BIRDSEYE VIEW POSTS

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 IOHurricanes@outlook.com 

 
 
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MY 2021 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #82

*******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 16 2021 10:03 PM EDT...

See Fred... Grace... and Henri (formerly tropical depression eight) sections below for an update on all active tropical cyclones in the Atlantic basin. All three are currently or are forecast to bring impacts to land areas in the coming days.


In addition...satellite imagery suggests the recent round of tropical waves emerging from Africa are being suppressed by dry Saharan air as they enter the Atlantic. None of the models forecast development from these waves at this time. Of note however… thunderstorm activity in the region has increased over the last 24 hours… therefore will watch to see if any of the waves become an area of Interest.


TROPICAL STORM FRED... Prior to this afternoon’s landfall on the western Florida panhandle… Fred pulled off a decent strengthening trend while the surface center regenerated northeastward into its sheared off thunderstorm mass. It also appeared the latent heat release of this mass built enough warm core anticyclonic flow overhead to reduce the light southwesterly shear that was being imparted by the upper vorticity over the north-central US. Fred will continue northward inland across the eastern US in deep-layer southerly flow between the upper vorticity and southwest side of the eastern US surface ridge. My updated forecast track is adjusted northeast due to the northeast regeneration of the surface center. After 24 hours… Fred could transition into a remnant non-tropical frontal low that turns north-northeast toward the northeast US coast while supported by the eastern divergence zone of the upper vorticity.


Tropical storm force winds have been in progress over the central Florida panhandle… southeast Alabama… and now southwest Georgia as the track of Fred has been more to the east. Interests here should be sheltered indoors until Fred and it’s winds weaken further from the landfall. Here are some of recent National weather service station reports of wind (in mph).

**Panama City FL...sustained 36… gust 48 (4:56 PM EDT)

**Apalachicola FL...sustained 49… gust 63 (4:53 PM EDT)

**Tallahassee FL...sustained 28… gust 46 (6:53 PM EDT)

**De Funiak Springs FL...sustained 9… gust 23 (8:53 PM EDT)

**Perry FL...sustained 18… gust 23 (7:35 PM EDT)

**Dothan AL...sustained 29… gust 44 (8:53 PM EDT)

**Mobile AL...sustained 9 (now)

**Bainbridge GA… sustained 35… gust 48 (6:53 PM EDT)

**Albany GA… sustained 16… gust 25 (now)


Based on the latest Doppler radar… Fred and the surface frontal zone to the north will produce heavy rains with flash flooding potential across Georgia… far east Alabama… the western Carolinas… and mountainous terrain of Virginia and West Virginia within the next 24 hours.

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

0 Hr Position (1800Z Aug 16)… 60 mph maximum sustained wind tropical storm centered over the western Florida panhandle at 29.9N-85.3W

IOH 24 Hr Forecast (1800Z Aug 17)… Remnant low centered over northwestern Georgia at 33.8N-84.8W


TROPICAL DEPRESSION GRACE... Despite the NHC aircraft recon locating a better defined center along the south coast of Haiti… and despite the thunderstorm activity being enhanced by split flow upper divergence between easterlies on the south side of west Atlantic upper ridging and westerlies on the south side of west Atlantic upper vorticity… Grace has still struggled to rise back into tropical storm status. This could be due to outflow suppression to the north caused by the upper vorticity which is trying to shift southwest into Grace’s path due to the strength of the west Atlantic upper ridge. Therefore I forecast Grace to stay a tropical depression for the next 48 hours. After that time the GFS shows the latent heat release of the thunderstorms break through the axis of the cool core upper vorticity… and this is when I begin to forecast Grace to become a tropical storm and then a hurricane as it moves across the western Gulf of Mexico… something many recent model runs show and the latest NHC intensity forecast shows. However I forecast a stronger hurricane than shown in the NHC forecast as of this writing due to the rather favorable widespread upper ridging forecast across the Gulf which will promote low shear and upper outflow… in addition to the fact waters in the Gulf are running at a very warm 29 to 30 deg C.


The track forecast is steady to the west-northwest through day 5 along the southwest edge of the surface ridge over the eastern US which will still be expansive into the Gulf of Mexico as it moves into the Atlantic. The north angle is sharper for the first 24 hours due to the ridge weakness of Fred… followed by a more west angle at 48 hours due to the ridge recovery once Fred weakens or pulls away to the north… followed by a more north angle again by 72+ hours due to the ridge weakness over western North America to be induced by a pair of western North America frontal systems. The 1200Z GFS was a southern outlier and showed landfall in central Veracruz by day 5 as the GFS forecasts the warm upper ridging in the Gulf to expand in the warm sector of the second of the two western North America frontal systems… with Grace being strong/tall enough to be deflected on a south angle from the expanding upper ridge. My forecast and other model runs are trending toward northern Veracruz or Tamaulipas for the day 5 landfall. However if the GFS scenario plays out… the forecast track will need southern adjustment in the long range.


With these forecast updates:

**Additional heavy rains and flooding risk remains for Haiti through tonight.

**Heavy rains and flash flooding are possible tomorrow for Jamaica and eastern Cuba… and possible Wednesday for the remainder of Cuba and the Cayman Islands. Tropical storm watches and warnings are in effect here as of this writing… prepare now for possible gusty winds and rough surf at the coast in case Grace does strengthen earlier than forecast. Preparations must be completed quickly for eastern Cuba and Jamaica as Grace is nearing the area.

**I recommend interests in the northern Yucatan peninsula of Mexico begin preparing early for possible tropical storm conditions (heavy rains… coastal rough seas… and gusty winds) expected to arrive by Thursday

**Interests in Tamaulipas and Veracruz on the east Mexico shoreline should be aware of Grace as it could move into the region as a strengthening hurricane late this week and into the weekend.

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

0 Hr Position (1800Z Aug 16)… 35 mph maximum sustained wind tropical depression centered located over the southeast coast of Haiti at 17.9N-72.4W

IOH 24 Hr Forecast (1800Z Aug 17)… 35 mph maximum sustained wind tropical depression centered between eastern Cuba and Jamaica at 19N-77.5W

IOH 48 Hr Forecast (1800Z Aug 18)… 35 mph maximum sustained wind tropical depression centered just west of the Cayman Islands at 19.8N-82.5W

IOH 72 Hr Forecast (1800Z Aug 19)… 45 mph maximum sustained wind tropical storm centered over the northeast Yucatan peninsula coast at 21N-87.5W

IOH 96 Hr Forecast (1800Z Aug 20)… 70 mph maximum sustained wind tropical storm centered over the southwest Gulf of Mexico at 22N-92.5W

IOH 120 Hr Forecast (1800Z Aug 21)… 85 mph maximum sustained wind hurricane centered over the northeast Mexico coast (southern Tamaulipas) at 23N-97.5W


TROPICAL DEPRESSION EIGHT (RECENTLY UPGRADED TO TROPICAL STORM HENRI).. Tropical depression eight now southeast of Bermuda has recently strengthened to tropical storm Henri. The center of Henri is located near 31N-62.9W with the thunderstorm activity remaining a bit displaced to the south of the center due to light northerly shear induced by the east edge of the upper ridging currently in the west Atlantic

The forecast track of this system is adjusted south and east in the short-term due to the current position of the storm. The track is expected to be a slow anti-cyclonic loop around the island of Bermuda while pushed around by the eastern US surface ridge as that ridge moves offshore into the northwest Atlantic. The slow speed in the track is due to the drag of the Atlantic surface ridge to the east which will try to oppose the force applied by the nearing eastern US surface ridge. By 96 hours the upper vorticity over the north-Central US will be heading into the northwest Atlantic... creating a surface ridge weakness with its eastern divergence zone that should carry Henri northeast and out to sea. However my longer term forecast points are adjusted more west as the upper vorticity is forecast to be more amplified… which will provide a more southerly steering flow in the upper levels (which Henri will be coupled to as a stronger/taller tropical cyclone) and thus delay the eastward turn. Regarding intensity… I forecast a ramp up to Hurricane strength as the west Atlantic upper ridging is forecast to shift east over Henri which will help end the shear and produce an excellent upper outflow environment. In addition to raising the intensity forecast due to Henri becoming a tropical storm sooner than I anticipated… I have also slowed the weakening rate by days 4 to 5 as the shear levels are lower due to the approaching upper vorticity being more amplified than shown before. In fact Henri could maintain strength or even strengthen in that window of time if the current upper wind forecast holds… and future adjustments to the intensity forecast may be needed.


Interests in Bermuda should be finishing preparations for Henri even though the forecast track is further from the island… in case the track wobbles back toward the island in the currently weak and potentially erratic steering with Henri being forced around by two surface ridges as noted in the prior paragraph. If Henri stays along the current forecast or changes a little… Bermuda will still get coastal sea swells. Coastal sea swells and rip currents will also be possible for the US east coast should Henri strengthen as forecast below.

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

0 Hr Position (1800Z Aug 16)…40 mph maximum sustained wind tropical depression centered southeast of Bermuda at 31N-62.9W

IOH 24 Hr Forecast (1800Z Aug 17)… 60 mph maximum sustained wind tropical storm centered south of Bermuda at 30.2N-65W

IOH 48 Hr Forecast (1800Z Aug 18)… 80 mph maximum sustained wind hurricane centered southwest of Bermuda at 31N-67W

IOH 72 Hr Forecast (1800Z Aug 19)… 95 mph maximum sustained wind hurricane centered in the western Atlantic near 33N-69W

IOH 96 Hr Forecast (1800Z Aug 20)… 90 mph maximum sustained wind hurricane centered in the northwestern Atlantic near 37N-69W

IOH 120 Hr Forecast (1800Z Aug 20)… 85 mph maximum sustained wind hurricane centered in the northwestern Atlantic near 38.5N-66W


...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 Tropical Storm Fred...after landfall the remnant low transtions into a frontal low pressure...which reaches the Massachusetts coast by 120 hours.

**For Tropical Depression Grace... initialized as a tropical wave of low pressure over southern Haiti... regains tropical storm strength over the Cayman Islands at 42 hours...becomes a compact and and strong tropical storm while passing between the west tip of Cuba and northeast tip of the Yucatan peninsula at 66 hours... makes landfall in northeast Mexico just south of the Texas border at 114 hours as a compact hurricane.

**For tropical depression eight... loops around Bermuda... opens to a surface trough of low pressure northwest of Bermuda near 35N-67W at 102 hours.

1200Z ECMWF Model Run...

**For Tropical Storm Fred... after landfall the remnant low transtions into a frontal low pressure...which reaches southeastern New York state by 96 to 120 hours.

**For Tropical Depression Grace... initialized as a tropical wave of low pressure over southern Haiti... at 24 hours becomes a compact tropical storm between Jamaica and eastern Cuba... at 48 hours becomes a compact hurricane over the western Cayman Islands... moves across the northeastern Yucatan as a compact hurricane at 72 hours... makes landfall over east-central Mexico at 120 hours as a weakening tropical storm.

**For tropical depression eight... becomes a tropical storm just south of Bermuda near 30.5N-64.5W at 24 hours... weakens to a remnant surface trough of low pressure between Bermuda and the US east coast near 32.5N-71W at 96 hours.

**Strong tropical wave of low pressure forecast to emerge from Africa at 72 hours... broad low pressure spin of wave passes over the Republic of Cabo Verde Islands between 96 and 120 hours.


1200Z GFS Model Run...

**For Tropical Storm Fred...post-landfall remnant low dissipates over northern Georgia at 33 hours.

**For Tropical Depression Grace... initialized as a tropical wave of low pressure over southern Haiti... re-establishes a closed circulation just west of the Cayman Islands at 54 hours... rapidly intensifies into a compact and strong tropical storm while approaching landfall in the northeastern Yucatan peninsula at 69 hours... moves west-southwest across the southwestern Gulf while strengthening further into a hurricane and makes landfall over east-central Mexico near 20N-96W at 123 hours.

**For tropical depression eight... strengthens into a tropical storm in next 3 hours... becomes a strong tropical storm just south of Bermuda near 31N-65W at 33 hours... weakens to a tropical depression between the US east coast and Bermuda at 108 hours near 33.5N-71W... tropical depression located near 35.5N-69.5W at 120 hours.

**Strong tropical wave of low pressure forecast to emerge from Africa at 78 hours... broad low pressure spin of wave passes over the Republic of Cabo Verde Islands at 108 hours... center of spin located near 15N-28W at 120 hours.


1200Z NAVGEM Model Run...

**For Tropical Storm Fred... after landfall the remnant low transtions into a frontal low pressure...which reaches coastal New Jersey and Long Island New York by 120 hours.

****For Tropical Depression Grace...initialized as a tropical wave of low pressure over southern Haiti...not forecast to regain tropical storm strength while moving west-northwest over the next few days...remnant wave of Grace makes landfall at the Texas/Mexico border at 120 hours.

**For tropical depression eight... loops around Bermuda... opens to a surface trough of low pressure west-northwest of Bermuda near 32.5N-67.5W at 96 hours.

**Strong tropical wave of low pressure forecast to emerge from Africa at 90 hours... broad low pressure spin of wave passes over the Republic of Cabo Verde Islands at 108 hours... center of spin located near 15N-28W at 120 hours.

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