jasons wrote:I'm pretty sure what I'm seeing here is sleet. The droplets are round and frozen solid. I've seen graupel a number of times in North Texas and it still had a slightly white almost flaky appearance to it. They were like a cross between snow grains and sleet. They always reminded me of the half-melted comet in Superman 1 as he got close to the earth (silly analogy, but I'm a visual person). These today are IP and solid through.
Then the only solution I can think of is that there must be a shallow above-freezing layer sandwiched between sub-freezing layers in that precip zone above 10,000 ft. Precip would starting out as snow, melt in the above-freezing layer then re-freeze as sleet somewhere above 10,000 ft. I don't see how rain cold form in temps close to 0F around 18,000 ft then freeze as sleet.
The model soundings clearly don't have a good grasp on the vertical temperature profile. Same as last February's freezing rain event when the models said it should all be snow.
Well, I'll need to see it myself to figure out what's falling. Graupel bounces, too. Hard to believe the model-projected sounding could be so far off reality.
Haven't seen anything in SW Houston, but I have a dark sheet spread out on the table in the back yard and my camera is ready. Will take a pic of what I see. Radar shows echoes overhead but nothing reaching the ground.
Sleet/graupel mix here in League city. I've been watching my radar and it seems that if returns are showing in .5 degree Base Reflectivity and also above at 1.4 and 2.5, indicates precip making it to the ground...just my 2 cents. Based on that, I'd bet you see some precip in SW Houston in next, say, 10 mins max.
Its sleet wxman57. The difference I see it the solid bounce off the cars with a ping versus graupel which hits and sticks without much movement. Must say I am quite surprised.
Just started here. Close examination of the precip confirms sleet and not graupel. But I've seen heavy graupel showers in southern Argentina when I was offshore back in 1980 that bounced nearly a foot.
So the soundings are way off, just like wxman57 said they were last year when freezing rain fell after snow was predicted. In these times of budget constraints, I wouldn't expect any upgrades from NOAA on their equipment in our area. Guess we just have to continue nowcasting in these types of events.
Apparently so. Here are a couple of wxman57's comments. Wxman57, can you further explain?
“The model soundings clearly don't have a good grasp on the vertical temperature profile.”
“Nothing in SW Houston. Jeff, are you sure you're seeing sleet and not graupel? Sounding has all precip forming in sub-freezing air above 700mb, which should be snow. There isn't any above-freezing followed by another sub-freezing layer (which would produce sleet) indicated. See the sounding below.”
wxman57 wrote:Well, I'll need to see it myself to figure out what's falling. Graupel bounces, too. Hard to believe the model-projected sounding could be so far off reality.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
602 PM CST SUN FEB 12 2012
.AVIATION...
UN UPPER LEVEL DISTURBANCE MOVING FROM WEST TO EAST ACROSS THE
REGION IS SPREADING AN AREA OF LIGHT RAIN MIXED WITH LIGHT SLEET
ACROSS THE AREA. EXPECT THIS TREND TO CONTINUE AND CEILINGS WILL
PROBABLY LOWER TO AROUND 050 BY 03Z. A SECOND UPPER LEVEL
DISTURBANCE WILL MOVE ACROSS THE AREA ON MONDAY SPREADING RAIN
ACROSS ALL OF THE REGION. CIGS WILL LOWER TO MVFR BY AROUND 15Z
AND NEAR IFR CONDITIONS AFTER 18Z. WARM FRONT IS EXPECT TO DRIFT
BACK NORTH FROM THE GULF OF MEXICO. THIS WILL ALLOW FOR ADDITIONAL
INSTABILITY AND THE POSSIBILITY OF TSTMS MAINLY NEAR THE COAST
FROM 15Z TO 00Z. SOME OF THESE STORMS COULD BE SEVERE AND CONTAIN
STRONG WINDS AND THE POSSIBILITY OF A WEAK TORNADO. DURING THE DAY
MONDAY CIGS WILL AT OR BELOW IFR AND VISIBLITIES WILL BE MVFR FOR
MOST OF THE DAY AFTER 15Z.
wxman57 wrote:Just started here. Close examination of the precip confirms sleet and not graupel. But I've seen heavy graupel showers in southern Argentina when I was offshore back in 1980 that bounced nearly a foot.
Sleet usually looks like pellets when they fall. Graupel looks more powdery.
Thought it was just rain...went outside and could hear the ice hitting the RV...still did not believe so I got a black blanket and a flashlight...yup...a little sleet falling here.
