Flow Channeling in the Flow Channeling in the Mohawk & Hudson ValleysMohawk & Hudson Valleys

A FURTHER INVESTIGATION OF A FURTHER INVESTIGATION OF MOHAWK HUDSON MOHAWK HUDSON

CONVERGENCECONVERGENCE

Tenth Annual Northeast Regional Operational Workshop/NWS/CESTM

Hugh W Johnson IVLance F. Bosart

Michael E. Augustyniak

Geography of New York & New EnglandGeography of New York & New England

Geography of New York & New EnglandGeography of New York & New England

DefinitionDefinition Mohawk-Hudson ConvergenceMohawk-Hudson Convergence occurs occurs

when surface air parcels traveling down when surface air parcels traveling down the upper Hudson Valley (from north to the upper Hudson Valley (from north to south) meet air parcels traveling down the south) meet air parcels traveling down the Mohawk Valley (from west to east)Mohawk Valley (from west to east)

The convergence of these airflows can The convergence of these airflows can generate vertical motion and precipitation generate vertical motion and precipitation (usually in the general vicinity of Albany)(usually in the general vicinity of Albany)

WHY PURSUE MHC CASES ?WHY PURSUE MHC CASES ? OPERATIONAL IMPACT WITH OPERATIONAL IMPACT WITH

REGARDS TO HIGHWAY CREWSREGARDS TO HIGHWAY CREWS IFR AVIATION ISSUESIFR AVIATION ISSUES PUBLIC PERCEPTION PUBLIC PERCEPTION POSSIBLY FOCUS FOR THE INITATION POSSIBLY FOCUS FOR THE INITATION

OF CONVECTIONOF CONVECTION

IN ADDITIONIN ADDITION WILL EXAMINE NOT ONLY THOSE CASES WILL EXAMINE NOT ONLY THOSE CASES

WHERE A NORTH WIND PERISTS IN THE WHERE A NORTH WIND PERISTS IN THE HUDSON VALLEY WHILE THE WIND BACKS HUDSON VALLEY WHILE THE WIND BACKS TO THE NORTHWEST OR WEST IN THE TO THE NORTHWEST OR WEST IN THE TERRAIN WEST OF THE HUDSON VALLEY…TERRAIN WEST OF THE HUDSON VALLEY…

BUT ALSO EXAMINE A CASE WHERE THERE BUT ALSO EXAMINE A CASE WHERE THERE IS A SOUTHERLY FLOW IN THE HUDSON IS A SOUTHERLY FLOW IN THE HUDSON VALLEY WHILE A WEST OR SOUTHWEST VALLEY WHILE A WEST OR SOUTHWEST WIND PREVAILS TO THE WESTWIND PREVAILS TO THE WEST

THANKS TO MIKE WE HAVE A DECISION THANKS TO MIKE WE HAVE A DECISION TREE THAT IS READY TO BE USED THIS TREE THAT IS READY TO BE USED THIS

WINTERWINTER

Is ∆p KGFL-KPOU between 1 & 5 hPa and ∆p KRME-KPSF greater than 4

hPa?

Will a surface low pass east or south of the

40°N- 70°W benchmark?

Mohawk-Hudson Convergence Not

Likely

Will synoptic forcing in the

vicinity of KALB be weak?

Is weak low-level CAA expected?

Is a north-to-south 850-hPa WFROPA

forecast?

Is moisture trapped under a low-level

inversion or isothermal layer?

YES

YES

YES

YES

YES

NO

NO

NO

NO

NO

LOOK FIRST AT A “CLASSIC” CASE ON JANUARY 2, 2008

09Z SFC PLT 01/02/0809Z SFC PLT 01/02/08

11Z SFC PLT 01/02/0811Z SFC PLT 01/02/08

KENX 0757ZKENX 0757Z

KENX IMAGE 0930ZKENX IMAGE 0930Z

KENX 1151ZKENX 1151Z

SUNRISE RADAR 1230ZSUNRISE RADAR 1230Z

KENX 1259ZKENX 1259Z

1659Z KENX1659Z KENX

SUMMARY…SUMMARY… PROLONGED MHC WITH SEVERAL PULSES PROLONGED MHC WITH SEVERAL PULSES

OF EPISODESOF EPISODES WIND MOSTLY NE AT KGFL/N AT KALB/NW WIND MOSTLY NE AT KGFL/N AT KALB/NW

KUCA(KRME)KUCA(KRME) SNOWFALL RATES UP TO AN INCH PER SNOWFALL RATES UP TO AN INCH PER

HOUR OBSERVEDHOUR OBSERVED VERY HIGH SNOW TO LIQUID RATIOSVERY HIGH SNOW TO LIQUID RATIOS NAM NOT PERFECTNAM NOT PERFECT UNDER AN INCH CESTM/OVER AN INCH MY UNDER AN INCH CESTM/OVER AN INCH MY

HOUSE/2+ INCHES BRUNSWICKHOUSE/2+ INCHES BRUNSWICK JACKPOT= 5.2 INCHES IN COHOES!JACKPOT= 5.2 INCHES IN COHOES!

SECOND CASE…A NULL CASESECOND CASE…A NULL CASE

ST. PATTY’S DAY STORM OF 07ST. PATTY’S DAY STORM OF 07 LOTS OF SNOWLOTS OF SNOW BUT VERY LITTLE MHCBUT VERY LITTLE MHC DID NOT MEASURE AT THE AIRPORT DID NOT MEASURE AT THE AIRPORT

OR CESTMOR CESTM

SAT MARCH 17 2007SAT MARCH 17 2007

08Z SAT MAR 17 200708Z SAT MAR 17 2007

0914Z MAR 170914Z MAR 17

0943Z 17 MAR

08Z SFC PLOT AGAIN08Z SFC PLOT AGAIN

SUMMARYSUMMARY SOME BRIEF MHCSOME BRIEF MHC THE WIND WAS MOSTLY NORTH AT THE WIND WAS MOSTLY NORTH AT

KGFL AND TO THE WESTKGFL AND TO THE WEST NO MEASURABLE AT ALBANYNO MEASURABLE AT ALBANY IMPLIES VERY LITTLE IF ANY IMPLIES VERY LITTLE IF ANY

CONVERGENCECONVERGENCE WHY DID THIS HAPPEN???WHY DID THIS HAPPEN???

HYBRID CASES HYBRID CASES OCCUR WHEN A SECONDARY OCCUR WHEN A SECONDARY

SHORT WAVE MOVES THROUGH SHORT WAVE MOVES THROUGH THE BACK OF THE MAIN TROUGH THE BACK OF THE MAIN TROUGH

FEB 27 2008 BEST EXAMPLE …FEB 27 2008 BEST EXAMPLE …COMBINED MHC AND SHORT COMBINED MHC AND SHORT WAVE HAD IT SNOWING ALL DAY WAVE HAD IT SNOWING ALL DAY (LIGHTLY) EVEN THOUGH (LIGHTLY) EVEN THOUGH SURFACE CYCLONE PAST THE SURFACE CYCLONE PAST THE GULF OF MAINE GULF OF MAINE

FINALLY WE WILL TAKE A LOOK AT CASE FINALLY WE WILL TAKE A LOOK AT CASE WITH A SOUTHERLY FLOW IN THE WITH A SOUTHERLY FLOW IN THE

HUDSON VALLEY AND A SOUTHWEST HUDSON VALLEY AND A SOUTHWEST WIND IN THE MOHAWK VALLEYWIND IN THE MOHAWK VALLEY

JUNE 22 2008JUNE 22 2008

SFC PLT 15Z 06/22/08SFC PLT 15Z 06/22/08

0.50.50.5 KENX BASE REFLECTIVITY LOOP FROM 9-10 AM0.5 KENX BASE REFLECTIVITY LOOP FROM 9-10 AM

0.5 BASE REFLECTIVITY KENX RADAR 0.5 BASE REFLECTIVITY KENX RADAR LOOP 2-3 PMLOOP 2-3 PM

0.5 BASE KENX REFLECTIVITY 3-4 PM0.5 BASE KENX REFLECTIVITY 3-4 PM

IN SUMMARYIN SUMMARY SOME EVIDENCE SUPPORTS SOME EVIDENCE SUPPORTS

POSSIBLE MHC FROM WITH A POSSIBLE MHC FROM WITH A SOUTHEAST WIND HUDSON SOUTHEAST WIND HUDSON VALLEY/SOUTHWEST WIND MOHAWK VALLEY/SOUTHWEST WIND MOHAWK VALLEY VALLEY

850 WINDS ESTIMATED TO BE ONLY 850 WINDS ESTIMATED TO BE ONLY 15-20 KTS AND 925 WINDS AROUND 15-20 KTS AND 925 WINDS AROUND 10KTS 10KTS

IN ADDITION…IN ADDITION… WRF WAS NOT AVAILABLEWRF WAS NOT AVAILABLE NAM DID NOT HANDLE LOW LEVEL NAM DID NOT HANDLE LOW LEVEL

WIND FIELD WELL WIND FIELD WELL DID NOT INDICATE SE WIND IN THE DID NOT INDICATE SE WIND IN THE

HUDSON VALLEY AND SW IN MOHAWK HUDSON VALLEY AND SW IN MOHAWK (HAD EVERYONE SOUTHWEST)(HAD EVERYONE SOUTHWEST)

MANY MORE CASES NEED TO BE MANY MORE CASES NEED TO BE EXAMINED EXAMINED

PLAN TO CONTINUE TO EXAM PAST AND PLAN TO CONTINUE TO EXAM PAST AND FUTURE MHC CASES AS AND SEE HOW THE FUTURE MHC CASES AS AND SEE HOW THE

WRF HANDLES THEM WRF HANDLES THEM

CONCLUSIONSCONCLUSIONS MHC COMES IN MANY FLAVORS (NOT MHC COMES IN MANY FLAVORS (NOT

AS MANY AS BEN AND JERRY’S)AS MANY AS BEN AND JERRY’S) MODELS USUALLY HAVE A “CLUE” BUT MODELS USUALLY HAVE A “CLUE” BUT

NOT ALWAYSNOT ALWAYS NEED TO SEE HOW WELL MIKE’S NEED TO SEE HOW WELL MIKE’S

CHECKLIST WORKS FOR THE CHECKLIST WORKS FOR THE UPCOMING WINTER SEASON UPCOMING WINTER SEASON

SEE HOW THE WRF DOES SEE HOW THE WRF DOES

Thank You!Thank You!

Questions?Questions?