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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 2023 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #10

Updated: Apr 13, 2023

*******Note that forecast 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.**********


...UPDATE...THURSDAY APRIL 13 2023 11:35 PM EDT...

Satellite image of surface low pressure over the southeastern United States as it became better organized during sunset time...taken at 2306Z:

The surface low pressure area that made landfall over the southeastern US from the Gulf of Mexico continued to strengthen and become better organized over land. Per the NHC TAFB surface analysis this system reached its lowest pressure of 998 mb while centered over central Mississippi at around 18Z and has recently begun to weaken to 1002 mb as of 00Z while now orbiting around the north side of its parent upper vortex where upper divergence is less. As discussed in the full update from 10:45 AM EDT below... conditions on the east side of the surface low favor cells of severe thunderstorms... with some severe weather risk to pivot north into the Carolinas over the next 24 hours (Check your local weather forecasts at weather.gov and local news media for the latest information on any severe weather watches/warnings to be issued).


Rainfall-wise... the most significant flooding appears to have occurred in the far eastern part of this storm system and over southeastern Florida (Fort Lauderdale and Miami region) where sustained thunderstorms produced several inches of rain yesterday which has resulted in damaging floodwaters (https://www.nytimes.com/2023/04/13/us/fort-lauderdale-flood-airport.html). As this system continues to weaken the rainfall intensity should decrease overall.


Regarding winds... because the system reached peak strength and organization over land gusty winds that spread onshore from coastal Mississippi and Alabama reached well inland across those states... extending as far northwest as southeastern Arkansas and as far northeast and east as southwestern Tennessee... western Georgia... and the Florida panhandle. The highest wind reports... gusting toward 40 mph... occurred over central Mississippi and central Alabama where a wind advisory was in effect for a few hours. The wind field tended to be lopsided toward the east as the northward acceleration of the surface low enhances the cyclonic wind field on that side... and due to the pressure gradient between the northeast side of the surface low and southwest side of a neighboring surface ridge in the region. Winds are also expected to decrease overall through tonight as the surface low continues to weaken. Here are some National Weather Service station reports of wind (in mph) from the last several hours... available at weather.gov:

**Pine Bluff AR... sustained 17... gust 25 (7:53 PM CDT)

**Memphis TN... sustained 21... gust 29 (1:54 PM CDT)

**Dyersburg TN... sustained 14... gust 23 (4:56 PM CDT)

**Nashville TN... sustained 17... gust 25 (3:50 PM CDT)

**Monroe LA... sustained 17... gust 25 (5:53 PM CDT)

**Baton Rouge LA... sustained 9... gust 23 (11:53 AM CDT)

**Jackson MS...sustained 15...gust 23 (4:53 PM CDT)

**Louisville MS... sustained 26... gust 37 (2:56 PM CDT)

**Greenwood MS... sustained 13... gust 23 (8:53 PM CDT)

**Clarksdale MS... sustained 22... gust 30 (3:35 PM CDT)

**Biloxi MS... sustained 28... gust 35 (6:55 AM CDT)

**Mobile AL... sustained 21... gust 39 (6:53 AM CDT)

**Demopolis AL... sustained 24... gust 40 (12:35 PM CDT)

**Tuscaloosa AL... sustained 21... gust 40 (2:53 PM CDT)

**Birmingham AL... sustained 16... gust 28 (1:53 PM CDT)

**Montgomery AL... sustained 21... gust 37 (10:53 AM CDT)

**Huntsville AL... sustained 17... gust 33 (4:53 PM CDT)

**Dothan AL... sustained 18... gust 29 (9:53 AM CDT)

**Panama City FL... sustained 25... gust 32 (6:55 AM CDT)

**Atlanta GA... sustained 16... gust 25 (9:53 PM EDT)

**Brunswick GA... sustained 14... gust 25 (11:53 AM EDT)


...THURSDAY APRIL 13 2023 10:45 AM EDT...

Pre-season Gulf of Mexico subtropical disturbance making landfall on the Mississippi coast... its potential for subtropical cyclone formation has ended as a result... see area of interest #2 section below for more information. For now will be ending daily updates on the Atlantic tropics... and will resume updates at the start of the Atlantic Hurricane season in June or if another pre-season disturbance develops prior to then.


As done on this site starting last year... I will be sequentially numbering up areas of interest for possible Atlantic tropical development throughout the year... resetting back to #1 at the start of each year. This scheme is so that each area of interest retains a numeric identity from update to update... which reduces confusion when simultaneous areas of interest begin and end when tropical activity increases during the Atlantic Hurricane Season. The current area of interest is tagged #2 as the first was tagged in late January (see earlier posts #1 through #4 on the home page of this site).


AREA OF INTEREST #2... The subtropical disturbance in the northern Gulf of Mexico... consisting of an upper vortex over Louisiana whose southeastern divergence zone triggered a surface low pressure spin-up over northern Gulf waters... is now seeing its surface low pressure center making landfall on the Mississippi coast while the surface low continues orbiting northward around the east side of the upper vortex. The combination of the current upper air temperatures and surface 24 deg C waters did not produce enough instability for strong widespread thunderstorms... and whatever thunderstorm activity did develop was sheared off to the north of the surface low pressure swirl due to the strength of the upper flow around the edge of the upper vortex. Initially the swirl had a distinct center on satellite imagery yesterday afternoon... as of this morning the swirl is still present but without a distinct center which indicates a larger/broader system indicative of a broad upper divergence zone lowering surface pressures over a larger area and hence the loss of a well-defined center needed for cyclone formation. All of these negative factors and the current landfall have ended the surface low's potential of becoming a subtropical cyclone. Models have trended more westward with the inland track of the remnant surface low pressure area while suggesting the north side of the upper vortex will try to arc its track... the 24-hour forecast position of the surface low in my updated outlook below is adjsuted accordingly.


Based on the latest doppler radar presentation and forecast track of the surface low... for the next several hours the heaviest rainfall appears poised to spread across central and northern Mississippi... southern Arkansas... and northern Louisiana with the current lengthy northeastern outer band of rain potentially bringing some heavy downpours to northern Alabama... central and northern Georgia... and southern South Carolina. The Storm Prediction Center (spc.noaa.gov) indicates potential for some severe thunderstorms in the southeastern quadrant of this system... caused by a combination of the surface southerly flow pulling in de-stabilizing warm moist air from the Gulf of Mexico in conjunction with the cooler upper air temps aloft... and also the combination of upper southwesterly flow ahead of (southeast of) the upper vortex and surface southerly flow on the east side of the surface low pressure area creating directional wind shear that may allow for some rotation of the severe thunderstorms. As a result a tornado watch as of this writing is in effect for parts of the Florida panhandle... southeastern Alabama... and southwestern Georgia. The current Storm Prediction Center outlook indicates some potential of severe thunderstorms spreading from this region northward through the remainder of Georgia and into the Carolinas over the next 24 hours as this system (surface low and upper vortex) lift northward out ahead of an approaching western US upper trough/surface frontal system. Check your local weather forecasts at weather.gov and local news media for the latest information on any severe weather watches/warnings to be issued over the next 24 hours.

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

IOH 24 Hr Outlook (1200Z Apr 14)... 0% chance of subtropical cyclone formation (Alabama/ Mississippi/ Tennessee border near 35N-88W)


...COMPUTER MODEL SUMMARY...

Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)


0000Z (Apr 13) CMC Model Run...

**For area of interest #2... makes landfall on Mississippi coast between 12 and 18 hours... while swinging northwest the surface low dissipates over northern Mississippi at 30 hours.


0000Z (Apr 13) ECMWF Model Run...

**For area of interest #2... makes landfall on Mississippi coast between 12 and 18 hours... dissipates over the northern Mississippi/Alabama border at 42 hours.


0600Z (Apr 13) GFS Model Run...

**For area of interest #2... makes landfall on Mississippi coast at 6 hours... while swinging northwest the surface low dissipates over northwestern Mississippi at 30 hours.


0000Z (Apr 12) NAVGEM Model Run...

**For area of interest #2... makes landfall on the Florida/Alabama border at 18 hours... dissipates over western Tennessee at 42 hours.

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