HPC Extended Discussion-VERY INTERESTING DISCUSSION

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
1012 AM EST TUE FEB 12 2013

VALID 12Z FRI FEB 15 2013 - 12Z TUE FEB 19 2013


THE PATTERN IS AN ACTIVE ONE FOR THE CONTIGUOUS UNITED STATES THIS
PERIOD, WITH ENERGY TRAVERSING THE NATION COAST TO COAST. THIS IS
PEAK CLIMATOLOGY FOR WINTER STORMS OVER THE EASTERN STATES, SO ANY
PHASING OF THE SPLIT FLOW COULD RESULT IN A HIGHLY IMPACTFUL
CYCLONE FOR THAT REGION. THERE ARE TWO SYSTEMS FATED ON PHASING
THAT MAY PROVE TO HAVE SUCH IMPACT. THE FIRST WILL BE COMPLEX
CYCLOGENESIS JUST OFF THE EAST COAST DAY 4. THE 00Z/12 GEM GLOBAL
PHASES ENERGY MORE QUICKLY AND AGGRESSIVELY THAN THE OTHER MODELS,
WITH THE 00Z/12 GEFS MEAN IMPRESSIVELY DEVELOPED AS WELL. THE
00Z/12 ECENS MEAN INDICATES MODEST PHASING JUST OFFSHORE, SLIGHTLY
MORE DEVELOPED THAN EITHER THE 00Z/12 DETERMINISTIC ECMWF OR THE
00Z/12 DETERMINISTIC GFS. CHOSE THE MIDDLE GROUND OF THE SKILLFUL
ECENS MEAN FOR THE HANDLING OF THIS SYSTEM--THE BAGGINESS IN ITS
SURFACE PRESSURES OFFSHORE ALLOWING WIGGLE ROOM FOR FURTHER
TRENDING. THE SECOND SYSTEM OF INTEREST IS EXPECTED TO COALESCE
OVER THE GREAT PLAINS LATE DAY 6 INTO DAY 7. THIS SYSTEM MAY BE OF
SUFFICIENT AMPLITUDE TO VIGOROUSLY TAP THE GULF OF MEXICO, WITH
IMPORT FOR BOTH CONVECTIVE POTENTIAL AS WELL AS MOISTURE TRANSPORT
INTO THE PRIMARY SURFACE LOW FARTHER NORTH. THE LION'S SHARE OF
ENERGY FEEDING THIS SYSTEM WILL BE DROPPING INTO THE FAR WEST MID
PERIOD IN THE MANNER OF MOST OF THE SHORTWAVES AT THE MEDIUM RANGE
OVER THAT REGION. THESE "INSIDE SLIDERS" PRECLUDE SIGNIFICANT
IMPORT OF PACIFIC MOISTURE BY THE NATURE OF THEIR TRAJECTORIES. AS
WITH THE EAST COAST SYSTEM EARLIER IN THE FORECAST, THE ECENS MEAN
APPEARS TO REPRESENT A MIDDLE ROAD AND IS THE MOST COHERENT OF THE
RECENT GUIDANCE WITH REGARD TO THE TEMPORAL PROGRESSION OF THE
FLOW.


CISCO