Southern Plains winter wx thread (2008-2009)

jinftl · #301 Postby **jinftl** » Fri Dec 05, 2008 11:22 am

Climate Prediction Center 8-14 Day Temperature Outlook:

Ed Mahmoud · #302 Postby **Ed Mahmoud** » Fri Dec 05, 2008 2:45 pm

HAPPY HAPPY JOY JOY! HAPPY HAPPY JOY JOY!

New 12Z GFS shows a significant ice changing to snow storm for Houston only 15 days away!!!!

I'm not 100% committed yet...

Extremeweatherguy · #303 Postby **Extremeweatherguy** » Fri Dec 05, 2008 4:13 pm

Latest discussion from the Norman, OK NWS...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
307 PM CST FRI DEC 5 2008

.DISCUSSION...HIGH PRESSURE HAD SHOVED OFF INTO THE SOUTHEAST STATES
THIS AFTERNOON. WINDS HAD TURNED TO THE SOUTHWEST...BUT MODIFIED
CANADIAN AIR WAS STILL CIRCULATING AROUND THE HIGH...KEEPING
TEMPERATURES IN THE 40S DESPITE FULL SUNSHINE. THE BACK EDGE OF THE
COLD AIR WAS MARKED BY A WARM FRONT IN AN ODD ORIENTATION...RUNNING
FROM NORTHEAST NEW MEXICO UP THROUGH THE DAKOTAS. WEST TO NORTHWEST
FLOW AT MID LEVELS WILL BRING THE WARM FRONT EASTWARD TONIGHT AND
SATURDAY. WITH DRY AIR IN PLACE...HOWEVER...AND WINDS LIKELY TO DIP
BELOW 7 KNOTS...WE EXPECT LOWS TONIGHT TO BE A LITTLE COOLER
THAN MOS GUIDANCE. FOR HIGHS ON SATURDAY...WE USED NAM 2 METER
TEMPS...YIELDING 50S AND LOW 60S.

A WEAKER CANADIAN FRONT WILL SLIDE IN THE BACK DOOR THROUGH
NORTHEAST OKLAHOMA SATURDAY NIGHT...BUT THIS LOOKS TO STALL AND
QUICKLY LIFT OUT OF THE REGION ON SUNDAY AS A LEE TROUGH BEGINS TO
DOMINATE. SUNDAY THROUGH TUESDAY WILL BE A PERIOD OF INTEREST.
BREEZY SOUTHERLY WINDS COULD CREATE FIRE WEATHER ISSUES SUNDAY
AFTERNOON...ESPECIALLY FOR OUR TEXAS COUNTIES...BUT WITH HUMIDITY
EXPECTED TO HIT ONLY THE 25-30 PERCENT RAIN WE CHOSE NOT TO ISSUE A
FIRE WEATHER WATCH. BY MONDAY...A MODEST RETURN OF GULF MOISTURE IS
ANTICIPATED. DESPITE SOME DIFFERENCE...THE MODELS ALL ARRIVE AT
THE SAME PLACE...WITH CYCLOGENESIS OCCURRING NEAR OR SOUTH OF THE
RED RIVER LATE MONDAY...BEFORE LOW PRESSURE TRACKS TO THE EAST...AND
COLD AIR SPILLS IN ON THE BACK SIDE OF THE SYSTEM FROM MONDAY NIGHT
THROUGH TUESDAY.

THE MODELS DIFFER ON THE STRENGTH AND TIMING OF A SMALL LEAD TROUGH
THAT WILL EJECT MONDAY OR MONDAY NIGHT. THIS FEATURE IS PINCHING OFF
FROM THE FLOW NEAR SOUTHERN CALIFORNIA THIS AFTERNOON...AND WILL BE
PICKED UP BY A NEW JET STREAK AS IT DIGS INTO THE WESTERN STATES ON
MONDAY. THE GFS SHOWS SOME ODD BEHAVIOR...MOVING THE CLOSED LOW
NORTHWARD FOR A SHORT TIME...AND THEN KEEPING IT CLOSED AND SLOW
MOVING WHILE IT IS KICKED FROM UPSTREAM. THE ECMWF IS PREFERRED...AS
IT OPENS THE WAVE AND MOVES IT FASTER...WHICH IS CONSISTENT WITH ITS
EXCEPTIONALLY SHORT WAVELENGTH. THIS SOLUTION WOULD BRING GREATER
LIFT ACROSS THE PLAINS ON MONDAY...SO WE KEPT THE PREVIOUS POP FIELD
WHICH IS HIGHER THAN THE 12Z MOS. WE ALSO EXPANDED THUNDER CHANCES
BASED ON THE MID LEVEL FORCING. BY TUESDAY...HOWEVER...THE GFS
CATCHES UP TO THE ECMWF...AND BOTH SHOW ENOUGH FRONTOGENESIS THROUGH
A DEEP LAYER TO SUPPORT CONTINUED PRECIP CHANCES. WITH COLD AIR ALSO
DEEPENING...A BRIEF CHANGEOVER TO SNOW IS A GOOD BET. SURFACE TEMPS
SHOULD BE WARM ENOUGH TO PREVENT ACCUMULATION...BUT THE FALLING ICE
OR SNOW WILL COMBINE WITH BLUSTERY NORTH WINDS TO MAKE FOR A
POTENTIALLY HAZARDOUS DAY. THE WINDS...IN FACT...COULD BE THE MAIN
STORY...WITH POTENTIAL FOR GUSTS OVER 50 MPH SIMILAR TO THE COLD
FRONT THAT CAME THROUGH A FEW DAYS AGO.

FINALLY...ALTHOUGH JUST PAST THE 7 DAY FRAME...THE MODELS ARE
SHOWING A SIGNIFICANT PATTERN CHANGE...AND ONE THAT DEVELOPS IN A
SYNOPTICALLY CONSISTENT MANNER. ARCTIC AIR IS FORECAST TO BUILD
FARTHER WEST THROUGH CANADA...AND EVENTUALLY DRIVE THE DEVELOPMENT
OF AN UPPER TROUGH TO OUR WEST. THIS COULD PLACE OUR REGION UNDER
SOUTHWEST FLOW...WITH SHALLOW ARCTIC AIR IN PLACE TOWARD DECEMBER
12TH AND BEYOND. THAT WOULD MEAN A MORE PROLONGED COLD SPELL AND A
GREATER CHANCE FOR ICE OR SNOW.

Ed Mahmoud · #304 Postby **Ed Mahmoud** » Fri Dec 05, 2008 4:37 pm

People may not put much stock in 360 hour plus progs from the GFS model, as they aren't always completely accurate, but I recall several GFS model runs available on my AccuWx PPV showed snow accumulation in the 10 to 15 day forecast period in the roughly 10 to 15 day period before the South Texas 2004 Christmas Snow Miracle.

jinftl · #305 Postby **jinftl** » Fri Dec 05, 2008 4:38 pm

You know, a broken clock is right twice a day...or throw enough arrows and eventually you hit the bulls eye....you get my point.

p.s. very cool photo...snow and palm trees in distance...

Ed Mahmoud wrote:People may not put much stock in 360 hour plus progs from the GFS model, as they aren't always completely accurate, but I recall several GFS model runs available on my AccuWx PPV showed snow accumulation in the 10 to 15 day forecast period in the roughly 10 to 15 day period before the South Texas 2004 Christmas Snow Miracle.

cctxhurricanewatcher · #306 Postby **cctxhurricanewatcher** » Fri Dec 05, 2008 4:45 pm

Ed Mahmoud wrote:People may not put much stock in 360 hour plus progs from the GFS model, as they aren't always completely accurate, but I recall several GFS model runs available on my AccuWx PPV showed snow accumulation in the 10 to 15 day forecast period in the roughly 10 to 15 day period before the South Texas 2004 Christmas Snow Miracle.

I need to post my pics from the 2004 snow in Corpus. Much more than they had in McAllen.

Ed Mahmoud · #307 Postby **Ed Mahmoud** » Fri Dec 05, 2008 4:54 pm

cctxhurricanewatcher wrote:
Ed Mahmoud wrote:People may not put much stock in 360 hour plus progs from the GFS model, as they aren't always completely accurate, but I recall several GFS model runs available on my AccuWx PPV showed snow accumulation in the 10 to 15 day forecast period in the roughly 10 to 15 day period before the South Texas 2004 Christmas Snow Miracle.

I need to post my pics from the 2004 snow in Corpus. Much more than they had in McAllen.

CRP during the 2004 South Texas Christmas Snow Miracle

Hmmmm, that image doesn't like me...

Harlingen, TX, also on the Mexico border

Edit to add a Corpus Christi Christmas Snow Miracle Picture that doesn't produce a little red "x".

Extremeweatherguy · #308 Postby **Extremeweatherguy** » Fri Dec 05, 2008 5:12 pm

iorange55 · #309 Postby **iorange55** » Fri Dec 05, 2008 5:26 pm

I'm excited for next Tuesday maybe we'll see a couple of flakes. But I'm more excited for all this talk about cold air coming down after 10 days, I hope it actually forms and is not just one big disappointment.

jinftl · #310 Postby **jinftl** » Fri Dec 05, 2008 5:27 pm

Not related...but such a cool pic....view from indoor ski complex in Dubai (called Ski Dubai)....fake snow on alpine trees and all...

Agua · #311 Postby **Agua** » Fri Dec 05, 2008 5:30 pm

iorange55 wrote:I'm more excited for all this talk about cold air coming down after 10 days, I hope it actually forms and is not just one big disappointment.

Same here... move the ducks on down! :ggreen:

jinftl · #312 Postby **jinftl** » Fri Dec 05, 2008 5:59 pm

CPC Discussion on 8-14 day outlook (map posted at top of page)

PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS, MD
300 PM EST FRI DEC 05 2008

8-14 DAY OUTLOOK FOR DEC 13 - 19 2008

FOR THE WEEK 2 PERIOD MODEL SOLUTIONS ARE IN BETTER AGREEMENT COMPARED TO THE
DAY 6-10 PERIOD AFTER THE EXPECTED LONGWAVE PATTERN CHANGE OCCURS. A LONGWAVE
TROUGH BECOMES ESTABLISHED ACROSS THE WESTERN CONUS, WHILE A WEAK RIDGE
DEVELOPS ACROSS THE SOUTHEASTERN CONUS. THE DEVELOPMENT OF A LONGWAVE TROUGH
ACROSS THE WESTERN CONUS RESULTS FROM A STRENGTHENING RIDGE OVER THE ALEUTIANS.
TELECONNECTIONS ON A LARGE POSITIVE 500-HPA HEIGHT ANOMALY CENTER OVER THE
ALEUTIANS SUPPORT THE AFOREMENTIONED TROUGH/RIDGE PATTERN. THE OFFICIAL BLENDED
HEIGHT CHART SHOWS A POSITIVELY TILTED TROUGH EXTENDING FROM HUDSON BAY
SOUTHWEST INTO THE DESERT SOUTHWEST, A RIDGE OVER THE ALEUTIANS, AND A RIDGE IN
THE NORTH ATLANTIC. THIS EXPECTED LONGWAVE PATTERN YIELDS BELOW NORMAL
TEMPERATURES ACROSS MUCH OF THE WESTERN AND CENTRAL CONUS WITH ABOVE NORMAL
TEMPERATURES ACROSS THE SOUTHEASTERN CONUS. THE PRESENCE OF THE RIDGE IN THE
NORTH ATLANTIC MAY SLOW THE MODERATION OF TEMPERATURES ACROSS THE NORTHEAST AND
NEW ENGLAND. AS THE WESTERN CONUS TROUGH BECOMES DEEPER, A TREND TOWARDS WETTER
CONDITIONS IS EXPECTED IN CALIFORNIA WHILE ABOVE NORMAL PRECIPITATION SHOULD
CONTINUE ACROSS THE ROCKIES AND SOUTHWEST. DOWNSTREAM OF THE WESTERN CONUS
TROUGH, ABOVE NORMAL PRECIPITATION IS FORECAST FROM THE OHIO VALLEY INTO THE
NORTHEAST AND NEW ENGLAND. A WEAK RIDGE SHOULD RESULT IN BELOW NORMAL
PRECIPITATION ALONG THE GULF COAST AND FLORIDA. ACROSS MUCH OF ALASKA, BELOW
NORMAL TEMPERATURES AND PRECIPITATION CAN BE EXPECTED.

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: ABOVE AVERAGE, 4 ON A SCALE OF
1 TO 5, DUE TO GOOD AGREEMENT AMONG THE GFS ENSEMBLE MEAN SOLUTIONS,
TEMPERATURE TOOLS, AND PRECIPITATION TOOLS.

Extremeweatherguy · #313 Postby **Extremeweatherguy** » Fri Dec 05, 2008 11:07 pm

iorange55 · #314 Postby **iorange55** » Fri Dec 05, 2008 11:45 pm

After day 7 the GFS 00 confuses and saddens me.

jinftl · #315 Postby **jinftl** » Sat Dec 06, 2008 12:47 am

For forecasts that go out 1-2 weeks or more with these models, i think the best approach to maintaining overall satisfaction with the prospects is to pick the long range run you want to see the most (or interests you most), and don't even look at any other runs for a few days. At least for those few days, there is continuity and less of a roller coaster ride. Check the latest runs again in 72 or 96 hours....so instead of being 14 days out, we are talking 10 or 11 days out.

Looking at every run for 300 hours out is like wobble watching a hurricane midway between the Cape Verde Islands and Barbados ("it's definitely moving w-nw at 285 degrees one camp will claim, the other will argue that it is plain to the eye it is moving due west at 270 deg, maybe 275 deg but it could be the satellite angle skewing the apparent motion")...and drawing implications from those wobbles for or against a north gulf coast landfall....in other words....time to step away from the computer.

iorange55 wrote:After day 7 the GFS 00 confuses and saddens me.

iorange55 · #316 Postby **iorange55** » Sat Dec 06, 2008 1:11 am

jinftl wrote:For forecasts that go out 1-2 weeks or more with these models, i think the best approach to maintaining overall satisfaction with the prospects is to pick the long range run you want to see the most (or interests you most), and don't even look at any other runs for a few days. At least for those few days, there is continuity and less of a roller coaster ride. Check the latest runs again in 72 or 96 hours....so instead of being 14 days out, we are talking 10 or 11 days out.

Looking at every run for 300 hours out is like wobble watching a hurricane midway between the Cape Verde Islands and Barbados ("it's definitely moving w-nw at 285 degrees one camp will claim, the other will argue that it is plain to the eye it is moving due west at 270 deg, maybe 275 deg but it could be the satellite angle skewing the apparent motion")...and drawing implications from those wobbles for or against a north gulf coast landfall....in other words....time to step away from the computer.

iorange55 wrote:After day 7 the GFS 00 confuses and saddens me.

Thanks for the advice. I'll talk to you in about three days.

Ed Mahmoud · #317 Postby **Ed Mahmoud** » Sat Dec 06, 2008 12:50 pm

12Z GFS and 0Z Canadian both suggest some flakes mixed in (I doubt accumulations in a big way) North Shore of Lake Ponchartrain.

(The lake is too big, near surface will modify and mix too much over it for flakes in NOLA)

Ed Mahmoud · #318 Postby **Ed Mahmoud** » Sat Dec 06, 2008 2:18 pm

1050 to 1055 mb high in Northwest Territories/Yukon at Day 9 weakens to 1045 mb on Day 10 as it moves a bit South, big trough axix swings West, but a piece looks ready to maybe dive South (rebuckle the trough back to the West a bit?) Day 9 to Day 10.

I think I'd like the main Day 10 500 mb trough further West, but I'm not completely sure the best way to make it snow in Houston. The ultimate goal for any weather afficionado (or is that the National Title in the NCAA to the Super Bowl, which would be snow in South Florida?)

ETA

Boatloads of difference between individual GFS ensemble members 500 mb heights at 240 hours.
No help there...

jinftl · #319 Postby **jinftl** » Sat Dec 06, 2008 2:28 pm

Interesting discussion from NWS Los Angeles reagarding the end of the upcoming week...

NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA

DISCUSSION...
.LONG TERM...EC AND GFS IN GOOD AGREEMENT THROUGH THURSDAY AFTERNOON AND THEN
DRIFT APART. GFS ENSEMBLES BOMB-BURST AT THE SAME TIME...SO TAKE
FRIDAYS AND SATURDAYS FORECAST WITH A GRAIN OF SALT.

WEDNESDAY AND THURSDAYS FORECAST LOOKS GOOD. A LARGE 589 DM RIDGE
WILL BE SITTING OVER CALIFORNIA WITH DECENT LOW LEVEL OFFSHORE FLOW.
NOT MUCH IN THE WAY OF UPPER OR THERMAL SUPPORT SO DO NOT EXPECT TOO
MUCH WIND. THE REAL EFFECT WITH BE ON TEMPS WHICH SHOULD WARM QUITE
NICELY INTO THE 80 FOR MANY CST AND VLY LOCATIONS.

DESPITE THE UNCERTAINTY IN THE FRIDAY FORECAST IT DOES LOOK LIKE THE
RIDGE WILL BREAK DOWN AND THINGS WILL COOL OFF. THE REAL QUESTIONS
ARE HOW MUCH AND HOW FAST. STAY TUNED.

Extremeweatherguy · #320 Postby **Extremeweatherguy** » Sat Dec 06, 2008 3:54 pm

Here is the latest cold and snowy forecast for Oklahoma City for next week...

Monday Night: A chance of showers and thunderstorms. Cloudy, with a low around 39. Chance of precipitation is 40%.

Tuesday: A chance of rain and snow before noon, then a chance of snow. Cloudy, with a high near 42. Chance of precipitation is 40%.

Tuesday Night: A 20 percent chance of snow. Mostly cloudy, with a low around 22.

Wednesday: Mostly sunny, with a high near 43.

Wednesday Night: Partly cloudy, with a low around 24.

Looks like fun!

Southern Plains winter wx thread (2008-2009)

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