December 2016- End Of Year Forecast

[MontgomeryCoWx]

Lord.... would like to see it more centered on Alaska but that will do as long as we don't have an overwhelmingly positive AO.

[srainhoutx]

The afternoon updated Climate Prediction Center Day 8+ Analogs as well as the temperature and precipitation outlook for days 6-10 suggest increasing moisture developing across the SE United States where they sorely need the rainfall to help with the ongoing wild fires. The pattern also suggests a fairly significant trough is anchored across the Central United States meaning unsettled weather is likely across our Region as well.

[srainhoutx]

12Z GFS is suggesting a very intense cyclone developing to our WSW with a very deep trough digging well into Northern Mexico as we begin December. I see an intense 1054mb Greenland blocking Ridge developing and with a crashing Arctic Oscillation (AO) as well as a tanking Eastern Pacific Oscillation (EPO), the teleconnection indices continue to support increasing chances of a colder regime developing into December. We will need to monitor the trends as we progress further into December for the potential of steadily colder shots of Canadian air as well as an active stormy pattern across Texas.

[srainhoutx]

The morning Updated CFSv2 Monthly Climate model that tends to have a warm bias continues to trend toward a much colder and somewhat 'wetter' December.

The attachment 11262016 CFSv2 December CFSv2_NaT2m_20161126_201612.gif is no longer available

[srainhoutx]

The afternoon ECMWF suggests a near 1050mb Arctic High dropping South across NW/W Canada in the extended range with an even stronger Arctic High moving out of Siberia into the Arctic Circle to follow. Even the GFS and Canadian models are 'sniffing' this Hemispheric Pattern change we equally strong Arctic Highs heading South.

[unome]

QPF in early Dec starts off soggy for some in our area, albeit 6-7 days out from now

http://www.wpc.ncep.noaa.gov/index.php#page=qpf

http://www.wpc.ncep.noaa.gov/discussion ... isc=pmdepd

[MontgomeryCoWx]

12z GFS, Hour 204-384 looks cold. There's a stretch where we don't get out of the 30s in my neck of the woods.

Not that it won't be chilly before that timeframe, it will be colder than normal to normal from Wednesday onward.

[MontgomeryCoWx]

The GFS, Euro and CMC all agree that the first true Arctic plunge should happen around the 8th/9th timeframe.

From this Wednesday (11/30) onwards, we don't get warmer than the mid 60s in Montgomery County.

[srainhoutx]

The afternoon ensemble guidance suggests a very cold shot of Arctic air will continue building across the Western 2/3 rds of North America beginning this coming weekend. In fact some of the reliable computer models are suggesting temperatures across portions of Alaska and NW Canada may approach -70F for overnight lows around December 4th. Also the afternoon updated Climate Prediction Center Day 6 to 10 Day Outlook agrees with the possibility.

The attachment ecmwf-ens_T850a_namer_11 (1).png is no longer available

[srainhoutx]

Confidence is slowly increasing regarding the upcoming weekend, but there remains some uncertainty as to how quickly the cut off upper low over Northern Mexico ejects East. The ECMWF and its ensemble members remain progressive or faster moving this cold core upper low out of Mexico into Texas. The UKMET has joined the GFS/Canada model solutions suggesting a meandering slow moving upper low over Northern Mexico/Southern Arizona and Southern New Mexico and finally moving into West Texas about 24 hours slower than the ECMWF schemes.

To further complicate the sensible weather forecast is the Coastal low/trough scenario depicted by the model solutions along the South Texas Coast moving NE toward the Upper Texas Coast Saturday night into Sunday, possibly extending into early Monday. Brisk chilly NE winds at the surface suggest colder temperatures in the mid to upper 40's inland with 50's near the Coast with over running precipitation increasing as the Coastal low/trough develops. There is growing concern for some elevated thunderstorms lending to the potential of a heavy rainfall event, depending on where the Coastal low/trough develops and just how quickly the cold core upper low ejects from Northern Mexico into Texas. To further complicate the sensible weather forecast is the possibility of some phasing with another storm system further North across the Great Plains which appears to have some very cold air associated with it.

Another feature to watch much further NW across Alaska and NW Canada is the arrival of the first Arctic Outbreak we have seen in a couple of years. The reliable computer models are suggesting 2 meter temperatures may plummet to near -50F with even some locations in Eastern Alaska and NW Canada approaching near -70F for overnight lows next Sunday into next Tuesday. Arctic air appears to be on the move South next week into the Rockies and the Great Plains. We will monitor that feature as it gets a bit closer.

For now, attention turns to the weekend and what appears to be a raw and wet pattern as Winter returns to Texas. Stay tuned!

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
134 AM EST TUE NOV 29 2016

VALID 12Z FRI DEC 02 2016 - 12Z TUE DEC 06 2016

...INCREASING CONFIDENCE OF HEAVY RAINFALL THIS WEEKEND ACROSS THE
WESTERN/CENTRAL GULF COAST...

...MODEL EVALUATION/PREFERENCES...

THE MAJOR FORECAST CHALLENGE WILL BE THE EVOLUTION OF A FORECAST
CLOSED LOW OVER THE SOUTHWEST US THIS WEEKEND. A SHORTWAVE IS
FORECAST TO AMPLIFY AND FORM A CUTOFF LOW ON FRIDAY SOMEWHERE
ACROSS SOUTHERN AZ/NM OR NORTHERN MEXICO. SPREAD INCREASES
DRAMATICALLY WITH RESPECT TO THIS FEATURE AFTER THE CUTOFF FORMS,
WITH THE 12Z ECMWF/UKMET SUGGESTING A MORE PROGRESSIVE EASTWARD
MOTION...WHICH PROVIDES A SECOND RUN OF A FASTER SOLUTION IN BOTH
MODELS.

THE 18Z GFS/12Z CMC AS WELL AS THE 18Z GEFS MEAN/12Z CMCE MEAN ALL
SUGGEST A MUCH SLOWER PROGRESSION, KEEPING THE CUTOFF ACROSS
NORTHERN MEXICO OR WEST TX THROUGH SUNDAY. THE GFS HAS SHOWN A
MODERATE TO HIGH LEVEL OF RUN-TO-RUN CONSISTENCY WITH RESPECT TO
THIS SLOWER PROGRESSION OF THE CUTOFF. THERE IS GOOD AGREEMENT
AMONG THE GFS AND ITS ENSEMBLE MEAN...AS THERE IS AMONG THE ECMWF
AND ITS ENSEMBLE MEAN...SO ITS HARD TO IDENTIFY AN INTERMEDIATE
SOLUTION (I.E. BLENDING SUCH DISPARATE FORECASTS WOULD LOOK
UNREALISTIC IN IDENTIFYING THE LOWS AND FRONTS).

A BLEND OF THE 12Z ECMWF ENSEMBLE MEAN AND 12Z OPERATIONAL ECMWF
WAS USED...WITH MORE WEIGHTING TOWARDS THE MEAN SOLUTION GIVEN THE
LARGE ENVELOPE OF POSSIBILITIES.
SUPPORT WAS GIVEN BY RUN TO RUN CONTINUITY IN THE ECMWF FROM LAST
NIGHT IN MOVING THE SOUTHWEST CLOSED LOW EAST FASTER, PLUS THE 12Z
UKMET 500 MB WAVE PATTERN SHOWING ABOVE AVERAGE AGREEMENT WITH THE
ECMWF IN PHASING THE SOUTHERN STREAM ENERGY WITH THE NORTHERN
STREAM WAVE CROSSING FROM THE PLAINS AND UPPER MS VALLEY. FINALLY
THE VAST MAJORITY OF ECMWF ENSEMBLE MEMBERS HAVE THE MORE
PROGRESSIVE CLOSED LOW/TROUGH FORECAST. THE 00Z UKMET SLOWED DOWN
THE PROGRESSION OF THE CLOSED LOW...AND CLUSTERS WELL NOW WITH THE
00Z GFS..SO CONFIDENCE IN ANY ONE SOLUTION REMAINS LOW.

IN THE NORTHEAST...THE MODELS ARE IN GENERALLY GOOD AGREEMENT ON A
CUTOFF LOW CENTERED OVER SOUTHEASTERN ONTARIO ON DAY 3 (FRI 02
DEC), WHICH WILL BE IN THE PROCESS OF OPENING INTO A SHORTWAVE AS
IT BEGINS TO MOVE MORE QUICKLY EAST ACROSS THE NORTHEAST ON FRI.
THE ASSOCIATED SFC LOW PRESSURE SYSTEM WILL MOVE QUICKLY EAST AWAY
FROM NEW ENGLAND ON FRI.

OUT WEST..THE MEAN EAST PACIFIC TROUGH DRIFTS EAST WITH
TIME...WITH NEGATIVE HEIGHT ANOMALIES DEVELOPING AS THE TROUGH
CROSSES THE GREAT BASIN EARLY NEXT WEEK. AMPLIFICATION IS EXPECTED
DOWN STREAM FROM THE AMPLIFYING NORTHEAST PACIFIC RIDGE BY THE
MIDDLE OF NEXT WEEK.


...WEATHER HIGHLIGHTS/THREATS...

THERE IS POTENTIAL FOR HEAVY RAINFALL THIS WEEKEND ACROSS PORTIONS
OF THE UPPER TEXAS AND LA GULF COASTS...WITH STRONG MOISTURE
INFLUXES AND INCREASES IN AVAILABLE MOISTURE ALONG WITH LIFT OVER
A FRONTAL ZONE IN THE AREA. THE SLOWER GFS/CANADIAN GLOBAL CLOSED
LOW PROGRESSIONS WOULD DELAY THE TIMING. THERE IS POTENTIAL FOR
WIDESPREAD RAIN ACROSS THE PARCHED SOUTHEAST ONCE THE WAVE CROSSES
THE REGION.

WITH THE FRONTAL WAVE IN NORTHERN NEW ENGLAND...SNOW IS EXPECTED
IN NORTHERN MAINE THU AND TAPERING AS THE WAVE DEPARTS FRI.
EXPECT VALLEY RAIN AND MOUNTAIN SNOW TO SPREAD INTO THE PAC NW BY
SATURDAY AS A PACIFIC SFC FRONT MOVES INLAND...WITH SNOW
CONTINUING IN THE PAC NW AND NORTHERN ROCKIES SUN AS MOIST ONSHORE
FLOW CONTINUES UNDERNEATH A STRONG WEST-EAST UPPER LEVEL JET.

ANOMALOUSLY LOW HEIGHTS WILL PROMOTE BELOW AVERAGE TEMPERATURES
ACROSS MUCH OF THE SOUTHERN PLAINS SAT INTO SUN WITH THE
COMBINATION OF CLOUDS AND COLD ADVECTION.
LIKEWISE...COLD ANOMALIES DEVELOP WITH LOWERING HEIGHTS AND THE
ARRIVAL OF PRECIP OVER THE WEEKEND.

HIGH PRESSURE BUILDING DOWN THE LEE SIDE OF THE CANADIAN ROCKIES
SUPPORTS THE FIRST ARCTIC OUTBREAK OF THE SEASON DEVELOPING AND
MOVING SOUTH INTO MT AROUND THE MIDDLE OF NEXT WEEK...SO TEMPS
COULD DROP TO DOUBLE DIGITS BELOW NORMAL ON TUE 06 DEC IN MT IF
THIS OCCURS. LOWERING HEIGHTS IN THE GREAT BASIN AND INTERMOUNTAIN
WEST SUPPORTS TEMPS DROPPING BELOW NORMAL ACROSS ID/UT/WY AS WELL
BY TUE 06 DEC.

PETERSEN

[unome]

the uncertainty in the models makes it a good time to pay close attn to local forecasters, looking forward to later discussions:

http://www.weather.gov/hgx/
https://www.facebook.com/NWSHouston
https://twitter.com/nwshouston

https://twitter.com/iembot_hgx

The cooler/drier weather in the wake of this front for Weds/Thurs is expected to come to an end Friday. The return of onshore winds and low-level moisture will be setting the stage for a wet/active weekend. A deep closed upper low/trof (developing in the vicinity of the California Baja) is progged to move east across nrn Mexico Sat/Sun with a coastal surface trof setting up over the middle to lower TX coast out ahead of it. These systems combined with possible PWs near 2" are all pointing to widespread unsettled weather for most of the weekend with heavy rain as the main issue. Models appear to be in slightly better agreement with these runs, but we are still seeing the biggest differences with timing. So for now, stay tuned. Will be adding some initial wording for this weekend in the HWO later this morning.


http://www.wpc.ncep.noaa.gov/index.php#page=frt

[srainhoutx]

Tuesday morning briefing from Jeff:

Significant rainfall event increasingly likely this weekend over SE TX.

Surface boundary stalled along the US 59 corridor yesterday evening and has returned slowly northward overnight in response to an incoming short wave over the Rockies. South of this boundary dewpoints are in the 70’s while north of the boundary dewpoints are in the 40’s and 50’s and this has resulted in widespread dense fog near the boundary. Recently radar has shown a few showers starting to develop over the region and this will continue through the morning and into the afternoon hours with modest heating along the boundary and a secondary stronger incoming cold front. Any severe weather should be east of the area…but a thunderstorm or two will be possible today.

Cool and dry across the region Wednesday-Friday with lows in the 40’s and highs in the 60’s.

Weekend:
A powerful upper level storm system will drop into the SW US/N MX late this week and slow down this weekend. Increasing SW flow aloft will help to foster the formation of a surface coast trough from the upper TX coast to the lower TX coast where surface convergence will be maximized. NE surface winds will lock in cold surface temperatures in the 40’s and 50’s while a few thousand feet off the ground warm moist southerly flow will overrun the surface cold dome…the result will be widespread rainfall…some heavy.

While models continue to disagree on the timing of this feature with the GFS/CMC/UKMET the slowest and the ECMWF the faster…the all agree that some significant QPF is looking likely with this event. The GFS has been producing 3.0+ inches at BUSH IAH for the last several runs in a row. Given forecasted PWS approaching an extremely high 2.0 inches feel the threat for heavy rainfall is growing for this weekend. Main question is does the active convection focus near the surface trough off the coast or in an elevated fashion inland of the coast. Both are possible at this point…but the results would be vastly different QPF.

For now will go with widespread rainfall of 2-4 inches starting late Friday and lasting into Monday with isolated amounts of 6 inches possible. This is falling in line with current WPC forecasted amounts. Should the coastal surface trough back northward or form closer to the coast this would increase the threat for prolonged cell training of heavy rainfall.

The entire period will be cold with temperatures hovering in the 40’s to lower 50’s much of the weekend as NE surface winds drain cold air into the region under rain and clouds.

Gatlinburg/Pigeon Forge Wildfire Complex:

An incredibly devastating night for the resort areas of eastern TN as at least 14 wildfires driven by 50-70mph winds burned through Gatlinburg, Sevierville, Kodak, and Pigeon Forge/Dollywood. The magnitude of the fire that swept across this area yesterday afternoon and evening is rare for the eastern US. This exact event is what has been feared for so many weeks as crews have battled to gain control of the many fires burning in the Great Smokey Mountains in fear that weather conditions would change rapidly (as is normal for this time of year) …yesterday was that day.

The same low level jet that was roaring overhead of SE TX yesterday moved over E TN late yesterday afternoon with frequent surface wind gust of 50-70mph. Fires that had been burning in the Great Smokey Mountains to the south of Gatlinburg for weeks exploded even with RH values of 50% or higher being driven by intense surface winds. At 400pm the fire complex was nearing Gatlinburg from the SE/S/SW.

Between 400pm-1100pm the wildfire erupted into a firestorm with forward burn rates of nearly 50mph at times racing the fire northward through large sections of Gatlinburg and into Pigeon Forge. Crews working fire lines to protect the towns during the day were rapidly overrun and tremendous spotting of embers in the strong winds resulted in the initial fire expanding into at least 14 different fires in the matter of a few hours. Air support was grounded due to the strong surface winds and ground crews Fire rapidly overran the primary evacuation route out of Gatlinburg…see images below. Visitors in many of the areas hotels were trapped in the hotels as fire rapidly surrounded many of the structures.

Radar data showed nearly 45dbz in the smoke plume indicating large amounts of ash and objects were being lofted into the air suggesting the fire had developed surrounding inflow winds and strong center updrafts…something only seen in the most intense of wildfires. To give a picture of how quickly the fire evolved attached is a weather station in Gatlinburg which was overrun by the fire. The surface temperature spiked to 118 degrees and the RH fell to 21%...clearly the fire was creating its own weather as other sites nearby were reporting 50-60% RH values. Also note the peak wind gust of 69mph about 2 hours before the site was overrun…showing intense surface winds near the fire line. Note the inside structure temperature was 64.9 degrees…clearly the fire was advancing on the structure at this moment…and this was the last report from this site.

11292016 Jeff 1 untitled.png (119.92 KiB) Viewed 4846 times

Officially 100 structures were lost in the areas surrounding Gatlinburg and Pigeon Forge including a 16 story hotel, but the scope of the devastation will not likely be known until today when the sun rises…some estimates suggest nearly 1/3rd of the town of Gatlinburg burned overnight. As one meteorologist said this morning “not since the Great Chicago Fire has a combination of weather events, combined to cause such an event east of the Mississippi River”

Evacuation Traffic Being Overrun by fire on HWY 441

Wind driven spot fire on primary evacuation route out of Gatlinburg…HWY 441

11292016 Jeff 3 untitled.png (246.68 KiB) Viewed 4846 times

Downtown Gatlinburg:

11292016 Jeff 4 untitled.png (209.18 KiB) Viewed 4846 times

Fire advances on Gatlinburg out of the mountains

11292016 Jeff 5 untitled.png (245.76 KiB) Viewed 4846 times

Gatlinburg:

[MontgomeryCoWx]

12z GFS brings quite the Arctic blast early next Thursday morning.

Would not get out of the 30s in MoCo on Thursday followed by a couple of freezes.

[srainhoutx]

12z GFS brings quite the Arctic blast early next Thursday morning.

Would not get out of the 30s in MoCo on Thursday followed by a couple of freezes.

Looks like the first true "Bue Norther" we have seen in a couple of years. We will need to watch the Winter Storm that develops to our S and W and moves into the Plains laying down a bunch of snow. If we see significant snow cover develop across the Central and Southern Plains, that tends to suggest less in the way of airmass modification for any future cold air intrusions. Stepping down...

[srainhoutx]

The 12Z GEFS Ensemble Mean agree with the other guidance suggesting the first real shot of Arctic air surges South late next week.

Still looking raw, stormy and wet this coming weekend.

[srainhoutx]

the 12Z ECMWF suggests a bit slower ejection of the cold core upper low this weekend and has trended toward the slower and deeper solutions with the trough to our West. That would mean the heavy rainfall potential could increase a bit with better agreement with the other guidance and the ECMWF shows a developing Coastal trough/low as well.

The attachment 11292016 12Z EC 120 f120.gif is no longer available

In the extended range, the "Blue Norther" is still showing up very well for arrival a week from tomorrow.

[srainhoutx]

The weekend forecast is becoming increasingly worrisome, but at this range still lacks confidence. The Global Models and their ensemble members have come into better agreement regarding the very deep trough that looks to settle well into Mexico near or just East of the Baja Peninsula. A very potent cold core low at the 500mb level is expected to deepen over Mexico and tap a very noisy sub tropical Jetstream with abundant tropical moisture at the mid and upper levels reaching back to near Hawaii. That moisture appears to have several embedded disturbances that will round the base of the deep trough with a couple of shortwaves dropping S along the Western flank of the trough along the Washington/Oregon/California areas adding some energy to the potent cold core low. Overrunning precipitation is expected to develop atop a shallow cold airmass at the surface Friday night into Saturday with a strong SW flow aloft. The reliable models have agreed today that a Coastal low/trough could organize near Brownsville to Corpus Christi with the potential of a Coastal low developing Saturday night into Sunday and possibly next Monday. Elevated thunderstorms are possible Saturday night into early Monday as the Coastal low moves along the Upper Texas and SW Louisiana Coast. The upper low looks to begin shearing out Sunday evening into Monday as it moves across Texas. The afternoon Update 7 Day Quantitative Precipitation Forecast suggest bouts of heavy rainfall may be possible, particularly along and offshore of the Texas Coast. This is a very complicated and challenging forecast, so expect changes as we near the end of the work week.

[DoctorMu]

Freezing down to the HOU area next Friday am (Dec 9)...off in fantasyland. Waiting for 18z run to complete.

[MontgomeryCoWx]

Long range keeps reloading cold air in our source region and putting it on the shot block down to our smiling faces

[Andrew]

Looks like an active period for SE Texas will occur over the coming weeks. The cutoff low/coastal low combination this coming weekend looks tricky as it will be a battle between the upper dynamics to the west and the coastal low to the east. On multiple occasions we have seen the coastal low "steal" much of the moisture that would make it more inland. As it stands right now I do expect locations along the coast will see highest totals and a relatively sharp gradient will exist as we move inland. With that said, the ECMWF is more encouraging with moisture streaming further inland (less influence from the coastal low) and isolated totals reaching 5-7 inches inland. Overall though much needed rain looks to occur for most across the region.

Next, the artic outbreak is looking more and more likely for the December 9th timeframe as both global models continue to keep the AO in a negative state. The ECMWF is most aggressive with the colder air showing dewpoints reaching close to the single digits over parts of SE Texas. The GFS keeps dewpoints in the mid to upper teens though. Still a longways out and modification and proper adjustments will need to be made.