CPAC: NIALA - Post-Tropical

[galaxy401]

Looks like no upgrade yet...

[Yellow Evan]

Code: Select all

                    * EAST PACIFIC SHIPS INTENSITY FORECAST          *
                    * IR SAT DATA AVAILABLE,       OHC AVAILABLE     *
                    *  INVEST      CP962015  09/23/15  18 UTC        *

TIME (HR)          0     6    12    18    24    36    48    60    72    84    96   108   120
V (KT) NO LAND    25    27    29    32    36    44    53    59    60    57    53    51    48
V (KT) LAND       25    27    29    32    36    44    53    59    60    57    53    51    48
V (KT) LGE mod    25    26    27    28    30    34    40    45    50    51    49    47    45
Storm Type      TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP

SHEAR (KT)         3     7     5     4     5     4     2     2     6    11    16    20    22
SHEAR ADJ (KT)    -3    -5    -7    -5    -5    -4    -5    -3    -1     1     0    -1    -1
SHEAR DIR          7    17     9    21   357    35    40   181   244   231   252   253   258
SST (C)         29.4  29.4  29.3  29.2  29.1  28.9  28.6  28.5  28.4  28.5  28.5  28.5  28.5
POT. INT. (KT)   156   157   156   154   153   151   149   148   146   146   145   145   145
200 MB T (C)   -51.8 -51.3 -51.3 -51.5 -51.8 -52.1 -52.5 -52.4 -52.8 -52.7 -53.2 -53.0 -53.4
TH_E DEV (C)       8     9     8     8     8     8     8     7     7     7     7     6     6
700-500 MB RH     61    60    62    62    62    59    59    62    59    59    58    58    56
MODEL VTX (KT)     6     6     6     7     8     9    10    11    11    10     8     8     7
850 MB ENV VOR    -2    -4    -1     2    10    19    21    31    30    25    27    36    24
200 MB DIV        30    31    33    42    51    69    20    39    11     7     2     4     9
700-850 TADV       0     0     0     0     0    -1     0     2     2     1     1     0     0
LAND (KM)       1241  1187  1133  1078  1024   932   818   688   563   468   437   398   390
LAT (DEG N)     11.6  11.9  12.2  12.5  12.8  13.3  13.9  14.7  15.6  16.4  16.6  16.9  17.1
LONG(DEG W)    146.6 147.0 147.4 147.8 148.2 148.9 149.8 150.7 151.4 151.8 152.0 152.2 152.1
STM SPEED (KT)     4     5     5     5     5     5     6     6     5     3     2     1     1
HEAT CONTENT      28    31    32    31    30    27    28    29    37    51    52    51    52

  FORECAST TRACK FROM BAMM      INITIAL HEADING/SPEED (DEG/KT):315/  3      CX,CY:  -1/  2
  T-12 MAX WIND:  25            PRESSURE OF STEERING LEVEL (MB):  552  (MEAN=581)
  GOES IR BRIGHTNESS TEMP. STD DEV.  50-200 KM RAD:  15.0 (MEAN=14.5)
  % GOES IR PIXELS WITH T < -20 C    50-200 KM RAD:  70.0 (MEAN=65.0)

                        INDIVIDUAL CONTRIBUTIONS TO INTENSITY CHANGE
                         6   12   18   24   36   48   60   72   84   96  108  120
                        ----------------------------------------------------------
  SAMPLE MEAN CHANGE     0.   0.   0.   1.   1.   1.   0.   0.  -1.  -1.  -2.  -2.
  SST POTENTIAL          0.   0.   1.   2.   8.  15.  21.  27.  30.  32.  34.  35.
  VERTICAL SHEAR MAG     1.   2.   3.   4.   6.   8.  10.  11.  11.  10.   8.   7.
  VERTICAL SHEAR ADJ     0.   1.   1.   2.   3.   3.   3.   2.   2.   2.   3.   3.
  VERTICAL SHEAR DIR     0.   1.   1.   1.   3.   5.   5.   3.   1.  -1.  -3.  -4.
  PERSISTENCE            0.   0.   0.  -1.  -1.  -1.  -1.  -1.  -1.  -1.   0.   0.
  200/250 MB TEMP.       0.  -1.  -2.  -3.  -5.  -7.  -9. -11. -11. -11. -11. -10.
  THETA_E EXCESS         0.   0.   0.   0.   0.   0.  -1.  -1.  -1.  -2.  -2.  -3.
  700-500 MB RH          0.   0.   0.   0.   1.   1.   1.   1.   1.   1.   2.   2.
  MODEL VTX TENDENCY     0.   0.   1.   2.   4.   5.   7.   7.   6.   4.   3.   2.
  850 MB ENV VORTICITY   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.
  200 MB DIVERGENCE      0.   0.   0.   0.   1.   1.   1.   1.   0.   0.   0.   0.
  850-700 T ADVEC        0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   1.
  ZONAL STORM MOTION     0.  -1.  -1.  -1.  -2.  -3.  -4.  -4.  -4.  -4.  -3.  -3.
  STEERING LEVEL PRES    0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.
  DAYS FROM CLIM. PEAK   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.
  GOES PREDICTORS        1.   1.   2.   2.   1.   0.  -1.  -2.  -3.  -3.  -4.  -3.
  OCEAN HEAT CONTENT     0.   0.   1.   1.   1.   2.   1.   1.   2.   2.   2.   1.
                        ----------------------------------------------------------
  TOTAL CHANGE           2.   4.   7.  11.  19.  28.  34.  35.  32.  28.  26.  23.

   ** 2013 E. Pacific RI INDEX CP962015 INVEST     09/23/15  18 UTC **
           ( 30 KT OR MORE MAX WIND INCREASE IN NEXT 24 HR)
 
 12 HR PERSISTENCE (KT):   0.0 Range:-22.0 to  38.5 Scaled/Wgted Val:  0.4/  0.8
 850-200 MB SHEAR (KT) :   4.8 Range: 18.7 to   1.4 Scaled/Wgted Val:  0.8/  1.2
 POT = MPI-VMAX (KT)   : 130.2 Range: 40.3 to 141.7 Scaled/Wgted Val:  0.9/  0.9
 STD DEV OF IR BR TEMP :  15.0 Range: 38.9 to   2.4 Scaled/Wgted Val:  0.7/  0.7
 Heat content (KJ/cm2) :  30.4 Range:  3.6 to  75.9 Scaled/Wgted Val:  0.4/  0.3
 D200 (10**7s-1)       :  37.4 Range:-11.0 to 135.3 Scaled/Wgted Val:  0.3/  0.2
 % area w/pixels <-30 C:  58.0 Range: 41.4 to 100.0 Scaled/Wgted Val:  0.3/  0.1
 850-700 MB REL HUM (%):  69.4 Range: 57.6 to  96.8 Scaled/Wgted Val:  0.3/  0.0
 
 Prob of RI for 25 kt RI threshold=    38% is   2.9 times the sample mean(13.1%)
 Prob of RI for 30 kt RI threshold=    28% is   3.2 times the sample mean( 8.7%)
 Prob of RI for 35 kt RI threshold=    19% is   3.2 times the sample mean( 6.0%)
 Prob of RI for 40 kt RI threshold=    16% is   3.6 times the sample mean( 4.3%)

[1900hurricane]

Nice low level banding spiraling into the center.

[weathernerdguy]

probably a tropical depression already

[Kingarabian]

Looks like banding has increased to its NE. Looks like at least a 2.0 to me.

[Yellow Evan]

I don't understand Dvorak too well pre-T2.5, but looks around T1.5 to me. Still, no idea why the CPHc hasn't pulled the trigger. T numbers are meant for the intensity of the system, not necessarily on whether it's a TC or not.

[jaguarjace]

TROPICAL WEATHER OUTLOOK
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
200 AM HST THU SEP 24 2015

For the central north Pacific, between 140°W and 180.

1. Showers and thunderstorms associated with an area of low pressure centered around 670 miles southeast of Hilo, Hawaii are gradually becoming better organized.
Environmental conditions will remain conducive for development and a tropical depression could form during the next 24 hours as the system moves slowly toward the northwest.

* Formation chance through 48 hours, high, 80 percent.

[Yellow Evan]

Now appears to becoming sheared, likely due to an upper trough to its northeast. Global moodels struggling in this data sparse region, as usual.

[Hurricanehink]

1. Thunderstorms associated with an area of low pressure centered around 550 miles southeast of Hilo, Hawaii are becoming better organized. Environmental conditions will remain conducive for development and a tropical depression will likely form soon as the system moves slowly toward the northwest. The Central Pacific Hurricane Center is likely to begin advisories on this system later today or tonight.

Looks like they're ready to pull the trigger.

[Yellow Evan]

As usual, the CPHC waits for a system to peak before pulling the trigger.

[Yellow Evan]

24/2330 UTC 14.1N 148.9W T2.0/2.0 96C -- Central Pacific

TXPN42 PHFO 250001
TCSNP2

CENTRAL PACIFIC TROPICAL CYCLONE SUMMARY - FIXES
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
0000 UTC FRI SEP 25 2015

A. Tropical disturbance 96C.

B. 24/2330Z.

C. 14.3°N.

D. 149.1°W.

E. Goes-15.

F. T2.0/2.0/d0.5/24 hrs.

G. Vis/ir/eir.

H. Remarks: A log10 wrap yields a 0.5 wrap for a DT of 2.0. MET and pt agree. FT based on DT.

I. Addl positions none.

$$

Foster.

[jaguarjace]

WTPA31 PHFO 250233
TCPCP1

BULLETIN
TROPICAL DEPRESSION SIX-C ADVISORY NUMBER 1
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI CP062015
500 PM HST THU SEP 24 2015

...TROPICAL DEPRESSION SIX-C FORMS SOUTHEAST OF THE HAWAIIAN
ISLANDS...


SUMMARY OF 500 PM HST...0300 UTC...INFORMATION
----------------------------------------------
LOCATION...14.5N 149.3W
ABOUT 525 MI...845 KM SE OF HILO HAWAII
ABOUT 735 MI...1180 KM SE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...NW OR 320 DEGREES AT 8 MPH...13 KM/H
MINIMUM CENTRAL PRESSURE...1004 MB...29.65 INCHES


WATCHES AND WARNINGS
--------------------
THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 500 PM HST...0300 UTC...THE CENTER OF TROPICAL DEPRESSION SIX-C
WAS LOCATED NEAR LATITUDE 14.5 NORTH...LONGITUDE 149.3 WEST. THE
DEPRESSION IS MOVING TOWARD THE NORTHWEST NEAR 8 MPH...13 KM/H...AND
THIS MOTION IS EXPECTED TO CONTINUE THROUGH 36 HOURS FOLLOWED BY
A TURN TOWARD THE WEST.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/H...WITH HIGHER
GUSTS. GRADUAL STRENGTHENING IS EXPECTED OVER THE NEXT 24 HOURS
FOLLOWED BY WEAKENING AFTER 36 HOURS.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1004 MB...29.65 INCHES.


HAZARDS AFFECTING LAND
----------------------
NONE.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...1100 PM HST.

$$
FORECASTER KODAMA

[euro6208]

THIS IS THE ELEVENTH TROPICAL CYCLONE IN
THE CENTRAL NORTH PACIFIC BASIN FOR THE 2015 SEASON AND TIES THE
RECORD FOR THE MOST ACTIVE SEASON WHICH WAS SET IN 1992 AND
REPEATED IN 1994.

Another weak CPAC born system.

[Extratropical94]

Advanced dvorak is calculating a current intensity of 2.5/35kt and raw values of 2.7/39kt.

2015SEP25 100000 2.5 1005.2 35.0 2.5 2.7 2.7

Several 30 knot barbs can be seen on the latest ASCAT pass well east of the center.



The sat presentation has also improved during the last couple of hours.



Based on that, I think 06C is on the verge of becoming a tropical storm.

[Kingarabian]

Looks like the shear finally relaxed. If it can continue tucking in under the anti cyclone to its west, it'll maybe get to hurricane strength. Looks like within 48 hours shear will be 40kts and it'll get shredded.

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.

[Yellow Evan]

WTPA41 PHFO 250908
TCDCP1

TROPICAL DEPRESSION SIX-C DISCUSSION NUMBER 2
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI CP062015
1100 PM HST THU SEP 24 2015

SATELLITE IMAGERY INDICATES TROPICAL DEPRESSION SIX-C REMAINS A
VIABLE TROPICAL CYCLONE THIS EVENING. THERE IS STILL SOME
UNCERTAINTY IN REGARDS TO THE EXACT LOCATION OF THE LOW LEVEL
CIRCULATION CENTER USING INFRARED AND MICROWAVE DATA. RECENT SSMS
IMAGES AVAILABLE ON THE FNMOC/NRL WEB SITES FROM 0416Z AND 0451Z
APPEARED TO SHOW DIFFERENT CENTERS IN THE UPPER AND LOWER
LEVELS...WHICH IS NOT SURPRISING FOR A SYSTEM THAT IS IN THE INITIAL
STAGES OF ORGANIZING. THE SUBJECTIVE DVORAK FIXES FROM JTWC...SAB
AND PHFO WERE UNANIMOUS WITH CURRENT INTENSITY ESTIMATES OF 2.0/30
KT. THEREFORE...WE WILL MAINTAIN SIX-C AS A 30 KT TROPICAL
DEPRESSION FOR THIS ADVISORY.

THE INITIAL MOTION OF THE DEPRESSION IS 315/6 KT. SIX-C IS MOVING
SLOWLY NORTHWESTWARD TOWARDS A WEAKNESS IN THE SUBTROPICAL RIDGE.
THIS GENERAL MOTION IS EXPECTED TO CONTINUE DURING THE NEXT 24
HOURS...WITH A GRADUAL TURN TOWARD THE WEST-NORTHWEST AT ABOUT THE
SAME SPEED BETWEEN 24 AND 36 HOURS. A LARGE MIDDLE AND UPPER LEVEL
LOW PRESSURE SYSTEM CURRENTLY FAR NORTHEAST OF THE HAWAIIAN ISLANDS
IS FORECAST TO SHIFT SOUTHEASTWARD. AN ASSOCIATED TROUGH IS
FORECAST TO EXTEND SOUTHWEST FROM THE LOW ALOFT. THIS TROUGH ALOFT
WILL LIKELY MOVE SOUTHWARD...WHICH WILL PRODUCE STRONG UPPER
LEVEL SOUTHWESTERLY WINDS...AND INCREASING VERTICAL WIND SHEAR IN
THE VICINITY OF THE TROPICAL CYCLONE. THE GLOBAL FORECAST MODELS
CONTINUE TO SUGGEST THIS INCREASING VERTICAL WIND SHEAR WILL LIKELY
WEAKEN AND DECOUPLE THE SYSTEM BEYOND 48 HOURS. AS A RESULT...THE
WEAKENED SHALLOW CYCLONIC CIRCULATION THAT REMAINS AFTER THE SYSTEM
IS SHEARED WILL BE TRANSPORTED WESTWARD BY THE LOWER LEVEL STEERING
FLOW. THE RELIABLE DYNAMICAL MODELS ARE IN GENERAL AGREEMENT WITH
THIS SCENARIO AND ARE FAIRLY CLOSE TO EACH OTHER WITH THE MAIN
DIFFERENCES BEING THE FORWARD SPEED AFTER THIS DECOUPLING OCCURS.
THE LATEST TRACK FORECAST IS VERY CLOSE TO THE PREVIOUS WITH SOME
SLIGHT ADJUSTMENTS TO THE LEFT TO MORE CLOSELY FOLLOW THE TVCN AND
GFEX CONSENSUS GUIDANCE.

TROPICAL DEPRESSION SIX-C IS PASSING OVER WARM WATER...28C TO 29C...
BASED ON THE LATEST SEA SURFACE TEMPERATURE ANALYSIS. IN ADDITION...
THE CIRA ANALYSIS OF OCEAN HEAT CONTENT SHOWS THESE VALUES
INCREASING ALONG THE FORECAST TRACK DURING THE NEXT COUPLE OF DAYS.
HOWEVER...THE MOST RECENT GUIDANCE FOR CURRENT VERTICAL WIND
SHEAR IN THE VICINITY OF SIX-C FROM UW-CIMSS AND SHIPS SUGGEST THAT
THERE IS MODERATE SHEAR OF ABOUT 15 KT FROM THE NORTHWEST. THE
SHEAR MAGNITUDE IS EXPECTED TO REMAIN ABOUT THE SAME DURING THE
NEXT 36 HOURS. THE SHEAR IS FORECAST TO INCREASE BEYOND 48 HOURS...
WHICH WILL LIKELY DECOUPLE THE SYSTEM. UNTIL THAT OCCURS...IT APPEARS
THAT SIX-C WILL BE ABLE TO INTENSIFY SLIGHTLY. THE LATEST INTENSITY
FORECAST...CLOSELY FOLLOWS THE PREVIOUS...WITH SIX-C FORECAST TO
BECOME A TROPICAL STORM EARLY FRIDAY. STEADY WEAKENING IS FORECAST
DURING THE 48 TO 72 HOUR TIME PERIOD. IF THIS SYSTEM DOES BECOME A
TROPICAL STORM...IT WILL BE NAMED NIALA...PRONOUNCED NEE-AH-LA.


FORECAST POSITIONS AND MAX WINDS

INIT 25/0900Z 14.7N 149.8W 30 KT 35 MPH
12H 25/1800Z 15.4N 150.5W 35 KT 40 MPH
24H 26/0600Z 16.3N 151.8W 40 KT 45 MPH
36H 26/1800Z 16.9N 153.3W 40 KT 45 MPH
48H 27/0600Z 17.0N 154.7W 40 KT 45 MPH
72H 28/0600Z 17.0N 156.5W 30 KT 35 MPH
96H 29/0600Z 17.0N 157.5W 30 KT 35 MPH
120H 30/0600Z 16.5N 159.5W 25 KT 30 MPH

$$
FORECASTER HOUSTON

[Yellow Evan]

25/1130 UTC 14.7N 149.7W T2.5/2.5 06C -- Central Pacific

CENTRAL PACIFIC TROPICAL CYCLONE SUMMARY - FIXES
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
1200 UTC FRI SEP 25 2015

A. Tropical depression Six-C.

B. 25/1130Z.

C. 14.8°N.

D. 149.8°W.

E. Goes-15.

F. T2.5/2.5/d1.0/24 hrs.

G. Ir/eir.

H. Remarks: A log10 wrap yields a 0.4 wrap for a DT of 2.5. MET and pt agree. FT based on DT.

[Extratropical94]

06C NIALA 150925 1200 14.9N 149.9W CPAC 35 1002

If the CPHC doesn't decide to ignore this then we should have the seventh named CPAC storm in less than an hour.

[jaguarjace]

WTPA21 PHFO 251431
TCMCP1

TROPICAL STORM NIALA FORECAST/ADVISORY NUMBER 3
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI CP062015
1500 UTC FRI SEP 25 2015

THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

INTERESTS IN THE MAIN HAWAIIAN ISLANDS SHOULD MONITOR THE PROGRESS
OF TROPICAL STORM NIALA. A TROPICAL STORM WATCH MAY BR REQUIRED FOR
THE BIG ISLAND LATER TODAY OR TONIGHT.

TROPICAL STORM CENTER LOCATED NEAR 15.1N 150.1W AT 25/1500Z
POSITION ACCURATE WITHIN 20 NM

PRESENT MOVEMENT TOWARD THE NORTHWEST OR 320 DEGREES AT 6 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 1002 MB
MAX SUSTAINED WINDS 35 KT WITH GUSTS TO 45 KT.
34 KT....... 65NE 50SE 0SW 25NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.

REPEAT...CENTER LOCATED NEAR 15.1N 150.1W AT 25/1500Z
AT 25/1200Z CENTER WAS LOCATED NEAR 14.9N 149.9W

FORECAST VALID 26/0000Z 15.9N 151.1W
MAX WIND 40 KT...GUSTS 50 KT.
34 KT... 70NE 55SE 0SW 35NW.

FORECAST VALID 26/1200Z 16.7N 152.4W
MAX WIND 45 KT...GUSTS 55 KT.
34 KT... 75NE 60SE 25SW 45NW.

FORECAST VALID 27/0000Z 17.0N 153.8W
MAX WIND 45 KT...GUSTS 55 KT.
34 KT... 75NE 55SE 30SW 60NW.

FORECAST VALID 27/1200Z 17.0N 155.1W
MAX WIND 40 KT...GUSTS 50 KT.
34 KT... 70NE 30SE 25SW 60NW.

FORECAST VALID 28/1200Z 17.0N 157.0W
MAX WIND 35 KT...GUSTS 45 KT.
34 KT... 60NE 0SE 0SW 55NW.

EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 125 NM
ON DAY 4 AND 150 NM ON DAY 5...AND FOR INTENSITY NEAR 15 KT EACH DAY

OUTLOOK VALID 29/1200Z 17.0N 158.0W
MAX WIND 30 KT...GUSTS 40 KT.

OUTLOOK VALID 30/1200Z 16.5N 159.5W
MAX WIND 30 KT...GUSTS 40 KT.

REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 15.1N 150.1W

NEXT ADVISORY AT 25/2100Z

$$
FORECASTER HOUSTON

[supercane]

899
WTPA41 PHFO 251448
TCDCP1

TROPICAL STORM NIALA DISCUSSION NUMBER 3
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI CP062015
500 AM HST FRI SEP 25 2015

A 0745Z ASCAT PASS SHOWED A BROAD SWATH OF 35 KT SURFACE WINDS IN
THE NORTHEAST AND EAST QUADRANTS OF SIX-C. INFRARED SATELLITE
IMAGERY SHOWS A MUCH BETTER DEFINED TROPICAL SYSTEM THAN WE WERE
SEEING THURSDAY EVENING. AS A RESULT...THE SUBJECTIVE DVORAK FIXES
FROM JTWC...SAB AND PHFO WERE UNANIMOUS WITH CURRENT INTENSITY
ESTIMATES OF 2.5/35 KT. THE 1330Z ADT ESTIMATE PROVIDED BY UW-CIMSS
IS 2.3/33 KT. THEREFORE...WE HAVE UPGRADED TROPICAL DEPRESSION
SIX-C TO A 35 KT TROPICAL STORM. THE DESIGNATED NAME FOR THIS SYSTEM
IS NIALA...PRONOUNCED NEE-AH-LA.

THE INITIAL MOTION OF TROPICAL STORM NIALA IS 320/6 KT. THE NEWLY
FORMED TROPICAL STORM IS MOVING SLOWLY NORTHWESTWARD TOWARDS A
WEAKNESS IN THE SUBTROPICAL RIDGE. THIS GENERAL MOTION IS EXPECTED
TO CONTINUE DURING THE NEXT 12 HOURS...WITH A GRADUAL TURN TOWARD
THE WEST-NORTHWEST AT ABOUT THE SAME SPEED BETWEEN 12 AND 36 HOURS.
A LARGE MIDDLE AND UPPER LEVEL LOW PRESSURE SYSTEM CURRENTLY FAR
NORTHEAST OF THE MAIN HAWAIIAN ISLANDS IS FORECAST TO SHIFT
SOUTHEASTWARD. AN ASSOCIATED DEEP LAYER TROUGH IS FORECAST TO EXTEND
SOUTHWEST FROM THE LOW ALOFT. THIS TROUGH ALOFT WILL LIKELY MOVE
SOUTHWARD...WHICH WILL PRODUCE STRONG UPPER LEVEL SOUTHWESTERLY
WINDS...AND INCREASING VERTICAL WIND SHEAR IN THE VICINITY OF NIALA.
THE GLOBAL FORECAST MODELS CONTINUE TO SUGGEST THIS INCREASING
VERTICAL WIND SHEAR WILL LIKELY WEAKEN AND DECOUPLE THE SYSTEM BEYOND
DAY 3. AS A RESULT...THE WEAKENED SHALLOW CYCLONIC CIRCULATION THAT
REMAINS AFTER THE SYSTEM IS SHEARED WILL LIKELY BE TRANSPORTED WESTWARD
BY THE LOWER LEVEL STEERING FLOW. THE RELIABLE DYNAMICAL MODELS
REMAIN IN GENERAL AGREEMENT WITH THIS SCENARIO WITH THE MAIN
DIFFERENCES BEING THE FORWARD SPEED DURING DAYS 3 TO 5 AFTER THIS
DECOUPLING OCCURS. THE LATEST TRACK FORECAST IS VERY CLOSE TO THE
PREVIOUS WITH SOME SLIGHT ADJUSTMENTS TO NUDGE THE TRACK CLOSER TO THE
TVCN AND GFEX CONSENSUS GUIDANCE.

TROPICAL STORM NIALA IS PASSING OVER VERY WARM WATERS OF ABOUT 29C
BASED ON THE LATEST SEA SURFACE TEMPERATURE ANALYSIS. IN ADDITION...
THE CIRA ANALYSIS OF OCEAN HEAT CONTENT SHOWS THESE VALUES
INCREASING ALONG THE FORECAST TRACK DURING THE NEXT COUPLE OF DAYS.
HOWEVER...THE MOST RECENT GUIDANCE FOR CURRENT VERTICAL WIND
SHEAR IN THE VICINITY OF NIALA FROM UW-CIMSS AND SHIPS SUGGEST THAT
THERE IS SHEAR OF 13 TO 17 KT FROM THE WEST. THE SHEAR MAGNITUDE IS
EXPECTED TO REMAIN ABOUT THE SAME DURING THE NEXT 36 HOURS. THE
SHEAR IS FORECAST TO INCREASE...ESPECIALLY STARTING ON DAY 2...WHICH
WILL EVENTUALLY BEGIN TO DECOUPLE THE SYSTEM. UNTIL THAT OCCURS...IT
APPEARS THAT THE TROPICAL CYCLONE WILL BE ABLE TO INTENSIFY
SLIGHTLY. THE LATEST INTENSITY FORECAST HAS BEEN NUDGED UPWARD
DURING THE NEXT 2 DAYS. STEADY WEAKENING IS FORECAST BEYOND 48
HOURS...WITH NIALA WEAKENING TO A TROPICAL DEPRESSION...AND POSSIBLY
A REMNANT LOW BY DAYS 4 AND 5. NOTE THAT THE WIND RADII WERE
ADJUSTED BASED ON THE 0745Z ASCAT PASS. THESE LARGER WIND RADII
HAVE CAUSED THE MOST RECENT TROPICAL CYCLONE WIND SPEED
PROBABILITIES TO INCREASE OVER THE EXTREME SOUTHERN END OF THE BIG
ISLAND. AS A RESULT...A TROPICAL STORM WATCH MAY BE REQUIRED FOR
THE BIG ISLAND LATER TODAY OR TONIGHT.


FORECAST POSITIONS AND MAX WINDS

INIT 25/1500Z 15.1N 150.1W 35 KT 40 MPH
12H 26/0000Z 15.9N 151.1W 40 KT 45 MPH
24H 26/1200Z 16.7N 152.4W 45 KT 50 MPH
36H 27/0000Z 17.0N 153.8W 45 KT 50 MPH
48H 27/1200Z 17.0N 155.1W 40 KT 45 MPH
72H 28/1200Z 17.0N 157.0W 35 KT 40 MPH
96H 29/1200Z 17.0N 158.0W 30 KT 35 MPH
120H 30/1200Z 16.5N 159.5W 30 KT 35 MPH