Randy Jennings
Supporter
- Joined
- May 18, 2013
- Messages
- 778
I read a very informative and funny area forecast discussion (shown bellow) this morning that was put out by the Ft Worth WFO. It got me to thinking, who's AFDs do you like? Who's are the most informative? Have you every seen one like the one bellow? There are several folks at the Ft Worth office who write very good AFDs. Dennis Cavanaugh is my favorite AFD writer. I'm not sure who wrote this one (I have a theory). I think the line in the second paragraph that says "USING MATH WE CAN FIND AREAS OF DIFFERENTIAL THERMAL ADVECTION BY USING THE LAPLACE OPERATOR TAUGHT IN A STANDARD DIFFERENTIAL EQUATIONS COURSE. OF COURSE DOING THAT WOULD PROBABLY GIVE ME PTSD..." is my favorite line of all time in and AFD. Here is the full AFD:
000
FXUS64 KFWD 240918
AFDFWD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
418 AM CDT TUE MAR 24 2015
.DISCUSSION...
AT 3 AM SURFACE ANALYSIS INDICATED A SURFACE LOW WAS LOCATED NEAR
DODGE CITY AND WAS MOVING FAIRLY QUICKLY OFF TO THE EAST. OVER
NORTH TEXAS...SOUTHERLY WINDS HAVE INCREASED IN RESPONSE TO THE
FALLING PRESSURES IN THE HIGH PLAINS. ONCE MIXING ENSUES THIS
MORNING...BREEZY AND OCCASIONALLY GUSTY SOUTH WINDS WILL OCCUR
UNTIL EARLY AFTERNOON WHEN WINDS BEGIN TO VEER TO THE SOUTHWEST
AND RELAX AHEAD OF A WEAK COLD FRONT THAT MOVES INTO THE NORTHWEST
ZONES. WHILE TRYING TO CLASSIFY THESE NEBULOUS SURFACE FEATURES IN
THE SPRING CAN BE TRICKY...THE NORTHWEST WINDS...RISING PRESSURES
AND WEAK COLD ADVECTION BEHIND THE BOUNDARY WOULD DEFINITELY ARGUE
A COLD FRONT RATHER THAN A DRY LINE WILL BE THE PRIMARY SURFACE
FEATURE THAT ARRIVES INTO THE AREA THIS AFTERNOON. WITH GENERALLY
SUNNY SKIES AND VEERING SURFACE WINDS...HAVE INCREASED HIGH TEMPS
TO THE LOW 90S IN THE WESTERN ZONES...AND MID-UPPER 80S ACROSS THE
I-35 CORRIDOR DUE TO ANTICIPATED PRE-FRONTAL SUBSIDENCE WARMING.
THE MAIN CHALLENGE IN THE FORECAST TODAY IS WHETHER CONVECTION CAN
INITIATE ALONG THE FRONTAL BOUNDARY LATE THIS AFTERNOON AND EARLY
EVENING. THE PRIMARY SHORTWAVE AND SURFACE LOW WILL TRACK MUCH TOO
FAR NORTH TO PROVIDE ANY DIRECT FORCING OVER THE REGION. THE CAP
WILL BE QUITE STRONG OVER THE REGION TODAY...BUT ALL GUIDANCE
SHOWS THE CAP LIFTING AND WEAKENING DURING THE COURSE OF THE DAY.
MOST OF THIS DYNAMIC LIFT TODAY IS A RESULT OF DIFFERENTIAL WARM
ADVECTION WHICH IS JUST AS IMPORTANT TO FINDING AREAS OF LIFT AS
THE MORE POPULAR CYCLONIC VORTICITY ADVECTION IS. USING MATH WE
CAN FIND AREAS OF DIFFERENTIAL THERMAL ADVECTION BY USING THE
LAPLACE OPERATOR TAUGHT IN A STANDARD DIFFERENTIAL EQUATIONS
COURSE. OF COURSE DOING THAT WOULD PROBABLY GIVE ME PTSD...SO THE
EASY WAY IS JUST TO LOOK FOR THE THERMAL ADVECTION THAT OCCURS
WITHIN A LOW LEVEL JET...SUCH THAT THE WARM ADVECTION FIELDS SHOW
A NOSE OR BULGE NORTHWARD. THE END RESULT IS THAT CINH BECOMES LOW
ENOUGH NORTH OF I-20 THAT GIVEN A SUFFICIENT MECHANICAL
PERTURBATION...CONVECTION WOULD DEVELOP. NEAR THE RED RIVER...CINH
IS EXPECTED TO BECOME ALMOST ZERO...AND THUS CONVECTIVE INITIATION
BECOMES MORE LIKELY FARTHER NORTH INTO OKLAHOMA.
GIVEN THE VEERING FLOW AHEAD OF THE FRONT...CONVERGENCE ALONG THE
BOUNDARY WILL NOT BE PARTICULARLY IMPRESSIVE. THERE IS VIRTUALLY
NO GUIDANCE...HIGH-RESOLUTION CONVECTION RESOLVING OR LOW-
RESOLUTION CONVECTION PARAMETERIZING...THAT FORECASTS INITIATION
TO OCCUR OVER OUR CWA TODAY. ALL OF THE GUIDANCE SHOWS US BEING
VERY CLOSE THOUGH...WITH INCREASING RH IN THE 800-900MB LAYER
ALONG THE FRONT. FURTHERMORE BECAUSE THIS BOUNDARY IS A FRONT
RATHER THAN A DRY LINE...THE FRONTOGENESIS LIFT ASSOCIATED WITH IT
IS ON THE WARM MOIST SIDE OF THE BOUNDARY. IN CONTRAST...THE
FRONTOGENESIS LIFT WITH A DRY LINE IS ON THE DRY AND WARMER
WESTERN SIDE...WHICH CAN BE A SIGNIFICANT IMPEDANCE TO CONVECTIVE
INITIATION. BECAUSE OF THIS WE ARE MORE INCLINED TO CONTINUE TO
KEEP POPS IN THE 10-20 PERCENT RANGE EAST OF A LINE FROM
GAINESVILLE TO WEATHERFORD LATE THIS AFTERNOON AND EVENING. WE
WILL LIKELY SEE CUMULUS CONGESTUS AND TOWERING CUMULUS ALONG THE
FRONT THIS AFTERNOON...AND IT IS REALLY UP TO A RANDOM CHANCE
EVENT THAT A STORM CAN FORM WHERE MECHANICAL FORCING IS STRONG
ENOUGH TO OVERCOME THE WEAK THERMODYNAMIC STABILITY. SHOULD A
STORM FORM AND GET GOING BEFORE TOO LONG AFTER SUNSET...IT WOULD
BECOME SUPERCELLULAR AND THE STEEP LAPSE RATES AND VERY COLD AIR
ALOFT WILL ALLOW FOR A POTENTIAL FOR VERY LARGE HAIL. FLOW IN THE
LOWER LEVELS LOOKS TOO WEAK TO BE CONCERNED ABOUT A TORNADO
THREAT...BUT OBVIOUSLY THIS THREAT IS NON-ZERO WHEN SURFACE BASED
SUPERCELLS ARE IN PLAY.
ON WEDNESDAY ANOTHER SHORTWAVE TROUGH WILL BE APPROACHING OUR
REGION ON A MORE SOUTHERLY TRACK THAN TODAYS SYSTEM. THIS WILL
CAUSE THE SURFACE LOW TO DEVELOP NEAR WICHITA FALLS...WITH AN
ATTENDANT DRYLINE S/SW OF THERE. THE GFS/ECMWF APPEAR TO BE MUCH
TOO FAR EAST WITH THE POSITION OF THE DRY LINE...AND PREFER THE
NAM/WRF MODELS WHICH HAVE THE DRYLINE JUST BEYOND OUR CWA DURING
THE AFTERNOON HOURS. MOST OF NORTH TEXAS WILL BE STRONGLY CAPPED
DURING THE DAYLIGHT HOURS...WITH ONLY THE CAP BECOMING BREAKABLE
WEST OF A COMANCHE TO MINERAL WELLS TO GAINESVILLE LINE BEFORE
SUNSET. ACROSS THE NW ZONES...SBCAPE WILL REACH 1500-2000 J/KG
AND LOW LEVEL WIND FIELDS WILL BE MORE STRONGLY SHEARED THAN THEY
ARE TODAY. THUS...ANY SUPERCELLS THAT FORM ON THE DRYLINE WILL BE
CAPABLE OF TORNADOES...IN ADDITION TO VERY LARGE HAIL AND DAMAGING
WINDS. WE DONT EXPECT THE STORMS TO DISSIPATE WHEN THEY REACH THE
MORE CAPPED AREAS ACROSS THE CENTRAL AND EASTERN ZONES WEDNESDAY
EVENING. INSTEAD THEY WILL KEEP TRACKING EAST...BUT JUST BECOME
ELEVATED ABOVE THE CAP WHERE VERY STEEP LAPSE RATES WILL STILL
YIELD 1000-1500 J/KG OF CAPE FOR THESE STORMS TO UTILIZE. SO WHILE
THE TORNADO THREAT WILL DROP OFF AS THEY REACH THE I-35
CORRIDOR...A HAIL AND WIND THREAT WILL CONTINUE TO EXIST...BUT THE
SEVERE THREAT WILL NOT BE AS SIGNIFICANT IN THIS REGION DUE TO THE
MORE LIMITED INSTABILITY.
THE COLD FRONT WILL PUSH THROUGH THE CWA RAPIDLY WEDNESDAY NIGHT
WITH PERHAPS MORE SCATTERED NON-SEVERE CONVECTION BEHIND THE
FRONT. ALL OF THIS ACTIVITY WILL PUSH SOUTHEAST AND OUT OF THE CWA
BY MIDDAY THURSDAY. MUCH COOLER TEMPERATURES ARE EXPECTED THURSDAY
WITH HIGHS NEAR 60. SKIES WILL CLEAR DURING THE DAY WITH A COUPLE
OF COOL NIGHTS THURSDAY NIGHT AND FRIDAY NIGHT. SOME PATCHY FROST
MAY BE POSSIBLE IN OUTLYING LOCATIONS THURSDAY NIGHT. OTHERWISE
THE WEEKEND LOOKS PRETTY PLEASANT WITH TEMPERATURES NEAR NORMAL
AND CLEAR SKIES. THE NEXT SYSTEM WILL ARRIVE EARLY NEXT WEEK...BUT
WILL KEEP POPS LOW ON MONDAY FOR NOW.
TR.92
&&
000
FXUS64 KFWD 240918
AFDFWD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
418 AM CDT TUE MAR 24 2015
.DISCUSSION...
AT 3 AM SURFACE ANALYSIS INDICATED A SURFACE LOW WAS LOCATED NEAR
DODGE CITY AND WAS MOVING FAIRLY QUICKLY OFF TO THE EAST. OVER
NORTH TEXAS...SOUTHERLY WINDS HAVE INCREASED IN RESPONSE TO THE
FALLING PRESSURES IN THE HIGH PLAINS. ONCE MIXING ENSUES THIS
MORNING...BREEZY AND OCCASIONALLY GUSTY SOUTH WINDS WILL OCCUR
UNTIL EARLY AFTERNOON WHEN WINDS BEGIN TO VEER TO THE SOUTHWEST
AND RELAX AHEAD OF A WEAK COLD FRONT THAT MOVES INTO THE NORTHWEST
ZONES. WHILE TRYING TO CLASSIFY THESE NEBULOUS SURFACE FEATURES IN
THE SPRING CAN BE TRICKY...THE NORTHWEST WINDS...RISING PRESSURES
AND WEAK COLD ADVECTION BEHIND THE BOUNDARY WOULD DEFINITELY ARGUE
A COLD FRONT RATHER THAN A DRY LINE WILL BE THE PRIMARY SURFACE
FEATURE THAT ARRIVES INTO THE AREA THIS AFTERNOON. WITH GENERALLY
SUNNY SKIES AND VEERING SURFACE WINDS...HAVE INCREASED HIGH TEMPS
TO THE LOW 90S IN THE WESTERN ZONES...AND MID-UPPER 80S ACROSS THE
I-35 CORRIDOR DUE TO ANTICIPATED PRE-FRONTAL SUBSIDENCE WARMING.
THE MAIN CHALLENGE IN THE FORECAST TODAY IS WHETHER CONVECTION CAN
INITIATE ALONG THE FRONTAL BOUNDARY LATE THIS AFTERNOON AND EARLY
EVENING. THE PRIMARY SHORTWAVE AND SURFACE LOW WILL TRACK MUCH TOO
FAR NORTH TO PROVIDE ANY DIRECT FORCING OVER THE REGION. THE CAP
WILL BE QUITE STRONG OVER THE REGION TODAY...BUT ALL GUIDANCE
SHOWS THE CAP LIFTING AND WEAKENING DURING THE COURSE OF THE DAY.
MOST OF THIS DYNAMIC LIFT TODAY IS A RESULT OF DIFFERENTIAL WARM
ADVECTION WHICH IS JUST AS IMPORTANT TO FINDING AREAS OF LIFT AS
THE MORE POPULAR CYCLONIC VORTICITY ADVECTION IS. USING MATH WE
CAN FIND AREAS OF DIFFERENTIAL THERMAL ADVECTION BY USING THE
LAPLACE OPERATOR TAUGHT IN A STANDARD DIFFERENTIAL EQUATIONS
COURSE. OF COURSE DOING THAT WOULD PROBABLY GIVE ME PTSD...SO THE
EASY WAY IS JUST TO LOOK FOR THE THERMAL ADVECTION THAT OCCURS
WITHIN A LOW LEVEL JET...SUCH THAT THE WARM ADVECTION FIELDS SHOW
A NOSE OR BULGE NORTHWARD. THE END RESULT IS THAT CINH BECOMES LOW
ENOUGH NORTH OF I-20 THAT GIVEN A SUFFICIENT MECHANICAL
PERTURBATION...CONVECTION WOULD DEVELOP. NEAR THE RED RIVER...CINH
IS EXPECTED TO BECOME ALMOST ZERO...AND THUS CONVECTIVE INITIATION
BECOMES MORE LIKELY FARTHER NORTH INTO OKLAHOMA.
GIVEN THE VEERING FLOW AHEAD OF THE FRONT...CONVERGENCE ALONG THE
BOUNDARY WILL NOT BE PARTICULARLY IMPRESSIVE. THERE IS VIRTUALLY
NO GUIDANCE...HIGH-RESOLUTION CONVECTION RESOLVING OR LOW-
RESOLUTION CONVECTION PARAMETERIZING...THAT FORECASTS INITIATION
TO OCCUR OVER OUR CWA TODAY. ALL OF THE GUIDANCE SHOWS US BEING
VERY CLOSE THOUGH...WITH INCREASING RH IN THE 800-900MB LAYER
ALONG THE FRONT. FURTHERMORE BECAUSE THIS BOUNDARY IS A FRONT
RATHER THAN A DRY LINE...THE FRONTOGENESIS LIFT ASSOCIATED WITH IT
IS ON THE WARM MOIST SIDE OF THE BOUNDARY. IN CONTRAST...THE
FRONTOGENESIS LIFT WITH A DRY LINE IS ON THE DRY AND WARMER
WESTERN SIDE...WHICH CAN BE A SIGNIFICANT IMPEDANCE TO CONVECTIVE
INITIATION. BECAUSE OF THIS WE ARE MORE INCLINED TO CONTINUE TO
KEEP POPS IN THE 10-20 PERCENT RANGE EAST OF A LINE FROM
GAINESVILLE TO WEATHERFORD LATE THIS AFTERNOON AND EVENING. WE
WILL LIKELY SEE CUMULUS CONGESTUS AND TOWERING CUMULUS ALONG THE
FRONT THIS AFTERNOON...AND IT IS REALLY UP TO A RANDOM CHANCE
EVENT THAT A STORM CAN FORM WHERE MECHANICAL FORCING IS STRONG
ENOUGH TO OVERCOME THE WEAK THERMODYNAMIC STABILITY. SHOULD A
STORM FORM AND GET GOING BEFORE TOO LONG AFTER SUNSET...IT WOULD
BECOME SUPERCELLULAR AND THE STEEP LAPSE RATES AND VERY COLD AIR
ALOFT WILL ALLOW FOR A POTENTIAL FOR VERY LARGE HAIL. FLOW IN THE
LOWER LEVELS LOOKS TOO WEAK TO BE CONCERNED ABOUT A TORNADO
THREAT...BUT OBVIOUSLY THIS THREAT IS NON-ZERO WHEN SURFACE BASED
SUPERCELLS ARE IN PLAY.
ON WEDNESDAY ANOTHER SHORTWAVE TROUGH WILL BE APPROACHING OUR
REGION ON A MORE SOUTHERLY TRACK THAN TODAYS SYSTEM. THIS WILL
CAUSE THE SURFACE LOW TO DEVELOP NEAR WICHITA FALLS...WITH AN
ATTENDANT DRYLINE S/SW OF THERE. THE GFS/ECMWF APPEAR TO BE MUCH
TOO FAR EAST WITH THE POSITION OF THE DRY LINE...AND PREFER THE
NAM/WRF MODELS WHICH HAVE THE DRYLINE JUST BEYOND OUR CWA DURING
THE AFTERNOON HOURS. MOST OF NORTH TEXAS WILL BE STRONGLY CAPPED
DURING THE DAYLIGHT HOURS...WITH ONLY THE CAP BECOMING BREAKABLE
WEST OF A COMANCHE TO MINERAL WELLS TO GAINESVILLE LINE BEFORE
SUNSET. ACROSS THE NW ZONES...SBCAPE WILL REACH 1500-2000 J/KG
AND LOW LEVEL WIND FIELDS WILL BE MORE STRONGLY SHEARED THAN THEY
ARE TODAY. THUS...ANY SUPERCELLS THAT FORM ON THE DRYLINE WILL BE
CAPABLE OF TORNADOES...IN ADDITION TO VERY LARGE HAIL AND DAMAGING
WINDS. WE DONT EXPECT THE STORMS TO DISSIPATE WHEN THEY REACH THE
MORE CAPPED AREAS ACROSS THE CENTRAL AND EASTERN ZONES WEDNESDAY
EVENING. INSTEAD THEY WILL KEEP TRACKING EAST...BUT JUST BECOME
ELEVATED ABOVE THE CAP WHERE VERY STEEP LAPSE RATES WILL STILL
YIELD 1000-1500 J/KG OF CAPE FOR THESE STORMS TO UTILIZE. SO WHILE
THE TORNADO THREAT WILL DROP OFF AS THEY REACH THE I-35
CORRIDOR...A HAIL AND WIND THREAT WILL CONTINUE TO EXIST...BUT THE
SEVERE THREAT WILL NOT BE AS SIGNIFICANT IN THIS REGION DUE TO THE
MORE LIMITED INSTABILITY.
THE COLD FRONT WILL PUSH THROUGH THE CWA RAPIDLY WEDNESDAY NIGHT
WITH PERHAPS MORE SCATTERED NON-SEVERE CONVECTION BEHIND THE
FRONT. ALL OF THIS ACTIVITY WILL PUSH SOUTHEAST AND OUT OF THE CWA
BY MIDDAY THURSDAY. MUCH COOLER TEMPERATURES ARE EXPECTED THURSDAY
WITH HIGHS NEAR 60. SKIES WILL CLEAR DURING THE DAY WITH A COUPLE
OF COOL NIGHTS THURSDAY NIGHT AND FRIDAY NIGHT. SOME PATCHY FROST
MAY BE POSSIBLE IN OUTLYING LOCATIONS THURSDAY NIGHT. OTHERWISE
THE WEEKEND LOOKS PRETTY PLEASANT WITH TEMPERATURES NEAR NORMAL
AND CLEAR SKIES. THE NEXT SYSTEM WILL ARRIVE EARLY NEXT WEEK...BUT
WILL KEEP POPS LOW ON MONDAY FOR NOW.
TR.92
&&
