WPAC: PEWA - Tropical Storm

[euro6208]

rapid strengthening followed by rapid weakening

[euro6208]

So in the WPAC, storms with clear eyes are considered Tropical Storms?

dvorak scale is screwed...at least JTWC upgraded to typhoon but severely underestimated

[hurricanes1234]

rapid strengthening followed by rapid weakening

The JTWC is saying that it will peak at 100 knots. But that would be when or if it reaches the favourable environment they are talking about. However, there is a very large ball of convection surrounding it, so maybe it could begin to strengthen from there.

Personal Forecast Disclaimer: The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

[Caribwxgirl]

Impressive looking storm there...what's the latest on it?

[Hurricane_Luis]

Impressive looking storm there...what's the latest on it?

1 day after your post. We have a weak 35 knot Tropical Storm.

[hurricanes1234]

The forecasted intensification is yet to materialise. Pewa continues to be affected by intense and destructive wind shear, which was expected to abate at least a day ago. Now this barely classifies as a tropical storm, when we saw a typhoon not too long ago.

[wxmann_91]

The forecasted intensification is yet to materialise. Pewa continues to be affected by intense and destructive wind shear, which was expected to abate at least a day ago. Now this barely classifies as a tropical storm, when we saw a typhoon not too long ago.

From what I remember reading from a few discussions ago, the Euro held onto the shearing influence of the ULL the longest. Looks like the Euro has been right.

[euro6208]

WDPN31 PGTW 220300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01C (PEWA)
WARNING NR 23//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 01C (PEWA), LOCATED APPROXIMATELY 242 NM
NORTHEASTWARD OF WAKE ISLAND, HAS TRACKED NORTH-NORTHWESTWARD AT
08 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS BUILDING CENTRAL CONVECTION WITH A FRAGMENTED
BANDING FEATURE WRAPPING INTO A PARTIALLY EXPOSED LOW-LEVEL
CIRCULATION CENTER (LLCC). THE WESTERN THROUGH SOUTHERN PERIPHERIES
OF THE STORM CONTINUE TO BE STRONGLY SHEARED. A 220157Z AMSU-B
MICROWAVE IMAGE BETTER REVEALS THE POSITION OF THE PARTIALLY EXPOSED
LLCC RELATIVE TO THE CENTRAL CONVECTION AS WELL AS DRY AIR
APPROACHING FROM THE NORTH AND SOUTH OF THE SYSTEM. THE IMAGE ALSO
SHOWS THE FRAGMENTED NATURE OF THE WEAKENING BANDING FEATURE TO THE
EAST OF THE LLCC. THE INITIAL POSITION IS BASED ON THE ABOVE
ANIMATION AND THE AFOREMENTIONED IMAGERY WITH FAIR CONFIDENCE. THE
INITIAL INTENSITY OF 35 KNOTS IS BASED ON CONGRUENT DVORAK ESTIMATES
FROM PGTW AND RJTD. PERSISTENT VERTICAL WIND SHEAR (VWS) ASSOCIATED
WITH THE PERIPHERAL FLOW AROUND A TROPICAL UPPER TROPOSPHERIC TROUGH
(TUTT) CELL TO THE NORTHWEST OF THE SYSTEM CONTINUES TO REMAIN A
MAJOR LIMITING FACTOR TO THE DEVELOPMENT OF THE SYSTEM. THE CYCLONE
CONTINUES TO TRACK NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF
A SUBTROPICAL RIDGE (STR) TO THE EAST.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING BULLETIN.
B. TS 01C WILL CONTINUE TO TRACK NORTHWESTWARD THROUGH TAU 48
UNDER THE INFLUENCE OF THE STR. THE NUMERICAL MODEL GUIDANCE IS IN
GOOD AGREEMENT DURING THIS PERIOD, LENDING HIGH CONFIDENCE TO THIS
PORTION OF THE FORECAST TRACK. THE CYCLONE IS EXPECTED TO INTENSIFY
SLOWLY AS THE TUTT CELL MOVES NORTHWESTWARD A BIT FASTER THAN TS
01C. THIS OPENING DISTANCE WILL ALLOW THE VWS TO SLOWLY DECREASE AND
POLEWARD OUTFLOW TO IMPROVE AS THE SYSTEM CONTINUES TO TRACK ACROSS
WARM WATER AND INCREASE TO A PEAK INTENSITY OF 60 KNOTS. AT THIS
POINT, APPROXIMATELY TAU 72, THE NUMERICAL GUIDANCE BECOMES SPREAD
AS TS O1C MOVES INTO A WEAK STEERING ENVIRONMENT AS AN APPROACHING
MID-LATITUDE TROUGH BREAKS THE STEERING RIDGE.
C. IN THE EXTENDED PERIOD, THE TRACK SPEEDS ARE EXPECTED TO SLOW
CONSIDERABLY DUE TO THE WEAK STEEERING ENVIRONMENT. ADDITIONALLY,
THE NUMERICAL GUIDANCE DIVERGES WITH RESPECT TO THE LOCATION AND
TIMING OF THE SLOW-DOWN. THEREFORE, THE FORECAST TRACK CONFIDENCE
FOR THE EXTENDED PERIOD IS LOW. AS TS 01C MEANDERS IN THE WEAK
STEERING ENVIRONMENT, COOLER SSTS AND DRY INTRUSION ARE EXPECTED
TO WEAKEN THE SYSTEM.//
NNNN

[jaguarjace]

Saved loop.

[hurricanes1234]

Continues to be terribly sheared by the TUTT that just refuses to let up. Otherwise, we would have had a decent Category 2 or 3 "fish". Instead, we have the pieces of what was once an impressive typhoon (now a minimal tropical storm with its center constantly separated from the convection and very poor banding features).

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

[Hurricane_Luis]

Wind shear has taken its toll, Pewa has weakened to a Depression



WDPN31 PGTW 230900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 01C (PEWA)
WARNING NR 28//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION 01C (PEWA), LOCATED APPROXIMATELY 436 NM
NORTH-NORTHEASTWARD OF WAKE ISLAND, HAS TRACKED NORTHWESTWARD AT
01 KNOT OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER
(LLCC) THAT HAS STARTED TO ELONGATE AS CONVECTION CONTINUES TO BE
SHEARED ACROSS THE EASTERN HALF OF THE SYSTEM. THE INITIAL POSITION
IS POSITIONED WITH LOW CONFIDENCE AS POSITION FIXES FROM ALL
AGENCIES HAVE BECOME WIDELY SPREAD AND THE LLCC HAS ELONGATED. THE
INITIAL INTENSITY HAS BEEN LOWERED TO 30 KNOTS BASED ON DVORAK
CURRENT INTENSITY ESTIMATES FROM PGTW AND KNES ALONG WITH THE
WEAKENING STRUCTURE OF THE SYSTEM. UPPER-LEVEL ANALYSIS CONTINUES TO
INDICATE STRONG (25-30 KNOTS) VERTICAL WIND SHEAR (VWS) ASSOCIATED
WITH A TROPICAL UPPER-TROPOSPHERIC TROUGH (TUTT) CELL TO THE
NORTHWEST OF THE SYSTEM PERSIST AND CONTINUES TO HAMPER TD 01C AND
LIMIT DEVELOPMENT DESPITE GOOD OUTFLOW INTO THE TUTT CELL AND A SOME
DEVELOPING OUTFLOW INTO THE JET LOCATED EAST OF THE SYSTEM. TD 01C
HAS BECOME QUASISTATIONARY AS THE SUBTROPICAL RIDGE (STR) POSITIONED
EAST OF THE SYSTEM HAS WEAKENED WHILE A TROUGH HAS STARTED TO DIG IN
FROM THE WEST.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TD 01C WILL TRACK NORTHWESTWARD THROUGH TAU 24 UNDER THE
INFLUENCE OF A WEAK EXTENSION OF AN STR POSITIONED TO THE NORTHEAST
AND THE TUTT CELL. AFTER TAU 24, A SLOW DRIFT TO THE WEST IS
EXPECTED AS THE SYSTEM MOVES INTO A WEAK STEERING ENVIRONMENT
BETWEEN THE MIDLATITUDE FLOW AND THE WEAKENING TUTT CELL. AFTER TAU
48, A MIDLATITUDE TROUGH IS FORECAST TO DIG IN AND ACCELERATE TD 01C
POLEWARD. SLIGHT INTENSIFICATION AT TAU 24 IS EXPECTED AS VWS IS
FORECAST TO SLIGHTLY RELAX. AFTER WHICH, TD 01C IS FORECAST TO BEGIN
EXTRATROPICAL TRANSITION BY TAU 48 AS THIS INCREASING VWS AHEAD OF
THE TROUGH ALONG WITH COOLER SEA SURFACE TEMPERATURES BEGIN TO
WEAKEN THE SYSTEM. THE POSSIBILITY OF DISSIPATION BELOW WARNING
THRESHOLD BEFORE THIS SYSTEM BEGINS EXTRATROPICAL TRANSITION REMAINS
DUE TO HIGH VWS AND DRY AIR BEGINNING TO SURROUND THE STORM. DESPITE
THE POSSIBILITY FOR EARLY DISSIPATION, CONFIDENCE IN THE TRACK FOR
THIS PORTION OF THE FORECAST IS HIGH.
C. IN THE EXTENDED PERIOD, TD 01C IS EXPECTED TO ACCELERATE
POLEWARD AND COMPLETE EXTRATROPICAL TRANSITION BY TAU 96. THE
NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGHOUT THE
FORECAST PERIOD WITH A SLIGHT SPREAD IN POSITION AND TRACK SPEEDS AT
THE LATER TAUS DUE TO VARYING INTERPRETATIONS OF THE EXTRATROPICAL
TRANSITION. THE JTWC FORECAST IS IN AGREEMENT WITH THE MULTI-MODEL
CONSENSUS, WHICH INDICATES RAPID ACCELERATION PAST TAU 48 INTO THE
WESTERLIES WITH EXTRATROPICAL TRANSITION BY TAU 96. THERE IS LOW
CONFIDENCE IN THE TRACK FOR THE EXTENDED PORTION OF THE FORECAST DUE
TO VARYING SOLUTIONS IN THE POSITION AND TRACK SPEED OF THE SYSTEM
DURING THE TRANSISTION.//
NNNN

[Meow]

Pewa is still a minimal TS.



TS 1313 (PEWA)
Issued at 09:45 UTC, 23 August 2013

<Analyses at 23/09 UTC>
Scale -
Intensity -
Center position N26°30'(26.5°)
E168°40'(168.7°)
Direction and speed of movement N 15km/h(8kt)
Central pressure 1004hPa
Maximum wind speed near the center 18m/s(35kt)
Maximum wind gust speed 25m/s(50kt)
Area of 30kt winds or more NE220km(120NM)
SW90km(50NM)

<Forecast for 24/09 UTC>
Intensity -
Center position of probability circle N27°50'(27.8°)
E167°20'(167.3°)
Direction and speed of movement NW Slowly
Central pressure 1000hPa
Maximum wind speed near the center 20m/s(40kt)
Maximum wind gust speed 30m/s(60kt)
Radius of probability circle 130km(70NM)

<Forecast for 25/06 UTC>
Intensity -
Center position of probability circle N28°30'(28.5°)
E165°25'(165.4°)
Direction and speed of movement NW Slowly
Central pressure 1000hPa
Maximum wind speed near the center 20m/s(40kt)
Maximum wind gust speed 30m/s(60kt)
Radius of probability circle 200km(110NM)

<Forecast for 26/06 UTC>
Intensity -
Center position of probability circle N29°05'(29.1°)
E164°05'(164.1°)
Direction and speed of movement WNW Slowly
Central pressure 1002hPa
Maximum wind speed near the center 18m/s(35kt)
Maximum wind gust speed 25m/s(50kt)
Radius of probability circle 300km(160NM)

It is still going to live for long time...

[xtyphooncyclonex]

I thought this will be a super typhoon!

[hurricanes1234]

I thought this will be a super typhoon!

We all thought this would become a major typhoon. But the TUTT never abated, in spite of forecasts for it to do so, and most likely it will remain that way or get worse for the rest of the storm's duration. 25 knots of wind shear? I am surprised that Pewa still exists, because that is nearly stronger than the storm's wind speed itself. I think the storm will continue to spin down, but at a slow rate, while the circulation intermittently becomes exposed, then returns to the convection several times. But strengthening seems highly unlikely.

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

[Meow]

I thought this will be a super typhoon!

At least it gave a short life of Unala, a 6-hour TS in the northwest Pacific.

[Iceman56]

No, not everyone was expecting a major typhoon. Just pointing out that some forecasters were noticing the shear while others were wishcasting this to be what they wanted it to be.

From CPHC advisory 2:

ALONG THE CURRENT FORECAST TRACK...THE SEA SURFACE TEMPERATURES ARE
EXPECTED TO REMAIN AROUND ITS CURRENT VALUE NEAR 28C AND OCEANIC
HEAT CONTENT WILL BE INCREASING. THE MAIN LIMITING FACTOR AT THIS
POINT WILL BE THE AMOUNT OF VERTICAL SHEAR WHICH IS FORECAST TO
INCREASE AFTER PEWA CROSSES THE DATELINE AND APPROACHES AN UPPER
LEVEL LOW. BASED ON THESE FACTORS...THE CURRENT PACKAGE CALLS FOR
PEWA TO REACH PEAK INTENSITY AT AROUND 36 TO 48 HOURS THEN WEAKEN.
THIS IS IN LINE WITH THE PREVIOUS PACKAGE AND IS CLOSE TO THE HWRF
TREND. IF THE VERTICAL SHEAR REMAINS STRONG ENOUGH BEYOND 72
HOURS...PEWA MAY WEAKEN MUCH FASTER.

From CPHC advisory 3:

HOWEVER...AFTER A COUPLE OF DAYS...PEWA WILL BEGIN TO FEEL THE
EFFECTS OF AN UPPER LEVEL LOW CURRENTLY NEAR 23N 173E. INCREASING
SOUTHWESTERLY SHEAR IS EXPECTED OVER THE SYSTEM WHICH SHOULD HALT
INTENSIFICATION...THEN INDUCE GRADUAL WEAKENING. HOW MUCH WEAKENING
WILL DEPEND ON THE EVOLUTION OF THE UPPER LOW.

From CPHC advisory 4:

THE LATEST INTENSITY FORECAST ASSUMES PEWA
CAN INTENSIFY TO A TYPHOON IN THE NORTHWEST PACIFIC OCEAN WITHIN 48
HOURS. AFTER THAT IS ASSUMED THAT THE INFLUENCE OF THE UPPER LEVEL
LOW WILL KEEP IT FROM INTENSIFYING FURTHER DURING DAYS 3 TO 5. NOTE
THAT THE INITIAL WIND RADII WERE ADJUSTED BASED ON THE 16/2353Z
OSCAT PASS.

I thought this will be a super typhoon!

We all thought this would become a major typhoon....