8/26 Updated - Sunny and hot, but in the mountains it's not!

We'll be watching the persistent afternoon cycle of the pop-up storm yet again today. Also, keeping an eye on "Isaac" as it makes it's way to Cuba.

8/26 Update - The weather around here is going to be practically a carbon-copy of yesterday (as the maps/discussion below indicate). Feel free to follow along with constantly updating maps posted with this blog post.

This update will concern ourselves primarily with "Isaac" as it remarkably splits between Cuba and the US on its way into the Gulf of Mexico. You can see the current National Hurricane Forecast and model tracking on the maps below, but I wanted to post a few other nifty things today. The first would be the 'model creep', or how the forecast guidance for "Isaac" has changed over the past few days. Here's a look:

Model Creep - "Isaac"

One interesting thing to note is that the earlier model consensus is actually close to what the present model consensus is-- with all sorts of wandering in between. The projected track of the storm had it coming close to the Florida coastline during the Republican convention, but now it's farther west, allowing the system to grab a ton more ocean (and a ton more opportunity to strengthen). So, where might it actually make landfall...? [With these tropical maps, you can click them for a pop-up of a larger image].

GDFM - Tuesday Afternoon NOAA - Sea Surface Temperatures

How 'bout them apples...

The model on the left has a strong Category 2 storm heading to the New Orleans peninsula (ugh) on Tuesday afternoon. The model also indicates a central pressure during that time in the 957mb range. That's more like a Cat 3 storm. Also, notice the wind bands heading directly into Lake Pontchartrain. That's where all the water would theoretically pile up (storm surge) ... spooky. It's just a model for now though. The right-hand image shows sea-surface temperatures for the Gulf and Atlantic. For a hurricane to strengthen, it needs around 80-degree water temperature. The Gulf is currently brimming with perfect warm bath-water. Once this storm frees itself away from large land masses, we should see some pretty rapid strengthening.


Happy Saturday to one and all-- It's the Weekend!

The August heat continues for most of us today, under mainly sunny skies. However, most of the same weather players are still in town, so we will yet again be watching for the pop-up showers and storms in the eastern mountains.

HPC - Surface Map - Saturday PM

I put the yellow arrow in there to help depict the gentle ascent-flow that's coming in from the Atlantic Ocean and hitting the Appalachians on their eastern facing ridgetops. At first it's not very noticeable, but once the heating of the day sets in, those showers and storms pop. Since this flow continues, and significant portions of the clouds are now elevated above mountain level, the storms themselves are carried slowly down the slopes toward the west. At the same time this occurs, they become farther removed from the initial triggering point (the elevation-based forcing), so they weaken slowly as they move slowly. Nevertheless, this type of situation is always good for a spot Flash Flood Warning and all that. It will be mainly out of our area, but as the afternoon approaches evening, we'll have to watch the Kanawha Valley and the I-79 corridor, as each successive day of this pattern proves to push the finishing line of these showers farther and farther west. A few jack-rabbits no doubt will make it across such a line in the sand too. Here's how the NAM bears out this cycle:

NAM - Saturday PM NAM - Sunday AM
NAM - Sunday PM

So the main elements in this pattern are: (1) the windflow coming in from the Atlantic and going up the mountains; (2) the mountains themselves providing extra lifting; (3) the 'diurnal' cycle of heating-- warmest in the afternoon, coolest in the morning. Notice how the loss of heating forces a dissipation of the showers locally, whereas the rain near the Delmarva peninsula is synoptically based (weather fronts). Given that the windflow, when continuing, will be going down the mountains on their western facing slopes, we'll be seeing two things occur-- the air will be drying out somewhat, and the temperatures warming.

This is why the large portion of us who are west of I-77 will not only stay dry, but see high temperatures hit the low 90s. Indeed, by the time Monday rolls around, we should be in heat-wave territory if no lucky shower makes it over to us by the close of the day.

The Next Change...

This pattern continues Sunday, and to a lesser extent on Monday. By then, a weather front approaches from the west, as high pressure has been significantly weakened and washed out by the mountain based showers and increase of humidity. This is what the picture looks like by the early morning hours of Tuesday:

GFS - Surface Map - Early Tuesday

You can see that low arcing line along the Ohio River, representing the incoming moisture we'll be monitoring. This, however, is not going to be a big deal. Notice instead the big blob of moisture in the Gulf of Mexico. That will be either Tropical Storm or Hurricane Isaac, and it does look to be a future landfalling storm-- one on which therefore to keep a very sharp eye. Here's the latest on the storm and it's track:

NHC - Tropical Storm Isaac - Current Information And Forecast Track Wunderground - Tropical Storm Isaac - Computer Models

 The latter parts of the track have not coalesced into any specific envelope yet, so we're still going to have to be patient to see what materializes as it relates to our own weather, but the past few runs have become more consistent in showing this storm emerge over Cuba, come across the Florida Keys, and head toward the southern Gulf Coast. The farther away from the Florida peninsula this storm migrates, the more dangerous it is sure to be.

Regional Radar/Satellite with Warnings Tracking

Accuweather Radar

From the Storm Prediction Center (below): Click For a Larger Image

Activity Overview Storm Outlook Watches Potential Watches Storm Reports
Temperatures HD Doppler Radar Estimated Rainfall Active Warnings
Current Temperatures HD Doppler Radar Estimated Rainfall Active NWS Warnings
Click For Larger Click For Interactive Radar Click For Larger Click For Larger

Have a great day everyone!


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