WTPZ41 KNHC 070301 RRA

TCDEP1



HURRICANE SERGIO DISCUSSION NUMBER  31

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP212018

800 PM PDT SAT OCT 06 2018



LITTLE OVERALL CHANGE HAS BEEN NOTED IN SERGIO'S SATELLITE

PRESENTATION THE PAST SEVERAL HOURS OTHER THAN CLOUD TOPS HAVE

WARMED SLIGHTLY. THE 30-NMI-WIDE EYE REMAINS QUITE DISTINCT AND

OUTFLOW IS STILL VERY IMPRESSIVE IN ALL QUADRANTS. HOWEVER, HE

WARMING TOPS HAVE RESULTED IN SLIGHTLY LOWER SATELLITE INTENSITY

ESTIMATES FROM ALL AGENCIES, SO THE INITIAL INTENSITY HAS BEEN

LOWERED TO 105 KT FOR THIS ADVISORY.



SERGIO IS LUMBERING ALONG TOWARD THE WEST, OR 270/06 KT. THERE IS NO

SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACK OR REASONING.

SERGIO SHOULD CONTINUE TO MOVE SLOWLY WESTWARD AROUND THE

SOUTHWESTERN PERIPHERY OF A WEAK DEEP-LAYER RIDGE FOR THE NEXT DAY

OR SO. BY EARLY NEXT WEEK, A STRONG TROUGH IS FORECAST TO DIG

SOUTHWARD OFF THE COASTS OF CALIFORNIA AND BAJA CALIFORNIA, WHICH

WILL ERODE THE RIDGE AND CAUSE SERGIO TO MAKE A SHARP NORTHEASTWARD

TURN AND ACCELERATE THROUGHOUT THE FORECAST PERIOD. THE LATEST NHC

TRACK GUIDANCE REMAINS IN GOOD AGREEMENT ON THIS DEVELOPING STEERING

FLOW PATTERN, AND THERE IS VERY LITTLE CROSS-TRACK SPREAD IN THE

MODELS. THE SPEED DIFFERENCES NOTED IN THE PREVIOUS DISCUSSION HAVE

DECREASED ON THIS FORECAST CYCLE, SO ONLY MINOR TWEAKS HAD TO BE

MADE TO THE PREVIOUS ADVISORY TRACK. THE NEW FORECAST TRACK LIES

CLOSE THE PREVIOUS ONE AND NEAR A BLEND OF THE VARIOUS CONSENSUS

TRACK MODELS.



OCEAN TEMPERATURES BENEATH THE CYCLONE ARE FORECAST TO DECREASE OVER

THE NEXT FEW DAYS DUE TO COLD UPWELLING BENEATH THE HURRICANE, SO