Another chilly morning across our Region, but dew points have risen, so no heavy frost issues today (we did have frost on roof tops in NW Harris County with a low temp of 33 F). The surface high pressure ridge over Louisiana will slide E today and a return flow off the Gulf will begin with SE winds and warming temps and increasing moisture as well as fog. Today should be the end of the sorely needed sunshine before clouds increase and sea fog develops and temperatures continue to moderate to above normal. As you can see by the December Update from NWS Houston/Galveston, we have been below normal for 3 weeks. (see Below)
The general synoptic pattern of a split zonal flow where the cold air is bottled up along the Northern US and a Ridge off the Pacific West Coast and a SE Ridge over the Bahamas should allow for further warming and streamer showers and drizzle to develop by Friday. Changes lurk ahead as a potent short wave dives S into the Baja/Southern California late Thursday and cuts off while a modified Polar front drops S into Texas on Friday.
Uncertainty arises as to how far S the front sags before stalling across Central Texas as well as when the SW upper low begins its journey E towards Texas. The GFS appears to be too fast moving the U/L to the E while the Euro and Canadian are slower. Since the slower ejection solution of similar patterns we have seen so far this fall season seems likely, more credence will be given to the non American guidance at this time.
Saturday should be the warmest day we see this week and also the most unsettled. Showers and storms, some possibly severe may warrant an increase in Severe Weather Watch mode and will need to be monitored later this week. It does appear that there is a chance for a bit of negative tilt to the trough which suggests all modes of severe weather may be possible. A surface low could develop over Central Texas on Saturday as the upper low approaches from NE Mexico. We will also need to monitor for the potential of heavy rainfall as moisture increases to near 3 standard deviation above normal for this time of year. Saturday evening could be very stormy, so be aware if you have Holiday party plans.
Sunday looks to turn much colder as the front finally pushes offshore. Another stronger front may pass on Monday as a wound up Winter Storm moves NE across the Mid Mississippi Valley towards the Upper Mid West early next week. With a general pattern of a Ridge to our West offshore of the Coast of California and another to our East offshore in the Atlantic, cooler and dry weather should arrive for Christmas.
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PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
744 AM CST SUN DEC 15 2013
...COLD START TO THE MONTH OF DECEMBER...
THE FIRST FOUR DAYS OF DECEMBER STARTED ABOVE NORMAL BEFORE AN
ARCTIC FRONT HEADED SOUTHWARDS AND DROPPED TEMPERATURES
DRASTICALLY ACROSS THE AREA. BEHIND THE FRONT TEMPERATURE
DEPARTURES OF 15 TO 20 DEGREES BELOW NORMAL WERE COMMON ACROSS
THE FOUR FIRST-ORDER CLIMATE SITES. THE EVEN MORE UNUSUAL NATURE
OF THE COLD AIR IS HOW LONG SOUTHEAST TEXAS HAS BEEN BELOW NORMAL
NOW. EVEN THOUGH THE ARCTIC AIR MASS HAS LONG SINCE MOVED OFF A
SERIES OF REINFORCING COLD FRONTS HAS KEPT SOUTHEAST TEXAS BELOW
NORMAL FOR AN EXTENDED PERIOD OF TIME. THE TABLE BELOW SHOWS THE
MONTH TO DATE (DEC 1ST - 14TH) DEPARTURE FROM NORMALS(1981 - 2010)
FOR THE FOUR FIRST- ORDER CLIMATE SITES IN OUR AREA:
SITE MONTHLY TEMP (DEPARTURE)
COLLEGE STATION (CLL) 47.5(-6.0)
CITY OF HOUSTON (IAH) 51.3(-4.4)
HOUSTON HOBBY (HOU) 52.4(-4.5)
CITY OF GALVESTON (GLS) 53.4(-5.3)
BUT HOW COLD IS THIS FOR THE FIRST 14 DAYS OF DECEMBER? FOR
COLLEGE STATION IT RANKS THE 7TH COLDEST START TO DECEMBER WITH
RECORDS GOING BACK TO 1902. THE CITY OF HOUSTON RANKS AS THE 16TH
COLDEST START TO DECEMBER WITH RECORDS GOING BACK TO 1892. THE
52.4 AT HOUSTON HOBBY RANKS AS THE 10TH COLDEST START TO DECEMBER
WITH RECORDS GOING BACK TO 1944. THE CITY OF GALVESTON RANKS AS
THE 12TH COLDEST START TO DECEMBER (TIED WITH 1936) WITH RECORDS
GOING BACK TO 1874.
23
...WARM UP POSSIBLE?...
SOUTHEAST TEXAS WILL BEGIN TO WARM UP AFTER ALMOST THREE WEEKS OF BELOW
NORMAL TEMPERATURES. THE PERIOD OF NOVEMBER 22ND THROUGH DECEMBER 15TH WAS
THE THIRD COLDEST ON RECORD FOR THE CITY OF HOUSTON AND THE CITY OF GALVESTON
AND THE SECOND COLDEST ON RECORD FOR COLLEGE STATION AND HOUSTON HOBBY AIRPORT.
HERE ARE THE FIVE COLDEST NOV 22 - DEC 15 FOR THE FOUR FIRST ORDER CLIMATE SITES.
CITY OF CITY OF HOUSTON COLLEGE
HOUSTON GALVESTON HOBBY STATION
47.0 1898 48.2 1898 49.2 1937 44.3 1972
48.9 1976 51.6 1937 50.4 2013 46.3 2013
49.4 2013 51.9 2013 50.5 1976 47.7 1937
50.3 1972 52.0 1976 52.2 1979 48.0 1976
50.8 1937 53.5 1911 52.9 1963 49.0 1963
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
118 AM EST TUE DEC 17 2013
VALID 12Z FRI DEC 20 2013 - 12Z TUE DEC 24 2013
...OVERVIEW...
GEFS...NAEFS AND EC ENSEMBLES RECOGNIZE SPLIT-FLOW PATTERN ALONG
THE WEST COAST OF NORTH AMERICA AND CONFLUENT PATTERN DOWNSTREAM
OVER THE CANADIAN MARITIMES AND NORTH ATLANTIC THIS MEDIUM RANGE
PERIOD.
NORTHERN STREAM IS EXPECTED TO BECOME ENTRAINED WITH A SERIES OF
MIGRATORY PACIFIC SYSTEMS AND WILL LIKELY CONTAIN THE WINTER-TYPE
PRECIPITATION--MAINLY FOR THE NORTHERN ROCKIES-PLAINS...GREAT
LAKES AND NORTHEAST THIS FORECAST PERIOD. FROM A SYNOPTIC-SCALE
PERSPECTIVE...THE PACIFIC STORM TRACK SHOULD BE A SERIES OF SUBTLE
BUT DISTINGUISHABLE MID-LEVEL CIRCULATIONS TRACKING FROM THE
SOUTHERN CANADIAN ROCKIES OF ALBERTA...EASTWARD THROUGH THE UPPER
MIDWEST AND ST LAWRENCE VALLEY THIS FORECAST PERIOD.
SOUTHERN STREAM ENERGY AND MOISTURE REMAINS THE VOLATILE 'WILD
CARD'...WITH WEST-SOUTHWESTERLY FLOW DRIVING DOWNSTREAM FROM THE
DESERT SOUTHWEST AND MID-RIO GRANDE VALLEY EASTWARD INTO THE
OZARKS AND OHIO VALLEYS. THE VOLATILITY WILL BE TWO-FOLD...A BROAD
MID-LEVEL CYCLONE OFF THE CENTRAL CALIFORNIA COAST MIGRATES INLAND
EARLY IN THE PERIOD...FOLLOWED BY A DIGGING EASTERN PACIFIC
SHORTWAVE...THAT BRIEFLY CLOSES OFF INVOF THE LOWER COLORADO RIVER
BASIN--THEN EJECTS EASTWARD ACROSS THE SOUTHERN ROCKIES AND
PLAINS. BOTH HAVE THE POTENTIAL TO DELIVER DECENT PULSES OF
PRECIPITATION TO THE SOUTHWEST...SOUTHERN ROCKIES AND DOWNSTREAM
THROUGH THE SOUTHERN TIER OF STATES THIS FORECAST PERIOD.
BOTH JET STREAMS MERGE DOWNSTREAM OVER THE NORTHEAST AND CANADIAN
MARITIMES...GENERATING A BROAD CYCLONIC FLOW SOUTHEAST OF
GREENLAND. AS PREVIOUSLY MENTIONED...THE MERGING STREAMS SERVE AS
THE WESTERN/NORTHWEST FLANKS OF STRONG RIDGING IN THE
BAHAMAS...FLORIDA AND THE EASTERN GULF OF MEXICO.
...MODEL PREFERENCES AND UNCERTAINTY ASSESSMENT...
FOLLOWING THE PREVIOUS WPC GRAPHICS THROUGH DAY 7 WAS AN EASY
TASK...WITH A COMBINATION OF THE 16/12Z EC ENSEMBLES MEAN AND
NAEFS MEANS MAINTAINING DECENT CONTINUITY WITH THE FRONTAL
PROGRESSION OF THE ARCTIC FRONT DAY 4-5...BUT THE MEANS GENERALLY
LOSE ANY/ALL SUBTLE NORTHERN STREAM FEATURES EXITING SOUTHERN
ALBERTA. GIVEN THE STRONGLY-SHEARED ENVIRONMENT ALOFT OVER CENTRAL
CANADA AND THE DRY ARCTIC AIRMASS IN PLACE...THE MEANS FOCUS OF
THE CENTERS OF HIGH PRESSURE RATHER THAN ANY MID-LEVEL CYCLONIC
FLOW MIGRATING DOWNSTREAM FROM WEST TO EAST. BOTH MEANS MAINTAIN
MORE OF A DOMINANT SOUTHERN STREAM FLOW FROM THE OZARKS
NORTHEASTWARD INTO THE OHIO VALLEY AND NORTHEAST-CANADIAN
MARITIMES BY THE END OF THIS PERIOD.
SOME ASPECTS OF THE GFS/ECMWF/CANADIAN AND UKMET WERE VALID AND
COULD ADD DETAIL TO THE PROJECTED FLOW PATTERN ACROSS THE CONUS
THIS PERIOD.
THE 16/12Z DETERMINISTIC UKMET...15/18Z GFS AND 15/12Z ECMWF HAD
THE GENERAL IDEA ALL ALONG...WITH A SECOND ALBERTA CLIPPER-TYPE
SYSTEM TRACKING THROUGH THE UPPER MIDWEST SATURDAY NIGHT AND
SUNDAY...AND ALL RECENT PIECES OF GUIDANCE CONTINUE TO REAFFIRM
THE FRONTAL POSITION AT THE START OF DAY 3 (20/12Z) BETWEEN LAKE
HURON AND THE SOUTHERN OZARKS. THIS HAS BEEN A TRACK-ABLE FEATURE
FOR 5 DAYS NOW...AND IS GOING TO BE RATHER CLOSE TO THE MODEL
PROGS FROM 12Z DECEMBER 13TH.
THE FACT THAT THE FLOW ALOFT OVER CENTRAL CANADA AND ARCTIC CANADA
HAS RESOLVED ITSELF...ADDS CONFIDENCE TO THE FORECAST...WITH THE
DAY 3 OPEN WAVE EXITING THE GREAT LAKES--SHEARING OUT QUICKLY OVER
EASTERN CANADA. IT IS FOLLOWED BY ANOTHER PACIFIC WAVE EXITING
SOUTHERN ALBERTA...BY DAY 4-5...AND TAKING A STORM TRACK THROUGH
SOUTH CENTRAL CANADA. A THIRD SYSTEM MOVES OUT OF THE SOUTHERN
CANADA ROCKIES DAYS 6-7.
THE SPACING BETWEEN NORTHERN STREAM SYSTEMS CONTINUES TO BE RATHER
ACCURATE AND PREDICTABLE. THIS DAY 4-5 WAVE TRACK THROUGH SOUTHERN
CANADA BRINGS THE ARCTIC AIRMASS INTO THE NORTHERN PLAINS AND
UPPER MIDWEST FOR FRIDAY AND SATURDAY. MORE IMPORTANTLY...IS OPENS
THE DOOR FOR MORE PACIFIC ENERGY TO ESTABLISH A NORTHWEST FLOW OFF
THE PACIFIC AND INTO/THROUGH THE PACIFIC NORTHWEST AND ROCKIES
THROUGH THE END OF THE MEDIUM RANGE PERIOD. THIS SERVES AS THE
RATHER STABLE NORTHERN STREAM SPLIT IN THE FLOW PATTERN ALONG THE
WEST COAST OF THE CONTINENT.
THE 16/12Z DETERMINISTIC GUIDANCE HAS COME INTO BETTER
AGREEMENT...THOUGH NOT PERFECT...WITH THE SOUTHERN STREAM AND
SURFACE WAVE DEVELOPMENT ALONG THE ARCTIC FRONT. THE LATEST IDEA
IS FOR AT LEAST TWO PULSES OF SHORTWAVE ENERGY AND PRECIPITATION
TO RIDE ALONG THE FRONT...WITH THE SOUTHERN PLAINS...OZARKS AND
OHIO VALLEY REGIONS TAPPING THE WESTERN GULF OF MEXICO.
HENCE...THE DEEPER LOW-LEVEL MOISTURE...AND HEAVY RAINFALL THREAT
BEGINS TO TAKE SHAPE ON SATURDAY OVER TEXAS/OKLAHOMA AND
LOUISIANA-ARKANSAS AND THE LOWER MS VALLEY...WESTERN OHIO VALLEY
SATURDAY NIGHT AND SUNDAY MORNING.
HERE...THE EC AND NAEFS MEANS BASICALLY STRETCH OUT THE SURFACE
TROUGH NORTH-NORTHEASTWARD FROM THE NORTHWEST GULF OF MEXICO INTO
THE MID-OHIO VALLEY...WITH THE INDIVIDUAL MEMBERS RUNNING AT
DIFFERENT PACES ALONG THE FRONT. THEREFORE...THE MEANS CONTINUE TO
SERVE AS THE BASELINE FOR THE SURFACE GRAPHICS. BUT THE 16/12Z
DETERMINISTIC GFS...CANADIAN AND/OR ECMWF WOULD SUGGEST A 996MB TO
1000MB SURFACE WAVE AND BROAD WARM FRONT DEVELOP IN THE SOUTHERN
STREAM...AND REMAINING SEPARATED FROM THE NORTHERN STREAM UNTIL
THEY CAN MERGE OVER THE ST LAWRENCE VALLEY AND NORTHERN NEW
ENGLAND ON SUNDAY NIGHT AND MONDAY.
THIS SEEMS TO FIT THE GENERAL IDEA THAT A CONFLUENT FLOW AND AREA
FOR MERGING JET STREAMS WILL REMAIN INVOF THE NORTHEAST AND
ATLANTIC CANADA THIS MEDIUM RANGE PERIOD.
...SENSIBLE WEATHER HIGHLIGHTS...
BROAD-SCALE WARM UP AHEAD OF THE ARCTIC BOUNDARY WILL CONTAIN A
MODIFIED WESTERN GULF OF MEXICO AIRMASS.
HEAVY RAINFALL EVENT(S) ARE GATHERING MODEL MOMENTUM AND CONSENSUS
INVOF THE MERGING JET STREAMS WITH EMPHASIS ON THE SOUTHERN
STREAM'S ABILITY TO GATHER LOW-LEVEL INFLOW OFF THE GULF. THIS
BEGINS TO DEVELOP IN EARNEST ACROSS THE SOUTHERN PLAINS OF
TEXAS...EASTERN OKLAHOMA...THE OZARKS EARLY IN THE FORECAST
PERIOD. AND THIS WEEKEND INTO MONDAY...THE OHIO VALLEY AND
PORTIONS OF THE SOUTHEAST AND NEW ENGLAND WILL BE UNDER THE
INFLUENCE OF MOIST SOUTH TO SOUTHWEST FLOW ALOFT.
VOJTESAK
Carla/Alicia/Jerry(In The Eye)/Michelle/Charley/Ivan/Dennis/Katrina/Rita/Wilma/Humberto/Ike/Harvey
Member: National Weather Association
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