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Tropical Storm Danny


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We've got a hot one! 

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 PM EDT Sun Jun 27 2021

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

1. Satellite imagery and nearby buoy and ship observations indicate 
that a small low pressure system has formed about 500 miles 
east-southeast of the Georgia-South Carolina border. Surface 
pressures have begun to fall across the area, and showers and 
thunderstorms have recently become better organized. Some additional 
development of this system will be possible later today, and 
especially on Monday when the system will move across the warmer 
waters of the Gulf Stream, and a tropical depression could form 
before the system makes landfall along the southern U.S. coast. The 
low is expected to move westward today, and then west-northwestward 
at about 15 mph on Monday, reaching the coast of the southeastern 
United States by late Monday.  An Air Force Reserve Unit 
reconnaissance aircraft is scheduled to investigate the system 
Monday afternoon, if necessary.
* Formation chance through 48 hours...medium...50 percent.
* Formation chance through 5 days...medium...50 percent.

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This wasn't totally shocking. The guidance, while not explicitly forecasting TC genesis, had been trending stronger with the disturbance. Given the SST profile, and window for lower shear, we're seeing what could be some modest development. 

Let's see what the convective trends are over the next 12 hours as it approaches a better SST environment. 

 

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This wasn't totally shocking. The guidance, while not explicitly forecasting TC genesis, had been trending stronger with the disturbance. Given the SST profile, and window for lower shear, we're seeing what could be some modest development. 
Let's see what the convective trends are over the next 12 hours as it approaches a better SST environment. 
 
Good instability. If the MCS can persist and drive due west, we might have a named TS at landfall.
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Beyond the marginal SSTs right now and few areas of interest, more importantly it's the overall synoptic pattern setting into place that is a bit eye-popping right now. July might have a few early MDR systems, but August may be far more active this year versus previous recent active years.

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Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 PM EDT Sun Jun 27 2021

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

1. A small low pressure system is located about 425 miles 
east-southeast of Savannah, Georgia.  The associated shower and 
thunderstorm activity has become less organized since earlier this 
afternoon, becoming displaced to the northwest of the surface center 
due to strong upper-level winds.  The low is forecast to move 
quickly west-northwestward at 15 to 20 mph, crossing over the 
warmer waters of the Gulf Stream Monday morning, and it has some
potential to become a tropical depression or tropical storm before 
reaching the coast of Georgia or southern South Carolina by Monday 
evening.  If the system becomes more organized overnight or on 
Monday, then tropical storm warnings could be required for a portion 
of the Georgia and South Carolina coasts with short notice. 
Regardless of development, a few inches of rain are possible along 
the immediate coasts of Georgia and southern South Carolina through 
Monday night.  An Air Force Reserve Unit reconnaissance aircraft is 
scheduled to investigate the system Monday afternoon, if necessary.
* Formation chance through 48 hours...medium...50 percent.
* Formation chance through 5 days...medium...50 percent.
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Tropical Depression Four Discussion Number   1
NWS National Hurricane Center Miami FL       AL042021
1100 AM EDT Mon Jun 28 2021

The area of disturbed weather and associated low pressure system 
that the NHC has been tracking the past couple of days has developed 
into a tropical depression off the coast of South Carolina this 
morning. The inner-core cloud structure noted in high-resolution 
visible satellite imagery has continued to tighten up and deep 
convection with cloud top temperatures of -60 deg C have persisted 
northwest through southwest of the center, yielding a Dvorak shear 
pattern intensity estimate of 30 kt. This intensity estimate is 
consistent with overnight scatterometer surface wind data of 31-32 
kt just north of the well-defined center.

The initial motion estimate is 300/14 kt. The small tropical cyclone 
is expected to maintain a west-northwestward to northwestward motion 
for the next couple of days, resulting in landfall along the 
south-central coast of South Carolina later this evening. The small 
cyclone is expected to dissipate by 48 hours, if not sooner, when 
the system will be located over the southern Appalachian Mountains. 
The NHC track forecast lies close to the tightly packed GFS- and 
ECMWF-based Beta-Advection models due to the lack of any significant 
inner-core convection, which is allowing the cyclone to be steered 
more by the low-level flow rather than the deep-layer flow as 
depicted by the global and regional models.

There is a narrow window of opportunity this afternoon for the 
depression to strengthen into a tropical storm before landfall 
occurs. During the next few hours, the small cyclone will be passing 
over the warmer Gulf Stream where sea-surface temperatures are 
around 28 deg C. In addition, as the outer wind field begins to 
interact with land, low-level frictional convergence along and just 
offshore should help to generate deep convection just prior to 
landfall, helping to spin up the wind field. The NHC forecast shows 
the system becoming a tropical storm before landfall, and as a 
result a tropical storm warning has been issued for a portion of 
the South Carolina coast.

An Air Force Reserve Unit reconnaissance aircraft will investigate 
the system this afternoon beginning around 1800 UTC, providing more 
detailed information on the cyclone's intensity.

Key Messages:

1. Heavy rainfall is possible from coastal southern South Carolina 
and Georgia, inland across the Piedmont of Georgia into northeast 
Alabama.  Isolated flooding is possible across urban areas of the 
southern South Carolina and Georgia coasts.

2. Tropical-storm-force winds are expected across portions of
the South Carolina coast late this afternoon and tonight where a 
Tropical Storm Warning is in effect.

3. Swells generated by the depression are expected to affect 
portions of the South Carolina coast this afternoon and tonight. 
These swells could cause life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  28/1500Z 31.9N  78.3W   30 KT  35 MPH
 12H  29/0000Z 32.8N  80.6W   35 KT  40 MPH...INLAND
 24H  29/1200Z 34.2N  83.3W   20 KT  25 MPH...POST-TROP/INLAND
 36H  30/0000Z 35.2N  85.6W   15 KT  15 MPH...POST-TROP/INLAND
 48H  30/1200Z...DISSIPATED INLAND

$$
Forecaster Stewart
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Tropical Storm Danny Tropical Cyclone Update
NWS National Hurricane Center Miami FL       AL042021
305 PM EDT Mon Jun 28 2021


...DEPRESSION STRENGTHENS TO A TROPICAL STORM...

Doppler radar data from Charleston, South Carolina, along with 
preliminary data from an Air Force Reserve reconnaissance aircraft, 
indicate that the depression has strengthened and is now Tropical 
Storm Danny. The maximum sustained winds are estimated to be 40 mph 
(65 km/h) with higher gusts.

A Weatherflow station at Folly Beach, South Carolina, recently 
reported a wind gust of 41 mph (66 km/h).

SUMMARY OF 305 PM EDT...1905 UTC...INFORMATION
----------------------------------------------
LOCATION...32.2N 79.7W
ABOUT 60 MI...95 KM ESE OF BEAUFORT SOUTH CAROLINA
ABOUT 45 MI...70 KM SSE OF CHARLESTON SOUTH CAROLINA
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...WNW OR 325 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...1014 MB...29.94 INCHES

$$
Forecaster Stewart

 

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Per radar and trends, we (SAV) look to get the heaviest rainfall from a couple of bands on the west/SW side of Danny starting shortly and going for a couple of hours on and off. I wouldn't want to be driving then as tropical bands like this are often very heavy. It looks to be coming at a bad time, drive home time. So far, only occasional very light rain has fallen with light winds but is getting dark now.

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