HURRICANE OHO DISCUSSION NUMBER 21
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI CP072015
1100 PM HST WED OCT 07 2015
OHO IS BEGINNING EXTRATROPICAL TRANSITION...WITH AN INCREASINGLY
SHEARED SATELLITE PRESENTATION. SHIPS AND UW-CIMSS ANALYSES SHOW 45
TO 50 KT OF SOUTH SOUTHWESTERLY SHEAR...WHILE SHIPS ALSO SHOWS OHO
MOVING ACROSS 23C WATER. THE LOW LEVEL CIRCULATION
CENTER...LLCC...REMAINS EXPOSED...WITH ALL REMAINING DEEP
CONVECTION PUSHED OFF TO THE NORTH NORTHEAST. SUBJECTIVE DVORAK
SATELLITE INTENSITY ESTIMATES WERE 4.0...65 KT...FROM PHFO AND
JTWC...WHILE UW-CIMSS ADT HAS OHO AT 55 KT. OHO IS SPINNING DOWN AS
A TROPICAL SYSTEM...SO SETTING THE INITIAL INTENSITY AT 65 KT FOR
THIS ADVISORY SEEMS REASONABLE.
INITIAL MOTION IS 030/34 KT. OHO HAS BEEN SCOOPED UP BY DEEP
TROUGHING TO ITS NORTHWEST AND IS NOW RACING NORTH NORTHEASTWARD
TOWARD THE MAINLAND. SINCE OHO WILL LIKELY COMPLETE EXTRATROPICAL
TRANSITION WITHIN 12 HOURS...WE COLLABORATED WITH THE OCEAN
PREDICTION CENTER...OPC...FOR ALL POINTS ALONG THE FORECAST TRACK.
OPC KINDLY CONTRIBUTED WIND AND SEAS RADII AS WELL. THE CURRENT
FORECAST TRACK KEEPS OHO HEADED TOWARD BRITISH COLUMBIA THROUGH 24
HOURS...THEN CURVES THE TRACK NORTHWESTWARD AT 36 AND 48 HOURS AS
THIS SYSTEM MOVES ALONG THE NORTHEASTERN FLANK OF A LARGE POLAR LOW
FORMING ACROSS THE ALEUTIANS. AS OHO BECOMES AN EXTRATROPICAL
STORM LOW...ITS WIND FIELD WILL EXPAND AND BECOME HIGHLY ASYMMETRIC.
OHO WILL WEAKEN THROUGH 24 HOURS...SPINNING DOWN AT THE MET RATE
ACCORDING TO CONCEPTUAL MODELS. HOWEVER...BAROCLINIC FORCES WILL
STRENGTHEN THE REMNANTS OF OHO BACK TO HURRICANE STRENGTH AS AN
EXTRATROPICAL STORM LOW BETWEEN 24 AND 36 HOURS. THIS STORM LOW
WILL THEN WEAKEN AGAIN BY 48 HOURS AS IT INTERACTS WITH THE ALASKAN
PANHANDLE...THEN DISSIPATE INLAND BY 72 HOURS.
THE CENTRAL PACIFIC HURRICANE CENTER WILL ISSUE ONE MORE ADVISORY
AFTER THIS ONE TO CLOSE THINGS DOWN WITH OHO PROPERLY. OHO WILL
BECOME EXTRATROPICAL BEFORE CROSSING 140W...SO AFTER THE 1500 UTC
ADVISORY CYCLE IT WILL BECOME THE RESPONSIBILITY OF OPC AND WILL BE
COVERED BY OPC HIGH SEAS FORECASTS.
TROPICAL STORM OHO DISCUSSION NUMBER 2
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI CP072015
500 AM HST SAT OCT 03 2015
SATELLITE IMAGERY SHOWS THAT THE CYCLONE CONTINUES TO ORGANIZE...
WITH A CURVED BAND OF DEEP CONVECTION WRAPPING INTO THE CENTER FROM
THE SOUTH AND SOUTHEAST...WHILE COLD CLOUD TOPS HAVE PERSISTED NEAR
THE CENTER. DVORAK INTENSITY ESTIMATES YIELDED DATA-T VALUES OF
2.5/35 KT...BUT WITH CONSTRAINTS...THE FINAL-T VALUES WERE LIMITED
TO 2.0/30 KT. GIVEN THAT THE PATTERN-T ALSO SUPPORTS 2.5...AND THE
PERSISTENCE OF THE STRONG CONVECTION OVER THE CENTER...THE INITIAL
INTENSITY FOR THIS ADVISORY HAS BEEN INCREASED TO 35 KT...AND THE
THE SYSTEM IS UPGRADED TO TROPICAL STORM OHO.
THE INITIAL MOTION FOR THIS ADVISORY IS 360/05 KT. THE STORM IS
EMBEDDED IN AN ENVIRONMENT CHARACTERIZED BY DEEP BUT RELATIVELY
LIGHT SOUTHERLY FLOW BETWEEN A RIDGE ALOFT TO THE EAST AND A LARGE
LONG WAVE TROUGH AND CLOSED LOW ALOFT TO THE NORTH. WHILE THIS
GENERAL MOTION IS FORECAST TO CONTINUE IN THE SHORT-TERM...STEERING
PATTERNS WILL BE RATHER DYNAMIC THROUGH THE FORECAST PERIOD...AND
HAVE RESULTED IN A FORECAST TRACK BEST DESCRIBED AS RESEMBLING AN
S...ESPECIALLY WHEN CONSIDERING PAST POSITIONS. THIS ARISES AS THE
CYCLONE IS FORECAST TO MOVE NORTH...THEN WEST-NORTHWEST...WITH A
FAIRLY SHARP TURN TOWARD THE EAST-NORTHEAST IN THE LATER FORECAST
PERIODS. OVER THE NEXT 36 HOURS...THE LOW ALOFT TO THE DISTANT NORTH
WILL LIFT QUICKLY NORTHWARD. THIS WILL ALLOW AN EAST PACIFIC MID-
LEVEL RIDGE TO BUILD TO THE NORTH OF THE SYSTEM...THEREBY IMPARTING
A MOTION TOWARD THE WEST-NORTHWEST. A NEW AND VIGOROUS TROUGH ALOFT
WILL DIG SOUTHWARD TO THE NORTHWEST OF THE CYCLONE BY
MONDAY...THEREBY WEAKENING ALREADY WEAK STEERING CURRENTS...WITH THE
CYCLONE MEANDERING TO THE SOUTH OF THE BIG ISLAND SUNDAY NIGHT AND
MONDAY. AS THE NEW TROUGH DIGS FURTHER SOUTH MONDAY NIGHT AND
TUESDAY... IT WILL STEER THE SYSTEM GENERALLY TOWARD THE EAST-
NORTHEAST.
THE COMPLEX FORECAST TRACK...WHICH CLOSELY FOLLOWS THE TVCN
CONSENSUS...HINGES ON THE EVOLUTION OF A VARIETY OF SYNOPTIC
SCALE FEATURES...AND CONTAINS A GREATER THAN NORMAL AMOUNT OF
UNCERTAINTY. ALSO ADDING TO THE UNCERTAINTY IS THE DEVELOPMENT OF
ANOTHER LOW TO THE SOUTHEAST OF OHO IN THE GFS...AND TO A LESSER
EXTENT...THE ECMWF. INTERACTION BETWEEN OHO AND THIS POTENTIALLY
SPURIOUS LOW IN THE LATER MODEL FORECASTS ADDS ANOTHER LAYER OF
UNCERTAINTY. WHILE THE OFFICIAL FORECAST KEEPS OHO AWAY FROM THE
ISLANDS...IT IS IMPORTANT NOT TO FOCUS TOO CLOSELY ON THE EXACT
FORECAST TRACK. ALSO...IT IS TOO EARLY TO TALK ABOUT SPECIFIC
WIND...RAIN OR SURF IMPACTS FROM OHO IN THE HAWAIIAN ISLANDS.
WITH THE DEPRESSION FORECAST TO BE SLOW-MOVING OVER VERY WARM
WATERS IN AN ENVIRONMENT CHARACTERIZED BY LIGHT SHEAR...SIGNIFICANT
INTENSIFICATION IS EXPECTED. IN FACT...SHIPS RAPID INTENSITY
GUIDANCE CONTINUES TO INDICATE A HIGH CHANCE OF RAPID
INTENSIFICATION OVER THE NEXT 24 HOURS. THE OFFICIAL FORECAST IS
A LITTLE LESS AGGRESSIVE...BUT ANTICIPATES THAT OHO WILL BECOME A
HURRICANE BY MONDAY...IN LINE WITH THE IVCN CONSENSUS. INCREASING
SHEAR AND GRADUALLY DIMINISHING WATER TEMPERATURES ALONG THE
FORECAST TRACK IN THE LATER PERIODS ARE EXPECTED TO LIMIT THE
INTENSIFICATION SEEN IN THE EARLIER PERIODS.
THE 53RD WEATHER RECONNAISSANCE SQUADRON HAS BEEN TASKED TO FLY
THIS SYSTEM IN SUPPORT OF CPHC OPERATIONS...AND INITIAL FLIGHTS INTO
THE SYSTEM ARE PLANNED FOR SUNDAY EVENING AND MONDAY MORNING. THE
G-IV AIRCRAFT IS ALSO HEADING BACK TO HAWAII TO FLY SYNOPTIC
MISSIONS...WITH HIGH-ALTITUDE FLIGHTS PLANNED FOR SUNDAY AND MONDAY
MORNINGS...IN ORDER FOR THE DATA TO BE UTILIZED BY AFTERNOON MODEL
RUNS.
TROPICAL DEPRESSION SEVEN-C DISCUSSION NUMBER 1
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI CP072015
1100 PM HST FRI OCT 02 2015
LATEST SATELLITE IMAGERY INDICATES THAT SHOWERS AND THUNDERSTORMS
ASSOCIATED WITH A DEVELOPING AREA OF LOW PRESSURE ABOUT 400 MILES
SOUTH OF THE BIG ISLAND HAVE PERSISTED AND CONSOLIDATED TO THE POINT
THAT THE SYSTEM CAN BE CLASSIFIED AS A TROPICAL CYCLONE. DVORAK
INTENSITY ESTIMATES AT 0530Z WERE 1.5/25 KT FROM PHFO/PGTW/KNES...
AND GIVEN THAT A STRENGTHENING CURVED BAND IS IN THE PROCESS OF
WRAPPING TOWARD THE CENTER FROM THE SOUTHEAST...THE INITIAL
INTENSITY FOR THIS ADVISORY IS 30 KT. GIVEN RECENT SATELLITE
TRENDS...THIS MAY BE A LITTLE CONSERVATIVE. THIS MARKS THE TWELFTH
TROPICAL CYCLONE IN THE 2015 CENTRAL NORTH PACIFIC SEASON. THIS IS
THE GREATEST NUMBER OF TROPICAL CYCLONES TO OCCUR IN THE BASIN ON
RECORD...WHICH RELIABLY DATES BACK THROUGH THE SATELLITE ERA...
SPANNING BACK TO LATE 1960/S.
AS IS TYPICAL FOR DEVELOPING LOW PRESSURE AREAS EMERGING FROM A
MONSOON TROUGH...THE INITIAL MOTION CONTAINS A SIGNIFICANT EASTERLY
COMPONENT...AND IS 050/06KT. THE COMPLEX FORECAST TRACK IS ALSO
SOMEWHAT TYPICAL FOR A LOW EMERGING FROM A MONSOON TROUGH...AND IS
BEST DESCRIBED AS AN S-TYPE TRACK. THE CYCLONE IS FORECAST TO
SLOWLY MOVE NORTHEAST...THEN WEST-NORTHWEST...AND THEN EAST AND
NORTHEAST THROUGH THE FORECAST PERIOD. THIS WILL OCCUR AS THE
STEERING CURRENTS EVOLVE...WITH THE CYCLONE INITIALLY MOVING
EAST-NORTHEAST UNDER THE INFLUENCE OF A LARGE CUT-OFF LOW ALOFT TO
THE NORTH OF HAWAII. THIS LOW IS FORECAST TO LIFT NORTH OVER THE
NEXT 24 TO 48 HOURS...ALLOWING AN EAST PACIFIC RIDGE TO BUILD TO THE
NORTH OF THE SYSTEM...THUS IMPARTING A WEST-NORTHWESTERLY MOTION. A
NEW AND VIGOROUS LOW ALOFT WILL DIG SOUTHWARD TO THE NORTHWEST OF
THE CYCLONE IN THE LATER FORECAST PERIODS. THIS WILL WEAKEN THE
RIDGE...AND TEMPORARILY WEAKENING STEERING CURRENTS...BEFORE THE LOW
ACTS TO LIFT THE CYCLONE TOWARD THE NORTHEAST. THE COMPLEX FORECAST
TRACK...WHICH CLOSELY FOLLOWS THE GFEX CONSENSUS...THUS HINGES ON
THE EVOLUTION OF A VARIETY OF SYNOPTIC SCALE FEATURES...AND CONTAINS
A GREATER THAN NORMAL AMOUNT OF UNCERTAINTY. HAVING SAID THAT...IT
IS TOO EARLY TO TALK ABOUT SPECIFIC WIND...RAIN OR SURF IMPACTS FROM
SEVEN-C IN THE HAWAIIAN ISLANDS.
WITH THE DEPRESSION FORECAST TO BE SLOW-MOVING OVER VERY WARM
WATERS IN AN ENVIRONMENT CHARACTERIZED BY LIGHT SHEAR...SIGNIFICANT
INTENSIFICATION IS EXPECTED. IN FACT...SHIPS RAPID INTENSITY
GUIDANCE INDICATES A 60 PER CENT CHANCE OF RAPID INTENSIFICATION
OVER THE NEXT 24 HOURS. THE OFFICIAL FORECAST IS JUST A LITTLE LESS
AGGRESSIVE...BUT ANTICIPATES THAT THE DEPRESSION WILL BECOME A
TROPICAL STORM BY SATURDAY MORNING...AND A HURRICANE ON MONDAY...IN
LINE WITH THE IVCN CONSENSUS. THE LATER PERIODS OF THE FORECAST
INDICATE LITTLE CHANGE IN THE INTENSITY OF THE CYCLONE AS INCREASING
SHEAR IS EXPECTED TO LIMIT INTENSIFICATION.
THE 53RD WEATHER RECONNAISSANCE SQUADRON HAS BEEN TASKED TO FLY THIS
SYSTEM IN SUPPORT OF CPHC OPERATIONS...AND INITIAL FLIGHTS INTO THE
SYSTEM ARE PLANNED FOR SUNDAY EVENING. THE G-IV AIRCRAFT WILL ALSO
BE HEADING TO HAWAII ONCE AGAIN TO FLY SYNOPTIC MISSIONS...WITH THE
INITIAL HIGH-ALTITUDE FLIGHT PLANNED FOR SUNDAY MORNING...IN ORDER
FOR THE DATA TO BE UTILIZED BY SUNDAY AFTERNOON MODEL RUNS.
組圖打開中，請稍候......