EPAC: Tropical Storm Hernan

[Chacor]

The eye feature is in the mid levels.

513
WTPZ44 KNHC 080240
TCDEP4
TROPICAL STORM HERNAN DISCUSSION NUMBER 6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP092008
800 PM PDT THU AUG 07 2008

THE CENTER OF HERNAN IS SOMEWHAT DIFFICULT TO LOCATE THIS EVENING.
RECENT MICROWAVE IMAGERY CONTINUES TO SHOW A MID-LEVEL EYE
FEATURE...BUT ALSO SHOWS THAT THIS IS DISPLACED TO THE WEST OR
SOUTHWEST OF THE LOW-LEVEL CENTER. ANALYSES FROM CIMSS AT THE
UNIVERSITY OF WISCONSIN INDICATE 15-20 KT OF EAST-NORTHEASTERLY
VERTICAL WIND SHEAR OVER HERNAN...WHICH IS THE LIKELY CAUSE OF THIS
STRUCTURE. SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB REMAIN
55 KT...AND THAT REMAINS THE INITIAL INTENSITY.

THE MICROWAVE DATA SHOWS THAT HERNAN HAS MOVED WESTWARD DURING THE
PAST SEVERAL HOURS...WITH THE INITIAL MOTION A SOMEWHAT UNCERTAIN
275/11. THE STORM IS CURRENTLY ON THE SOUTH SIDE OF A MID-LEVEL
RIDGE AND HEADING FOR A LARGE MID/UPPER-LEVEL TROUGH THAT COVERS
THE AREA NORTH OF 22N BETWEEN 130-150W. THE LARGE-SCALE MODELS
FORECAST THE TROUGH TO LIFT OUT TO THE NORTH DURING THE FORECAST
PERIOD...WITH ENOUGH MID-LEVEL RIDGING DEVELOPING TO STEER HERNAN
GENERALLY WEST-NORTHWESTWARD FOR THE NEXT 48-72 HR. AFTER THAT
TIME...HERNAN WILL BE WEAKENING OVER COOLER SEA SURFACE
TEMPERATURES...AND LOW-LEVEL FLOW SHOULD CAUSE THE CYCLONE TO TURN
WESTWARD AND EVENTUALLY WEST-SOUTHWESTWARD. THE NEW FORECAST TRACK
IS SIMILAR TO...BUT SOUTH OF...THE PREVIOUS FORECAST BASED ON THE
CURRENT LOCATION AND MOTION...AND CALLS FOR HERNAN TO RESUME A
WEST-NORTHWEST MOTION DURING THE NEXT FEW HOURS. THE NEW TRACK IS
DOWN THE MIDDLE OF THE GUIDANCE ENVELOPE IN GOOD AGREEMENT WITH THE
MODEL CONSENSUS.

IT SHOULD BE NOTED THAT THE MICROWAVE IMAGERY HINTS THAT THE CENTER
OF HERNAN IS SOUTH OF THE ADVISORY POSITION. IF SUBSEQUENT DATA
SHOW THIS IS INDEED THE CASE...AN ADDITIONAL ADJUSTMENT TO THE
FORECAST TRACK MAY BE NECESSARY ON THE NEXT ADVISORY.

ON THE FORECAST TRACK...THE CENTER OF HERNAN WOULD REACH THE 26C SEA
SURFACE TEMPERATURE ISOTHERM IN ABOUT 36 HR. THE ECMWF...GFS...AND
NOGAPS FORECAST A GRADUAL DECREASE IN SHEAR DURING THIS TIME...
WHICH COULD ALLOW GRADUAL STRENGTHENING. ON THE OTHER HAND...THE
UKMET SHOWS LITTLE CHANGE OR EVEN SOME INCREASE IN THE SHEAR. THE
VARIOUS INTENSITY GUIDANCE MODELS CALL FOR SOME STRENGTHENING WITH
PEAK INTENSITIES IN THE 60-70 KT RANGE. GIVEN THE CURRENT
STRUCTURE AND SHEAR...THE NEW INTENSITY FORECAST CALL FOR A SLOWER
INTENSIFICATION RATE THAN THE PREVIOUS FORECAST...WITH HERNAN
REACHING HURRICANE STRENGTH IN ABOUT 24 HR. AFTER 36 HR...THE
FORECAST MOTION OVER COOLER WATER SHOULD CAUSE WEAKENING...WITH THE
CYCLONE EXPECTED TO DECAY TO A NON-CONVECTIVE LOW IN ABOUT 120 HR.


FORECAST POSITIONS AND MAX WINDS

INITIAL 08/0300Z 14.9N 117.8W 55 KT
12HR VT 08/1200Z 15.3N 119.4W 60 KT
24HR VT 09/0000Z 15.8N 121.2W 65 KT
36HR VT 09/1200Z 16.2N 122.8W 65 KT
48HR VT 10/0000Z 16.8N 124.5W 60 KT
72HR VT 11/0000Z 18.0N 128.0W 45 KT
96HR VT 12/0000Z 18.5N 130.5W 30 KT
120HR VT 13/0000Z 18.0N 134.0W 20 KT...REMNANT LOW

$$
FORECASTER BEVEN

[HURAKAN]

Feature persists.

[HURAKAN]

381
WTPZ44 KNHC 080829
TCDEP4
TROPICAL STORM HERNAN DISCUSSION NUMBER 7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP092008
200 AM PDT FRI AUG 08 2008

THE CLOUD PATTERN HAS NOT CHANGED VERY MUCH DURING THE PAST SEVERAL
HOURS AND DUE TO SHEAR...THE LOW-LEVEL CENTER STILL APPEARS TO BE
LOCATED ON THE EDGE OF THE DEEP CONVECTION. LATEST MICROWAVE DATA
REVEAL THAT THE LOW- AND MID -LEVEL CENTERS ARE A LITTLE MORE
ALIGNED THAN A FEW HOURS AGO BUT MOST OF THE DEEP CONVECTION REMAINS
SOUTH OF THE CENTER. THE OUTFLOW IS ESTABLISHED ONLY IN THE
WESTERN SEMICIRCLE. DVORAK T-NUMBERS HAVE BEEN STEADY FOR ABOUT 18
HOURS SUGGESTING AN INITIAL INTENSITY OF 55 KNOTS. INTENSITY
GUIDANCE IS NOT SHOWING ANY SIGNIFICANT INTENSIFICATION. IN
FACT...MOST OF THE MODELS SUGGEST THAT HERNAN HAS PEAKED ALREADY.
BASED ON CONTINUITY...THE OFFICIAL FORECAST STILL SHOWS A VERY
MODEST STRENGTHENING DURING THE NEXT 24 HOURS BRINGING HERNAN TO
HURRICANE STATUS. THIS IS BECOMING LESS LIKELY TO OCCUR SINCE THE
SHEAR IS NOT RELAXING AS ANTICIPATED. A GRADUAL WEAKENING SHOULD
BEGIN BEYOND 24-36 HOURS AS HERNAN APPROACHES COOLER WATERS.

HERNAN HAS BEEN MOVING TOWARD THE WEST OR 270 DEGREES AT 11 KNOTS.
HOWEVER...A WEAKNESS IN THE SUBTROPICAL RIDGE ALONG 130 DEGREES
WEST WILL PROBABLY INDUCE A MORE WEST-NORTHWEST TRACK IN THE NEXT 2
TO 3 DAYS. THEREAFTER...HERNAN IS FORECAST TO WEAKEN AND BECOME
STEERED WESTWARD OR EVEN SOUTH OF DUE WEST BY THE LOW-LEVEL FLOW.
MOST OF THE TRACK GUIDANCE SHOWS THE INITIAL WEST-NORTHWEST TRACK
AND THE TURN TO THE WEST AND WEST-SOUTHWEST BEYOND 96 HOURS...AND
SO DOES THE OFFICIAL FORECAST.

THE INITIAL WIND RADII WAS ADJUSTED USING LATEST AVAILABLE QUIKSCAT.


FORECAST POSITIONS AND MAX WINDS

INITIAL 08/0900Z 15.0N 118.9W 55 KT
12HR VT 08/1800Z 15.1N 120.4W 60 KT
24HR VT 09/0600Z 15.4N 122.2W 65 KT
36HR VT 09/1800Z 16.0N 124.0W 55 KT
48HR VT 10/0600Z 17.0N 125.5W 50 KT
72HR VT 11/0600Z 18.0N 128.5W 45 KT
96HR VT 12/0600Z 18.0N 131.5W 30 KT
120HR VT 13/0600Z 17.5N 134.0W 20 KT...REMNANT LOW

$$
FORECASTER AVILA

855
WTPZ34 KNHC 080828
TCPEP4
BULLETIN
TROPICAL STORM HERNAN ADVISORY NUMBER 7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP092008
200 AM PDT FRI AUG 08 2008

AT 200 AM PDT...0900 UTC...THE CENTER OF TROPICAL STORM HERNAN WAS
LOCATED NEAR LATITUDE 15.0 NORTH...LONGITUDE 118.9 WEST OR ABOUT 800
MILES...1290 KM...SOUTHWEST OF THE SOUTHERN TIP OF BAJA CALIFORNIA.

HERNAN IS MOVING TOWARD THE WEST NEAR 13 MPH...20 KM/HR. A GRADUAL
TURN TO THE WEST NORTHWEST IS EXPECTED LATER TODAY.

MAXIMUM SUSTAINED WINDS REMAIN NEAR 65 MPH...100 KM/HR...WITH HIGHER
GUSTS. SOME STRENGTHENING IS FORECAST DURING THE NEXT 24 HOURS AND
HERNAN COULD BECOME A HURRICANE LATER TODAY.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 85 MILES...140 KM
FROM THE CENTER.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 994 MB...29.35 INCHES.

REPEATING THE 200 AM PDT POSITION...15.0 N...118.9 W. MOVEMENT
TOWARD...WEST NEAR 13 MPH. MAXIMUM SUSTAINED WINDS...65 MPH.
MINIMUM CENTRAL PRESSURE...994 MB.

THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT
800 AM PDT.

$$
FORECASTER AVILA

[KWT]

Very deep convection with Hernan even if it is mainly on the southern side I think it looks pretty good right now, hasn't got a bad shape either IMO.

[Chacor]

[HURAKAN]

08/1200 UTC 14.7N 119.6W T4.0/4.0 HERNAN -- East Pacific Ocean

[KWT]

4.0, may well see a hurricane out of that if the agencies agree on that rating, though the NHC may just wait another 6hrs to see what happens.

[Chacor]

WTPZ34 KNHC 081439
TCPEP4
BULLETIN
HURRICANE HERNAN ADVISORY NUMBER 8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP092008
800 AM PDT FRI AUG 08 2008

...HERNAN BECOMES FIFTH HURRICANE OF THE EASTERN NORTH PACIFIC
SEASON...

AT 800 AM PDT...1500 UTC...THE CENTER OF HURRICANE HERNAN WAS
LOCATED NEAR LATITUDE 14.7 NORTH...LONGITUDE 119.9 WEST OR ABOUT 865
MILES...1390 KM...SOUTHWEST OF THE SOUTHERN TIP OF BAJA CALIFORNIA.

HERNAN IS MOVING TOWARD THE WEST NEAR 13 MPH...20 KM/HR...AND THIS
GENERAL MOTION IS EXPECTED TO CONTINUE WITH A GRADUAL DECREASE IN
FORWARD SPEED DURING THE NEXT COUPLE OF DAYS.

MAXIMUM SUSTAINED WINDS HAVE INCREASED AND ARE NOW NEAR 75 MPH...120
KM/HR...WITH HIGHER GUSTS. SOME ADDITIONAL STRENGTHENING IS
FORECAST DURING THE NEXT DAY OR SO.

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 25 MILES...35 KM...FROM
THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 105
MILES...165 KM.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 987 MB...29.15 INCHES.

REPEATING THE 800 AM PDT POSITION...14.7 N...119.9 W. MOVEMENT
TOWARD...WEST NEAR 13 MPH. MAXIMUM SUSTAINED WINDS...75 MPH.
MINIMUM CENTRAL PRESSURE...987 MB.

THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT
200 PM PDT.

$$
FORECASTER KNABB/KIMBERLAIN

[KWT]

Well there we go another EPAC hurricane then, though interesting to see that none have gone on to be majors just yet however...

[UKane]

yay!

[UKane]

[UKane]

Its interesting that no EPAC cyclones have crossed over as a cyclone yet.

[RL3AO]

[Chacor]

Its interesting that no EPAC cyclones have crossed over as a cyclone yet.

What?

[RL3AO]

Its interesting that no EPAC cyclones have crossed over as a cyclone yet.

What?

That would be pretty crazy to see an EPac storm go right into the NIO or SHem.

[Chacor]

Forecast for 80 kts.

WTPZ44 KNHC 081459
TCDEP4
HURRICANE HERNAN DISCUSSION NUMBER 8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP092008
800 AM PDT FRI AUG 08 2008

AFTER A NOTICEABLE BURST OF DEEP CONVECTION THIS MORNING...SATELLITE
IMAGERY INDICATES A CDO FEATURE NOW PRESENT WITH A HINT OF A RAGGED
EYE WITHIN THE PAST FEW HOURS. WITH DVORAK SATELLITE ESTIMATES NOW
AT T4.0 FROM BOTH TAFB AND SAB AND GIVEN RECENT TRENDS...HERNAN IS
UPGRADED TO A HURRICANE. IN THE SHORT-TERM...SHIPS MODEL OUTPUT
SUGGESTS LIGHT EASTERLY SHEAR AMONGST OTHER FAVORABLE FACTORS
AND...ALONG THE FORECAST TRACK...HERNAN SHOULD REMAIN OVER 26
CELSIUS SSTS FOR AT LEAST THE NEXT 48 HOURS. ON THIS BASIS...THE
EXPECTATION IS THAT HERNAN SHOULD CONTINUE STRENGTHENING FOR THE
NEXT 24 HOURS BUT SHOULD BEGIN WEAKENING AFTER IT REACHES COOLER
WATERS AND A MORE STABLE ATMOSPHERE...ESPECIALLY BEYOND 48 HOURS.
GIVEN THE INCREASING ORGANIZATION APPARENT IN RECENT SATELLITE
IMAGERY...AND NO APPARENT HINDRANCES TO STRENGTHENING...THE NEW
OFFICIAL INTENSITY FORECAST IS HIGHER THAN THE PREVIOUS ADVISORY
AND ABOVE NEARLY ALL OF THE OBJECTIVE GUIDANCE.

THE INITIAL MOTION IS SET AT 275/11...WHICH IS VERY SIMILAR TO THE
HEADING DURING THE LAST 24 HOURS. THE TRACK IS ADJUSTED
SOUTHWARD...HOWEVER...AFTER REVIEWING A HOST OF MICROWAVE IMAGERY
THIS MORNING...WHICH ALSO SUGGESTS THAT THE LOW-LEVEL AND MID-LEVEL
CENTERS ARE NOW VERTICALLY ALIGNED. MID-LEVEL RIDGING EXTENDING
FROM NORTHERN MEXICO SOUTHWESTWARD TO NORTH OF THE TROPICAL CYCLONE
SHOULD CONTINUE THE HURRICANE ON A GENERAL WESTWARD TO
WEST-NORTHWESTWARD TRACK THE NEXT FEW DAYS...WITH THE OFFICIAL
TRACK ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE. THEREAFTER...A
GRADUAL WEAKENING SHOULD CAUSE THE STORM TO BE STEERED MORE WITH
THE LOW- TO MID-LEVEL FLOW...ON A MORE WESTWARD AND POSSIBLY
WEST-SOUTHWESTWARD COURSE BY THE END OF THE PERIOD.


FORECAST POSITIONS AND MAX WINDS

INITIAL 08/1500Z 14.7N 119.9W 65 KT
12HR VT 09/0000Z 14.8N 121.6W 75 KT
24HR VT 09/1200Z 15.1N 123.4W 80 KT
36HR VT 10/0000Z 15.5N 125.0W 75 KT
48HR VT 10/1200Z 16.1N 126.6W 65 KT
72HR VT 11/1200Z 17.0N 130.0W 45 KT
96HR VT 12/1200Z 17.0N 132.5W 35 KT
120HR VT 13/1200Z 16.5N 135.0W 25 KT

$$
FORECASTER KNABB/KIMBERLAIN

[HURAKAN]

Its interesting that no EPAC cyclones have crossed over as a cyclone yet.

What?

No EPAC has crossed to the CPAC this year.

[HURAKAN]

My 85 knots forecast is becoming a more real possibility!

[UKane]

Its interesting that no EPAC cyclones have crossed over as a cyclone yet.

What?

That would be pretty crazy to see an EPac storm go right into the NIO or SHem.

No... as in Epac to CPac

[KWT]

Indeed Hurakan is getting a pretty good look now, eye and eyewall has really developed well looking at the microwave imagery.