Since 2012 on the now retired Weather Underground blogs, I have been posting annotated "birdseye view" charts of the Atlantic basin, with a detailed explanation and forecasting that references the chart. From there you may know me as "NCHurricane2009." While I now do these "birdseye view" posts here, I will continue to do comments at Yale Climate Connections via Disqus where the former Weather Underground community has moved to. Feel free to reply to me there, at my Disqus feed at this link, or via e-mail at 

  • NCHurricane2009


*******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 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 dot gov) for the latest watches/warnings and official forecasts on active tropical cyclones.**********

...SATURDAY OCTOBER 26 2019 5:09 PM EDT...

See Tropical Storm Pablo section below for the only active tropical cyclone in the Atlantic basin. See remnants of Olga section below for an update on Tropical Storm Olga which has transitioned into a frontal cyclone over the central United States. See area of interest section below for details on another storm expected to form at a location west of the Azores in the next couple of days. Elsewhere...will be on the lookout in the next couple of days for the formation of a tropical disturbance in the southern Gulf of Mexico and northern Yucatan peninsula beneath the low shear/upper outflow environment of the upper ridge axis in the region. Activity here could be boosted by the cold front being driven into the area by the remnant circulation of Olga. In addition...a tropical wave to the the western Caribbean interacting with the eastern divergence zone of a weakening upper vortex that once belonged to a cut-off upper trough to produce widespread thunderstorms...and any tropical low pressure that forms here would continue westward and add to the weather in the southern Gulf/northern Yucatan region.

REMNANTS OF OLGA...Tropical Storm Olga has completed the transition to a frontal cyclone in the last 24 hours while moving across the south-central United States from the western Gulf of Mexico...and is moving into the Great Lakes region of North America while maintaining strength from the supportive divergence zone of the upper trough approaching from the central United States. In the next 24 hours...expect Olga to produce heavy flash flooding rain and gusty potentially damaging winds in the Great Lakes region and into parts of southeastern Canada...see the special messages section at the top of the home page of this website for more details on the affected land areas and expected timing. By 48 hours...the remnant frontal cyclone of Olga and its supporting upper trough are expected to lose their identity in the much larger frontal cyclone and upper trough currently heading to the Hudson Bay region of central Canada. This is my final statement on Olga on this blog as it is no longer a tropical feature.

TROPICAL STORM PABLO...Once again including a zoomed-in inset in the above birdseye chart to show where tiny Tropical Storm Pablo is within the much larger frontal cyclone surrounding it. Even though the tropical storm is over mild water temeratures...the instability to drive Pablo's thunderstorm core is induced by the cold upper air temperatures of the overhead upper trough supporting the frontal cyclone. Pablo can be thought of as a tiny chimney of spinning thunderstorms within the much larger frontal cyclone surrounding it...with its latent heat release producing a small warm core upper ridge with supporting outflow just beneath the much larger overhead upper trough. In the next 24 hours...wind shear should increase as the overhead upper trough loses its identity to the much larger upper trough of area of interest #1...which should throw the chimney out of vertical alignment...and not to mention the waters temps at the 24 hour forecast point are much colder such that Pablo's thunderstorms should be diminished. Therefore I forecast Pablo to be downgraded into a remnant frontal cyclone...or alternatively lose its identity inside the much larger frontal cyclone surrounding it. Pablo is finally hooking northward in its eastward track...and this is expected to continue as Pablo and the surrounding frontal cyclone will be swung around the rapdily developing storm in area of interest #1...and my forecast track is where I assess in the latest GFS model run to be the location of the supportive divergence region on the east side of the current overhead upper trough and absorbing upper trough of area of interest #1. My updated forecast track is adjusted south and east to account for Pablo's current position and heading. The center of the frontal cyclone surrounding Pablo is actually where I forecasted Pablo would be for Pablo's more southeast location probably means that it has decoupled from the frontal cyclone's center and is now being swung around its center...which will take the tiny tropical storm just east of Sao Miguel in the Azores and perhaps this island will see the western rain bands of Pablo's tiny core in the next few hours. The risk of gusty winds and coastal sea swells will reduce in the Azores in the next 24 hours as Pablo and the surrounding frontal cyclone move away...but will later increase again from area of interest #1...see area of interest #1 section below for more details.

****** forecast. Visit (hurricanes dot gov) for official forecast***********

0 Hr Position (1800Z Oct 26)...60 mph maximum sustained tropical storm centered just south of Sao Miguel at 36.3N-25.6W

IOH 24 Hr Forecast (1800Z Oct 27)...Frontal cyclone centered northeast of the Azores at 43N-20W

AREA OF INTEREST #1...A surface cold front is currently pivoting eastward across the northwestern Atlantic waters southeast of Newfoundland while driven by a broad frontal low pressure and its upper trough emerging into the northwestern Atlantic from eastern Canada. Computer models continue to agree a very large and intense frontal cyclone will form along this front over the next couple of days while settling at a location west of the Azores islands. The genesis of this storm is expected to be from an impressive upper divergence zone to form on the east side of the aforementioned upper trough as that trough soon enters the northern Atlantic and amplifies into a rather impressive and large cut-off upper vortex. This will be in response to amplification of upper ridging over eastern Canada in the warm sector of a strong frontal cyclone currently heading into the Hudson Bay region of central Canada. Forecast positions of this storm shown in the outlook below are based on the location of the divergence zone of the amplifying upper trough through 24 hours from this afternoon's 1800Z GFS model run...followed by an assumption that this system whirls into the center of the cut-off upper vortex from 48 to 96 hours. As short-term forecast positions are adjusted northwestward in response to the latest evolution of the upper trough/cut-off upper vortex shown in the GFS...followed by a northeastward adjustment in the long range as the cut-off upper vortex is forecast to de-amplify back into a trough while kicked by the nearing upper trough of the central Canada frontal cyclone. I have peak odds of subtropical cyclone formation only at 20% as the updated forecast track puts the center of this system only over 20 deg C water...thus the formation of any thunderstorms will be strongly dependent on the cold upper air temperatures of the forecast cut-off upper vortex. Odds are dropped back to 0% by 120 hours due to cooler water temperatures along the forecast track. Regardless of acquisition of tropical characteristics or not...this storm is expected to bring large sea swells in the north-central Atlantic reaching the shores of the Azores islands...with the circulation possibly being large enough to deliver gusty winds to the islands in 2 to 4 days (48 to 96 hours) even while centered well west of the islands.

****** outlook. Visit (hurricanes dot gov) for official outlook***********

IOH 24 Hr Outlook (1800Z Oct 27)...0% chance of subtropical cyclone formation (central Atlantic near 40N-41W)

IOH 48 Hr Outlook (1800Z Oct 28)...10% chance of subtropical cyclone formation (central Atlantic near 40N-38W)

IOH 72 Hr Outlook (1800Z Oct 29)...20% chance of subtropical cyclone formation (central Atlantic near 40.5N-36W)

IOH 96 Hr Outlook (1800Z Oct 30)...10% chance of subtropical cyclone formation (central Atlantic near 42N-35W)

IOH 120 Hr Outlook (1800Z Oct 31)...0% chance of subtropical cyclone formation (northeastern Atlantic near 48N-26W)

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