EPAC: Tropical Storm Hernan

[HURAKAN]

131
WHXX01 KMIA 061857
CHGE77
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1857 UTC WED AUG 6 2008

DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.

EAST PACIFIC OBJECTIVE AIDS FOR

DISTURBANCE INVEST (EP092008) 20080806 1800 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
080806 1800 080807 0600 080807 1800 080808 0600

LAT LON LAT LON LAT LON LAT LON
BAMS 12.6N 111.1W 13.5N 112.9W 14.5N 114.7W 15.4N 116.5W
BAMD 12.6N 111.1W 13.4N 113.6W 14.1N 116.0W 14.9N 118.2W
BAMM 12.6N 111.1W 13.6N 113.3W 14.6N 115.4W 15.6N 117.6W
LBAR 12.6N 111.1W 13.6N 113.7W 14.5N 116.7W 15.4N 119.5W
SHIP 25KTS 31KTS 39KTS 51KTS
DSHP 25KTS 31KTS 39KTS 51KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
080808 1800 080809 1800 080810 1800 080811 1800

LAT LON LAT LON LAT LON LAT LON
BAMS 16.5N 118.7W 18.1N 123.2W 19.1N 128.2W 19.3N 133.0W
BAMD 15.6N 120.4W 16.9N 124.7W 18.0N 129.2W 18.7N 133.4W
BAMM 16.5N 119.9W 17.9N 124.6W 18.9N 129.5W 19.1N 133.9W
LBAR 16.4N 122.3W 19.0N 127.4W 22.4N 131.0W 25.3N 131.1W
SHIP 56KTS 56KTS 52KTS 48KTS
DSHP 56KTS 56KTS 52KTS 48KTS

...INITIAL CONDITIONS...
LATCUR = 12.6N LONCUR = 111.1W DIRCUR = 290DEG SPDCUR = 14KT
LATM12 = 11.7N LONM12 = 108.4W DIRM12 = 294DEG SPDM12 = 14KT
LATM24 = 10.9N LONM24 = 106.3W
WNDCUR = 25KT RMAXWD = 40NM WNDM12 = 25KT
CENPRS = 1006MB OUTPRS = 1009MB OUTRAD = 225NM SDEPTH = D
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM

$$
NNNN

[Cyclenall]

348
ABPZ20 KNHC 061745
TWOEP
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1100 AM PDT WED AUG 6 2008

FOR THE EASTERN NORTH PACIFIC...EAST OF 140 DEGREES WEST LONGITUDE..

THE LOW PRESSURE SYSTEM CENTERED ABOUT 600 MILES SOUTHWEST OF
MANZANILLO MEXICO CONTINUES TO BECOME BETTER ORGANIZED...AND A
TROPICAL DEPRESSION APPEARS TO BE FORMING. IF THIS TREND
CONTINUES...ADVISORIES WILL BE INITIATED LATER THIS AFTERNOON. THE
SYSTEM HAS BEEN MOVING WEST-NORTHWESTWARD AT ABOUT 15 MPH.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER KNABB

That is the 2nd highest degree of potential formation in TWO's. The highest one of all is this; "A tropical depression has formed, advisories will be issued starting immediately". I've only seen that one a few times over the last 3 years though.

[cycloneye]

WTPZ44 KNHC 062043
TCDEP4
TROPICAL DEPRESSION NINE-E DISCUSSION NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP092008
200 PM PDT WED AUG 06 2008

THE LOW PRESSURE SYSTEM WELL SOUTHWEST OF THE PACIFIC COAST OF
MEXICO HAS STEADILY BEEN GAINING ORGANIZATION TODAY...WITH A
GRADUAL INCREASE IN CONVECTIVE COVERAGE AND A WELL-DEFINED SURFACE
CIRCULATION EVIDENT IN VISIBLE SATELLITE IMAGERY. DVORAK
CLASSIFICATIONS AT 18Z FROM BOTH TAFB AND SAB WERE T2.0...AND THE
SYSTEM IS DESIGNATED A TROPICAL DEPRESSION WITH ESTIMATED MAXIMUM
WINDS OF 30 KT.

AS IS USUALLY THE CASE FOR EASTERN PACIFIC TROPICAL CYCLONES...THE
FORWARD MOTION IS BEING DICTATED BY A SUBTROPICAL RIDGE OVER
MEXICO...AND THE INITIAL MOTION ESTIMATE IS 290/14. WATER VAPOR
IMAGERY DEPICTS A MID- TO UPPER-LEVEL TROUGH JUST OFF THE COAST OF
CALIFORNIA. AS A RESULT...THE FORWARD SPEED OF THE DEPRESSION IS
FORECAST TO SLOW DOWN A LITTLE DURING THE NEXT COUPLE OF DAYS AS IT
APPROACHES A WEAKNESS IN THE RIDGE. BEYOND 48 HOURS...THE
DYNAMICAL MODELS FORECAST THE WEST COAST TROUGH TO LIFT OUT AND
ALLOW THE RIDGE TO BUILD WESTWARD A LITTLE OVER THE EASTERN
PACIFIC...KEEPING THE TROPICAL CYCLONE ON A GENERAL
WEST-NORTHWESTWARD HEADING. ONCE THE CYCLONE REACHES COOLER WATERS
IN ABOUT THREE DAYS AND WEAKENS...IT SHOULD BECOME A MORE SHALLOW
SYSTEM AND TURN WESTWARD WITH THE LOW-LEVEL FLOW. MODEL GUIDANCE
IS IN GOOD AGREEMENT ON THIS GENERAL SCENARIO...AND THE OFFICIAL
TRACK FORECAST IS JUST NORTH OF THE MODEL CONSENSUS.

THE DEPRESSION IS CURRENTLY OVER SEA-SURFACE TEMPERATURES OF ABOUT
28 CELSIUS...AND THAT WILL REMAIN THE CASE FOR ABOUT THE NEXT 24
HOURS ALONG THE FORECAST TRACK...FOLLOWED BY STEADILY COOLER
WATERS. MODERATE EASTERLY WIND SHEAR IS CURRENTLY AFFECTING THE
CYCLONE...BUT MODELS FORECAST THE SHEAR TO WEAKEN A LITTLE AND
REMAIN WEAK THROUGHOUT THE FIVE-DAY FORECAST PERIOD. AS A RESULT
OF THESE CONDITIONS...A FAIRLY TYPICAL RISE AND FALL IN THE
INTENSITY FOR AN EASTERN PACIFIC CYCLONE IS FORECAST. THE OFFICIAL
FORECAST CALLS FOR A PEAK CLOSE TO HURRICANE INTENSITY IN A COUPLE
OF DAYS...FOLLOWED BY A RAPID DECLINE OVER COOL WATERS...IN GENERAL
AGREEMENT WITH BUT SLIGHTLY ABOVE THE SHIPS GUIDANCE.


FORECAST POSITIONS AND MAX WINDS

INITIAL 06/2100Z 12.9N 111.8W 30 KT
12HR VT 07/0600Z 13.6N 113.8W 40 KT
24HR VT 07/1800Z 14.5N 116.1W 45 KT
36HR VT 08/0600Z 15.2N 118.1W 55 KT
48HR VT 08/1800Z 16.0N 120.2W 60 KT
72HR VT 09/1800Z 17.5N 124.5W 50 KT
96HR VT 10/1800Z 18.0N 128.5W 30 KT...REMNANT LOW
120HR VT 11/1800Z 18.0N 132.0W 20 KT...REMNANT LOW

$$
FORECASTER KNABB

http://asp1.sbs.ohio-state.edu/tropical ... scussions/

[cycloneye]

[cycloneye]

[Matt-hurricanewatcher]

This is a tropical storm as far as I'm concerned. Deep convection and banding forming...If Edouard was a tropical storm with 1.5t at times this is.

[HURAKAN]

Closer to Hernán.

[Chacor]

viewtopic.php?f=25&t=102354

TD9E forecast challenge.

[HURAKAN]

07/0000 UTC 13.1N 112.1W T2.5/2.5 09E -- East Pacific Ocean

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 7.2.3
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 06 AUG 2008 Time : 233000 UTC
Lat : 13:07:28 N Lon : 112:22:14 W

CI# /Pressure/ Vmax
1.8 /1010.2mb/ 28.0kt

Final T# Adj T# Raw T#
(3hr avg)
1.8 1.9 4.0

Latitude bias adjustment to MSLP : +0.0mb

Center Temp : -68.1C Cloud Region Temp : -59.5C

Scene Type : CURVED BAND with 0.54 ARC in WHITE

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : EAST PACIFIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : 0.2T/hour
Weakening Flag : OFF
Rapid Dissipation Flag : OFF

****************************************************

[Chacor]

CI1.8 is quite possibly the lowest I've seen from CIMSS, but how the hell did they get a raw-T of 4.0?

[cycloneye]

Hello Hernan!


EP, 09, 2008080700, , BEST, 0, 135N, 1120W, 35, 1005, TS, 34, NEQ, 0, 30, 30, 30, 1008, 225, 30, 0, 0, E, 0, , 0, 0, HERNAN, D,


ftp://ftp.tpc.ncep.noaa.gov/atcf/tcweb/

[RL3AO]

I guess we know what they thought of that 1.8.

[HURAKAN]

I guess we know what they thought of that 1.8.

[Derek Ortt]

I'd have rather this been kept as a TD as the center is on the far eastern edge of the convection

[Mecklenburg]

Eastern Pacific is really active this year...

[HURAKAN]

Eastern Pacific is really active this year...

Impressive fact. With the formation of Hernán today, this means that the EPAC 2008 season is six days ahead of the 1997 season in the naming of the 8th storm.

Note: When Hilda formed in 1997, the season had had 10 depressions. The 2008 season has only had 9 depressions.

Link: http://weather.unisys.com/hurricane/e_p ... index.html

Of course, if the Atlantic season is above average, then historically speaking the EPAC season has to be below average or about average. Their average is 16 TS, 9 H, and 4 IH.

[RL3AO]

Good luck to this Hernan living up to the last one in 2002.

[RL3AO]

Here's the climatological data for the EPac for formation of the 8th named storm.

1970 to present average formation of 8th storm date: August 15
1970 to 1987 (when East Pacific Hurricane Center was RSMC): August 10
1988 to present (when National Hurricane Center was RSMC): August 19


Number of years 8th named storm formed before August 7 (1970 to present): 12 of 39 (31%)
1970 to 1987: 9 of 18 (50%)
1988 to present: 3 of 21 (14%) - First since 1992


Either the EPac has gotten less active in the past 20 years, or the NHC is naming fewer storms than the EPHC.

[cycloneye]

WTPZ34 KNHC 070245
TCPEP4
BULLETIN
TROPICAL STORM HERNAN ADVISORY NUMBER 2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP092008
800 PM PDT WED AUG 06 2008

...THE EIGHT TROPICAL STORM OF THE YEAR FORMS OVER THE OPEN
WATERS OF THE EASTERN PACIFIC...

AT 800 PM PDT...0300 UTC...THE CENTER OF TROPICAL STORM HERNAN WAS
LOCATED NEAR LATITUDE 13.8 NORTH...LONGITUDE 112.5 WEST OR ABOUT 650
MILES...1050 KM...SOUTH-SOUTHWEST OF THE SOUTHERN TIP OF BAJA
CALIFORNIA.

HERNAN IS MOVING TOWARD THE WEST-NORTHWEST NEAR 14 MPH...22 KM/HR.
A CONTINUED WEST-NORTHWESTWARD MOTION WITH A GRADUAL DECREASE IN
FORWARD SPEED IS FORECAST DURING THE NEXT COUPLE OF DAYS.

MAXIMUM SUSTAINED WINDS ARE NEAR 40 MPH...65 KM/HR...WITH HIGHER
GUSTS. GRADUAL STRENGTHENING IS FORECAST DURING THE NEXT COUPLE
OF DAYS.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 35 MILES...55 KM
FROM THE CENTER.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB...29.68 INCHES.

REPEATING THE 800 PM PDT POSITION...13.8 N...112.5 W. MOVEMENT
TOWARD...WEST-NORTHWEST NEAR 14 MPH. MAXIMUM SUSTAINED WINDS...40
MPH. MINIMUM CENTRAL PRESSURE...1005 MB.

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

$$
FORECASTER BROWN

249
WTPZ44 KNHC 070246
TCDEP4
TROPICAL STORM HERNAN DISCUSSION NUMBER 2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP092008
800 PM PDT WED AUG 06 2008

THE OVERALL CLOUD PATTERN OF THE TROPICAL CYCLONE HAS GRADUALLY
IMPROVED THIS EVENING. HOWEVER...CONVENTIONAL AND MICROWAVE
SATELLITE IMAGERY INDICATE THAT THE CENTER IS LOCATED NEAR THE
NORTHEASTERN EDGE OF THE DEEP CONVECTION...DUE TO EAST-
NORTHEASTERLY SHEAR. THE LATEST DVORAK INTENSITY ESTIMATES FROM
SAB AND TAFB ARE T2.5 OR 35 KT...WHICH SUPPORTS AN UPGRADE TO
TROPICAL STORM STRENGTH. HERNAN BECOMES THE EIGHTH NAMED STORM TO
FORM IN THE EASTERN PACIFIC THIS YEAR.

THE CENTER HAS BEEN RELOCATED A LITTLE NORTHEAST OF THE EARLIER
ESTIMATES. THIS RESULTS IN A SOMEWHAT UNCERTAIN INITIAL MOTION
ESTIMATE OF 295/12. THE TRACK FORECAST REASONING REMAINS UNCHANGED
AS HERNAN IS FORECAST TO CONTINUE IN A GENERAL WEST-NORTHWESTWARD
MOTION DURING THE NEXT FEW DAYS. A TROUGH THAT EXTENDS SOUTHWARD
OFF THE COAST OF CALIFORNIA SHOULD CAUSE HERNAN TO SLOW DOWN IN THE
NEXT COUPLE OF DAYS. THE TRACK GUIDANCE REMAINS IN GENERALLY GOOD
AGREEMENT ON HERNAN'S HEADING...BUT IS NOT AS FAST AS BEFORE. AS A
RESULT...THE NEW TRACK FORECAST IS A LITTLE SLOWER THAN THE
PREVIOUS ADVISORY AND IS REASONABLE AGREEMENT WITH THE CORRECTED
MODEL CONSENSUS.

THE MODELS SUGGEST THAT THE SHEAR CURRENTLY AFFECTING HERNAN WILL
RELAX IN ABOUT 24 HOURS. MOST OF THE INTENSITY GUIDANCE CALLS FOR
GRADUAL STRENGTHENING DURING THE NEXT COUPLE OF DAYS AS HERNAN
REMAINS OVER WARM WATERS. THE OFFICIAL INTENSITY FORECAST FOLLOWS
THE SHIPS GUIDANCE CLOSELY WHICH CALLS FOR HERNAN TO REACH
HURRICANE STRENGTH IN A COUPLE OF DAYS. THEREAFTER...THE CYCLONE
WILL BE MOVING OVER PROGRESSIVELY COOLER WATERS WHICH SHOULD INDUCE
STEADY WEAKENING.

FORECAST POSITIONS AND MAX WINDS

INITIAL 07/0300Z 13.8N 112.5W 35 KT
12HR VT 07/1200Z 14.5N 114.1W 45 KT
24HR VT 08/0000Z 15.2N 116.3W 50 KT
36HR VT 08/1200Z 15.8N 118.2W 55 KT
48HR VT 09/0000Z 16.4N 119.9W 65 KT
72HR VT 10/0000Z 17.6N 123.2W 55 KT
96HR VT 11/0000Z 18.5N 127.0W 40 KT
120HR VT 12/0000Z 19.0N 130.5W 25 KT...REMNANT LOW

$$
FORECASTER BROWN

[Matt-hurricanewatcher]

Wow those are some cold cloud tops. I would guest that the winds are closer to 40 and maybe 45 knots. This looks more impressive then Edouard ever did.

http://www.ssd.noaa.gov/goes/west/tpac/avn-l.jpg