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03-09-2020, 09:19   #1
Gaoth Laidir
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2020-21 Typhoon season (Pacific, Indian oceans)

The Northwest Pacific is finally starting to come to life after an extremely inactive season so far. Three hurricanes formed in the past week as a strong MJO pulse moved into the Maritime Continent. The Indian Ocean had two systems back in late May/early June as the Indian Ocean Dipole was in a positive phase, but nothing since. The southern hemisphere has had no activity yet this season (2020-21 season started in July).





Typhoon Maysak hit South Korea yesterday, though it had weakened substantially from its earlier peak of 125 knots (around 85 knots at landfall). Another one is brewing to the southeast Okinawa and should hit the islands early Sunday at an intensity of around 120 knots before taking roughly the same path as Maysak for another landfall in the South Korea on Monday. Two very similar systems taking very similar paths within a week of eachother.

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04-09-2020, 09:29   #2
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Haishen rapidly intensified by 50 knots in 24 hours and is now a 135-knot supertyphoon located well southeast of Kadena US Air Force Base in Okinawa. It should hold this intensity for the next 36 hours before weakening as it moves northwards off the west coast of Japan and towards South Korea. But it should give a direct hit to some of the islands over the weekend.

Quote:
WDPN32 PGTW 040300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 11W (HAISHEN) WARNING NR
015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUPER TYPHOON (STY) 11W (HAISHEN), LOCATED APPROXIMATELY 493
NM SOUTHEAST OF KADENA AB, OKINAWA, HAS TRACKED NORTHWESTWARD AT
08 KNOTS OVER THE PAST SIX HOURS. STY 11W HAS RAPIDLY INTENSIFIED
50 KNOTS OVER THE PAST 24 HOURS FROM 85 KNOTS TO THE CURRENT
INTENSITY OF 135 KNOTS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
SHOWS A 35NM ROUND EYE, WHICH SUPPORTS THE INITIAL POSITION WITH
GOOD CONFIDENCE. A 032200Z SSMIS 91GHZ MICROWAVE IMAGE DEPICTS A
COMPACT EYEWALL, APPROXIMATELY 100NM DIAMETER, WITH SPIRAL BANDING
OVER THE SOUTHERN SEMICIRCLE. THE INITIAL INTENSITY IS ASSESSED AT
135 KNOTS BASED ON DVORAK CURRENT INTENSITY ESTIMATES RANGING FROM
6.5 (127 KNOTS) TO 7.0 (140 KNOTS). UPPER-LEVEL ANALYSIS REVEALS A
FAVORABLE ENVIRONMENT WITH LOW VERTICAL WIND SHEAR (VWS) AND RADIAL
OUTFLOW. ADDITIONALLY, SST VALUES (30-31C) AND HIGH OCEAN HEAT
CONTENT VALUES ARE CONDUCIVE FOR FURTHER DEVELOPMENT. THE 03/1200Z
500MB ANALYSIS SHOWS A DEEP MIDLATITUDE SHORTWAVE TROUGH OVER THE
EAST CHINA SEA AND WESTERN JAPAN WITH A BROAD SUBTROPICAL RIDGE
ENTRENCHED NORTH OF THE SYSTEM AND A WEAK EXTENSION OF THIS STR
EXTENDING SOUTHWESTWARD TO ABOUT 25N 130E. STY 11W IS TRACKING WEST-
NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE DEEP-LAYERED
SUBTROPICAL RIDGE (STR) AND IS TRACKING TOWARD A COL REGION
POSITIONED JUST SOUTH OF OKINAWA.
3. FORECAST REASONING.
A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE LAST PROGNOSTIC REASONING MESSAGE.
B. THE STR IS FORECAST TO BUILD AND REMAIN STATIONARY OVER JAPAN
WITH THE SHORTWAVE TROUGH GRADUALLY FILLING OVER THE KOREAN
PENINSULA. THE NUMERICAL MODEL TRACKERS ARE NOW IN CLOSER AGREEMENT
NEAR OKINAWA WITH A SPREAD OF 70NM. THE FORECAST TRACK REMAINS
HIGHLY CONSISTENT WITH THE PREVIOUS FORECAST AND INDICATES A NORTH-
NORTHWESTWARD TRACK OVER AMAMI OSHIMA THEN JUST WEST OF KYUSHU AT
TAU 72. NUMERICAL MODEL GUIDANCE HAS REMAINED STABLE AND THE 03/12Z
ECMWF ENSEMBLE ALSO SUPPORTS THE FORECAST TRACK, HOWEVER, THE SYSTEM
COULD TRACK CLOSER TO SASEBO / KYUSHU DUE TO UNCERTAINTY IN THE
MODELS, WHICH ARE IN OVERALL FAIR AGREEMENT WITH A 100NM SPREAD IN
SOLUTIONS NEAR TAU 72. STY 11W IS FORECAST TO MAINTAIN STY INTENSITY
THROUGH TAU 36 WITH GRADUAL WEAKENING AFTER TAU 36 AS THE SYSTEM
TRACKS POLEWARD.
C. IN THE EXTENDED PERIOD, NUMERICAL MODEL GUIDANCE DIVERGES WITH
INCREASING UNCERTAINTY IN THE EXACT TRACK OVER SOUTH KOREA. STY 11W
IS FORECAST TO BEGIN EXTRA-TROPICAL TRANSITION (ETT) NEAR TAU 72 AS
IT INTERACTS WITH THE SHORTWAVE TROUGH AND WILL ACCELERATE POLEWARD
AND COMPLETE ETT BY TAU 96 WHEN IT GAINS FRONTAL CHARACTERISTICS
OVER NORTH KOREA. SIGNIFICANT WEAKENING WILL OCCUR OVER THE KOREAN
PENINSULA DUE TO INCREASING VWS AND INTERACTION WITH MOUNTAINOUS
TERRAIN. OVERALL, THERE IS MODERATE CONFIDENCE IN THE JTWC FORECAST
TRACK, WHICH IS POSITIONED CLOSE TO THE MULTI-MODEL CONSENSUS.//
NNNN
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04-09-2020, 09:34   #3
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https://meteologix.com/ie/satellite/...ml#play-0-33-8
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04-09-2020, 20:17   #4
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Haishen is still 135 knots and looks like passing about 30 miles to the west of Minami Daito Jima tomorrow afternoon, which would bring the worst conditions of its eastern flank right over the island. The local airport is ROMD, if you want to check Metars.

Quote:
WDPN32 PGTW 041500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 11W (HAISHEN) WARNING NR
017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUPER TYPHOON (STY) 11W (HAISHEN), LOCATED APPROXIMATELY 385 NM
SOUTHEAST OF KADENA AB, OKINAWA, HAS TRACKED NORTHWESTWARD AT 09 KNOTS
(KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY REVEALS A 29 NM DIAMETER ROUND EYE, PLACING GOOD CONFIDENCE IN
THE INITIAL POSITION. A 041238Z MHS 89 GHZ MICROWAVE IMAGE DEPICTS A
MICROWAVE EYE FEATURE WITH A COMPACT EYEWALL (75 NM IN DIAMETER) AND
BANDING OVER THE SOUTHERN AND EASTERN SEMICIRCLES. THE PROBABILITY OF
AN IMMINENT EYEWALL REPLACEMENT CYCLE HAS DECREASED IN THE CIMSS M-
PERC PRODUCT. THE INITIAL INTENSITY REMAINS AT 135 KTS BASED ON MULTI-
AGENCY DVORAK CURRENT INTENSITY ESTIMATES RANGING FROM T6.5 (127 KTS)
TO T7.0 (140 KTS) AND A 041236Z SATCON ESTIMATE OF 132 KTS WITH GOOD
CONFIDENCE. STY 11W IS TRANSITING THROUGH AN OVERALL FAVORABLE
ENVIRONMENT CHARACTERIZED BY LOW VERTICAL WIND SHEAR (VWS), RADIAL
OUTFLOW, AND WARM (30-31 CELSIUS) SEA SURFACE TEMPERATURES (SST). THE
04/0000Z 500MB ANALYSIS SHOWS A DEEP MIDLATITUDE SHORTWAVE TROUGH OVER
THE EAST CHINA SEA AND WESTERN JAPAN WITH A BROAD SUBTROPICAL RIDGE
(STR) ENTRENCHED NORTH OF THE SYSTEM WITH A WEAK STR EXTENSION
EXTENDING SOUTHWESTWARD. STY 11W IS TRACKING WEST-NORTHWESTWARD UNDER
THE STEERING INFLUENCE OF THE DEEP-LAYERED STR AND IS TRACKING TOWARD
A COL REGION POSITIONED SOUTH OF OKINAWA.
3. FORECAST REASONING.
A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE LAST PROGNOSTIC REASONING MESSAGE.
B. IN THE NEAR-TERM, THE STR IS EXPECTED TO BUILD, REMAINING
STATIONARY OVER JAPAN AS THE SHORTWAVE TROUGH SLOWLY FILLS OVER THE
KOREAN PENINSULA. NUMERICAL MODEL GUIDANCE REMAINS IN GOOD AGREEMENT
NEAR OKINAWA WITH A SPREAD OF 42 NM AT TAU 36. THE CURRENT FORECAST
TRACK IS VERY CONSISTENT WITH THE PREVIOUS FORECAST AND DEPICTS A
NORTH-NORTHWESTWARD TRACK THROUGH TAU 48, PASSING JUST EAST OF AMAMI
OSHIMA. AFTER TAU 48, THE SYSTEM WILL TURN POLEWARD AND IS FORECAST TO
TRACK JUST WEST OF KYUSHU. HOWEVER, DUE TO INCREASING SPREAD IN THE
MODELS (80 NM NEAR SASEBO), THE SYSTEM COULD SHIFT CLOSER TO SASEBO /
KYUSHU. SIMILARLY, AS THE SYSTEM MAKES LANDFALL IN SOUTH KOREA, THE
LARGE MODEL SPREAD LEADS TO SOME UNCERTAINTY IN THE EXACT TRACK OVER
SOUTH KOREA. THROUGH TAU 24, STY 11W IS EXPECTED TO MAINTAIN SUPER
TYPHOON INTENSITY. AFTERWARDS, AS THE SYSTEM TRACKS POLEWARD, IT WILL
WEAKEN FIRST GRADUALLY AND THEN MORE RAPIDLY AS IT INTERACTS WITH THE
MOUNTAINOUS TERRAIN OF THE KOREAN PENINSULA.
C. IN THE EXTENDED PERIOD, NUMERICAL MODEL GUIDANCE MAINTAINS A
SPREAD OF 125-130 NM THROUGH TAU 96, LEADING TO UNCERTAINTY IN THE
TRACK. BY TAU 72, STY 11W IS EXPECTED TO COMMENCE EXTRATROPICAL
TRANSITION (ETT) AS IT INTERACTS WITH THE SHORTWAVE TROUGH. THE SYSTEM
WILL ACCELERATE POLEWARD AND SIGNIFICANTLY WEAKEN AS IT TRANSITS OVER
THE KOREAN PENINSULA DUE TO INCREASING VWS AND TERRAIN INTERACTION.
ETT COMPLETION IS EXPECTED BY TAU 96 AS THE SYSTEM GAINS FRONTAL
CHARACTERISTICS AND NEARS THE JET. OVERALL, THERE IS MODERATE
CONFIDENCE IN THE JTWC FORECAST TRACK WHICH IS PLACED NEAR THE MULTI-
MODEL CONSENSUS.//
NNNN


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04-09-2020, 22:17   #5
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And this is just from the remnants of Typhoon Maysak


https://twitter.com/WeatherSarov1/st...058932736?s=20

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05-09-2020, 07:41   #6
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Haishen has weakened slightly to 125 kts and is approaching the island of Ninamidaitojima now, where pressure is 978 hPa and 10-minute mean wind is 81 kph. It should pass its closest point at around 12-15Z today.


Last edited by Gaoth Laidir; 05-09-2020 at 10:47.
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05-09-2020, 12:09   #7
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It has further weakened to 115 knots as an eyewall-replacement cycle seems to be taking place. That might save the Minamidaitojima population of 2000 a bit as the storm comes within 20 km at around 14Z today. The mean windspeed at the airport had been rising through the morning as the storm approaches but it's leveled off for now. Latest pressure on the island 961.7 hPa.

https://meteologix.com/ie/observatio...905-1000z.html

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05-09-2020, 12:13   #8
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Latest image, showing the island near the northeast eyewall.

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05-09-2020, 19:45   #9
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Looks like Minamidaitojima dodged a major bullet as it only barely registered hurricane-force sustained winds and may have found itself between the two concentric eyewalls. Those were hourly reports, so it could have received higher winds between reports, but it still shows that it's not always as destructive as the satellite intensity estimates would lead you to believe.

It's making a beeline straight for the small island of Kikaigashima later tonight.

https://twitter.com/Fergaltierney/st...14228355825666



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06-09-2020, 01:19   #10
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Haishen is weakening more quickly than expected as shear has increased and dry air has wrapped around and into the centre. It now looks like making landfall in South Korea at only around 55 knots, down from the 90 knots shown in earlier forecasts.

It's currently approaching Kikai Island (small kidney-shaped lone island northwest of the centre), where pressure is falling at around 1 hPa every 8 minutes. Latest winds there northeast 44 gust 61 knots, down slightly from earlier.

Quote:
METAR RJKI 060000Z AUTO 03044G61KT 0600 -RA FG FEW008 SCT011 BKN013 //////TCU 27/27 Q0964=
SPECI RJKI 052337Z AUTO 04046G64KT 0300 -RA FG FEW008 SCT011 BKN013 //////TCU 27/27 Q0967 RMK A2857 TCU 20KM S MOV SW P/FR=
METAR RJKI 052300Z AUTO 05043G65KT 1200 BR SCT011 BKN013 OVC019 //////TCU 27/27 Q0971=
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06-09-2020, 08:56   #11
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Haishen passed almost right over but just to the east of Kikaishima overnight. Max winds reported were westerly 55 gust 80 knots, with a minimum pressure of 946 hPa. The JTWC had its intensity around 95 kts at that time but its 03Z location (green symbol) in the map below seems too far south as the wind direction at Kikaishima had already backed around to 320 by then, meaning the centre was to the northeast of the island, not southeast. The JTWC only seem to use satellite imagery for both location and intensity estimates (and in this cases used a 5-hour old microwave scan) and don't mention actual surface observations, which is odd.

Metars
https://www.ogimet.com/display_metar...f=59&send=send

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27-10-2020, 20:21   #12
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The Pacific season is getting going now, with five named systems having formed in October. The strongest of these has been Molave, which is about to make landfall in eastern Vietnam after crossing central Phillipines as a Cat 1 typhoon Sunday.

NW Pacific season stats to date, with 1981-2010 averages in brackets. It's well below average activity on all parameters. The recent activity is down to a strong pulse of the MJO stationary over the eastern Maritime continent.

Named storms: 19 (22.4)
Named storm days: 59.50 (114.3)
Typhoons: 10 (14.1)
Typhoon days: 22.25 (55.6)
Super typhoons: 4 (7.2)
Super-typhoon days: 6.00 (18.7)
Total ACE: 101.0 (245.6)



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29-10-2020, 21:57   #13
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After Molave now comes Goni, which will follow a very similar track through the central Philippines in 2-3 days. Currently 120 knots, it should reach a peak of 140 knots but weaken to a Cat 3 before hitting central Luzon. It rapidly intensified by 40 knots in 6 hours today as it was in an area low shear and very high ocean heat content of around 200 kJ/cm².

Behind it is Tropical Depression 23W, which will become typhoon Atsani as it takes a more northwesterly direction towards Okinawa, also becoming a Cat 3 by day 5.







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01-11-2020, 22:24   #14
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Supertyphon Goni became a monster before hitting the Philippines yesterday, reaching an intensity of 170 knots, equaling that of Haiyan in 2013. It quickly weakened after landfall and is now lost most of its structure as it heads towards central Vietnam, the same area that got Molave last week.

Here is a sequence of IR satellite images before and after landfall.



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10-11-2020, 21:18   #15
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Vamco is the 23rd named storm of the NW Pacific and will take a very similar path to Goni and Molave. Max intensity should be limited to Cat 1-2.

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