Good Thursday morning to you all...
We start the day with just about the exact same weather picture as yesterday (everything is moving slowly and butting heads). High pressure moves across the Ohio valley and through the Mid-Atlantic states, and the combination of that and the sinking air from the outflow of Isaac will give us another glass-like quiet day of skies.
|HPC - Surface Map - Thursday|
You can consider the two systems (the high pressure center and Isaac) as warring with each other. The high will slide off to the east and gradually permit an opening for the storm to head to the north. The Mississippi Valley is going to be in for some good ground-soaking rains. Yes, flooding is also possible, but the ground is ridiculously parched.
Speaking about the heavy rains... here's what has happened in Louisiana, and what is expected to happen in the coming days as a result of Isaac:
|HPC - Rainfall Projections - Next 120 Hours||Weather Underground - Radar Estimated Rainfall Totals, New Orleans Area|
It's pretty wild to see how quickly the rainfall drops off with this system (the western section of Louisiana itself has received almost no rain). Anyway, take a look at the finger of heaviest rains as it moves up through the Mississippi and Ohio Valleys. Now look at the current drought picture for the same area:
Targeted rainfall can do well for this area, though getting it all in one day isn't that great. Gotta take what we can get though.
Isaac and the Labor Day Weekend...
So now we wonder what our weather's going to be like when what's left of Isaac gets to us. Good question :-)
It's a tricky call indeed, because you can already see how 50-100 miles can make a huge difference in what we get around here. A forecast still looking out a few days can easily have that amount of play in it. Nevertheless, we shall have a look...
First, the easy part... the next few days of sunshine and heat. The maps that will describe the weather the best are as follows:
|GFS - MaxTemps - Thursday||GFS - MaxTemps - Friday||GFS - MaxTemps - Saturday|
Initially we have a 'dry heat' in place, as humidities are around the 30% line in the afternoons. This makes for the hot afternoons but also pleasant evening and morning weather. By the time we get to the weekend, enough humidity should get in here for all that to end. Notice the 70s temperatures in the middle of Illinois and Indiana on Saturday. This reflects the anticipated location of whats left of Isaac (and it's best clouds/rain).
This presents a quandry for us, because if the center of the action is just to our north, we'll miss out on the best moisture for a while longer. This certainly puts your weekend plans in a better light, but we also need the rain (though they need it more). Also, consider this: there will still be rain out there, but a little less organized or predictable locally.
|NAM - Hi-Res Simulated Radar - Saturday 2am|
You can see the indications of a warm front forming along I-70 in Illinois/Indiana, and a traling cold front back through Arkansas. The initial inflow of the tropical system will be weakening with continued interaction with land, but you can see some hints of it in western Tennessee and Kentucky. The area bounded by the black dots is called the "warm sector" of a frontal storm system. Notice that there are a bunch of holes of rain-free air there. It would appear the current trajectory of the remnants of Isaac will be passing us to our north and west on Saturday. Initially, we'll get clipped by that warm front rainfall, but then will have to be satisfied with "hit and miss downpours" as the disjointed remnants of deep moisture and entrained dry air create a bit of a mess in that "warm sector". Later on in the Labor Day weekend, we'll get another dose of more organized rainfall when the back edge (cold front) swings through.
I wish I could be more precise with this, but it's a difficult call regardless of how little threat we may actually face from 'severe' weather per se. Flooding would be the only possible issue with this, as it's not going to be a Tropical Storm or anything by the time it comes to town. Nevertheless, the core of the system will still be there, and remnant Tropical Storms have been known to have a few tricks up their sleeves long after they've made landfall (check out Tropical Storm Allison from 2001 if you're interested).
|Regional Radar/Satellite with Warnings Tracking||
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|
|Click For Larger||Click For Interactive Radar||Click For Larger||Click For Larger|
Have a great day everyone!