MY 2020 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #68
*******Note that forecasts and outlooks in this post are NOT the official forecast from the National Hurricane Center (NHC). They are my own detailed views on the Atlantic tropics based on current observations and latest computer model runs. As such do not make decisions based on my posts...consult news media...watches and warnings from your local weather office...and any evacuation orders issued by local governments to make the most informed and best decisions. Visit the NHC website hurricanes.gov (hurricanes dot gov) for the latest watches/warnings and official forecasts on active tropical cyclones.**********
...WEDNESDAY JULY 22 2020 1:15 PM EDT...
See area of interest sections below for disturbances being monitored for tropical cyclone formation. Elsewhere...some long range computer models suggest that a tropical wave of low pressure to emerge from western Africa in 48 hours could develop in the open tropical Atlantic Ocean next week. Should this tropical wave show signs of organization in the coming days...will consider adding it as another area of interest on this blog.
TROPICAL STORM GONZALO...The compact central tropical Atlantic low pressure spin seeded from a broad tropical wave of low pressure that exited Africa a few days ago has continued to become better organized...strengthening into tropical depression seven as of yesterday afternoon and then briskly strengthening into a moderately strong Tropical Storm Gonzalo late this morning. Positives for Gonzalo include low shear and upper divergence supplied by the south side of broad tropical upper ridging in the region which is expected to persist during the entire 120-hour forecast period...and 28 to 29 deg C warm water along the forecast path. The one negative factor in the region is a large swath of dry saharan air getting pushed southwest toward Gonzalo by a large tropical wave to the east. Mixed messages are also in the current state of Gonzalo...on the one hand the National Hurricane Center has had to quickly raise the estimated strength of the storm due to an eye-type feature seen faintly on visible satellite...on the other hand the thunderstorm intensity on infrared satellite is less than it was last night and maybe from the dry air. In the last 24 hours the computer models have likewise split into two camps...one camp showing Gonzalo strengthening while producing thunderstorms that wall off the dry air and hitting the southern Lesser Antilles as a possibly strong tropical cyclone in a few days...the other camp showing Gonzalo weakening to a tropical wave just before getting to the islands. In response...I have raised my intensity forecast somewhere in the middle to show Gonzalo maintain strength as a high-end tropical storm of 65 mph maximum sustained winds during much of the forecast period...a similar approach to the National Hurricane Center...but with the National Hurricane Center also showing a period where Gonzalo reaches category 1 hurricane force. I forecast weakening to begin once Gonzalo reaches the Caribbean Sea as most of the global models (the NAVGEM being the exception) agree that Gonzalo will have weakened to a tropical wave or begin weakening by that time. My updated forecast track is adjusted slightly west due to the current position of Gonzalo...with an increasing northward angle shown in the Caribbean Sea with the assumption Gonzalo will be sufficiently strong/tall enough to be tugged by the upper vorticity currently in the Caribbean and western Atlatnic which is forecast to still be present...albeit at a further west position...by 120 hours. Due to the highly uncertain intensity forecast...interests in the southern Lesser Antilles should very closely monitor the progress of Gonzalo and be ready to make preparations for tropical storm...possibly hurricane conditions...to arrive on Saturday evening.
0 Hr Position (1200Z Jul 22)...50 mph maximum sustained wind tropical storm centered at 9.9N-43.6W
IOH 24 Hr Forecast (1200Z Jul 23)...65 mph maximum sustained wind tropical storm centered at 10N-48W
IOH 48 Hr Forecast (1200Z Jul 24)...65 mph maximum sustained wind tropical storm centered at 10N-53W
IOH 72 Hr Forecast (1200Z Jul 25)...65 mph maximum sustained wind tropical storm centered east-southeast of the Lesser Antilles at 10.5N-58W
IOH 96 Hr Forecast (1200Z Jul 26)...60 mph maximum sustained wind tropical storm centered in the southeastern Caribbean Sea just offshore of the Venezuela coast at 11.5N-63W
IOH 120 Hr Forecast (1200Z Jul 27)...50 mph maximum sustained wind tropical storm centered in the eastern Caribbean Sea at 13.5N-68W
AREA OF INTEREST #1...The north end of a tropical wave of low pressure from the Caribbean Sea has spun up into a surface low pressure in the central Gulf of Mexico overnight...the surface low pressure formation enhanced by upper divergence on the northeast quadrant of upper vorticity in the region. Thunderstorm bursts and bands that cover the center of low pressure and areas extending well to the east are being enhanced by the outflow of an upper anticyclone that exists between the upper vorticity to the southwest and a lengthy axis of upper vorticity in the western Atlatnic. Due to recent rapid expansion and organization of the thunderstorm activity about the center of surface low pressure...I have raised odds of tropical cyclone formation to a peak of 80% for the next 48 hours...especially considering the atmospheric conditions will only become increasingly favorable for development as the upper vorticity to the southwest dissipates and gives way to upper anticyclonic flow...and as this system passes over very warm 30 deg C waters. I have adjusted my forecast track points in the outlook below northwestward given the current position of the organizing surface low at 26N-89W...with the steering to the west-northwest into the southeast Texas coast and into eastern Texas expected to be straightfoward around surface ridging over the eastern United States to be supported by the western convergence zones of uppper troughs passing over the US/Canada border region.
Unlike Tropical Storms Cristobal and Fay which made landfall in the United States when/where the COVID-19 virus outbreak was less severe...this system will be approaching the southeast Texas/western Louisiana area at a time and location where a signficant COVID-19 emergency is ongoing. Interests along the southeast Texas coast from Matagorda Bay to the Texas/Louisiana border...as well as the southwest Louisiana coast...as well as areas just inland from this coastal region...should use today to gather supplies to manage impacts such as power outages or coastal storm surge...to avoid a last minute rush to potentially crowded stores in the event this disutrbance strengthens briskly in the favorable conditions that lie ahead for it. Avoiding crowds reduces the potential for contracting COVID-19. In the event you must retreive supplies in a crowded situation...frequent sanitizing of your hands and wearing a face mask will be necessary to protect you and those around you from COVID-19. Sanitize the packaging of purchased supplies before use in your residence. In the event you may have to leave due to a concern such as storm surge...consider planning the use of a family/friend residence further inland or a hotel location further inland in case you may need it..as a crowded public shelter may not as ideal for controlling your exposure to COVID-19. This system will be bringing impacts to the southwest Louisiana and southeast Texas coastal regions by Friday.
IOH 24 Hr Outlook (1200Z Jul 23)...75% chance of tropical cyclone formation (central Gulf of Mexico near 27N-92W)
IOH 48 Hr Outlook (1200Z Jul 24)...80% chance of tropical cyclone formation (Texas coast near Galveston Bay at 29N-95W)
IOH 72 Hr Outlook (1200Z Jul 25)...0% chance of tropical cyclone formation (eastern Texas near 31.5N-97W)
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
0000Z CMC Model Run...For Tropical Storm Gonzalo...shown to strengthen as a very compact tropical cyclone by 36 hours while near 10.5N-47W...weakens to a tropical wave while moving across the southern Lesser Antilles in 90 hours. For area of interest #1...surface low shown to form near 26N-90W in 18 hours...makes landfall on the Texas coast near Matagorda Bay still as a surface low in 72 hours. Elsewhere...large tropical wave shown to emerge from western Africa in 48 hours...organizes into tropical low near 12N-40W in 120 hours...strengthens into possible tropical cyclone while mvoing into Barbados and the southern Lesser Antilles in 174 hours.
0000Z ECMWF Model Run...For Tropical Storm Gonzalo...weakens to a tropical wave while crossing the southern Lesser Antilles in 96 hours. For area of interest #1...surface trough shown to amplify while south of Louisiana in 48 hours...surface trough makes landfall on the Texas coast in 72 hours. Elsewhere...has large broad tropical wave emerge from western Africa in 48 hours...shown to organize into a tropical low pressure spin near 12N-39W in 120 hours...shown to strengthen into a possible tropical cyclone while approaching the Lesser Antilles near 15N-55W in 168 hours.
0600Z GFS Model Run...For Tropical Storm Gonzalo...shown to strengthen as a very compact tropical cyclone by 42 hours while near 10N-50W...crosses the southern Lesser Antilles as a possibly strong compact tropical cyclone in 90 hours while centered near 12N-60.5W...weakens to a tropical wave in the eastern Caribbean Sea at 65W longitude in 108 hours.For area of interest #1...surface low pressure shown forming near 26.5N-92.5W in 36 hours...makes landfall on the Texas coast in 66 hours as a surface trough.
0600Z NAVGEM Model Run...For area of interest #1...shows surface low forming just offshore of southeastern Louisiana near 27.5N-91.5W in 36 hours...making landfall on the Texas coast and just west of Louisiana at 60 hours as a surface trough. For Tropical Storm Gonzalo...shows strengthening into a strong tropical cyclone...moves into the southern Lesser Antilles at high strength while passing near 13.5N-60.5W in 84 hours...makes landfall at high strength over the south coast of Haiti in 138 hours.