January Weather Discussion: Slight Chance Severe Storms

[brazoria121]

alrighty thank you very much steve..ill be watching and reading lol

[wxman57]

Let's compare yesterday's 12Z (6am) GFS run for IAH and last evening's 00Z (6PM) run. Note that temps indicated are for 6am and 6pm, they're NOT the morning low or afternoon high, though the 6am temp isn't too far from the morning low. Have to add 4-7 deg to the 6pm temp for the afternoon high.

12Z run is cold, and it does show precip:


The 00Z run is colder but with less moisture.

[srainhoutx]

The HPC moring Prelim Update explains well the differences in the medium range (this week into the weekend). Those wondering why some NWS offices were cautious regarding next week will see that many details shorter term still lack continuity. Models often struggle with the individual features with such driving forces of AO/NAO.

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
829 AM EST TUE JAN 04 2011

VALID 12Z SAT JAN 08 2011 - 12Z TUE JAN 11 2011


PRELIMINARY UPDATE...

THE PRELIMINARY FRONTS AND PRESSURES FOR DAYS 3 THROUGH 7 WERE
UPDATED USING THE 00Z/04 ECENS MEAN. THE ECENS MEAN AFFORDS A
YARDSTICK OF SORTS FOR THE LOWER THAN AVERAGE CONFIDENCE IN
PREDICTING THE FLOW PATTERN ACROSS CENTRAL NORTH AMERICA AT THE
MEDIUM RANGE. THE MAIN METEOROLOGICAL COMPONENTS ARE THE ONGOING
NEGATIVE NAO SIGNAL AT HIGH LATITUDES AND A STRONG PACIFIC JET
SPLITTING OVER THE WESTERN UNITED STATES. THE DETERMINISTIC
MODELS HAVE SHOWN A HIGH DEGREE OF RUN-TO-RUN VOLATILITY WITH THE
HANDLING OF SHORTWAVES...WITH NO PARTICULAR SOLUTION EMERGING AS A
CONSISTENT THEME. THE MOST PRESSING CONCERN IS WHAT BECOMES OF
THE ENERGY CROSSING THE CENTRAL AND EASTERN STATES LATE IN THE
PERIOD. OLDER EUROPEAN CENTRE GUIDANCE KEPT CYCLOGENESIS
SUPPRESSED TOWARD THE GULF COAST AT THIS TIME RANGE...WHILE THE
LAST COUPLE RUNS...AS WELL AS THE 00Z GEM GLOBAL...ALLOW THE
SUBTROPICAL RIDGE TO EXERT INFLUENCE OVER THE SOUTHEAST. THE
GFS...GEFS MEAN...AND 00Z UKMET ARE CONSIDERABLY SLOWER WITH THE
ENERGY IN QUESTION...ABOUT A DAY SLOWER WITH THE GFS/GEFS...AND
MORE THAN A DAY WITH THE UKMET. FELT THAT STICKING CLOSE TO THE
MORE STABLE ECENS MEAN WAS THE BEST BET FOR THIS FORECAST COAST TO
COAST.


CISCO

AO heading back toward record negative territory...



NAO still negative...

[wxman57]

For now, we (at work) are just concerned about the potential for a hard freeze at our client locations (refineries/petrochemical facilities). Extended periods of temperatures below 25-28 degrees could cause as much damage to such a facility as a hurricane - if they don't take the precautions early enough. I certainly wouldn't trust any model runs as far as predicting precip 8-14 days out. But I think there's enough consensus to give me more confidence that some Arctic air will spill south next week. We don't know how much will make it down here yet.

[brazoria121]

pretty extreme for being so far out..

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORMAN OK
500 AM CST TUE JAN 4 2011


OTHER HAZARDOUS WEATHER...
A MASSIVE BUILD-UP OF ARCTIC AIR WILL OCCUR OVER WESTERN CANADA
LATER THIS WEEK AND WILL EXPAND SOUTH OVER THE WEEKEND...
LEADING TO A PROLONGED PERIOD OF POTENTIALLY SEVERE ARCTIC COLD OVER
THE SOUTHERN PLAINS BEGINNING LATE THIS WEEKEND OR EARLY NEXT WEEK.
THE INITIAL BLAST OF ARCTIC AIR APPEARS MOST LIKELY TO ARRIVE IN THE
SOUTHERN PLAINS LATE SUNDAY OR SUNDAY NIGHT. THIS COULD BE THE START
OF A PROLONGED STRETCH OF SUBFREEZING TEMPERATURES THAT MAY LAST
THROUGH MOST OR ALL OF NEXT WEEK. RESIDENTS OF OKLAHOMA AND NORTH
TEXAS ARE ENCOURAGED TO BEGIN PREPARING NOW FOR THE POSSIBILITY OF
DANGEROUSLY COLD CONDITIONS NEXT WEEK.

IN ADDITION TO THE ARRIVAL OF VERY COLD WEATHER... THERE IS A
POSSIBILITY OF SNOW AND BLOWING SNOW SUNDAY INTO MONDAY...
ESPECIALLY OVER NORTHERN OKLAHOMA.

THE NEXT SCHEDULED HAZARDOUS WEATHER OUTLOOK WILL BE ISSUED AT NOON
TODAY.

[Andrew]

For now, we (at work) are just concerned about the potential for a hard freeze at our client locations (refineries/petrochemical facilities). Extended periods of temperatures below 25-28 degrees could cause as much damage to such a facility as a hurricane - if they don't take the precautions early enough. I certainly wouldn't trust any model runs as far as predicting precip 8-14 days out. But I think there's enough consensus to give me more confidence that some Arctic air will spill south next week. We don't know how much will make it down here yet.

Thanks for the update wxman. Let us know if you hear anything else.

[srainhoutx]

E-mail from Jeff...

Radar already showing numerous showers along and south of I-10 from San Antonio to western Harris County. Showers and maybe a clap of thunder are forming north of a returning warm front currently located along the upper TX coast from offshore of Matagorda Bay to roughly 20 miles south of Galveston. Warm moist Gulf air mass is being lifted over the retreating shallow cold dome resulting in lifting and the formation of showers. Fog has also developed across the region as is typical north of a warm front.

Noisy SW flow aloft will provide a few small scale disturbances today and tonight to help interact with the warm front and a developing surface trough over the NW Gulf to keep decent rain chances in place. Strong mid level capping inversion should keep thunderstorms on the low side except maybe near the coast. Overall foggy, rainy, and cool conditions through tonight. Warm front may push slightly inland this evening allowing mid 60 degree dewpoints to spread across mid 50 degree water temperatures. This would support an episode of dense sea fog starting late this afternoon through about mid morning on Wednesday along the beaches and the coastal bays. Weak cold front will cross the area Wednesday afternoon pushing fog offshore and drying the area under increasing offshore flow.

Thursday and Friday will be dry and “mild” or near normal for early January standards with lows in the 40’s and highs in the 60’s under mostly sunny skies.

Next storm system heads toward the region this weekend as a strong cut-off low pressure system off southern CA coast gradually becomes dislodged and forced eastward. After being in decent agreement yesterday, forecast models have once again developed some timing differences on when this system will impact the state. Models are typically too fast in ejecting cut-off lows eastward and will side with the slower solution focusing the highest rain chances on Sunday morning or possibly during the day Sunday versus the faster GFS showing the system Saturday evening. Track of the short wave has also bounced around some overnight and now is expect to be slightly further north. Still expect a good shot at widespread rainfall Saturday evening-Sunday midday with strong upper level dynamics coming in to play with a moist Gulf air mass. A little too early to look at severe parameters, but we could be talking about some severe weather especially along and S of I-10 with a 120kt jet streak overhead by early Sunday morning. Widespread rains of 1-2 inches looks likely with this system with a few isolated totals upwards of 3 inches which will be welcomed in the drought areas.


Potential Arctic Outbreak:

Very cold air mass will be building over NW Canada late this week with potential delivery into the US late this weekend.

Upper level pattern will undergo significant amplification with a building ridge over Alaska and NW Canada and high latitude blocking downstream over eastern and central Canada. Extremely cold air mass now over northern Siberia (-60F to -80F) will begin to slide across the north pole and southward into NW Canada where building surface pressures will begin to brew a massive arctic high pressure cell. Models continue to advertise at least a 1060mb+ arctic high over NW Canada by late this weekend with a favorable upper level delivery pattern southward. Will taper the severity of this potential outbreak at least for the initial shot early next week. Bitter cold should enter the US via Montana Saturday and surge rapidly southward down the plains as the cold and dense air mass dams up against the Rockies. Shallow arctic air masses tend to move southward faster than models predict and this will need to be watched for a faster arrival than currently expected. Arctic boundary should reach TX Monday and clear the coast Tuesday with very cold air spreading across the entire state. Expect lows well into the 20’s by Wednesday morning and highs only in the 30’s and 40’s for the middle of next week. Appears that moisture may make an attempt at spreading into the cold air mass toward the end of next week or the following weekend. GFS shows a secondary strong surge arriving around the 16th of the month with several days at or below freezing. In fact the GFS guidance for DFW shows temperatures below freezing from the 12th to the 20th during the entire period. At this point this does not appear to be a historic outbreak (such as Dec 1983 or Dec 1989), but possibly as severe as last January. The real bad outbreaks in the past have come in waves with each surge building on the previous surge and keeping sub-freezing temperatures locked in place for days and days. The models are showing this “surge” type pattern in the extended ranges…the questions remain as to how much cold air comes southward and does it all dump at once for a quick hit or do we get front after front keeping the cold air locked in place for several days.

[redneckweather]

It's entertaining to read the latest AFD's this morning after the latest Euro run. Yesterday they were using the term 'historic' and 'the coldest air in decades' and now after 1 model run, that has come to a hault. It seems like when we see a strong arctic high in the models over the past few years, we instantly start comparing it to big outbreaks in '83 and '89, just like this one.

IMO, we will get pretty darn cold but nothing near historic. I'm just hoping we get some moisture with this and have a few snow flakes fall from the sky. That would be really nice!

[ronyan]

It's entertaining to read the latest AFD's this morning after the latest Euro run. Yesterday they were using the term 'historic' and 'the coldest air in decades' and now after 1 model run, that has come to a hault. It seems like when we see a strong arctic high in the models over the past few years, we instantly start comparing it to big outbreaks in '83 and '89, just like this one.

IMO, we will get pretty darn cold but nothing near historic. I'm just hoping we get some moisture with this and have a few snow flakes fall from the sky. That would be really nice!

About 6 inches of snow would be really nice! I still don't think we know exactly how strong the high will be in a few days, but it's always fairly safe to not predict record breaking events so far in advance.

[tireman4]

I do hope this all pans out, well at least a white January 2011. Great running weather though. Cool, crisp and lovely. Cannot imagine why cyclists would not want it cold. LOL

[srainhoutx]

1058mb in Western Canada is mighty impressive...

[srainhoutx]

1060mb heading into MT...

[Andrew]

12z coming in stronger than 6z at the surface. Haven't looked at upper levels (on phone) but it should be pretty impressive.

[srainhoutx]

Classic Arctic Outbreak signature folks...

[helloitsb]

oh man not sure if im right or not but is the 12z what i think it is around hour 228?

[Andrew]

[BiggieSmalls]

Can't wait to see what this has in store for Dallas

[wxman57]

http://www.nco.ncep.noaa.gov/pmb/nwprod ... p_228l.gif

See my "sticky" thread above about interpreting these maps. That precip you see on the map may actually be 12 hours prior to the temperature contours reaching the positions on that map.

In this case, though, temps are indicated to be cold enough for winter precip in the 12 hours prior to that 228hr map. However, it's a long-range forecast of precip, something the models have a hard time forecasting several days in advance.

One thing I notice is the 12Z GFS isn't as cold as yesterday's runs toward the end of next week. It still forecasts a low at IAH of 19-20 next Wed/Thu, but then a slow warm-up.

[Andrew]

http://www.nco.ncep.noaa.gov/pmb/nwprod ... p_228l.gif

See my "sticky" thread above about interpreting these maps. That precip you see on the map may actually be 12 hours prior to the temperature contours reaching the positions on that map.

I know. I was posting the image for the temps. It's impossible to predict moisture that far out.

[Mr. T]

http://www.nco.ncep.noaa.gov/pmb/nwprod ... p_228l.gif

See my "sticky" thread above about interpreting these maps. That precip you see on the map may actually be 12 hours prior to the temperature contours reaching the positions on that map.

The 0c line reaches us at 168 and does not leave until beyond 300. That's definitely snow