SPAC: DONNA - Post-Tropical

[Digital-TC-Chaser]

[doomhaMwx]

As of 05/01/17 00z
"GLOBAL MODELS ARE IN AGREEMENT THAT THE DISTURBANCE WILL TRACK TO THE EAST OVER THE NEXT FEW DAYS, BUT BECOME SPLIT AS TO THE TRACK AND INTENSITY IN THE LATER TAUS."

AN AREA OF CONVECTION (INVEST 99P) HAS PERSISTED NEAR 11.8S 165.4E, APPROXIMATELY 785 NM WEST-NORTHWEST OF NADI, FIJI. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS AN ELONGATED CIRCULATION WITH FLARING CONVECTION LOCATED OVER THE DISTURBANCE. A 302158Z AMSU-B METOP-B 89GHZ MICROWAVE IMAGE SHOWS FRAGMENTED CONVECTION ASSOCIATED WITH A VERY ELONGATED LOW LEVEL CIRCULATION. THE DISTURBANCE IS LOCATED IN A MARGINAL ENVIRONMENT DUE TO MODERATE VERTICAL WIND SHEAR (15-20 KNOTS), BUT IS OFFSET BY GOOD UPPER LEVEL OUTFLOW AND WARM SEA SURFACE TEMPERATURES (28-29 CELSIUS). GLOBAL MODELS ARE IN AGREEMENT THAT THE DISTURBANCE WILL TRACK TO THE EAST OVER THE NEXT FEW DAYS, BUT BECOME SPLIT AS TO THE TRACK AND INTENSITY IN THE LATER TAUS
MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 10 TO 15 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1008 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS LOW.

[doomhaMwx]

05/01/17 06z
JTWC upgrades to MEDIUM chance...

THE AREA OF CONVECTION (INVEST 99P) PREVIOUSLY LOCATED NEAR 11.8S 165.4E, IS NOW LOCATED NEAR 11.9S 167.6E, APPROXIMATELY 350 NM NORTH OF PORT VILA , VANUATU. ANIMATED MULTI-SPECTRAL SATELLITE IMAGERY AND A 010256Z GMI 37GHZ MICROWAVE PASS SHOWED PERSISTENT DEEP FLARING CONVECTION AND FRAGMENTED BANDING ASSOCIATED WITH AN ELONGATED LOW LEVEL CIRCULATION (LLC), WHICH WAS EXTRAPOLATED FROM A 302159 25KM METOP-B DESCENDING ASCAT PASS, AND ALSO SUGGESTED IN AN 850MB VORTICITY PRODUCT. PERIPHERAL WINDS ON THE EQUATORWARD SIDE OF THE NORTHWEST TO SOUTHEAST ORIENTED LLC ARE 15-30 KNOTS AND 15-20 KNOTS ON THE POLEWARD SIDE. UPPER-LEVEL ANALYSIS REVEALS A MARGINALLY FAVORABLE ENVIRONMENT WITH MODEST RADIAL OUTFLOW ASSOCIATED WITH A POINT SOURCE OVERHEAD AND LIGHT TO MODERATE (10-20 KNOTS) VERTICAL WIND SHEAR, IN ADDITION TO WARM SEA SURFACE TEMPERATURES (28-29 CELSIUS). GLOBAL MODELS ARE IN AGREEMENT THAT THE DISTURBANCE WILL TRACK EAST-SOUTHEASTWARD OVER THE NEXT COUPLE OF DAYS BEFORE HOOKING BACK WESTWARD.
MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 10 TO 15 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1008 MB. BASED ON DATA ANALYZED AND IMPROVED STRUCTURE OF THIS DISTURBANCE, THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS UPGRADED TO MEDIUM.

[Digital-TC-Chaser]

.
EC boms this system



Looks to be dry air in the mix the south.

[doomhaMwx]

.
EC boms this system

Yeah, ECMWF is consistent in strengthening this significantly once it arrives over the Coral Sea...

[doomhaMwx]

Burst of a symmetric area of very deep convection, but I'm not entirely sure if the circulation center is beneath it...

[doomhaMwx]

05/01/17 21z
TCFA issued...

REMARKS:
ANIMATED INFRARED/MULTI-SPECTRAL SATELLITE IMAGERY AND A 011909Z SSMIS 91 GHZ MICROWAVE PASS SHOWED DEEP, PERSISTENT AND FLARING CONVECTION WITH FRAGMENTED BANDING WRAPPING INTO A LOW-LEVEL CIRCULATION CENTER (LLCC). A 011032Z 25KM (METOP-B) PARTIAL ASCAT PASS REVEALS PRIMARILY 20-25 KNOT WINDS WITH A FEW 30 KNOT WIND BARBS AROUND THE EASTERN PERIPHERY OF AN EXTRAPOLATED LLCC. UPPER-LEVEL ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH A MODERATE POLEWARD OUTFLOW CHANNEL ASSOCIATED WITH A POINT SOURCE OVERHEAD AND LIGHT TO MODERATE (10-15 KNOTS) VERTICAL WIND SHEAR, IN ADDITION TO WARM SEA SURFACE TEMPERATURES (28-29 CELSIUS). GLOBAL MODELS ARE IN AGREEMENT THAT THE DISTURBANCE WILL TRACK EAST-SOUTHEASTWARD OVER THE NEXT COUPLE OF DAYS BEFORE HOOKING BACK TOWARD A SOUTHWESTWARD DIRECTION.
MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 25 TO 30 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1000 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS HIGH.

[doomhaMwx]

Tropical Cyclone Outlook for Vanuatu's Area(10S to 23S and 160E to 175E):
Issued by the Vanuatu Meteorology and Geo-Hazards Department, Port Vila at 6:00am May 02, 2017 (local time)

*Existing Cyclones in the Vanuatu Area
NIL.

*Potential Cyclone
A tropical low about 12.4S170.E near east notheast of TORBA. Possibility of the tropical low to develop into tropical cyclone is Moderate to high within the next 5 days.

*Likelihood of a Tropical Cyclone(s) in the Vanuatu Area:
Wednesday: Moderate to High
Thursday: Moderate to High
Friday: High
Saturday: High
Sunday: High

*NOTES: Chance of the event occurring for each day
Low: 10 -30%
Moderate: 40 - 60%
High: 70 – 100%

[doomhaMwx]

Bullseye! Latest ASCAT Metop-B pass this Tuesday morning(my time zone) reveals the very elongated circulation of Invest 99P...

[1900hurricane]

Not looking too bad, that's for sure.

[Digital-TC-Chaser]

Two earlier EC runs captured off FB gives some weight to the hurricane models intensity output.
https://i.imgsafe.org/81ee3abb71.png

https://i.imgsafe.org/81ef280bdf.png

[doomhaMwx]

05/02 00z ECMWF is showing the poleward turn to occur earlier/more east, very close or over the Vanuatu island chain, compared to the previous runs...



There's still some uncertainty on when will that poleward turn occur(and looks like how fast it'll intensify will be a big factor), but regardless, majority, if not all, of the models agree that Vanuatu will see some effects/impacts from a strong cyclone on the coming days...

[Digital-TC-Chaser]

Spawned from a passing ER-wave.


Mets office

GLOBAL MODEL DATA TIME 00UTC 02.05.2017



TROPICAL DEPRESSION 99P ANALYSED POSITION : 12.9S 170.4E



VERIFYING TIME POSITION STRENGTH TENDENCY

-------------- -------- -------- --------

00UTC 02.05.2017 12.9S 170.4E WEAK

12UTC 02.05.2017 13.7S 170.7E WEAK LITTLE CHANGE

00UTC 03.05.2017 13.2S 170.8E WEAK LITTLE CHANGE

12UTC 03.05.2017 13.1S 170.4E MODERATE LITTLE CHANGE

00UTC 04.05.2017 13.1S 169.2E MODERATE LITTLE CHANGE

12UTC 04.05.2017 13.3S 168.7E MODERATE INTENSIFYING SLIGHTLY

00UTC 05.05.2017 14.1S 168.6E STRONG INTENSIFYING SLIGHTLY

12UTC 05.05.2017 15.0S 168.3E STRONG INTENSIFYING SLIGHTLY

00UTC 06.05.2017 15.3S 168.3E STRONG LITTLE CHANGE

12UTC 06.05.2017 15.6S 169.4E STRONG INTENSIFYING SLIGHTLY

00UTC 07.05.2017 16.6S 170.7E STRONG WEAKENING SLIGHTLY

12UTC 07.05.2017 17.8S 171.6E STRONG LITTLE CHANGE

00UTC 08.05.2017 18.6S 172.4E STRONG LITTLE CHANGE

[wxman57]

It's a depression according to Fiji met office, the official RSMC of the region.

[Yellow Evan]

12z ECMWF brings a Cat 4 to Vanuatu after deepening in the Coral Sea. This could be a major mess to the island nation. GFS is weaker, however.

[Digital-TC-Chaser]

WTPS31 PGTW 022100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 18P (EIGHTEEN) WARNING NR 001//
REF/A/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI/012051ZMAY2017//
AMPN/REF A IS A TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. TROPICAL CYCLONE 18P (EIGHTEEN) WARNING
022100Z POSITION NEAR 13.0S 172.0E.
TROPICAL CYCLONE 18P (EIGHTEEN), LOCATED APPROXIMATELY 484 NM
NORTHWEST OF SUVA, FIJI, HAS TRACKED EASTWARD AT 07 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS
DEEP CENTRAL CONVECTION WITH FORMATIVE BANDING SHOWING RAPID
CONSOLIDATION OVER THE LAST SIX HOURS. THE INITIAL POSITION IS
EXTRAPOLATED FROM A LOW REFLECTIVITY FEATURE OBSERVED IN A 021521Z
89 GHZ GMI IMAGE WITH HIGH CONFIDENCE. THE INITIAL INTENSITY
ASSESSMENT OF 40 KNOTS IS BASED ON AN AVERAGE OF AVAILABLE
SUBJECTIVE DVORAK ESTIMATES RANGING FROM T2.5 TO T3.0 (35 TO 45
KNOTS). ENVIRONMENTAL ANALYSIS SUGGESTS VERY FAVORABLE CONDITIONS
WITH SSTS NEAR 30 CELSIUS AND OCEAN HEAT CONTENT RELATIVELY HIGH. A
MIDLATITUDE TROUGH TO THE SOUTH IS PROVIDING EXCELLENT POLEWARD
OUTFLOW, AND VERTICAL WIND SHEAR IS LOW. CURRENTLY TC 18P IS IN A
WEAK STEERING ENVIRONMENT WITH WEAK MID-LEVEL RIDGES TO THE
NORTHEAST AND WEST COMPETING FOR STEERING. A QUASI-STATIONARY TRACK
IS FORECAST FOR THE NEXT 24 TO 36 HOURS WITH GRADUAL INTENSIFICATION
EXPECTED WHILE OVER THE WARM WATER. AS THE TROUGH TO THE SOUTH
PASSES THROUGH THE REGION OVER THE NEXT 24 HOURS, RIDGING WILL BUILD
IN TO THE SOUTH ACCELERATING THE SYSTEM WESTWARD AROUND TAU 36.
ANOTHER LONGWAVE TROUGH IS EXPECTED TO APPROACH FROM THE WEST AROUND
TAU 72 PROVIDING ANOTHER PERIOD OF ENHANCED EXHAUST IN THE UPPER
LEVELS. PEAK INTENSITY IS EXPECTED TO REACH 110 KNOTS BY TAU 96 AS
THE SYSTEM ROUNDS THE RIDGE AXIS TURNING SOUTHWARD. NUMERICAL MODEL
GUIDANCE SHOWS SIGNIFICANT SPREAD IN POSSIBLE TRACK MOTION DUE TO
THE NEAR-TERM COMPLEX STEERING SCENARIO. OVERALL, EACH SOLUTION
SHOWS AGREEMENT WITH THE TRACK PHILOSOPHY BUT VARIES IN THE EXACT
POSITION AND TIMING OF THE TURNS. DUE TO THE COMPLEX MOTION OF THE
SYSTEM, THERE IS LOW CONFIDENCE IN THE FORECAST TRACK. MAXIMUM
SIGNIFICANT WAVE HEIGHT AT 021800Z IS 14 FEET. NEXT WARNINGS AT
030900Z AND 032100Z. THIS CANCELS AND SUPERSEDES REF A (WTPS21 PGTW
012100).//
NNNN

RSMC Fiji met office has not updated from yesterday.
http://gwydir.demon.co.uk/advisories/

[wxman57]

Fiji is still identifying it as a tropical depression with a low to moderate chance of developing into a TC over the next 3 days. They're the official RSMC of the basin. Haven't seen any ASCAT to confirm TC winds, but I wouldn't be surprised if it had 35-40kt winds now. Fiji may require 35kt winds in 4 quadrants for an upgrade, though.

[Yellow Evan]

Slightly OT, but why do people always refer FMS to Fiji or Nadi?

Anyway, JTWC is giving this a T3.5, which despite dry air, may not be terribly off.

[Digital-TC-Chaser]

Tropical Depression [TD21F]
http://www.met.gov.fj/aifs_prods/65648.html

Tropical Cyclone Warning Number 1 issued 0204 UTC Wednesday 3 May 2017

Name: Tropical Depression [TD21F]
Situation At: 0000 UTC Wednesday 3 May 2017
Location: 13.0S, 171.0E
Recent Movement: Slow Moving

Fiji time is UTC +12 hours.
For example, 0000 UTC Saturday is 1200 Saturday Fiji time.
For example, 1800 UTC Saturday is 0600 Sunday Fiji time.

Category Cyclone 1 has mean winds 34-47 knots with a central pressure greater than 985 hPa
Category Cyclone 2 has mean winds 48-63 knots with a central pressure 985-970 hPa
Category Cyclone 3 has mean winds 64-85 knots with a central pressure 970-945 hPa
Category Cyclone 4 has mean winds 86-107 knots with a central pressure 945-910 hPa
Category Cyclone 5 has mean winds greater than 107 knots with a central pressure less than 910 hPa


The next TC Threat Track Map is scheduled to be issued within six hours.

[doomhaMwx]

Now named "Donna" by RSMC Nadi...
=====================================================================
HURRICANE WARNING 003 ISSUED FROM RSMC NADI May 030716 UTC.

TROPICAL CYCLONE DONNA CENTRE 994HPA CATEGORY 1 WAS LOCATED NEAR 13.1 SOUTH
171.2 EAST AT 030600 UTC.
POSITION FAIR.
REPEAT POSITION 13.1S 171.2E at 030600 UTC.
CYCLONE MOVING EAST SOUTHEAST AT 2 KNOTS. CYCLONE INTENSIFYING.
EXPECT SUSTAINED WINDS OF 40 KNOTS CLOSE TO THE CENTRE INCREASING TO 70 KNOTS BY
040600 UTC.

EXPECT WINDS OVER 33 KNOTS WITHIN 90 NAUTICAL MILES IN NE QUADRANT
AND WITHIN 150 NAUTICAL MILES IN SE QUADRANT
AND WITHIN 120 NAUTICAL MILES IN SW QUADRANT
AND WITHIN 90 NAUTICAL MILES IN NW QUADRANT

FORECAST POSITION NEAR 13.3S 170.7E AT 031800 UTC
AND NEAR 13.7S 169.7E AT 040600 UTC.

ALL VESSELS WITHIN 300 NAUTICAL MILES OF CENTRE ARE REQUESTED TO SEND REPORTS
EVERY THREE HOURS TO RSMC NADI. VOS REPORTING SHIPS USE NORMAL CHANNELS. OTHER
VESSELS FAX PLUS 679 6720190 OR EMAIL NADITCC AT MET DOT GOV DOT FJ

THIS WARNING CANCELS AND REPLACES WARNING 002.