April Weather Discussion.

[srainhoutx]

Although we are still a ways out and folks normally have a lot of activities planned, guidance suggests that we may see some stormy weather during the Easter Weekend time frame. We shall see.

ECMWF @ 216 Hours



GFS @ 216 Hours

[Ptarmigan]

I remember Good Friday and Easter Day night in 1992 was very stormy. The Good Friday event was a heavy rain event. There was lots of lightning, hail, and heavy rain from that storm on Easter Day.

[wxdata]

Noticed that the Euro has slowed the upper system down a bit (at least for this run.)

http://www.ecmwf.int/products/forecasts ... !chart.gif

[wxman57]

It does look like it could be a stormy Easter Sunday. We may be able to escape the storms Friday and Saturday, though. Too early to be sure about Saturday's storm potential. I'll be in Florida next week at the NHC, where it'll be just as cold as it's been here. Can't even get an above-80F day in Florida in early April!

[wxman57]

Overnight GFS run moves the front through next Saturday, leaving Sunday warm. 2-meter temps in the low 80s for Easter. First prediction of 80+ temps by the GFS this season.

[srainhoutx]

Those 80's temps certainly look nice on the GFS finally. Of coarse that does raise the chances that we are heading toward some active weather as well. I noticed that FWD is already mentioning the chance of severe weather from the storm system on Easter Weekend. Timing will be an issue on which model will be correct though.

[srainhoutx]

12Z GFS continues the trend for some rather rough weather on the Saturday before Easter.

[srainhoutx]

Interestingly guidance suggests a very stormy pattern for Easter weekend as a very deep trough forms out W and a stout ridge builds in the E. It appears that a frontal boundry will stall near E TX/W LA on Easter Sunday. HPC Morning Update also suggests things could become rather stormy in TX and the Southern Plains with this clash of airmasses.



PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
740 AM EDT SAT MAR 27 2010

VALID 12Z WED MAR 31 2010 - 12Z SAT APR 03 2010

LATEST GUIDANCE CONTINUES THE THEME OF A VERY ACTIVE ERN PAC THRU
CNTRL NOAM PATTERN WHILE DOWNSTREAM RIDGING INTO ERN NOAM SHOULD
GRADUALLY PUSH AWAY A SLOW MOVING SYSTEM FCST TO BE NEAR THE EAST
COAST TUE-WED. WITH BOTH ERN PAC/WRN NOAM FLOW AND THE EAST COAST
SYSTEM... THE 00Z GFS IS GENERALLY NOT AS EXTREME COMPARED TO THE
CURRENT MODEL/ENSEMBLE SPREAD AS THE GFS WAS 24 HRS AGO BUT ENOUGH
QUESTION MARKS EXIST TO FAVOR LEANING AWAY FROM ITS DETAILS FOR
THE MEDIUM RANGE FCST.

STARTING FROM VERY LATE IN THE SHORT RANGE PERIOD... CONSENSUS OF
00Z MODELS AND 12Z ECMWF/CANADIAN ENSEMBLES INDICATES A PREFERENCE
TOWARD AN OVERALL ERN PAC/WRN NOAM TROF THAT IS SLIGHTLY BROADER
THAN THE 00Z GFS DURING THE FIRST HALF OF THE MEDIUM RANGE PERIOD.
AS THE TROF CROSSES THE WEST AND EJECTS INTO THE PLAINS... THE
GFS AND GEFS MEAN ARE THE FASTEST SOLNS AND THE 00Z ECMWF/UKMET
AND 12Z ECMWF ENS MEAN ARE SLOWEST. BASED ON RECENT EXPERIENCE
THE ECMWF MAY RUN THE RISK OF BEING A LITTLE TOO SLOW BUT THE
AMPLIFIED LARGE SCALE PATTERN WOULD SUGGEST THAT TIMING IN THE
SLOWER HALF OF THE SOLN ENVELOPE IS PROBABLY BEST. BEHIND THIS
SYSTEM THE GFS IS ON THE FAST EDGE OF GUIDANCE WITH UPSTREAM
ENERGY REACHING THE WEST COAST BY LATE THU NIGHT OR FRI.

WITH THE SYSTEM GRADUALLY DRIFTING AWAY FROM THE EAST COAST...
LATE IN THE SHORT RANGE PERIOD THE 00Z ECMWF TRENDED DEEPER TO THE
CANADIAN SOLN. DEEP BIASES IN THE CMC QUESTION THE DEPTH ALOFT
AND EXTREME WWD SFC POSN OF THE ECMWF/CMC AS OF EARLY DAY 3 TUE.
ON THE OTHER HAND THE GFS LEANS TO THE ERN SIDE OF THE SPREAD.
CONTINUITY/TRENDS OF GUIDANCE AS A WHOLE AND SEPARATION OF THIS
SYSTEM FROM NRN STREAM FLOW FAVOR A SOLN IN THE SLOWER HALF OF THE
ENVELOPE WITH THE 12Z ECMWF PROVIDING A MORE MODERATE
REPRESENTATION OF THIS PREFERENCE COMPARED TO THE 00Z ECMWF/CMC
EARLY IN THE PERIOD.

EARLY PRELIMS USE FOR THE FCST FOR DAYS 3-4 TUE-WED STARTS WITH A
NEARLY EVEN BLEND OF THE 00Z ECMWF/12Z ECMWF/12Z ECMWF ENSEMBLE
MEAN TO PROVIDE GREATER EMPHASIS ON 12Z ECMWF DATA FOR THE SYSTEM
NEAR THE EAST COAST AND TO REPRESENT THE PRIMARY NON-GFS
CLUSTERING FARTHER WWD. DAYS 5-7 THU-SAT ADJUST TO A SIMPLER 00Z
ECMWF/12Z ECMWF ENSEMBLE MEAN BLEND AS THE BEST WAY TO CAPTURE THE
SLOWER HALF OF THE SOLN SPREAD WITH ERN PAC TO CNTRL NOAM FLOW AND
THE SYSTEM DEPARTING FROM THE EAST COAST.

UPDATED MORNING PRELIMS FOLLOW SAME PATTERN WITH A SUBSTITUTION OF
THE 00Z ECMWF ENS MEAN FOR PRIOR 12Z EC MEAN. SOME MINOR FRONTAL
CHANGES OCCUR IN THE NRN PLAINS/UPPER MS VALLEY OTHERWISE
FEATURES/FRONTS REMAIN THE SAME.

A SIGNIFICANT COOLING IN STORE FOR WRN CONUS WITH THE DEEP WRN
TROF AND CLOSED LOW DROPING SOUTHEAST AND SWINGING THRU THEH
SOUTHWEST ALONG WITH WET CONDITIONS OVER THE PAC NORTHWEST
SHIFTING SOUTHWARD THRU CA AND EWD THRU THE ROCKIES AND INTO THE
NRN PLAINS MID-LATE WEEK. SLOW MOVING N-S FRONTAL BOUNDARY THRU
THE CENTRAL PLAINS NWD INTO THE UPPER MS VALLEY LIKELY TO BE THE
FOCUS OF SOME HVY RAINFALL AND STRONG CONVECTION FRI INTO SUNDAY
WITH A STRONG BAROCLINIC CLASH OF A COLD TROF AND SIGNIFICANT WARM
ADVECTION AHEAD OF IT THRU THE SRN PLAINS ALONG WITH GOOD INFLOW
OF GULF MOISTURE SPREADING WELL NWD OVER A PERIOD OF DAYS.

EASTWARD HVY RAIN EVENT SETTING UP DAY 3 TUES VA-NEW ENG WITH
CONSIDERABLE DRYING AND WARMING FOLLOWING AS MID LEVEL HTS RISE
AND STRONG WARM ADVECTION OCCURS FROM THE MS VALLEY EWD TO THE
EAST COAST BY THE WEEKEND. FIRST TRUE WIDESPREAD WARMING EVENT OF
THE SPRING TO OCCUR LATE WEEK INTO EASTER WEEKEND. GREATEST
TEMPERATURE ANOMALIES TO OCCUR FROM NEW ENG TO THE GREAT LAKES
REGION WHERE H850 TEMP ANOMALIES ARE IN THE RANGE OF THREE
STANDARD DEVIATIONS ABOVE NORMAL YIELDING A LARGE AREA OF TEMPS IN
THE 60-70S OVER THIS AREA WITH UPPER 70S-LOW 80S COMMON SOUTHWARD
FROM THE NORTHEAST TO OH VALLEY AND SOUTH TO THE GULF COAST.
RAUSCH/ROSENSTEIN

[wxdata]

0z ECMWF still hints at a stalling front somewhere over SE TX.

[wxdata]

12z GFS has added a new wrinkle for Easter (deja vu of last year!)

[wxdata]

The cold was two years ago. Last year, a large closed off upper low drifted across Texas Easter Sunday. A squall line moved through the area around noon. However the Easter afternoon was beautiful!

[Ptarmigan]

The cold was two years ago. Last year, a large closed off upper low drifted across Texas Easter Sunday. A squall line moved through the area around noon. However the Easter afternoon was beautiful!

The cold Easter was in 2007. I remember last Easter. It was stormy than nice. Does not happen too often in the daytime.

[srainhoutx]

Friday and Saturday are beginning to look very stormy across TX. Appears that moisture return will be rather strong as well as some very robust wind shear at multiple levels and a slow moving Upper Low will across the Panhandle. This may be the first real wide spread severe weather event of the year for much of TX and our area. Surface based Super Cells look likely from Central TX and points N and E into the Southern Plains IMHO.

[don]

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 AM CDT SUN MAR 28 2010

VALID 311200Z - 051200Z

...DISCUSSION...
IN MID-UPPER LEVELS...SIGNIFICANT PATTERN CHANGE FCST ACROSS CONUS
AS RIDGING BUILDS OVER APPALACHIANS REGION AND MEAN TROUGHING
DEVELOPS OVER WRN STATES. AS THIS OCCURS...STG SHORTWAVE TROUGH
WILL MOVE INLAND CENTRAL/SRN CA THEN EWD ACROSS AZ/NM DAYS
5-6/1ST-3RD. CONSIDERABLE DISAGREEMENT IS EVIDENT WITHIN MREF SUITE
AND BETWEEN OPERATIONAL PROGS...WHERE SPECTRAL/UKMET FAVOR FASTER
TROUGH TRANSLATION AND SLOWER EMBEDDED CYCLOGENESIS ALOFT...WHILE
ECMWF PREDICTS CYCLONE CLOSURE FARTHER W WITH LATER MOVEMENT OF THIS
PERTURBATION ACROSS SRN ROCKIES. DESPITE TIMING DIFFERENCES...MOST
PROGS REASONABLY EJECT DEAMPLIFYING VERSION OF THIS TROUGH NEWD BY
LATE DAY-7/3RD-4TH. MEANWHILE...PROGS ARE IN MORE AGREEMENT THAT
SLOW-MOVING HEIGHT WEAKNESS OVER SERN GULF...CUBA AND YUCATAN
REGION...S OF MS/AL ANTICYCLONE ALOFT...WILL YIELD REX PATTERN
ACROSS SERN NORTH AMERICA. SEVERAL DAYS OF SWLY FLOW ALOFT WILL
PERMIT STG ELEVATED MIXED LAYER TO BUILD OVER WRN CONUS AND ADVECT
TO CENTRAL/SRN PLAINS...ATOP UNCERTAIN QUALITY OF RETURN-FLOW
MOISTURE. WHILE AT LEAST MRGL SVR THREAT IS QUITE LIKELY OVER SRN
PLAINS AHEAD OF EJECTING SWRN TROUGH...GIVEN UNCERTAINTIES
ABOVE...IT IS TOO SOON TO OUTLINE AOA 30% UNCONDITIONAL SVR RISK FOR
ANY OF THESE SPECIFIC DAYS.

..EDWARDS.. 03/28/2010

[wxdata]

12z GFS still wants to close off a low over Texas next weekend; 0z ECMWF drifts upper low further north...

edit to add: For now it appears that the GFS is the outlier model in forecasting the low to cut off over Texas next weekend.

HPC-

"BY DAYS 6-7 SAT-SUN THE GFS BECOMES EXCESSIVELY FAST
COMPARED TO CONSENSUS WITH ANOTHER SYSTEM REACHING THE WEST
COAST... AND LIKELY BRINGS THE PLAINS CLOSED LOW TOO FAR EWD INTO
THE ERN CONUS MEAN RIDGE. "

[sleetstorm]

Would Supercells be feasible in the deep south including SE Texas this coming weekend? What about Hook Echo thunderstorms & Bow Echos?

[Ptarmigan]

The GFS model is predicting a wet Easter.

[Ptarmigan]

The ECMWF is adament about the low pressure being north of us on Easter.

[wxdata]

The GFS model is predicting a wet Easter.

It's doing so by cutting off an upper low over the state. At least for now, it's the only model doing so and the HPC thinks the model is advancing another upper system too fast into the west coast forcing the upper low to move east instead of north (as the ECMWF is showing.)

It will be interesting to watch to see if the GFS is ahead of the curve and forecasting the cut-off low in Texas or if it just hasn't caught on yet to what the Euro is forecasting......

[srainhoutx]

A bit of a change in the overnight guidance. The GFS and ECMWF are more in line with open trough than a closed low that the GFS has depicted the past several runs and the ECMWF has switched from moving the Upper Low NE from the Panhandle and stalling the front to moving everything E on Saturday Morning. The SPC is mentioning the fact the there will likely be some severe weather with the Dryline/Cold Front that will sweep across TX on Good Friday and off the TX Coast on Saturday morning.



DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0350 AM CDT MON MAR 29 2010

VALID 011200Z - 061200Z

...DISCUSSION...
ERN CONUS RIDGING WILL OCCUR N OF HEIGHT WEAKNESS LOCATED ACROSS
PORTIONS SERN GULF...YUCATAN AND WRN CUBA AREA -- SHOWN TO SOME
EXTENT IN ALL OPERATIONAL MODELS...MANY MREF MEMBERS...AND IN
SPECTRAL/UKMET MODELS...CLOSED 500 MB LOW BY DAY-4/1ST-2ND.
MEANWHILE...STG TROUGH MAKING LANDFALL CA COAST LATE DAY-3 INTO
DAY-4 SHOULD TRACK SEWD THEN EWD ACROSS LOWER CO RIVER VALLEY AND AZ
DAY-4...WITH VERY STG AGREEMENT THERE AMONG ALL OPERATIONAL MODELS
AND MOST SREF PROGS. BY 3/00Z DAY-5...THIS TROUGH SHOULD CROSS W
TX...PERHAPS INCLUDING CLOSED 500 MB LOW...AS PRECEDING SWLY FLOW
ENTRAINS AT LEAST PART OF SERN GULF VORTICITY PLUME. STRONG
ELEVATED MIXED LAYER WILL BE IN PLACE OVER SRN PLAINS AHEAD OF
EJECTING TROUGH...GIVEN SEVERAL PRECEDING DAYS OF SWLY FLOW OFF WRN
PLATEAU/MOUNTAINS.

LITTLE DOUBT REMAINS THAT SOME SVR IS PROBABLE DURING DAYS 4-5 OVER
PORTIONS SRN PLAINS...ESPECIALLY ACROSS TX...GIVEN INCREASING
LIKELIHOOD THAT STG DEEP-LAYER FLOW WILL SPREAD ACROSS SOME PARTS OF
MOIST SECTOR SE OF FRONTAL ZONE AND E OF DRYLINE. HOWEVER...IT
STILL IS TOO SOON TO PEG SPECIFIC AREAS OF COVERAGE AT 30%
PROBABILISTIC CONCENTRATIONS GIVEN LINGERING DIFFERENCES IN PROGS OF

1. SFC MASS-FIELD RESPONSES FROM MID-LATE DAY-4 ONWARD...
2. QUALITY AND WIDTH OF RETURN-FLOW MOIST SECTOR POTENTIALLY
SUITABLE FOR SVR...AND
3. SOMEWHAT RELATED PROSPECTS FOR NARROWED MOIST SECTOR AND
ANTECEDENT GULF PRECIP RELATED TO PERTURBATION THERE.

..EDWARDS.. 03/29/2010