MY 2020 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #70
*******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.**********
...FRIDAY JULY 24 2020 1:05 PM EDT...
See Tropical Storm Gonzalo and Tropical Storm Hanna sections below for all active tropical cyclones being monitored in the Atlantic basin. Elsewhere...the tropical wave of low pressure that has emerged from western Africa in the last 24 hours has become introduced into the National Hurricane Center tropical weather outlook...see area of interest section below for details. And finally...the north end of a tropical wave of low pressure moving through the eastern Caribbean Sea is producing thunderstorms north of the Dominican Republic in an area of upper divergence on the east side of western Atlantic upper vorticity. Although this upper vorticity is forecast to weaken which would reduce unfavorable wind shear in the region...satellite animation suggests quick westward movement of the tropical wave and thunderstorms...so its possible this disturbance moves directly beneath the unfavorable upper vorticity before it has a chance to weaken. Therefore due to these observations and lack of computer model support...not considering this disturbance an area of interest for development at thist ime.
TROPICAL STORM GONZALO...It appears that the large dry saharan air layer to the north of Gonzalo...being pushed southwestard toward the tropical storm by a large tropical wave to the east...is getting the better of the storm...with the thunderstorm activity of Gonzalo becoming increasingly disorganized and frquently interrupted. These trends have caused Gonzalo to weaken to 50 mph maximum sustained winds in what would be an otherwise favorable environment for strengthening given the warm 29 deg C waters and upper ridging providing low shear and upper outflow in the region. Computer models remain split into two camps...one camp (GFS and NAVGEM) 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 the next day or so...the other camp (CMC and ECMWF) showing Gonzalo weakening to a tropical wave as it crosses the islands or just after crossing the islands. It is interesting to note that the models that show high strength initialize Gonzalo as a strong tropical storm...while the models that keep Gonzalo weak initalize Gonzalo as a small weak tropical low as Gonzalo is perhaps too small to be accurately represented in those lower-resolution models. The low-resolution NAVGEM intializes Gonzalo as a strong tropical storm but larger than it currently is...perhaps to get this low-resolution model to be more accurate regarding intial strength...so I think this makes this model is overdoing the strength of Gonzalo with this strategy.
Given the weakening trends due to the prominence of the dry saharan air...I have leaned my intensity foercast toward the CMC and ECWMF which show Gonzalo gradually weakning to a tropical wave going forward. I also think the 0600Z NAVGEM and GFS initializations may have Gonzalo a bit too strong while relying on older information from a few hours ago when Gonzalo was estimated to be a bit stronger. My forecast track points are adjusted a bit the west based on the current position and heading of Gonzalo...and the chances that Gonzalo will be strong/tall enough to be bent northward in track by the western Atlantic to Caribbean upper vorticity are decreasing. Interests in the southern Lesser Antilles should use today to finish preparations for tropical storm condtions to arrive by Saturday evening...and the chances of hurricane conditions here are now reducing. Its also possible the southern rain bands of Gonzalo could deliver some heavy rains and/or gusty winds to Trinidad and Tobago and the northeast coast of Venezuela given that Gonzalo's track has been staying further south.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (1200Z Jul 24)...50 mph maximum sustained wind tropical storm centered at 10N-54.2W
IOH 24 Hr Forecast (1200Z Jul 25)...50 mph maximum sustained wind tropical storm centered east-southeast of the Lesser Antilles at 10.5N-59W
IOH 48 Hr Forecast (1200Z Jul 26)...45 mph maximum sustained wind tropical storm centered in the southeastern Caribbean Sea just offshore of the Venezuela coast at 11.5N-64W
IOH 72 Hr Forecast (1200Z Jul 27)...Remnant tropical wave in the eastern Caribbean Sea at 69W longitude
TROPICAL STORM HANNA...Tropical depression eight moving toward the northwestern Gulf of Mexico has finally strengthened into Tropical Storm Hanna overnight...continuing the hyperactive pace of the 2020 Atlatnic Hurricane Season while becoming the earliest eighth named storm for the Atlantic basin on record...beating Tropical Storm Harvey of 2005 which was named on August 3. Conditions for strengthening include an upper ridge expanding from the southern United States that now entirely coveres Hanna with low shear and upper anticyclonic outflow...and the rather warm 30 deg C Gulf of Mexico waters. Thunderstorm bands are well organized and prominent on the south and east sides of the tropical storm...wrapping into a bit of an eye type feature at the center of circulation. Activity on the north and west sides on the other hand seems a bit hampered...and a closer look at upper-level winds reveals a shortwave upper trough over eastern North America amplifying southward toward Hanna...an equal and opposite reaction to the amplifying southern United States upper ridge being boosted by warm air advection ahead of a frontal zone moving into the north-central United States. Convergence on the west side of the amplifying shortwave upper trough maybe producing some dry sinking air that explains the lessened activity on the north and west sides of Hanna. Given that the GFS moreso amplifies the upper trough and now sends a fragment of it southwestward around the upper ridge and chasing Hanna...I have slightly reduced my intensiy forecast from special update #69A to a peak of 60 mph max sustained winds as its possible such an upper trough fragment may dirsupt Hanna with some northerly wind shear as well. My forecast track points are adjusted south and east due to the current position and heading...and the insistence in model runs that show going forward that Hanna will no longer be curving around the eastern United States surface ridge...instead getting drawn west-southwest toward a surface monsoonal low pressure field over Mexico...and Hanna may probably become strong/tall enough soon to be kept southward by upper northerly winds on the west side of the approaching upper trough fragment.
Previous runs of the ECMWF have liked to show Hanna re-strenghten over south Texas after landfall...and recently the 0000Z CMC and 0600Z GFS seem to join the party. I think this maybe a suggestion by the models that there coudl be an area of supportive split flow upper divergence between the southwest side of the approaching upper trough fragment and south side of the amplifying southern US upper ridge that slows Hanna's post-landfall weakening rate. Therefore on the home page of this site...I mention some impacts over inland southern Texas...spreading into northern Nuevo Leon and eastern Coahuila provinces of Mexico...with impacts further west of these locations I think less likely as becomes suppressed when the upper trough fragment arrives directly overhead by 72 hours per the 0600Z GFS model run.
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 coastal Texas at a time and location where a signficant COVID-19 emergency is ongoing. Interests along the Texas coast near the Matagorda Bay all the way to the Mexico border...and areas just inland from this coastal region...should use today to make preparations for strong tropical storm conditions such as coastal storm surge and some wind damage...so if 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 Texas coastal region as early as tomorrow morning.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (1200Z Jul 24)...45 mph maximum sustained wind tropical storm centered in the northwestern Gulf of Mexico at 27.2N-93.2W
IOH 24 Hr Forecast (1200Z Jul 25)...60 mph maximum sustained wind tropical storm centered just southeast of Matagorda Bay Texas at 27.5N-95.5W
IOH 48 Hr Forecast (1200Z Jul 26)...40 mph maximum sustained wind tropical storm centered over southern Texas at 27N-98.5W
IOH 72 Hr Forecast (1200Z Jul 27)...Remnant low pressure over northern Mexico centered at 26N-102W
AREA OF INTEREST #1...The National Hurricane Center in thier tropical weather outlook has introduced a large tropical wave of low pressure that has recently emerged from the west coast of Africa and into the eastern tropical Atlantic...due to computer model support from the ECMWF model that shows this tropical wave developing in the long range as it moves toward the Lesser Antilles. The CMC model also showed this wave developing at a similar location...but has dropped this solution as of today. During the 120-hour forecast period...the tropical wave will remain in favorable low shear and upper outflow beneath a broad tropical upper ridge in the region and over warm waters...and the tropical wave currently shows some signs of organization while bands of thunderstorms suggest a center of low pressure just southeast of the Republic of Cabo Verde Islands. On the other hand the north side of the tropical wave is becoming increasingly covered by the dry saharan air layer. Therefore I give very low 5% odds of development in the next 48 hours due to lack of short-term computer model support and while assuming this tropical wave will become increasingly dried out by the saharan air layer just like its predecessor wave currently at 37W longitude. Since the ECMWF is the only model showing development of this wave...my peak odds of development at 120 hours is only 10%...lower than the National Hurricane Center's 30% odds.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Jul 25)...5% chance of tropical cyclone formation (just southwest of the Republic of Cabo Verde Islands near 13N-25W)
IOH 48 Hr Outlook (1200Z Jul 26)...5% chance of tropical cyclone formation (tropical Atlantic near 13N-31W)
IOH 72 Hr Outlook (1200Z Jul 27)...0% chance of tropical cyclone formation (tropical Atlanic near 13N-37W)
IOH 96 Hr Outlook (1200Z Jul 28)...0% chance of tropical cyclone formation (tropical Atlanic near 13N-43W)
IOH 120 Hr Outlook (1200Z Jul 29)...10% chance of tropical cyclone formation (tropical Atlantic near 13N-50W)
...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 cross the southern Lesser Antilles as a tropical wave in 42 hours...in very long range (168 hours) the remnant tropical wave shown to regenerate into a tropical cyclone in the Bay of Campeche. For Tropical Storm Hanna...additional strengthening shown until landfall on Matagorda Bay Texas in 36 hours...continues west-southwestward inland across south Texas and into northeast Mexico where it loses its identity in 84 hours. For area of interest #1...no tropical cyclone formation shown. Elsewhere...frontal zone currently over north-central United States shown to reach northwest Atlantic in about 150 hours...frontal zone decays beneath persistent northwest Atlantic upper ridging and triggers a pair of frontal cyclones by 180 hours...one near 35N-70W...another near 40N-58.5W.
0000Z ECMWF Model Run...For Tropical Storm Gonzalo...shown to cross the southern Lesser Antilles perhaps as a weak tropical cyclone just before 48 hours...weakens to a tropical wave just north of the northwest Venezuela coast near 13.5N-70W in 72 hours. For Tropical Storm Hanna...additional strengthening shown until landfall just south of Matagorda Bay Texas just after 24 hours...continues west-southwestward inland across south Texas and into northeast Mexico where it loses its identity by 72 hours. For area of interest #1...organizes into possible tropical cyclone while moving toward the Lesser Antilles near 14.5N-56W in 120 hours...shown to strengthen into a strong tropical cyclone in the northeastern Caribbean Sea by 144+ hours.
0600Z GFS Model Run...For Tropical Storm Gonzalo...shown to cross the southern Lesser Antilles as a possibly strong compact tropical cyclone in 42 hours while centered near 13.5N-60.5W...weakens to a tropical wave in the central Caribbean Sea near 70W longitude in 84 hours. For Tropical Storm Hanna...no strengthenign shown till landfall over far south Texas in 36 hours upon which time brisk strengthening is shown...continues west into northeastern Mexico where it loses its identity in 60 hours. For area of interest #1...no tropical cyclone formation shown.
0600Z NAVGEM Model Run...For Tropical Storm Gonzalo...shows strengthening into a strong tropical cyclone...moves into the central Lesser Antilles at high strength while passing near 15N-60.5W in 48 hours...moves into the south coast of Puerto Rico as a strong tropical cyclone in 78 hours...continues west-northwestward over the north coast of the Dominican Republic in 90 hours...as a weaker tropical cyclone disrupted by earlier land interaction moves across the eastern Bahamas in 108 hours...reaches the waters between Cuba and the Bahamas while restrengthening at 120 hours. For Tropical Storm Hanna...additional strengthening shown till landfall just south of Matagorda Bay Texas in 36 hours...continues west-southwest into central Mexico where it loses its identity in 96 hours. For area of interest #1...no tropical cyclone formation shown.