BIRDSEYE VIEW POSTS

Since 2012 on the Weather Underground (www.wunderground.com) 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 via Disqus on Weather Underground at www.wunderground.com/cat6. You can see my Disqus feed at this link for my latest comments. Feel free to reply to me with your disqus account or e-mail at IOHurricanes@outlook.com 

 
 
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MY 2020 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #103

*******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.**********


...WEDNESDAY AUGUST 26 2020 1:40 PM EDT...

See Hurricane Laura section below for the only currently active tropical cyclone in the Atlantic basin. See area of interest section below for an eastern Atlantic tropical wave of low pressure being monitored for tropical cyclone formation. Elsewhere...another tropical wave of low pressure emerging from the west coast of Africa and into the eastern tropical Atlantic has become less active and organized compared to yesterday. Therefore not adding this feature as an area of interest for tropical development at this time.


MAJOR HURRICANE LAURA...Overnight...Laura developed a tight core with a well-defined eye...and the surrounding thunderstorm bands once biased to the south of the center have become symmetrically distributed around the increasingly defined eye. Not suprisingly aircraft reconaissance throughout the morning horus has found that Laura has already rapidly intensified into a major category 3 hurricane. The increased symmetry of the thunderstorm bands around the center indicates Laura has moved directly below the expansive western Atlantic upper ridge axis instead of being south of it where northerly winds shear was previously having some negative effect on the storm...and given the rather warm 30 deg C Gulf of Mexico waters it wouldn't suprise me if Laura becomes a 150 mph or higher maximum sustained wind category 4 or 5 hurricane later today.


Laura is a touch southwest of my previous forecast track...but given the current northwest angle in track in satellite loops it appears the eye remains poised for a landfall at or very close to the Texas/Louisiana border in the next 24 hours. Thus my updated track forecast below is the same as my previous. After landfall...the central United States upper trough currently drawing Laura northwestward will be pushed eastward by another upper trough incoming from western Canada...which should quickly curve Laura more eastward in track toward the Kentucky/southern Ohio valley/Appalachian mountain region as it transitions into a remnant low supported by the eastern divergence zone of the eastward-shifting upper trough. It is interesting to note that the 0000Z CMC and 0600Z GFS dissipate Laura's remnant low before it gets to the Ohio Valley/Appalachain region...perhaps as those runs see the remnant low getting caught beneath the western convergent size of the upper trough from western Canada...while the 0000Z ECMWF and 0600Z NAVGEM shows the remnant low holding onto some vigor and then strengthening over or offshore of the northeastern United States and southeastern Canada as a frontal cyclone while those runs shows Laura's remnant low aligning with the supportive eastern divergence zone of the upper trough. Thus there is some uncertainty as to exactly which side of the upper trough Laura's remnant will engage with...thus long term uncertainty as to the fate of the remnants.


Regarding strength...above in my initial observations I have noted that Laura might exceed 150 mph maximum sustained winds as a high end category 4 or possibly category 5 hurricane later today. By tonight and tomorrow morning as the hurricane makes landfall...Laura will be near enough to the central United States cut-off upper trough such that the upper trough will begin to block the western outflow of the hurricane or perhaps shear it (in fact not far west of the hurricane and over Houston Texas for example the upper winds are southwesterly and would negatively affect Laura right now if the hurricane were located more to the northwest). My intensity forecast below assumes Laura becomes a high-end category 4 or category 5 in the next 12 hours...then by 24 hours weakens to a low end category 4 with 135 mph maximum sustained winds from the negative effect of the central United States upper trough and landfall. If this intensity forecast verifies...Laura will come into the Texas/Louisiana border region stronger than when Rita hit this region in 2005 as that hurricane made landfall at category 3. Expect life-threatening coastal storm surge flooding...damaging winds with catastrophic damage near where the eye makes landfall and just inland of the landfall area...and heavy flash flooding rains to stretch well northeastward from the landfall region. See bulletins at the home page of this site for an update on Laura's impact potential given this current outlook.

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

0 Hr Position (1200Z Aug 26)...125 mph maximum sustained wind major hurricane centered in the Gulf of Mexico south of Louisiana at 27N-92W

IOH 24 Hr Forecast (1200Z Aug 27)...135 mph maximum sustained wind major hurricane centered just inland and over the Texas/Lousiana border at 30.5N-94W

IOH 48 Hr Forecast (1200Z Aug 28)...40 mph maximum sustained wind tropical storm centered over northeastern Arkansas at 35.5N-91.2W

IOI 72 Hr Forecast (1200Z Aug 29)...Remnant low pressure centered over Kentucky/West Virginia border at 37.5N-82.5W


AREA OF INTEREST #1...A tropical wave of low pressure in the eastern tropical Atlantic appears to be located further to the west than previously thought...the latest NHC TAFB surface analysis shows the wave axis now at 35W longitude. Visible satellite pictures show spiral cloud bands around this wave axis...but thunderstorm activity on infrared satellite remains limited by dry saharan air in the region. Outside of the dry air...conditions in the tropical Atlantic will be favorable for this tropical wave to develop as a tropical upper ridge axis with low shear and upper outflow will prevail in the region. However my peak 5-day odds of tropical cyclone formation are only 10% at the present time as dry saharan air has recently had a history of hampering development in the tropical Atlantic to the east of the Lesser Antilles. These odds are lower than my previous outlook as the thunderstorm activity associated with this wave is less than 24 hours ago. Some of the current northeast Atlantic upper vorticity is getting pushed south toward the Atlantic tropics..as the current west Atlantic upper ridge is expanding into the north Atlantic due to warm air advection ahead of a vigorous frontal cyclone emerging from eastern Canada...with the expanded upper ridge pushing on the upper vorticity. However I do not expect this upper vorticity to negatively affect this tropical wave's development as the upper vorticity is forecast to retrograde rapidly westward and away around the expanded upper ridge. The 0600Z GFS shows the strong tropical wave to the east...currently emerging from western Africa...being close to this wave by 120 hours. This is also another reason I keep this wave's development odds on the low side...as I am uncertain if this wave will lose its identity to the wave to the east.

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

IOH 24 Hr Outlook (1200Z Aug 27)...0% chance of tropical cyclone formation (tropical Atlantic near 10.5N-41W)

IOH 48 Hr Outlook (1200Z Aug 27)...10% chance of tropical cyclone formation (tropical Atlantic near 11N-46W)

IOH 72 Hr Outlook (1200Z Aug 28)...10% chance of tropical cyclone formation (tropical Atlantic near 11.5N-51W)

IOH 96 Hr Oulook (1200Z Aug 29)...10% chance of tropical cyclone formation (tropical Atlantic east of the Lesser Antilles near 12N-56W)

IOH 120 Hr Outlook (1200Z Aug 30)...10% chance of tropical cyclone formation (southern Lesser Antilles near 12.5N-61W)


...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 Major Hurricane Laura...makes landfall in southeastern Texas between the Texas/Louisiana border and Houston in 30 hours...rapidly weakens to a remnant low pressure over northwestern Arkansas which dissipates by 66 hours. For area of interest #1...no tropical cyclone formatio shown.


0000Z ECMWF Model Run...For Major Hurricane Laura...makes landfall at the Texas/Louisiana border just after 24 hours...slowly weakens while located inland over southwestern Arkansas in 48 hours...remnant low pressure only gradually weakens while accelerating eastward into western North Carolina by 96 hours...rapidly intensifies as an offshore frontal cyclone southeast of Massachusetts in 120 hours. For area of interest #1...no tropical cyclone formation shown.


0600Z GFS Model Run...For Major Hurricane Laura...makes landfall at the Texas/Louisiana border in 24 hours...remnant low pressure located over northern Kentucky in 72 hours and loses its identity shortly thereafter. For area of interest #1...no tropical cyclone formation shown.


0600Z NAVGEM Model Run... For Major Hurricane Laura...makes landfall at the Texas/Louisiana border in 24 hours...remnant low pressure begins to re-intensify as a non-tropical frontal cyclone over Massachusetts in 96 hours...strong remnant frontal cyclone shown over southeastern Canada in 120 hours. For area of interest #1...no tropical cyclone formation shown.

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