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August 2013 Pattern & Discussion


LithiaWx

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Who cares about summer! Bring me a loooonnngggg cool and dry fall. I can wait until Dec 24th for my first 10" snowfall. Lol.

This pattern is truly amazing and i cant wait to see the post mortems that analyze why the predictions were so far out of whack this summer. From svr wx to hurricane predictions, temps and moisture.....nothing was accurate for the east coast. I dont monitor central and western forecasts but they must have been off as well given the index charts posted earlier.

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The 06z GFS Ensemble does build a stout ridge centered over Kansas / Oklahoma by Sun-Mon, but the east coast remains in normal to below normal temperatures with a back door cold front dropping down into the SE as a trough exits off the NE coast.  Thereafter, the ensembles work the Plains ridge into the western U.S. and we get right back into general troughing in the SE.  It simply looks like it is going to be difficult to break down this summer pattern any time soon.

 

Here's the 00z GFS Ensemble 850mb temperature anomaly map for Sunday, with the blue contours in the SE showing the below normal 850mb temps behind the cold front.

 

x0hh.png

 

Nice break down. Seems like every time the models want to bring in the heat in the long range it really fails. Has been for the most part this whole summer. Euro is looking normal to below normal for the next week or two. No surprise there. The heat remains out West as has been the case.

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Nice break down. Seems like every time the models want to bring in the heat in the long range it really fails. Has been for the most part this whole summer. Euro is looking normal to below normal for the next week or two. No surprise there. The heat remains out West as has been the case.

 

 

What the global models are showing for next week is similar to a pattern we had after all the massive rains of early July. The Eastern US and Southeast in particular will be on the east and southeast flank of a sprawling ridge...which means the winds will veer from northwest, to north and eventually northeast.

 

This pattern resulted in some hot and humid weather back in middle July. Now that we're in late August, chances are higher and higher that colder and drier air will slide down the east side of that ridge.

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With ten days to go, KATL is now only 2.53" away from tieing the 2005 alltime (back to 1879) record high JJA rainfall of 25.82" and it has done this with no help from tropical cyclones! OTOH, 2005 was helped by a whopping four TC's!

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WxSouth

I like central NC to central VA for record lows Monday Morning #vawx #ncwx Upper 40's. Yes Upper 40's in August. Many in low 50s to #gawx

Currently lots of 60s dew points everywhere (even up towards DC). For us to have a chance we'll have to have some mixing today to pull dryer air down to the surface. RAH from last night still looking at the possibility of records tonight:

TEMPERATURES TONIGHT SHOULD FALL INTO THE LOWER TO MID 50S. RECORD

LOWS TONIGHT RANGE FROM 49 AT KGSO...54 AT KRDU AND KFAY. GUIDANCE

FOR TONIGHT HAS TRENDED SLIGHTLY COOLER DURING THE PAST FEW DAYS AND

GIVEN FAVORABLE RADIATIONAL COOLING CONDITIONS WITH LIMITED CIRRUS

AND THE PROXIMITY OF THE SURFACE HIGH...MIN TEMPERATURES WILL

THREATEN A TIE OF THE RECORD AT KRDU. THE AIR MASS MODERATES 2-3

DEGREES ON MONDAY AS THE LIGHT LOW LEVEL FLOW BECOMES MORE

SOUTHERLY. EXPECT MAXES IN THE 83-85 RANGE AND LOWS MONDAY NIGHT

WITHIN A FEW DEGREES OF 60. -BLAES

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Well the un-official end of summer is right around the corner (Labor Day). RAH is forecasting very typical summer temps to end the season. I suppose I can live with that; it could be worse...

 

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
AS OF 300 PM MONDAY...
THERE IS GOOD AGREEMENT THAT WE WILL SEE VERY LITTLE CHANGE IN THE
LONGWAVE PATTERN THROUGH THE LONG TERM...WITH THE UPPER RIDGE
PERSISTING OVER THE CENTRAL/SOUTHERN PLAINS...AND MEAN TROUGHS
POSITIONED ACROSS THE PACIFIC NORTHWEST AND WESTERN ATLANTIC.

BELOW NORMAL RAIN CHANCES ARE EXPECTED THROUGH THE PERIOD OWING TO
THE DEEP NWLY FLOW DOWNSTREAM OF THE STRONG RIDGE OVER THE CENTRAL
US. OUR BEST CHANCE OVER THE NEXT SEVERAL DAYS WILL LIKELY
ACCOMPANY A WEAK COLD FRONT/SURFACE TROUGH PASSAGE SOUTHWARD THROUGH
THE CAROLINAS LATE WEDNESDAY AND INTO THURSDAY. POPS/COVERAGE AS
WELL AS STRENGTH/SEVERITY WILL BE HIGHLY DEPENDENT ON THE PRESENCE
AND CHARACTER OF UPSTREAM CONVECTION IN RESPONSE TO SHORTWAVE ENERGY
DIVING SEWD AROUND THE UPPER RIDGE AND INTO THE OHIO VALLEY/AND
MID-ATLANTIC STATES LATE TUESDAY NIGHT/WEDNESDAY MORNING.
GIVEN THE LOW PREDICTABILITY WITH SUCH MESOSCALE FEATURES...WILL
STAY WITH LOW CHANCE POPS FOR NOW...BEGINNING WEDNESDAY AFTERNOON
ACROSS THE NORTH...WITH A GRADUAL SHIFT TO THE SOUTH ON THURSDAY AS
SURFACE FRONT SAGS TOWARDS THE SAVANNA RIVER VALLEY.

OTHERWISE...PROJECTED LOW-LEVEL THICKNESSES HOVERING AROUND THE 30
YEAR AVERAGE WILL SUPPORT SEASONABLE TEMPERATURES IN THE MID 80S TO
AROUND 90. LOWS IN THE MID 60S TO AROUND 70
.

&&

 

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12z Euro takes our current upper low from the Florida Keys to the Panhandle and into the Southeast US by late this weekend. The big ridge currently in place over the central US begins to break down by late this week, leaving an opening for any feature to come northward.

 

At this time, don't think we're talking anything tropical in nature but after a nice stretch of weather, the humidity and unsettled conditions are showing signs of returning late this week for some areas.

 

 

sat_wv_us_loop-12.gif

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Good write-up from Raleigh for Fri-Tues period...

THE STRONG UPPER LEVEL RIDGE OVER THE CENTRAL US WILL BEGIN TOWEAKEN AND RETROGRADE WESTWARD ON FRIDAY...WITH NORTHWESTERLY FLOWALOFT PERSISTING OVER NC.  MEANWHILE...THE WEAK FRONTAL ZONECROSSING THE CWA EARLY THURSDAY WILL SINK SOUTH OF THE AREA ANDEVENTUALLY WASH OUT BY FRIDAY. WITH NORTHWESTERLY FLOW ALOFT...THELEE TROUGH WILL STRENGTHEN THROUGH THE WEEKEND...AND RETURN FLOWWILL BRING PW VALUES BACK UP TO AROUND 2 INCHES.  UPPER DISTURBANCESCURRENTLY MOVING AROUND THE UPPER RIDGE WILL INEVITABLY DIVESOUTHEAST ACROSS THE APPALACHIANS...BUT ITS DIFFICULT TO FIND ANYSIGNIFICANT FEATURES IN MODEL GUIDANCE AT THIS POINT.  EXPECT AMOSTLY DRY DAY FRIDAY...WITH AN INCREASING SLIGHT CHANCE TO CHANCEPOP SATURDAY AND SUNDAY.  BY MONDAY...MORE SUBSTANTIAL SHORTWAVE ISEXPECTED TO MOVE ACROSS THE NORTHERN GREAT LAKES AND EASTERNCANADA..LEADING TO A DEEPER TROUGH OVER THE EASTERN US.  AS THE FLOWALOFT BECOMES MORE CYCLONIC AND A COLD FRONT APPROACHES FROM THENORTHWEST...CONVECTIVE COVERAGE SHOULD INCREASE MONDAY AND TUESDAY.IN ADDITION...BOTH THE ECMWF INDICATE THAT THE CYCLONIC CIRCULATIONCURRENTLY OVER SOUTHERN FLORIDA WILL DRIFT SLOWLY INTO THE GULF ANDEVENTUALLY BE DRAWN NORTHEASTWARD ACROSS THE SOUTHEAST AND ABSORBEDBY THE LOWER HEIGHTS OVER THE EASTERN US.  HOWEVER...THE IMPACTS OFTHIS FEATURE ARE LESS CERTAIN AT THIS TIME.  WITH THICKNESSESHOLDING RELATIVELY STEADY THROUGH MONDAY.... HIGH TEMPS OVER THEWEEKEND WILL REBOUND TO AT OR JUST ABOVE NORMAL IN THE UPPER 80S TOAROUND 90.  LOWS WILL BE IN THE UPPER 60S AND LOWER 70S.  SLIGHTLYCOOLER CONDITIONS ARE THEN POSSIBLE BY THE MIDDLE OF NEXT WEEK ASTHE PATTERN BECOMES DOMINATED BY THE STRONGER TROUGH MENTION ABOVE.
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GSP longterm overnight:

 

*note the last paragraph

 

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 245 AM EDT THU...AN ERN U.S. LONGWAVE TROUGH WILL DEEPEN IN
EARNEST SUNDAY THROUGH MONDAY. THE FIRST SHORTWAVE MOVING INTO THE
DEVELOPING TROUGH WILL BE ACCOMPANIED BY A BRIEF INCREASE IN
MOISTURE SUNDAY AFTN...AS WELL AS IMPROVED MID LEVEL LAPSE RATES.
WILL CONTINUE TO FEATURE SOLID CHC POPS FOR AFTN
CONVECTION...ESPECIALLY OVER THE MTNS...WITH TEMPS RECOVERING AN
ADDITIONAL DEGREE OR SO IN THE PIEDMONT.

LAPSE RATES WILL STEEPEN FURTHER ON MONDAY AS A COLD FRONT
APPROACHES FROM THE WEST AND UPPER LEVEL HEIGHTS CONTINUE FALLING.
COVERAGE OF AFTN AND EVENING SHOWERS AND THUNDERSTORMS THUS LOOKS A
BIT MORE ROBUST...ESPECIALLY OVER THE MTNS LATE DAY.

THE COLD FRONT WILL CROSS THE REGION MONDAY NIGHT INTO TUESDAY.
SHEAR AND INSTABILITY IN THE PROFILES DO NOT LOOK PARTICULARLY
THREATENING...ESPECIALLY WITH THE DIURNALLY UNFAVORED TIME OF FROPA.
THE BEST LINGERING INSTABILITY WILL BE IN SE SECTIONS THROUGH MIDDAY
TUESDAY BEFORE POST FRONTAL DRYING SETS IN.

THE ERN TROUGH WILL LIKELY BEGIN TO BE REINFORCED BY A POLAR VORTEX
DROPPING SWD THROUGH CANADA ON WED...HOWEVER...SFC HIGH PRES WILL
SETTLE IN BEHIND THE FRONT BRIEFLY WED TO PRODUCE A DRIER AND COOLER
DAY.

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