MY 2021 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #48
*******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.**********
...MONDAY JULY 12 2021 7:25 PM EDT...
The low-latitudes of the tropical Atlantic remain less favorable for tropical cyclone development due to suppressing upper vorticity in the western and central tropical Atlantic as well as dry Saharan air. However in the northwest Atlantic…conditions are less hostile for development…and a surface frontal zone is forecast to shift southeast into the region which may help seed development in the waters north or northeast of Bermuda in the coming days. See area of interest #1 section below for details.
AREA OF INTEREST #1…A rather lengthy continuous surface frontal zone separating cool air to the north and warm air to the south stretches from the current frontal low over the central US to the remnant low of Elsa located just offshore of southeast Greenland. The portion of the surface front currently over the northeast US is forecast to become pushed southeast into the open northwest Atlantic due to a strengthening surface ridge to the north to be supported by the western convergence zone of the shortwave upper trough currently over eastern Canada (the surface ridge and western convergence zone of the upper trough will strengthen as the trough has been amplifying in response to strong upper ridging associated with another heat wave ongoing over western North America). Water temps in the region are running at a warm 26 deg C…and upper-level winds could become conducive for tropical development over the fragment of the surface front as the north cell of the western North America upper ridge (currently over central Canada) will move offshore…helping to create a large upper anticyclonic ridge in the northwest Atlantic with low shear and upper outflow as it merges with the other upper ridge cell currently offshore of North Carolina.
I have initiated the portion of the surface front as an area of interest as the more reliable GFS and ECMWF models still show a defined surface low pressure forming along the front (meanwhile the surface low pressure signature in recent NAVGEM and CMC runs is not as defined). However I have low 10% odds of development at this time as the GFS and ECMWF forecast surface low pressure area is not particularly strong. My forecast positions in the Outlook below tend to be west of the model runs…toward 65W longitude…as this is where the forecast center of the favorable upper anticyclonic ridge is located. Odds are kept at 0% where the forecast position is over waters below 26 deg C…over the next 24 hours…then again at 96 hours when whatever surface low pressure area forms will be shifting north while rounding the west side of the strengthening surface ridge mentioned in the previous paragraph. At 96 hours I end the Outlook as the forecast track beyond that point would continuously bring this system into cooler waters.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1800Z Jul 13)…0% chance of tropical cyclone formation (offshore of the northeastern US near 39N-68W)
IOH 48 Hr Outlook (1800Z Jul 14)…10% chance of tropical cyclone formation (northwest Atlantic near 37.5N-65W)
IOH 72 Hr Outlook (1800Z Jul 15)…10% chance of tropical cyclone formation (northwest Atlantic near 38N-65W)
IOH 96 Hr Outlook (1800Z Jul 16)…0% chance of tropical cyclone formation (northwest Atlantic near 42N-60W)
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z CMC Model Run...
**For area of interest #1...surface frontal low becomes cut-off near 37.5N-62W at 36 hours…dissipates at 54 hours.
1200Z ECMWF Model Run...
**For area of interest #1...surface frontal low becomes cut-off near 39N-59W at 24 hours…drifts southwest to 35N-65W by 72 hours…weakens to a surface trough just northwest of Bermuda at 120 hours.
1200Z GFS Model Run...
**For area of interest #1...surface frontal low becomes cut-off near 39N-62.5W at 24 hours…drifts south to 36N-61W by 72 hours…while drifting north weakens to a surface trough near 38.5N-61W
1200Z NAVGEM Model Run...
**For area of interest #1...no defined cut-off frontal low pressure shown in the northwest Atlantic