Post by Randy - Brandon, MS on Mar 16, 2008 19:27:37 GMT -6
Good Lawd!
A very nice discussion out of Jackson tonight!
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
815 PM CDT SUN MAR 16 2008
.DISCUSSION...CURRENT FORECAST FOR THE NEXT 6-12 HRS LOOKS GOOD AND
MAY ONLY HAVE TO TWEAK HOURLY TEMPS UPWARD TO MATCH OBS.
MAIN REASON FOR THIS UPDATE IS TO DISCUSS THE TUE NIGHT AND WED
PERIODS AND WHAT MAY BE ANOTHER SVR WX OUTBREAK. I DID MAKE A FEW ADJ
TO THE FORECAST FOR THOSE PERIODS...MAINLY TO GO WITH 100% POPS TUE
NIGHT AND TO LOWER POPS FOR THE FIRST PART OF WED. IN A GENERAL
PERSPECTIVE...A SQUALL LINE WILL RACE ACROSS THE AREA TUE EVENING AND
EVERYONE WILL GET RAIN. A VERY STRONG DRY PUNCH WILL PUSH THROUGH AND
LIKELY PUSH THE RAIN OUT OF THE AREA BY 2-3 AM...THUS THE REASON TO
LOWER POPS WED. I BROKE DOWN THE WX GRIDS TO BETTER DESCRIBE TIMING
THROUGH TUE EVENING. I ALSO LOWERED TEMPS BACK TO 12Z MAV GUID WED
MORNING. THIS IS B/C WITH THE SVR CONVECTION EXPECTED AND HIGH
PROBABILITY VERY COOL AIR WILL BE BROUGHT DOWN FROM ALOFT IN THE
SQUALL LINE...REACHING LOWS IN THE LOWER TO MID 50S WILL BE QUITE
POSSIBLE. NOW FOR TIMING EVOLUTION AND KEY FORECAST PARAMETERS.
NEARLY ALL MODELS ARE SHOWING THE MAKINGS OF A NASTY SQUALL LINE TO
RACE ACROSS THE CWA TUE EVENING. TIMING IS QUITE GOOD WITH THE
MAJORITY OF THE ACTIVITY OCCURRING BETWEEN 5PM IN THE FAR W TO AROUND
1 AM IN THE FAR EAST. MODELS SHOW THE SQUALL LINE WILL BE ONGOING TO
OUR W TUE AND OCCURRING IN A PRE-FRONTAL TROUGH. LARGE HEIGHT FALLS
(100-200M) WILL SPREAD OVER THE AREA ALONG WITH VERY STRONG WIND
FIELDS. THE WINDS WILL BE RESPONDING TO THE LARGE HEIGHT FALLS AND
DEEPENING SFC LOW PRESSURE WHICH WILL LIFT NE ACROSS AR WITH SFC
PRESSURE VALUES BETWEEN 1000-995 MB. WINDS AT 925MB WILL BE AROUND
50-60KTS AND 850MB WILL SEE 60-70KTS. INTENSE FORCING WILL MOVE IN
FROM THE WEST WITH +100 KTS AT 500MB AND 80KTS AT 700MB ASSOCIATED
WITH A PRONOUNCED DRY PUNCH. THIS IS THE REASON THE MODELS ARE
SHOWING SUCH A QUICK PROGRESSION EASTWARD. THE LOW LEVEL SHEAR WILL
BE QUITE STRONG WITH 0-1KM SHEAR 40-47KTS. THE QUESTION MARKS ARE
WITH THE INSTABILITY. GRIDDED VALUES ARE QUITE LOW WITH ONLY 100-300
J/KG OF MLCAPE INDICATED. HOWEVER...BUFR SOUNDINGS SHOW A BIT MORE
AND RANGE BETWEEN 500-900 ACROSS THE CWA JUST ALONG/AHEAD OF THE
SQUALL LINE. LAPSE RATES WILL BE POOR...BUT WE WILL SEE SFC DEWPTS IN
THE MID 60S IF NOT HIGHER. CURRENTLY LOWER 70 SFC DEWPTS AREA ALL
ACROSS THE CENTRAL GULF AND WE HAVE 2 FULL DAYS TO BRING THAT
NORTHWARD. MID 60 DEWPTS LOOK TO BE GOOD ENOUGH TO SUPPORT THE
INSTABILITY THE FORECAST SOUNDINGS ARE SHOWING.
AS FOR ANY NEGATIVES THAT WOULD LIMIT SVR STORMS...ITS HARD TO FIND
ANY. THE ONLY THING I CAN SEE WOULD BE IF THE COLD POOL COULD
ACCELERATE OUT AHEAD OF THE LINE AND DISRUPT THE BALANCE OF A FORWARD
PROPAGATING LINEAR MCS. THAT IS ONE OF THOSE STORM SCALE DEALS THAT
WE WON`T KNOW ABOUT UNTIL ITS OCCURRING. I STILL THINK THAT EVEN IF
THAT HAPPENS...THERE WILL STILL BE QUITE A BIT OF WIND DAMAGE...BUT
WILL HAVE SOME OF THE AREA THAT IS SKIPPED OVER WHILE THE LINE IS OUT
OF BALANCE. WE`LL SEE.
I CAN SEE A FAST EVOLVING LINE WITH BOWING SEGMENTS AND A LINE ECHO
WAVE PATTERN. THE TORNADO RISK LOOKS TO BE HIGH AS WELL BECAUSE OF
THE STRONG LOW LEVEL SHEAR. THEY WOULD OCCUR FROM THE BOWING
SEGMENTS. AS WAS THE CASE WITH THE MAR 3RD EVENT TWO WEEKS
AGO...BOWING SEGMENTS IN A +40KT 0-1KM SHEARED ENVIRONMENT USUALLY
PROVE TO BE EFFICIENT TORNADO PRODUCERS. DUE TO THE VERY STRONG WINDS
JUST OFF THE SFC...CONVECTIVE WIND GUSTS COULD GET AS HIGH AS 80-100
MPH.
THIS ALL FITS WELL WITH THE SPC DAY 3 OUTLOOK WHICH HAS 15-30%
HATCHED FOR OUR AREA.
IF THE SVR WX IS NOT ENOUGH...REGULAR GRADIENT WINDS AHEAD OF THE
SYSTEM WILL BE QUITE IMPRESSIVE. THE WIND WILL START TOMORROW AND WE
HAVE THAT COVERED WITH A LAKE WIND ADV AT THIS POINT. TUE WILL OFFER
THE STRONGEST WINDS. WE WILL WARM INTO THE UPPER 70S AND LOWER 80S
AND WILL BE ABLE TO TAP SOME OF THAT 925MB AIR WHICH WILL BE BLOWING
AROUND 50KTS. I CAN SEE SUSTAINED WINDS 25-35MPH WITH SOME GUSTS
40-50MPH. THIS WILL LIKELY BE A WIND ADV DAY IF NOT A HIGH WIND
WARNING. THE GRADIENT WINDS WILL LIKELY CAUSE DAMAGE IN ADVANCE OF
THE SQUALL LINE WITH THE LINE ITSELF POSING A SUBSTANTIAL SVR RISK.
THAT SHOULD COVER IT FOR NOW...MORE ON THIS POTENTIAL SIGNIFICANT SVR
WX EPISODE IN THE COMING FORECASTS.
A very nice discussion out of Jackson tonight!
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
815 PM CDT SUN MAR 16 2008
.DISCUSSION...CURRENT FORECAST FOR THE NEXT 6-12 HRS LOOKS GOOD AND
MAY ONLY HAVE TO TWEAK HOURLY TEMPS UPWARD TO MATCH OBS.
MAIN REASON FOR THIS UPDATE IS TO DISCUSS THE TUE NIGHT AND WED
PERIODS AND WHAT MAY BE ANOTHER SVR WX OUTBREAK. I DID MAKE A FEW ADJ
TO THE FORECAST FOR THOSE PERIODS...MAINLY TO GO WITH 100% POPS TUE
NIGHT AND TO LOWER POPS FOR THE FIRST PART OF WED. IN A GENERAL
PERSPECTIVE...A SQUALL LINE WILL RACE ACROSS THE AREA TUE EVENING AND
EVERYONE WILL GET RAIN. A VERY STRONG DRY PUNCH WILL PUSH THROUGH AND
LIKELY PUSH THE RAIN OUT OF THE AREA BY 2-3 AM...THUS THE REASON TO
LOWER POPS WED. I BROKE DOWN THE WX GRIDS TO BETTER DESCRIBE TIMING
THROUGH TUE EVENING. I ALSO LOWERED TEMPS BACK TO 12Z MAV GUID WED
MORNING. THIS IS B/C WITH THE SVR CONVECTION EXPECTED AND HIGH
PROBABILITY VERY COOL AIR WILL BE BROUGHT DOWN FROM ALOFT IN THE
SQUALL LINE...REACHING LOWS IN THE LOWER TO MID 50S WILL BE QUITE
POSSIBLE. NOW FOR TIMING EVOLUTION AND KEY FORECAST PARAMETERS.
NEARLY ALL MODELS ARE SHOWING THE MAKINGS OF A NASTY SQUALL LINE TO
RACE ACROSS THE CWA TUE EVENING. TIMING IS QUITE GOOD WITH THE
MAJORITY OF THE ACTIVITY OCCURRING BETWEEN 5PM IN THE FAR W TO AROUND
1 AM IN THE FAR EAST. MODELS SHOW THE SQUALL LINE WILL BE ONGOING TO
OUR W TUE AND OCCURRING IN A PRE-FRONTAL TROUGH. LARGE HEIGHT FALLS
(100-200M) WILL SPREAD OVER THE AREA ALONG WITH VERY STRONG WIND
FIELDS. THE WINDS WILL BE RESPONDING TO THE LARGE HEIGHT FALLS AND
DEEPENING SFC LOW PRESSURE WHICH WILL LIFT NE ACROSS AR WITH SFC
PRESSURE VALUES BETWEEN 1000-995 MB. WINDS AT 925MB WILL BE AROUND
50-60KTS AND 850MB WILL SEE 60-70KTS. INTENSE FORCING WILL MOVE IN
FROM THE WEST WITH +100 KTS AT 500MB AND 80KTS AT 700MB ASSOCIATED
WITH A PRONOUNCED DRY PUNCH. THIS IS THE REASON THE MODELS ARE
SHOWING SUCH A QUICK PROGRESSION EASTWARD. THE LOW LEVEL SHEAR WILL
BE QUITE STRONG WITH 0-1KM SHEAR 40-47KTS. THE QUESTION MARKS ARE
WITH THE INSTABILITY. GRIDDED VALUES ARE QUITE LOW WITH ONLY 100-300
J/KG OF MLCAPE INDICATED. HOWEVER...BUFR SOUNDINGS SHOW A BIT MORE
AND RANGE BETWEEN 500-900 ACROSS THE CWA JUST ALONG/AHEAD OF THE
SQUALL LINE. LAPSE RATES WILL BE POOR...BUT WE WILL SEE SFC DEWPTS IN
THE MID 60S IF NOT HIGHER. CURRENTLY LOWER 70 SFC DEWPTS AREA ALL
ACROSS THE CENTRAL GULF AND WE HAVE 2 FULL DAYS TO BRING THAT
NORTHWARD. MID 60 DEWPTS LOOK TO BE GOOD ENOUGH TO SUPPORT THE
INSTABILITY THE FORECAST SOUNDINGS ARE SHOWING.
AS FOR ANY NEGATIVES THAT WOULD LIMIT SVR STORMS...ITS HARD TO FIND
ANY. THE ONLY THING I CAN SEE WOULD BE IF THE COLD POOL COULD
ACCELERATE OUT AHEAD OF THE LINE AND DISRUPT THE BALANCE OF A FORWARD
PROPAGATING LINEAR MCS. THAT IS ONE OF THOSE STORM SCALE DEALS THAT
WE WON`T KNOW ABOUT UNTIL ITS OCCURRING. I STILL THINK THAT EVEN IF
THAT HAPPENS...THERE WILL STILL BE QUITE A BIT OF WIND DAMAGE...BUT
WILL HAVE SOME OF THE AREA THAT IS SKIPPED OVER WHILE THE LINE IS OUT
OF BALANCE. WE`LL SEE.
I CAN SEE A FAST EVOLVING LINE WITH BOWING SEGMENTS AND A LINE ECHO
WAVE PATTERN. THE TORNADO RISK LOOKS TO BE HIGH AS WELL BECAUSE OF
THE STRONG LOW LEVEL SHEAR. THEY WOULD OCCUR FROM THE BOWING
SEGMENTS. AS WAS THE CASE WITH THE MAR 3RD EVENT TWO WEEKS
AGO...BOWING SEGMENTS IN A +40KT 0-1KM SHEARED ENVIRONMENT USUALLY
PROVE TO BE EFFICIENT TORNADO PRODUCERS. DUE TO THE VERY STRONG WINDS
JUST OFF THE SFC...CONVECTIVE WIND GUSTS COULD GET AS HIGH AS 80-100
MPH.
THIS ALL FITS WELL WITH THE SPC DAY 3 OUTLOOK WHICH HAS 15-30%
HATCHED FOR OUR AREA.
IF THE SVR WX IS NOT ENOUGH...REGULAR GRADIENT WINDS AHEAD OF THE
SYSTEM WILL BE QUITE IMPRESSIVE. THE WIND WILL START TOMORROW AND WE
HAVE THAT COVERED WITH A LAKE WIND ADV AT THIS POINT. TUE WILL OFFER
THE STRONGEST WINDS. WE WILL WARM INTO THE UPPER 70S AND LOWER 80S
AND WILL BE ABLE TO TAP SOME OF THAT 925MB AIR WHICH WILL BE BLOWING
AROUND 50KTS. I CAN SEE SUSTAINED WINDS 25-35MPH WITH SOME GUSTS
40-50MPH. THIS WILL LIKELY BE A WIND ADV DAY IF NOT A HIGH WIND
WARNING. THE GRADIENT WINDS WILL LIKELY CAUSE DAMAGE IN ADVANCE OF
THE SQUALL LINE WITH THE LINE ITSELF POSING A SUBSTANTIAL SVR RISK.
THAT SHOULD COVER IT FOR NOW...MORE ON THIS POTENTIAL SIGNIFICANT SVR
WX EPISODE IN THE COMING FORECASTS.
