*******Note that forecast 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.*********
...UPDATE...MONDAY AUGUST 19 2024 11:31 PM EDT...
The surface and upper air charts that were not previously included in this update (to ensure the update was released in a timely manner) have now been added.
Hurricane Ernesto has begun to weaken due to the combined effects of southwesterly shear and cooler water temperatures... and as of 11 PM EDT was rated at 80 mph maximum sustained winds. The center of Ernesto is passing just offshore of southeastern Newfoundland while heavy rains and gusty winds are currently occurring over southeastern Newfoundland. Environment Canada (https://weather.gc.ca/canada_e.html) just recorded sustained winds of 37 kph (27 mph) gusting to 51 kph (32 mph) at St John's.
...MONDAY AUGUST 19 2024 2:30 PM EDT...
See Ernesto section below for an update on the northeastward-accelerating western Atlantic tropical cyclone which is brining impacts to Nova Scotia and Newfoundland.
For the tropical latitudes of the Atlantic... tropical activity has been limited by dry Saharan air. The latest tropical wave of low pressure now entering the Atlantic from Africa is departing Africa at an unusually far north location... in the vicinity of coastal Mauritania... such that it has already seen a reduction in thunderstorm activity while ingesting dry air from the north Africa Sahara desert. Further east... satellite imagery over Africa (https://www.goes.noaa.gov/FULLDISK/GMIR.JPG) shows a vigorous tropical wave of low pressure with rotation and thunderstorms at a further south location away from the north Africa Sahara desert. As such this will see if this wave has a chance at development when it later moves into the Atlantic tropical waters over the next week.
For the mid-latitudes of the Atlantic... the current upper trough and surface frontal system over eastern North America is depositing the tail end of a surface cold front across the Gulf of Mexico and western Atlantic. The western Atlantic portion of the surface front is not expected to undergo tropical development as southwesterly shear levels remain elevated as the upper trough pushes offshore. For the Gulf of Mexico... over the next week... a portion of the current western North America upper trough energy is forecast to make an anticyclonic revolution around the periphery of the current central North America upper ridge... taking the energy south across the eastern United States as a shortwave upper trough through through day 4 then west across the Gulf of Mexico and into the Texas/Mexico border region through day 7 as an upper vortex. Will watch to see if divergence between the periphery of the forecast upper vortex and surrounding upper flow results in a tropical disturbance along the decaying Gulf of Mexico portion of the surface front.
HURRICANE ERNESTO... On Sunday Ernesto... located in the northwestern Atlantic... ventured on a more north and less east track while bumping into the Atlantic surface ridge. At the same time an expansive warm core upper ridge developed over Ernesto due to surface warm southerly flow ahead of the approaching surface frontal system/upper trough over eastern North America. The expansive upper outflow environment provided by the upper ridge helped the tropical cyclone re-build thunderstorms and a small eye feature... and Ernesto became a hurricane again by 5 PM EDT Sunday. As of today the eastern North America upper trough and once-overhead upper ridge have both shifted east... now placing Ernesto in deep-layer southwesterly flow between the two upper features and Atlantic surface ridge. This has caused the northward track to regain an eastward angle. The upper-layer southwesterly flow... and also the small upper vortex to the southwest that has been chasing Ernesto while guided by the upper southwesterlies... have impinged on the southern outflow of the hurricane as seen by the thunderstorms being limited on the southern side of the small eye. Moreover the hurricane has recently crossed over the 26 deg C sea surface temperature isotherm into cooler waters. Despite these negative factors... as of 11 AM EDT the NHC has assessed Ernesto has strengthened further to 90 mph maximum sustained winds. Some of the recent increase in wind speed may be attributed to the increasingly faster northeastward track enhancing the winds on the southeast side of the center... and the increasingly fast forward heading is also parallel to the upper southwesterly flow such that the upper flow is not drastically shearing the hurricane. Also noting the estimated surface pressure has fallen further to 968 mb... therefore Ernesto's surface low pressure field may be getting enhanced by the divergence zone of the aforementioned small upper vortex. Over the next 24 hours... as Ernesto tracks into even cooler waters... the negative factors will begin to outweigh the positive factors and the hurricane is expected to transition into a gradually weakening non-tropical frontal cyclone. The gradual weakening is due to the remnant cyclone being positioned away from the upper divergence maximum of the approaching eastern North America upper trough. Models also agree that the gradually weakening remnant cyclone loses its identity to a larger frontal low that roams the North Atlantic... to be supported by the divergence zone of the approaching eastern North America upper trough.
Surf has reached the shores of Nova Scotia and Newfoundland. Within the next 12 hours... a period of heavy rainfall and strong gusty winds will reach southeastern Newfoundland. The period of strong weather over southeastern Newfoundland will be short-lived as Ernesto is now moving rapidly.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (1200Z Aug 19)... 90 mph maximum sustained wind hurricane centered in the northwestern Atlantic at 41.8N-58.5W
IOH 24 Hr Forecast (1200Z Aug 20)... Remnant frontal cyclone centered in north Atlantic at 48.8N-56W
*****National Hurricane Center (hurricanes.gov) official forecast as of 11 AM EDT************************
2-Day Position (1200Z Aug 21)... 45 mph maximum sustained wind remnant frontal low becoming absorbed by larger frontal low to the north while located at 52.2N-24.4W
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/).
0000Z (Aug 19) CMC Model Run...
**For Hurricane Ernesto… center passes just offshore of southeastern Newfoundland at 30 hours while transitioning into a non-tropical frontal cyclone... while racing east in the open North Atlantic loses identity to larger frontal cyclone to the north by 60 hours
**Tropical wave currently over central Africa moves into the eastern tropical Atlantic at 102 hours... evolves into a broad tropical low near 11.5N-41W by 162 hours
0000Z (Aug 19) ECMWF Model Run...
**For Hurricane Ernesto… center passes just offshore of southeastern Newfoundland at 30 hours while transitioning into a non-tropical frontal cyclone... while racing east in the open North Atlantic loses identity to larger frontal cyclone to the north by 72 hours while positioned just offshore of the British Isles
0600Z (Aug 19) GFS Model Run...
**For Hurricane Ernesto... center passes just offshore of southeastern Newfoundland between 21 and 24 hours while transitioning into a non-tropical frontal cyclone... while racing east in the open North Atlantic loses identity to larger frontal cyclone to the north by 72 hours while positioned just offshore of the British Isles
0600Z (Aug 19) NAVGEM Model Run...
**For Hurricane Ernesto... center passes just offshore of southeastern Newfoundland at 24 hours while transitioning into a non-tropical frontal cyclone... while racing east in the open North Atlantic loses identity to larger frontal cyclone to the north by 72 hours while positioned just offshore of the British Isles
**Tropical wave currently over central Africa moves into the eastern tropical Atlantic at 120 hours... evolves into a broad tropical low over the Republic of Cabo Verde Islands through 168 hours
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