MY 2021 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #88 (Weekend Edition)
*******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 AUGUST 23 2021 6:56 AM EDT...
Satellite image as of 0950Z. Areas of interest circled in yellow are not mentioned in the NHC tropical weather outlook. Areas circled in a green dashed line are in the NHC 5-day tropical weather outlook. Areas circled in a solid green line are in the NHC 2-day tropical weather outlook:
NHC TAFB Surface Analysis 1200Z:
GFS Model Upper-Level Winds 1200Z:
See Henri section below for an update on this system which has been affecting the northeastern United States. See area of interest #1 through #4 sections below for the latest on tropical wave activity across the Atlantic basin… area of interest #4 poses concern for affecting land areas while forecast to be near Nicaragua and Honduras in 4 to 5 days. Elsewhere… the remnants of Grace have regenerated in the eastern Pacific as Tropical Storm Marty located southwest of the Baja California peninsula… visit hurricanes dot gov (hurricanes.gov) for more info on Marty.
TROPICAL STORM HENRI (RECENTLY DOWNGRADED TO REMNANT LOW)… Satellite and Radar imagery concur the center of what was Tropical Storm Henri has stalled over southeast New York this morning after whirling beneath the north side of the upper vortex that has been steering it where the steering is neutral. Henri resembles a post-mature non-tropical frontal low that whirls beneath its parent upper trough/vortex… and thus will continue to remain weak while now aligned directly under the upper vortex where upper divergence is lacking. The upper vortex and remnant surface low of Henri are forecast to move east-northeast… bringing heavy rains with flash flooding potential from its current position over southeast New York and New Jersey to Connecticut… Rhode Island… Massachusetts… southern Vermont… southern New Hampshire… and possibly southern Maine over the next day or so. This is my final statement on Henri on this blog as it is no longer a tropical cyclone.
In closing… here are some of the strongest winds logged from National Weather Service station (in mph) over the last 24 hours as Henri passed through the region:
**Barnstable MA (Cape Cod region)…sustained 16… gust 32 (8:56 AM EDT)
**Boston MA… sustained 24… gust 37 (11:54 AM EDT)
**Greenfield MA… sustained 14… gust 30 (3:52 PM EDT)
**Newport RI… sustained 30… gust 48 (11:53 AM EDT)
**New London CT… sustained 31… gust 46 (10:56 AM EDT)
**Hartford CT… sustained 22… gust 43 (2:53
**Bridgeport CT… sustained 20 … gust 30 (7:52 PM EDT)
**Stamford CT… sustained 18… gust 29 (6:56 PM EDT)
**Montauk NY (East end of Long Island)… sustained 24… gust 43 (11:54 AM EDT)
**Islip NY (central Long Island)… sustained 21… gust 32 (10:56 AM EDT)
**New York City NY… sustained 7 (2:51 PM EDT)
**Peekskill NY… sustained 13… gust 23 (7:45 PM EDT)
**Nashua NH… sustained 9… gust 21 (11:56 AM EDT)
**Concord NH… sustained 10… gust 26 (11:51 AM EDT)
**Keene NH… sustained 10…. gust 21 (6:56 PM EDT)
**Bennington VT… sustained 9… gust 22 (6:54 PM EDT)
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (0000Z Aug 23)… 35 mph maximum sustained wind tropical depression centered over northwestern Connecticut at 41.7N-72.8W
IOH 24 Hr Forecast (0000Z Aug 24)… Remnant low centered over the Massachusetts/ Vermont/ New Hamsphire border at 42.5N-72.5W
AREA OF INTEREST #1… The tropical wave of low pressure in the central Atlantic has lost all of its thunderstorm activity and surface inflow to the dominating wave to the east… area of interest #2. This is my planned final statement on this wave on this blog.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Aug 24)… 0% chance of tropical cyclone formation (central tropical Atlantic near 13N-53W)
AREA OF INTEREST #2… A rather large tropical wave of low pressure in the eastern tropical Atlantic is currently passing between 30 and 35W longitude. The wave continues to have a broad northern circulation and a defined low pressure spin with somewhat organized thunderstorm activity on its southeast side that was located near 15N-32.5W as of 0000Z early this morning. Some computer model runs suggest this wave has some development potential while moving west-northwest into the open central Atlantic… and based on the persisting low pressure spin notes above I have to agree. The north angle in track is expected due to a surface ridge weakness being induced by the divergence zones of some of the current west Atlantic upper vorticity string and also the current North Atlantic upper trough. By day 3 even though the surface ridge weakness closes… some of the west Atlantic upper vorticity string will coalesce into a vortex near the Bahamas whose divergence zone will continue a surface ridge weakness to the west… and thus a north angle in track is still expected. The steering forecast becomes more erratic and fuzzy by days 4 and 5 as the upper trough of the current east Canada frontal low will be in the North Atlantic… driving a cold front that creates a surface ridge weakness that traps this system into a north turn. If this forecast for this weakness shifts however… the forecast track by days. 4 and 5 may need adjustments. In the meantime my overall forecast track points for the first 4 days are shifted south and east due to the current position of the wave’s defined low pressure spin relative to my prior forecast.
Due to the definition of the surface low pressure spin and its thunderstorm activity…. my odds of development are higher than the NHC as of this writing. The models also show some of the west Atlantic upper vorticity string coalescing into a nearby upper vortex to the west. The upper vortex may prove to be helpful rather than disruptive by creating an upper divergence zone on its east side as it also retrogrades westward out of the way due the current west Atlantic upper ridging forecast to expand across the mid-latitudes of the Atlantic… which would prevent the upper vortex from shearing this system. Also the upper vortex is forecast to gradually weaken while cut-off from high-latitude cold air… and this system is forecast to end up underneath the low shear and upper outflow of the mid-latitude upper ridging later in the forecast period. In regards to the dry Saharan air… the southerly flow on the east side of the broad northern circulation of the tropical wave has continues to create a visible clearing in the dry air by pushing the dry air northward and away… which is also favorable for the seedling surface low pressure spin on the southeast side of the wave. By day 5… I stop raising development odds and keep them at 50% as the current forecast track would take this system toward the north side of the mid-latitude upper ridging where northwesterly upper winds may shear this system.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Aug 24)… 20% chance of tropical cyclone formation (central tropical Atlantic near 17.5N-38W)
IOH 48 Hr Outlook (0000Z Aug 25)…30% chance of tropical cyclone formation (central Atlantic near 21N-44W)
IOH 72 Hr Outlook (0000Z Aug 26)…40% chance of tropical cyclone formation (central Atlantic near 23N-51W)
IOH 96 Hr Outlook (0000Z Aug 27)… 50% chance of tropical cyclone formation (central Atlantic near 25N-57.5W)
IOH 120 Hr Outlook (0000Z Aug 28)… 50% chance of tropical cyclone formation (southeast of Bermuda near 30N-61.5W)
AREA OF INTEREST #3… The tropical wave of low pressure just offshore of Western Africa appeared to produce a low pressure spin with thunderstorms near 7.5N-17.5W through much of the day on Sunday… but as of this morning the thunderstorm activity is less organized and off to the southwest of that spin. Due to its South position away from dry Saharan air and favorable widespread tropical upper ridging with low shear and upper outflow as the wave continues west… I have introduced it as an area of interest for tropical development… but keep odds of development on the low side as the thunderstorm activity is not currently organized as noted above.
IOH 24 Hr Outlook (0000Z Aug 24)… 10% chance of tropical cyclone formation (eastern tropical Atlantic near 8.5N-22.5W)
IOH 48 Hr Outlook (0000Z Aug 25)… 15% chance of tropical cyclone formation (eastern tropical Atlantic near 10N-27.5W)
IOH 72 Hr Outlook (0000Z Aug 26)… 20% chance of tropical cyclone formation (eastern tropical Atlantic near 10.5N-32.5W)
IOH 96 Hr Outlook (0000Z Aug 27)… 20% chance of tropical cyclone formation (eastern tropical Atlantic near 11N-37.5W)
IOH 120 Hr Outlook (0000Z Aug 28)… 20% chance of tropical cyclone formation (central tropical Atlantic near 11.5N-42.5W)
AREA OF INTEREST #4…A tropical wave of low pressure is currently crossing the Lesser Antilles and entering the eastern Caribbean Sea with increasing but disorganized thunderstorm activity. Models have converged on developing this wave moves across the southern Caribbean and encounters an expanding upper ridge with low shear and upper outflow to develop in the wake of the current west Atlanfic upper vorticity near the Bahamas as the vorticity weakens while remaining cut-off from high-latitude cold air. I have assigned higher odds of development than the NHC as of this writing due to the marked model support showing development potential… Interests in Nicaragua and Honduras should be aware of this wave as it will be in the region by days 4 and 5.
IOH 24 Hr Outlook (0000Z Aug 24)… 0% chance of tropical cyclone formation (southeastern Caribbean Sea near 12.5N-67.5W)
IOH 48 Hr Outlook (0000Z Aug 25)…0% chance of tropical cyclone formation (South-Central Caribbean Sea near 13N-72.5W)
IOH 72 Hr Outlook (0000Z Aug 26)…20% chance of tropical cyclone formation (South-Central Caribbean Sea near 13N-77.5W)
IOH 96 Hr Outlook (0000Z Aug 27)… 30% chance of tropical cyclone formation (just east of northern Nicaragua near 14N-82W)
IOH 120 Hr Outlook (0000Z Aug 28)… 40% chance of tropical cyclone formation (north coast of Honduras near 15.7N-86W)