February 1-5, 2011 Arctic Blast/Winter Storm Discussion

[ronyan]

31.6 F here and dropping fast, only made it to 33.0 F today.

[Paul]

probably the coldest night of the year, IMO....winds are light, CAA should do the trick...

[srainhoutx]

I see flurries are falling for our neighbors to the E...


AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAKE CHARLES LA
502 PM CST FRI FEB 4 2011

.UPDATE...MINOR UPDATE TO ZONES. HAVE NOW RECEIVED SEVERAL REPORTS
OF FLURRIES OVER SOUTHEAST TEXAS. DEVELOPMENT APPEARS TO BE
ALIGNED WITH 850 MB TROF AXIS ADVANCING ACROSS THE AREA. WENT
AHEAD AND UPDATED ZONES/GRIDS MENTIONING POSSIBLE FLURRIES DURING THE
EVENING HOURS.

[harpman]

srain, TV mets here mention possible flurries here later tonight. Is this what they are seeing?

[srainhoutx]

srain, TV mets here mention possible flurries here later tonight. Is this what they are seeing?

Yes sir.

[Andrew]

probably the coldest night of the year, IMO....winds are light, CAA should do the trick...

Yea that is what I was thinking since earlier this week models have indicated this and with the skies clearing I can see temps sinking.

[ronyan]

29.1 F, tanking.

[txsnowmaker]

Wonder what AZ_Arizona_Desert must be thinking...

[Mr. T]

The accidents and deaths were due to people not expecting the ice problem in the area, and driving too fast. This was not a major event.

lol

Part of measuring a weather event is its impact on the area. With the most amount of ice related accidents since 1997, I'd say this was a "major" event. When you have people out there being KILLED on icy roads, that's pretty damn major

People not expecting the ice problems? Are you f'n serious?

From the winter storm warning issued at 4:42 am thursday:

IMPACTS: DUE TO EVAPORATIVE COOLING IN THE VERY DRY AIRMASS...
TEMPERATURES WILL RUN 5 TO 7 DEGREES COLDER WITH THIS EVENT THAN
DURING THE LAST FEW WINTER WEATHER EVENTS TO IMPACT THIS AREA.
THESE COLDER TEMPERATURES WILL RESULT IN A MUCH HIGHER LIKELIHOOD
OF ROADS BECOMING ICED OVER...EVEN WITH LIGHT PRECIPITATION
AMOUNTS. THIS WILL ESPECIALLY BE THE CASE WITH ELEVATED SURFACES
LIKE BRIDGES AND OVERPASSES. ROAD CONDITIONS ARE EXPECTED TO
DETERIORATE BEGINNING AROUND SUNSET THURSDAY. IN ADDITION...POWER
OUTAGES WILL BE POSSIBLE ESPECIALLY IN THE FREEZING RAIN THREAT
AREA.

How much more clear can that be?

Regardless of whether we recieved ice or snow, bridges and overpasses were going to be icy, and the public was warned with the winter storm warning well ahead of time

Biggerbyte, I've never had a problem with you, but you are way off base here

A system that closes schools, ices up bridges, and causes accidents, injuries, and even fatalities as we saw today, is pretty freaking major for the Houston area. The NWS winter storm warning actually verified, just not with the snow

[Mr. T]

Also, today's high of 31 at IAH was the first time we have seen a sub-freezing high temperature since January 13th, 1997, our last ice storm

Today's low max record was 28 in 1989, so we just missed that. But yesterday's high of 34 degrees was a low max record, breaking the previous record of 35 in 1956

Tonight's record low of 23 in 1996 will likely be in jeopardy.

[ronyan]

27.0 F! I can't remember seeing it so cold this early.

[jasons2k]

Me either- already down to 26 here.

[perk]

26 degrees here in Richmond.

[Ptarmigan]

Also, today's high of 31 at IAH was the first time we have seen a sub-freezing high temperature since January 13th, 1997, our last ice storm

Today's low max record was 28 in 1989, so we just missed that. But yesterday's high of 34 degrees was a low max record, breaking the previous record of 35 in 1956

Tonight's record low of 23 in 1996 will likely be in jeopardy.

It has been a while since we saw sub-freezing high temperatures, 14 years!

[ejburas]

Hooks is down to 23 already, but the dewpoint is holding steady at 21.

[redneckweather]

What an awesome cold blast this has been which won't soon be forgotten. The only thing that would of made it so much sweeter is if I would of gotten to see some accumulationg snow. Hmmmmmm, well....why not? So I got the family and we headed to our ranch up in Madison County and were greeted to an oh so refreshing site. We played in the snow till our hearts were content and even had an all out snowball fight! Now THAT was the way I wanted this cold snap to end so bring on the next one!!!

[redneckweather]

A few more.

snowy4 (450 x 338).jpg

snowy3 (450 x 338).jpg

snowy2 (450 x 338).jpg

[Andrew]

A few more.

snowy4 (450 x 338).jpg

snowy3 (450 x 338).jpg

snowy2 (450 x 338).jpg

Wow very nice. Maybe next week we will get that.

[tireman4]

This is from Air Force Met at Storm2k. The rundown on our ice storm/not snow storm science I have heard. Meteorology 101.


I've got lots of lessons learned for this past event. I am putting a bust review together and will be glad to share when its completed.

I already know where the forecast when wrong...and looking via hind site...it was very obvious that SE TX would see a freezing rain event...even with the available guidance.

BASICALLY: I saw the negatives...and dis-regarded them because the models themselves were putting down snow. The GFS/NAM/Euro/GEM were all putting out snow depths of varying degrees. I falsely assumed (and that is because I don't know how the models do the calculating) that the "snow" parameters were built into the models and that THEY would QC themselves...and if certain parameters were not met...then they wouldn't put a 1" snow depth over an area. I assumed the model would know the critical thicknesses. That's why when I noticed that critical temps and critical thicknesses were not being met...I assumed I wasn't reading something right.

Well...I was reading it right and the model was ignoring it. That makes it even more frustrating. It's one thing to blow a forecast because you didn't see something. Its another thing to blow it when you know what the rules of thumb are saying...and you ignore them because the model said something different. THAT'S being a model reader and I've always hated it when forecasters do that (since so many today have lost the true skills of forecasting and instead read the models).

Another critical value that I saw lacking...spoke about it here and talked at length to Jeff about it on Tuesday/Wednesday (and with several other mets as well) was the -8C critical temp rule of thumb. That rule says "If you have a melting layer, then the temp of the cold layer below MUST be -8C somewhere in the column. If not, freezing rain is the result."

None of the models showed that -8C mark at anything below 600MB...and above 500-600mb...it was dry...so no snow being made there. THEN...even when it was moist...the melting layer at 850-700 was thick enough to melt the snow above it...and there was no -8C below it...so it fell as sleet and freezing rain. If the snow melts...you must reach -8C for it to re-freeze into snow. If not...it remains super-cooled and liquid until it reaches the ground...or it turns to sleet.

So yes...a very frustrating forecast...especially given that temps were never below -8C...and the critical thicknesses of 1000-500, 850-500, and 700-500 (the last two are VERY important if you have a warm layer...which we did) were all above the threshold. And in this instance...the last 2 were spot on if you took a blend of them. ALSO...using the partial thickness table...the Rules state...if you have a 1000-850 thickness of 129-131 DM...and a 850-700 thickness of >154 DM, you should expect "Freezing rain, with sleet near 154DM on the 850-700."

At 06z, Houston had thicknesses of 129 and 155. So...freezing rain mixed with sleet...
At 12Z...127 and 154. That rules states: "Freezing rain/freezing drizzle and sleet" with weak upper level forcing and little/no CAA at the surface.

I will have more in my bust review...but the best thickness values for this event (due to the warm layer) was the 850-500 thickness. It was almost spot on...

[Andrew]

000
FXUS64 KHGX 050409
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1000 PM CST FRI FEB 4 2011

...HARD FREEZE WARNING IN EFFECT THROUGH 10 AM...

.UPDATE...
ANOTHER VERY CHILLED EVENING AS THE ENTIRE FA HAS BEEN SUB-FREEZING
SINCE SUNSET. WITH NOT MUCH SUN TO THE SURFACE THROUGH THE MAJORITY
OF THE DAY...AFTERNOON TEMPERATURES STRUGGLED TO HOVER ABOVE
FREEZING. A RECORD LOW MAXIMUM TEMPERATURE RECORD WAS TIED ON THE
ISLAND AT 34 F. UPPER TROUGH AXIS PASSING OVER US THIS EVENING...WITH
SIGNIFICANT DRYING OCCURRING FROM THE TOP DOWN (SURFACE PWATS
UNDER 0.20 INCHES)...IN TANDEM WITH (NEAR) CALM WINDS BROUGHT ON
BY THE WESTERN EXPANSION OF SURFACE RIDGING. THIS ALL TRANSLATES
TO A VERY COLD NIGHT REMINISCENT OF WHAT WAS EXPERIENCED TWO
MORNINGS AGO. UPPER TEENS ACROSS THE FAR NORTH...LOWER TO MID 20S
OVER METRO...UPPER 20S AT COAST. A NEAR 100 YEAR RECORD MAY BE
TIED IN KCLL (19F IN 1912)...AS WELL AS AT THE OTHER TWO OFFICIAL
SITES WITH A MIN TEMP FORECAST OF 23F AT IAH (23F IN 1996) AND
DOWN ON THE ISLAND...28F IN 1917. MID-LEVELS WARM FROM THE CURRENT
NEGATIVE SINGLE DIGITS BACK UP TO AROUND 2 OR 3 C...AMPLE INSOLATION
WILL LIFT INTERIOR AFTERNOON TEMPERATURES INTO THE LOWER 50S.
INCREASING CLOUDINESS SUNDAY AND SIGNIFICANTLY WARMER AS REGION
FALLS DOWNSTREAM OF AN PASSING (DRY) COLD FRONT LATE IN THE DAY. 31