HGX discussion & Univ of WA WV Loops
Posted by cypresstx on 8/25/2021, 12:15 pm
from https://forecast.weather.gov/product.php?site=HGX&issuedby=HGX&product=AFD&format=CI&version=1&glossary=0


.LONG TERM [Friday through Wednesday]...

The strong ridge of high pressure that has been over Texas the past few days will be eroding and sliding eastward over the weekend allowing for an influx of moisture into the region (PWATs up to 2.25 inches on Friday). A shortwave will be moving through the area on Friday, which combined with the increase in moisture available in the atmosphere will lead to scattered showers and thunderstorms through the evening. Precipitation coverage on Saturday will be less compared to Friday with the lack of any upper level support, but daytime heating should be enough to initiate scattered showers and thunderstorms. However, on Saturday all focus will be on the southern Gulf for potential tropical development.

Currently, the NHC is monitoring a disturbance (Invest 99L) in the southern Caribbean that has a High chance (70%) of tropical cyclone formation within the next five days as it moves into the western Caribbean. There is still a lot of uncertainty with how strong and where this system will go. This is unlike with Grace, which had high confidence in its track due to a strong high pressure over the northern Gulf guiding it almost due west across the Yucatan Peninsula. For this system, high pressure will exist over SE CONUS and a trough will be digging down across the Northern Rockies this weekend. The exact location, strength, and timing of these features will play a large roll in the track of Invest 99L and we just do not have that information right now with much confidence.

So what do we know? - We know that there is potential that a tropical cyclone will be moving through the western Gulf through the weekend and into early next week. Potential impacts will be increased wave heights and rip currents as early as this weekend with the potential of heavy rainfall early to mid week next week.

When will we know more? - It remains just too early for any specifics on track and intensity of this system. By the end of this week we should have a better clue on the upper level pattern going into the weekend. And once this system actually forms, if it ever does, then model guidance will hopefully get a better handle on its track. Exactly where the center of rotation forms plays an important part in a storms evolution, so once that develops and guidance has a known starting point, the ending point becomes clearer.

What should you do? - Keeping monitoring the forecast from us and from the NHC for any updates on this system. If monitoring model cycles on social media, do not put too much stock into individual model runs. There will be many changes in these from run to run and from model to model in the next few days as the details remain in flux. Review your hurricane preparedness plans and kits to make sure they are up to date. We are entering the climatological peak of the Atlantic hurricane season, so making sure those are complete won`t hurt even if you don`t need them with this potential system.

Fowler


https://a.atmos.washington.edu/~ovens/wxloop.cgi?wv_east+/48h/

https://a.atmos.washington.edu/~ovens/wxloop.cgi?wv_east_enhanced+/48h/
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Invest 99L in the Caribbean - Chris in Tampa, 8/24/2021, 9:12 pm
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