1/25/2014, Sat. Night, 1040 PM ~~ Technical Model Briefing: Other forecast models have yet to arrive, but I do have one that I have examined already tonight, which is the original Nam. Heres the time table of the computations I made from that, for Tuesday, 1/28 & Tuesday night for New Orleans: 6 AM - 12 Noon Tuesday -->> Freezing rain and light rain mixture, with surface temperatures 31-33° at 6 AM. Up to 0.04. (Why?) Above freezing layer of 1,487 meter depth, aloft, of 4°C Temp avg at 6 AM, shrinking to 953 meter depth of above freezing layer, w/ avg. Temp of 2.1° at 12 Noon. 12 Noon - 6 PM, Tuesday, 1/28 -->> Freezing rain and sleet (ice pellets) mixture, with surface temperatures, 29-32°. Up to 0.26 (Why?) Above freezing layer, aloft, of 953 m depth w/ avg. Temp of 2.1°C at 12 Noon, eroding & shrinking to 487 meter depth of above freezing Temp avg. of 0.7°C at 6 PM. 6 PM, Tuesday - 12 Midnight -->> Sleet, (ice pellets), and snow mixture. Up to 0.23. (Why?) Above freezing layer aloft, of 487 m depth w/ avg. T of 0.7°C at 6 PM, erodes further & withers away to no above-freezing layers left, aloft, by 12 AM, Midnight, gives way to snow by or just before 12 AM, Midnight. My 7-point snow checklist gives way to 5 yess and 2 nos in favor of snow. The 2 nos pertained to the 700 mb temp. and b/c of a 1000-500 mb thickness value of only 545. 12 Midnight - 6 AM, Wednesday -->> Snow. Up to 0.24 of melted equivalent. 10:1 ratio yields snowfall of 2.4. (Why?) No above freezing layers left aloft, between 12 Midnight to 6 AM Wednesday. My 7-point snow checklist gives way to 6 yess and 1 no. The 1 no, pertains to a thickness value that only reaches 542. So, are you still with me? Did you survive all that technical, fancy talk?? Okay, my thoughts on this. I think this model is generating too much precipitation as it typically does in its 72-84 hour, extended range output. Best to wait 48 hours out, and see if it can stand the test of time; then well talk again. I think it looks too cold at the surface on Tuesday, as Im just now able to peek at the next inter-comparison of model against it. Typically, my past experiences are that if THIS much QPF, precipitation amounts are being generated, its a tell tale sign that the surface temperatures are not yet ready to get cold enough, and that if indeed a goodly amount of precip. falls, then itll likely start as rain, with some question as to whether 32° and lower at the surface can make it in time for an all-out ice storm, with huge amounts of icing. In my years of living here since 1996, Ive not ever seen it happen here in New Orleans. To the models credit just b/c it hasnt happened since Ive lived here doesnt mean that it cant happen, but it does show the test of time of how IN-frequent it happens. Keep an eye on the temperatures on Tuesday. If its at 32° or below during daylight hours, then some significant icing & an ice storm will begin. Im not sold on the temps being at 32° and below during the daylight hours on Tuesday as this model asserts, especially given the new data of Gfs that has arrived, advertising temperatures of 34-36-39° for New Orleans on Tuesday, 1/28, and I also had a look at its 850 temps which are toasty during the day, 5° to 4° to 2°C from 6 AM to 12 Noon, to 6 PM Tuesday. That spells mostly rain on Tuesday, if the surface temperature cant get to, nor maintain 32°, like the 1st model details. If it does get to 32° during the day on Tuesday, then itll be a freezing rain and rain mixture. Tuesday night? Thats a horse of a different color! I still yet have to examine the thermal structure of the newer Gfs coming in. But you see as I showed above with the 1st model, that it becomes all snow, for Tuesday night, and LATE, LATE Tuesday night, but itll likely start as a sleet occurrence, then sleet / snow mixture, before turning over to snow late, near the end of the precipitation shield. Okay, thats enough for this text post writing.
Posted on: Sun, 26 Jan 2014 04:54:07 +0000
Trending Topics
Recently Viewed Topics
© 2015