August 11th, 2019: Heat Abates Slightly, Front OTW

The sweltering weekend continues, with a lowering of high temperatures and a rise in humidity. Precipitation chances are higher along the coast, and cooler weather is on the way next week. Finally, when will the Atlantic wake up and start producing tropical cyclones?

8-11-19 TI

LOCAL WEATHER:

Temperatures:

  • High temperatures will be in the mid 90s for most locations, a drop from the upper 90s yesterday.
  • Warmest locations will be in Jasper and Hampton Counties where upper 90s are likely to occur.
  • High temperatures will occur about 4pm, and fall shortly after.
  • The sea breeze will make a notable progression inland today, so it is likely the coast will cool down quicker than the past few days. Just before the arrival of the seabreeze, temperatures will rise slightly. They then will fall 5-7 degrees after passage.

Precipitation/Cloud Cover:

  • Mid-level and upper-level clouds will be scattered across the area for most of the day.
  • Starting around 2pm. cumulus development will begin in earnest across most of the area.
  • Clearest skies will be the southern Intracoastal corridor
  • Precipitation will be possible across all areas, but mode will be scattered and shower-like.
  • Strong thunderstorms are possible in the evening, but overall there is a low severe weather threat.
  • Storm movement will be out of the north for most of the day which is relatively rare.

Heat Index/Humidity:

  • Heat Advisories will not be issued for the Low Country this afternoon. Heat Index must reach 110 degrees.
  • Highest heat indexes will be in Beaufort and Jasper Counties, where 107-109 degrees is possible.
  • Most of the Low Country will have a peak heat index around 102-103 degrees.
  • The immediate coast will be cooler with a heat index around 99-100 degrees
  • Dew points will remain in the mid to lower 70s all day, so humidity will be very high.
  • It WILL feel very uncomfortable today

As of Sunday morning, a weak front was located to the north of the Low Country and is expected to move south into the area throughout the day. This front will help to provide necessary lift in the atmosphere for convection to form. Interactions with the sea breeze (bringing in moisture from the ocean) will likely fire storms this afternoon. Per CHS NWS, most precipitation will remain in the southern area of the Low Country and along the coastal corridor.

Latest runs of the NAM 3km show a weak band of vorticity making its way into the northern zones by 18z. This feature may also play a role in firing more convection to the northern areas than anticipated. Storm movement today will actually be out of the north-northeast, so storms forming to the north would travel down along the coast towards the CHS metro.

Late Wednesday, a significant cold front will reach the northern parts of the Low Country. While the front will not be strong enough to push through the area and bring us cool dry air, it will bring plenty of moisture convergence and direct the atmospheric flow to bring tropical Gulf air. Precipitation will be likely, and high temperatures will be much cooler. It is possible that a low pressure system forms over Florida or Georgia, and tracks northeast into the Low Country. In this scenario, increased rainfall and wind will be possible. Details are not yet fine tuned into this development though.

HURRICANE SEASON:

Since the start of Hurricane Season, we have had a singular named storm in the Atlantic Basin. Hurricane Barry formed in mid July before landfalling in Southern Louisiana. Subtropical Storm Andrea also formed in May (before the start of Hurricane Season). Since Barry, there have been a few tropical waves that have been given a chance of development, before wind shear or dry air tore them apart. Currently, a persistent -NAO pattern is lowering heights in the subtropical Atlantic, and forcing higher pressure into the Main Development Region. Paired with the unfavorable phase of the MJO, tropical development is unlikely over the next week. Starting in late August, a convectively  coupled Kelvin Wave will pair with the favorable branch of the MJO to help bring rising air to the tropical Atlantic. This should occur close to the peak of Hurricane Season, so a burst of activity is likely to occur. NOAA is still predicting an additional 8-15 named storms.

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