Area Forecast Discussion
Issued by NWS Mobile, AL
Issued by NWS Mobile, AL
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780 FXUS64 KMOB 221051 AFDMOB Area Forecast Discussion National Weather Service Mobile AL 551 AM CDT Sun Sep 22 2024 ...New AVIATION... .AVIATION... (12Z TAFS) Issued at 551 AM CDT Sun Sep 22 2024 VFR conditions are expected through the period with the exceptions of some early morning and late night patchy fog. Light and variable winds become easterly around 5 knots over interior areas today, with a southerly flow at 5 to 10 knots developing near the coast in the afternoon. Light and variable winds are expected for tonight. /29 && .PREV DISCUSSION... /issued 454 AM CDT Sun Sep 22 2024/ ..New NEAR TERM, SHORT TERM, LONG TERM, MARINE... NEAR TERM... (Now through Monday) Issued at 454 AM CDT Sun Sep 22 2024 An upper ridge over the region is slowly deflected mostly into the Gulf through the period in response to a large upper trof which evolves over the central CONUS. A surface ridge generally persists over the southeast states with a light and mostly easterly flow expected today except for a sea breeze circulation developing near the coast. The surface flow looks to become southeasterly or southerly over the entire area on Monday. Subsidence associated with the upper ridge should preclude convective development, though can`t rule out a stray shower or storm on Monday as the upper ridge begins to be pushed out of the area. Highs today and Monday will be 90 to 95. Lows tonight and Monday night tend to range from around 70 inland to the lower 70s near the coast. A low risk of rip currents is expected through Monday night. /29 SHORT and LONG TERM... (Tuesday through Saturday) Issued at 454 AM CDT Sun Sep 22 2024 We continue to monitor an area of low pressure that is slated to develop over the southern Gulf by midweek. This eventual feature, which is expected to form off of a developing Central American Gyre (CAG), now has a 70 percent chance of developing into a tropical cyclone over the next 7 days. Unfortunately, there still remains a lot of uncertainty when it comes to the strength, timing, and trajectory of this system. I will once again break down the remainder of the discussion into a "what we know" section and a "what we don`t know at this time" section. What we know... Satellite imagery and model analysis suggests that the CAG is continuing to mature over Central America this morning. Although activity is still rather scattered and sprawled out, pockets of deep convection are now developing around this feature, with a decent blowup of clouds and storms forming just off the coast of Nicaragua and Honduras. Whether or not this new convection will eventually become the trackable feature is yet to be seen, however, latest guidance is beginning to pick up on a more concentrated area of low pressure developing near this activity by around the Monday night timeframe. This feature will likely be steered north- northwestward around the larger-scale CAG feature, crossing over the Yucatan Peninsula or through the Yucatan Pass and arriving in the southern Gulf on Wednesday. At this point, the system will start to break off from the CAG and will start feeling the steering effects of the upper-level features to its north. The known upper features at this point include: an upper ridge located over the southeast US and a longwave trough digging into the central US. Yesterday, an additional cutoff upper low over the south central US was mentioned, however, model trends over the past day are beginning to drop this feature in favor of a more vigorous upper trough. More about this trend in the next section, as this change will likely play a big role in the storm`s eventual path. As the system enters the Gulf, strengthening is likely due to the very warm Gulf waters and being located underneath an upper-level anticyclone (giving way to low shear values). Additionally, models are suggesting that this system will be quite large, so even though the eventual track of this system is rather murky, marine and coastal/surf impacts will likely be felt across a majority of the Gulf Coast region, regardless of track. We will begin honing into the details of these impacts as we get closer in time. What we don`t know at this time... The feature still has not developed yet. Although we are starting to see the signs that a trackable feature may soon be forming, as of right now models are still unsure of what to latch onto. As mentioned yesterday, when this lack of data gets inputted into the various models and then we look out at the solutions 5-7 days out, this leads to a plethora of inaccuracies within each model run that ultimately affects the model run`s overall output. This is why there continues to be so much run-to-run and model-vs-model variability in the overall strength, trajectory, and timing of this storm. Once the feature finally develops in the next day or so, this issue should start to resolve itself and we should start to see guidance begin to converge on a most probable solution. The other big uncertainty is with regards to the upper-level steering features at play. There were a few notable changes in the recent model suite that are different then what the models were showing 1-2 days ago. Previously, much of the guidance suggested that as the upper longwave trough digs into the central US, a weak cutoff low would break off from the main trough and travel into the Texas/Oklahoma/New Mexico region. This led to the tropical system feeling its influence and caused it to take a path more in the western/central Gulf. Today, instead of a lobe breaking off from the main trough, most guidance now suggests that the actual longwave trough will strengthen and dig far enough south to break off from the northern jet stream. This now results in an anomalously massive upper low parking itself over the Mississippi River Valley. The strength and eastward extent of this upper low helps to break the ridge down a bit quicker, ultimately resulting in an eastward shift in a good majority of model guidance over the past day for the tropical system. With that being said, these sudden changes in model guidance tells me that the upper features at play are extremely complex and fickle and, at this time, any one model run should not be taken at face value, especially since we still do not have a trackable feature. Expect models tracks to continue to shift back and forth a bit longer until guidance has a better handle of the system and the upper features at play, and by that time, we can begin focusing on our local impacts. As stated earlier, even if the center does not directly impact our CWA, impacts will likely be felt far removed from the center of the system due to its expected size. We will continue to monitor trends closely and we urge residents and visitors across the entire Gulf Coast to continue to monitor the forecast over the coming days. /96 MARINE... Issued at 454 AM CDT Sun Sep 22 2024 No impacts are expected through Wednesday, then winds become moderate to strong Wednesday night with similar conditions expected for Thursday. Seas build significantly Thursday in response to a potential tropical system in the Gulf. Please see the National Hurricane Center for more information on this possible system. Winds and seas will be higher near storms beginning mainly by Tuesday night. /29 && .PRELIMINARY POINT TEMPS/POPS... Mobile 93 71 93 70 91 72 87 72 / 0 0 0 0 10 10 50 40 Pensacola 91 74 90 74 88 75 86 74 / 0 0 0 0 10 10 50 50 Destin 89 75 90 75 88 76 86 75 / 0 0 0 0 10 10 50 50 Evergreen 94 69 95 69 92 68 90 69 / 0 0 0 0 10 10 50 40 Waynesboro 93 70 93 69 92 69 88 68 / 0 0 0 0 10 10 50 30 Camden 92 70 93 70 92 68 89 69 / 0 0 0 0 0 10 50 40 Crestview 94 69 94 69 92 69 89 70 / 0 0 0 0 10 10 50 40 && .MOB WATCHES/WARNINGS/ADVISORIES... AL...None. FL...None. MS...None. GM...None. && $$ This product is also available on the web at: www.weather.gov/mob