from 0900 UTC – 1600 UTC on 04/06/17. *Preliminary, Non-Operational Data* Click to Enlarge
GOES-16 10.3 “Clean” infrared imagery with 5-minute GLD-360 lightning density overlaid, valid 0900 UTC – 1600 UTC on 04/06/17. *Preliminary, Non-Operational Data* Click to Enlarge
Jorge Aguirre-Echevarria (TAFB Forecaster) noted that “the striking cloud/convective signature and associate lightning activity observed that day over the waters of the far southern Gulf of Mexico.” In particular, these events are rather rare at such a low latitude in the TAFB Offshore Zones. The GOES-16 10.3 μm infrared imagery proved to be very helpful in seeing the overshooting tops and the cold cloud canopy temperatures which signified the activity would persist west of Key West, FL.
Hurricane Matthew. . .a storm that will be remembered for the challenges, strange structures, maneuvering path, weird (sinister) face images in satellite imagery, and unusually low (observed) pressures regardless of satellite appearance.
The 10/06/16 5 pm EDT NHC forecast track for Hurricane Matthew.
GOES-13 (east) 10.7 um infrared animation showing Hurricane Matthew’s trek through the middle Bahamas on 10/06/16.
As you can see in the GOES-13 infrared animation above, the structure of Matthew has gone through a few changes today with some northerly shear blunting the northern portion of the hurricane, although this hasn’t lead to any notable weakening as of yet. In the last couple of frames, very strong convection fires again as the hurricane is approaching Grand Bahama. Also of note is the strong area of convection that fired to the northeast of Matthew today, though not as strong as what was seen in the Caribbean over the weekend.
GOES-13 10.7 um infrared imagery with Vaisala GLD-360 lightning density overlaid at 15 minute intervals.
The GOES-13 infrared imagery with GLD-360 15-minute lightning density overlaid shows a couple distinct areas of lightning activity, the aforementioned convection to the northeast and another area in the northeast eyewall. This latter area has been pulsing all day and may suggest that the shear mentioned earlier was being fought off by the deep pulses of convection. Note that this area passed over the western portion of Providence Island and is getting ready to move ashore in southwest Grand Bahama. This is where the aircraft is showing the strongest winds (near 120 kts or 140 mph).
NOAA Unique Combined Atmospheric Profiles (NUCAPS) pass overlaid on GOES-13 10.7 um infrared imagery in AWIPS II. The black circle represents the sounding location provided below.
NUCAPS sounding (black circle on above image) showing some drying and warming above 700 mb to the north of Hurricane Matthew. Note that this isn’t a clean sounding since there are clouds in the scene, but the multiple warm layers are certainly interesting.
So, where did this shear originate from? I haven’t quite found the source, but I did pull up a NOAA Unique Combined Atmospheric Profiles (NUCAPS) sounding that may not be the most representative of the northern portion of the cyclone due to clouds, but does show an interesting drying at mid-levels. Note there are no winds as this is a satellite-borne sounding looking down, not to be confused with a raob.
GOES-13 10.7 um infrared imagery with the GOES-R Rain Rate/QPE product overlaid showing nearly instantaneous, 15 minute rain rates during Hurricane Matthew’s path over western Haiti and eastern Cuba.
Another product that has been available to forecasters at the National Hurricane Center, Weather Prediction Center, and NESDIS Satellite Analysis Branch is the GOES-R Rain Rate/QPE product provided by Bob Kuligowski at NESDIS. These are 15 minute rain rates that are derived using infrared brightness temperatures, then calibrated with microwave imagery. Note the values near the eyewall approaching 1″-1.50″ per 15 minutes!!!
GOES-R Rain Rate/QPE product showing the 7-day accumulated precipitation along Hurricane Matthew’s path.
The 7-day QPE accumulation image above shows many values over western Haiti and eastern Cuba approaching and exceeding 20″, which might even be conservative in the higher terrain areas. Note other interesting features like the rain shadow in northern Dominican Republic and amounts that exceed (then re-accumulate) 20″-45″ near where Matthew slowed north of Columbia. The now infamous “convective blob” is where the largest totals are located and might be reasonable for this case considering the extreme lightning and intensely cold cloud tops.
GOES-13 10.7 um infrared imagery with Vaisala GLD-360 lightning density overlaid during Hurricane Matthew’s rapid intensification cycle from 09/30/16 – 10/02/16.
This final animation shows the very intense lightning activity associated with the inner core organization and infamous “convective blob” that was trailing Hurricane Matthew through the southern Caribbean. The persistent lightning in the northern eyewall is interesting in that it’s rather atypical for rapid intensification in Atlantic hurricanes. Meanwhile, the lightning associated with the blob is very intense at 15 minute increments and helps support those extreme rain amounts that fell over the Caribbean.
Thank you for reading and feel free to comment/ask questions!
While West African tropical waves continue to propagate out into the tropical North Atlantic, none are expected to develop into a tropical cyclone soon. Today, the 2:00 PM EDT NHC Two-Day Graphical Tropical Weather Outlook shows one of these waves accompanied by a broad low pressure system, which particularly looks impressive on satellite imagery (see image below). Still, environmental conditions are not too favorable for a cyclone to form.
NHC Two-Day Graphical Tropical Weather Outlook on July 29 at 2:00 PM EDT depicting a West African tropical wave accompanied by a broad low pressure system with low chance of cyclone formation
Generally, tropical waves are accompanied with areas of disturbed weather that along with other dynamics of the atmosphere (that include climatological and synoptic conditions) could lead to cyclogenesis. One of the main favorable atmospheric conditions for tropical cyclone development is sustained, deep, moist convection. However, constant and extensive episodes of Saharan Air Layer (SAL) outbreaks are disrupting the formation of a nearly-saturated middle troposphere, which has contributed to the overall weak tropical waves pattern.
Below, enhancements of Meteosat satellite imagery with the TAFB surface analysis overlaid depict various tropical waves being affected by SAL outbreaks during mid July. The imagery show how the dry air (orange and yellow shades) and dust (pink shade) associated with this Saharan airmass cover a large part of the waves environment, thus acting to suppress any convection originating in the marine layer.
Meteosat SAL tracking product and TAFB 1800 UTC surface analysis on July 13
Meteosat SAL tracking imagery ranging from 1500 UTC to 2030 UTC on July 13
Meteosat Dust tracking product and TAFB 1800 UTC surface analysis on July 13
Meteosat Dust tracking imagery ranging from 1500 UTC to 2030 UTC on July 13
The Gulf of Mexico and Gulf Coast states have seen a plethora of thunderstorms since about mid-April. One of these episodes was a multi-day event that spanned April 16 – April 20. Multiple rounds of thunderstorms with very heavy rainfall (especially in and around Houston) and some significant severe weather (more hail and wind than tornadoes) traversed the region. The below animation shows these events and I included an example Mesoscale Precipitation Discussion (MPD) from WPC as a reference to the heavy rain.
GOES-13 Infrared imagery with GOES-R Lightning Detection (Density) spanning five days (04/16-4/20).
The Weather Prediction Center (WPC) Mesoscale Precipitation Discussion (MPD) for southeast Texas on 04/18/15.
More recently, on the evening of 04/22/15, a couple strong supercell thunderstorms moved off the Texas coast near the Corpus Christi area and traversed the offshore waters passing relatively close to a couple oil platforms. One of the more amazing attributes to the storms was the strong reflectivities of near 75 dbz! Although these were measured at high altitudes (based on the beam height), it’s interesting to note that large hail may have been occurring well offshore in the Tropical Analysis and Forecast Branch (TAFB) offshore zones. I have included a few animations showing the evolution of these supercells.
Animation of the GOES-R Convective Initiation product with GLD-360 lightning strokes overlaid valid 4/22-4/23.
National WSR-88D Mosaic base reflectivity with the Overshooting Top Magnitude (OTM) product overlaid highlighting the most intense updrafts associated with the supercells. The OTM product provides the difference between the overshoot and the surrounding cirrus clouds.
National WSR-88D Mosaic base reflectivity overlaid with the GOES-R Lightning Detection (Density) product in 5-minute increments. Note the extreme amount of lightning occurring with the dominant supercells in the Gulf of Mexico.
Here is a post from the National Weather Service Office in Houston-Galveston which nicely summarizes the threat posed to mariners from offshore supercells.
All mariners out there…this is why you should ALWAYS heed a Special Marine Warning. Buoy 42019 measured a 76 kt / 87 mph wind gust at 729 PM associated with this Gulf of Mexico thunderstorm!
