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Lecture 4: Map Discussion

Lecture 4: Map Discussion. In Wednesday’s class I noted the weather office comment that “A COLOSSAL WEATHER PATTERN CHANGE IS UNDERWAY OVER THE PRAIRIES”…. … with a switch to a flow from the far north, and formation of a closed upper low over BC.

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Lecture 4: Map Discussion

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  1. Lecture 4: Map Discussion

  2. In Wednesday’s class I noted the weather office comment that “A COLOSSAL WEATHER PATTERN CHANGE IS UNDERWAY OVER THE PRAIRIES”…. … with a switch to a flow from the far north, and formation of a closed upper low over BC

  3. SIGNIFICANT WEATHER DISCUSSION FOR THE CANADIAN PRAIRIES ISSUED BY THE PRAIRIE AND ARCTIC STORM PREDICTION CENTRE OF ENVIRONMENT CANADA AT 7:00 AM CDT THURSDAY SEPTEMBER 14 2006… SNOWFALL WARNING IN EFFECT FOR THE MOUNTAIN PARKS. DISCUSSION...THE PATTERN CHANGE IS UNDERWAY OVER AB, WITH PLENTY OF COLD AIR FLOODING INTO THE PROVINCE.  THIS IS DESTABILIZING THE AIRMASS OVER ALBERTA AND TIGHTENING THE BAROCLINIC ZONE LOCATED OVER THE EASTERN PRAIRIES.  THUS, THERE WILL BE MANY CONCERNS OVER THE NEXT FEW DAYS. AB...UPPER TROF CONTINUES TO DIG OVER WESTERN CANADA WITH BROAD CLOSED CIRCULATION DEVELOPING.  RAIN WILL CONTINUE FOR THE REST OF THE WEEK WITH TOTAL VALUES NEAR 60MM. …PRECIP TYPE IS STILL THE MAIN CONCERN AS THE FIRST SNOWFALL WARNINGS OF THE SEASON HAVE BEEN ISSUED.   END/CARLSEN/MARK (The forecaster David Carlsen is an EAS graduate)

  4. Received the following bulletin at Thu Sep 14 08:55:15 2006 GMT … FCST PRBLM IS HOW FAR TO THE E AWAY FROM THE FOOTHILLS MIGHT SOME OF THIS SNOW CREEP. REG GEM** BRINGS EDGE ABT AS FAR E AS A PEACE RIVER-EDSON-CALGARY LINE BY ABT 30-36HRS..AS SFC LOW HEADS FOR ND..ALLOWING FOR MORE ARCTIC AIR TO PUSH SWD & SEWD..A TRICKY SITN..AS THE FIRST SIG SNOWFALL OF THE SEASON USUALLY IS. (** Regional GEM, Regional run of the CMC Global Environmental Model)

  5. closed low • coastal ridge • wind // height • weak prairie winds • T = ? • Td = ? CMC 500 mb analysis, Thurs 14 Sept 2006, 12Z

  6. upslope C. Ab • ovc entire W. Cda • steady rain, Edm, Cgry Surface Convergence?

  7. height • upslope Ab wind • how high is 850 mb sfc over Edmonton? • baroclinic zone (strong temperature gradient, “T”) - - - 0oC isotherm CMC 850 mb analysis, Thurs 14 Sept 2006, 12Z

  8. uppr lo + sfc cnvgnc absence of deep cloud consistent with the rain proving light and intermittent Thursday am Low cloud over Ab Correlates with the 500 mb current around base of closed low

  9. wind profile consistent with analysis charts • entire troposphere saturated (or nearly) Light, upslope

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