Post Reply 
T. Scott Barry's thoughts on this week
12-20-2004, 08:25 AM
Post: #1
T. Scott Barry's thoughts on this week
T. Scott's Discussion:

December 20, 2004
this Monday morning

The time is 330 AM this Monday morning. I have 2 items here to intice your attention. It's my hope to please both storm lovers, with severe weather, and winter weather weenies, (www's), alike in the same week, and that's hard to do in these parts. This weather I'm alluding to is NOT coming today or tomorrow; this is the extended range forecasting objective of mid-to-late this week.

Briefly, storm lovers get the attention first near mid-week this week; winter weather weenies get the attention late this week.

I have not gone through the laborious 20-item checklist over severe weather yet for Wednesday as variable factors are continuously changing and is too soon to evaluate with reputable, trusting numbers just yet, but there is enough data I've reviewed for 72 hrs out (3 days out), that suggests that you will see another episode of severe weather warnings get issued for Southeast Louisiana region. I'm not going to pour through the aerial extent of this, nor types yet, but I do see all 3 types of severe weather on the table. Quality of moisture return and temperature recovery are a couple negatives, but there are also several good positives that lean toward severe weather as well. Since severe weather occurs more times out of the calendar year than does wintery weather, I'll have to put storm lovers on hold, for the moment, while I tend to the www's right here.

Based ONLY off the 00Z data from a long-range model, shows a continued threat for wintery precipitation for Southeast Louisiana region. Many times you've been seeing this particular scenario get put on hold, go away, then only to re-appear again as a re-newed prospect for snow. It has re-newed its vow again. No cheerleading here now, nor applause, because as simple as just another short 12-hour run later, then things can swap right back to NO SNOW as it had done 24 hours ago. I'll go over a short listing of items here.

In brief, I review a checklist of about 7 items for snow. In it, more than half of these items have had their respective criteria met from the model run last night for late this week, by Friday. Things begin changing one by one starting Thursday. The lowest thickness layers criteria gets met, first. Then, by Friday, the mid-layer thickness of 850 to 700 Hpa level get met. All this while H85 temperatures meet and exceed thresholds, and so too does H7 temperatures as well. For those of you who utilize only the traditional, conventional 1000 to 500 HPa thicknesses, don't!---because you can get burned! There's much more to this science than a simple inspection of that rain/snow line! A saturated layer is forecast on area profile soundings on Friday of this week, at least above the surface. This means that surface temperatures could wet-bulb down a third of the way down toward the dewpoint in the lower layers, if virga started up, which would better the surface temperatures that'll likely be struggling to hover near the freezing mark. The freezing levels as shown on the skew-T vs. Ln P diagrams shows the entire temperature profile to be below freezing for Friday. (We'll see about that!) Getting below 32 has been a chore, and still hasn't been achieved officially yet, in New Orleans, at the surface! This means on this 108 to 120 hour forecast, which is a 4 1/2 to 5 day forecast, that given such a PROPOSED profile, then it would precipitate all as snow; no mix. Gang, you're not new to meteorology, and you've been around the block a few times. A 4 1/2 to 5 day forecast is subject to change another 4 more times, so no celebrating or dancing on your desks just yet. It is also understood that you come into this discussion this morning, accepting the fact that a 4 1/2 to 5 day forecast is BARELY held together with bubble gum and barbed wire at best!!! So remember my words here in the event it doesn't come to fruition, but don't forget what's about to be said when it does. Let me continue with some age old FALSE myths, particularly addressing the native New Orleanians here, who are not well-versed with snow:

False Myth #1: The surface temperature has to be 32 degrees F, or lower, in order to snow. This is false. Many people have a hard time believing this is false, unless, you're one who is well-versed with snow situations in northern climates. Did you know that even wet snow or sleet can still occur with surface temperatures as warm as the upper 30's and even lower 40's? This comes with a stiff, stipulation though. And it is this...The above freezing temperatures must be CONFINED TO THE LOWEST 500 ft of the ground, and the temperature profile must be freezing from 500 ft and above; otherwise all bets are off.

False Myth #2: There must be a surface low in the Gulf of Mexico for snow or wintry precipitation to occur here. There doesn't have to be. I've even witnessed snow flurries and sleet here in New Orleans--both of which were non-measureable and occured a few years ago, and in the '96-'97 winter whereby they sent everyone home for non-measureable sleet that occured one winter morning. (What do you mean non-measureable?) This means a trace; it doesn't collect on the ground. It's not a necessary condition; though, this typically would promote the best ideal situation for accumulating snows. Trace amounts that are not visible on the ground and only in the air, melting upon reaching the ground, are easier to get here in New Orleans. I've counted at least 3 times when this occurred in just the 8 years I've taken up residence here. Once, non-measureable, trace amounts occurred when I worked for Nash Roberts in the '96-'97 winter and again on January 1, 2001, and yet a third time on January 2, 2002. (Why does nobody remember these times, then?) They don't remember or recall these 3 times because there was NO accumulation on the ground in New Orleans, that's why. It was only trace amounts flying in the air, for which you had to be looking hard for, and at least in 2 of those 3 events, it occurred at nighttime when everyone was in bed. These events go unnoticed, unless there are accumulations that rest on the ground, which is far, far much harder to get here in New Orleans. A simple TRACE of snow FLURRIES or sleet are easier to get during any given season.

False Myth #3: The 540 thickness has to be over or to the right of New Orleans to get wintery precipitation. This is not true either. The entire atmospheric sounding profile must be inspected to gauge a determinant toward freezing or frozen precipitation types.

Heaviest snows w.r.t. a surface low's position can vary quite dramatically, anywhere being between 150 miles to 240 miles north of a surface low, with even more exceptions to this bounded range given, than ever thought possible. This correlates to about roughly 2 to 2.5 degrees of latitude to the LEFT of the track of a surface low. It also corresponds to about 1.5 degrees to the left of an H85 low.

Well, we could go on and on here, but what's the point, really, with a 5-day forecast?

The next writing I release to you will be one on severe weather in another day from now. Then, if it still continues looking like wintery weather comes to fruition late this week, then I will once again write on that subject as time draws nearest.

The more times I have to write this week, then the bigger that either event looks to me.

If you'd like to do more read-up on what is meant by thicknesses, then I have an excellent posting that I composed a couple days ago and have placed it on my website there on Saturday for you all to view, which is sitting BENEATH the picture appearing there: It is still there for you to view.

T. Scott Barry
Meteorologist, OU grad. '95
[email protected]

Twitter updates we will follow you back
Now on Facebook We will like you back

Visit this user's website Find all posts by this user
Quote this message in a reply
12-20-2004, 04:07 PM
Post: #2
T. Scott Barry's thoughts on this week
Very captivating dicussion...I just don't think it will happen. First of all you have to have highs at the most in the mid to upper 30's, which would be a miracle in itself and then you would have to have an area of disturbed weather, that doesn't wrap around warm air from the GOM! Even here in Long Island, it's hard to squeeze out snow yesterday night with 35 F temps...and believe me we had a favorable profile and now today I had a high of 17 with 40 NE winds, with about 2-3 inches of snow on the ground. My car doors froze to such a point that right now, even with pouring hot water on it, it doesn't open! So unless your getting the storm of the century and highs 30-40 degrees below normal, nothing more then possibily flurries will come out of it, but heh that's what I think, just don't get your hopes up!
Find all posts by this user
Quote this message in a reply
12-20-2004, 04:28 PM
Post: #3
T. Scott Barry's thoughts on this week
Don't dash Rollie's dream of a white Christmas just yet...granted it's a LONG shot, but it COULD happen...check out the graphic below:
Find all posts by this user
Quote this message in a reply
Post Reply 

Forum Jump:

User(s) browsing this thread: 1 Guest(s)