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Bob McDavitt's ideas for sailing weather around the South pacific

28 November 2020

Bob Blog 29 Nov

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

Compiled Sun 29 Nov 2020

 

Australian Heat wave

A depression (low pressure centre) crossing inland Australia is expected to bring a five to six-day heatwave for millions of people in eastern Australia, with exceptional temperatures and duration.

See www.abc.net.au/news/2020-11-28/first-heatwave-of-australian-summer-2020/12928746

Despite the strong La Nia in the Pacific, rains have held off over northern Australia due to the recent dry phase of the MJO (Madden Julian Oscillation). However, the wet phase of the MJO is expected to move in for early to mid-December, bringing tropical rain to North Australia.

 

The Tropics

The latest cyclone activity report is at tropic.ssec.wisc.edu and Tropical Cyclone Potential is from www.ssd.noaa.gov/PS/TROP/TCFP/index.html

Things are quiet for now with no cyclones around but some potential areas for formation around Indonesia/Philippines.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

SPCZ is slightly north of its normal position from Solomon Islands to Samoa and extends further east than normal across French Polynesia.

A trough is moving east across s the Tongan/Niue area today/tomorrow, and another around mid-week.

 

Subtropical ridge (STR)

HIGH 1016 in north Tasman Sea is expected to travel east along 25S and fade to north of NZ on local Monday.

Another High is expected to cross Tasmania on Monday and then cross the Tasman Sea reaching central NZ on Wednesday then drifting off to north.

Another High should enter Tasman Sea on Thursday and cross northern NZ on Saturday.

 

NZ/Tasman troughs

LOW deepening to 986 off Tasmania tonight expected to travel across central NZ on local Monday and move off on Tuesday brining large swells and followed by vigorous southerly winds.

Low around 950hPa in Southern Ocean near 58S on Wednesday expected to travel east past south of NZ on Thursday/Friday with westerly gale for southern NZ.

 

Fiji/Tonga to NZ:

Avoid arriving on Monday 7 Dec, otherwise mostly OK.

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If you would like more detail for your voyage, then check metbob.com to see what I offer.

Or Facebook at /www.facebook.com/metbobnz/

Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom).

Weathergram archive (with translator) is at weathergram.blogspot.co.nz.

Contact is bob@metbob.com or txt 6427 7762212

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23 November 2020

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22 November 2020

Bob Blog 22 Nov

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

Compiled Sun 22 Nov 2020

 

LA NINA strengthens

La Nina is caused by cooler than normal seas along the equatorial eastern Pacific. It shifts the subtropical ridge away from the equator and strengthens the trade winds.

The Atmosphere:

The parameter we watch from the atmosphere is the Southern Oscillation Index SOI (30 day running mean) which is basically the (normalised) air pressure difference Tahiti-Darwin.  This entered La Nina territory last month and has relaxed a little in past few weeks.

 

The Ocean:

The parameter we use here is the average sea surface temperatures in the equatorial eastern Pacific zone NINO 3.4. This index has been steadily dropping for weeks and entered La Nina territory late November. The atmosphere and ocean have “coupled” in their behaviour, or are doing the same thing.

 

Sea temperature anomaly: Wwarmer than normal seas between New Caledonia and New Zealand are likely to enhance low pressure systems in the Tasma sea and increase the risk of tropical cyclone formation over next few months.

 

According to the International Research Institute of the Climate Prediction Centre, this La NINA should peak early in 2021 and has a 65% chance of lasting until May 2021.

 

The Tropics

TC IOTA brought more deluging rain to Central America in the past week.

Things seem to be quietening now, with a tropical depression about to make landfall onto the horn of Africa., and some potential areas for formation around Indonesia.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

SPCZ is in its normal position from Solomon Islands to Northern Vanuatu to between Fiji and Samoa..

A trough is expected to form over Samoa early in the week and travel over Niue/Southern Cooks around mid-week.

 

Subtropical ridge (STR)

HIGH/ridge is expected to travel east across the North island on Monday and then go east along 30 to 40South.

Next High is expected to arrive in Tasman Sea on Wednesday and linger there until the weekend, drifting northwards.

 

NZ/Tasman troughs

LOW 990hPa is expected to move from Tasman Sea onto North Island on Tuesday and off to the east on Wednesday followed by southerly flow.

Low below 960hpa is expected to travel east near 60South on Wed/Thu/Friday bringing vigorous west to SW wind flow to South Island.

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If you would like more detail for your voyage, then check metbob.com to see what I offer.

Or Facebook at /www.facebook.com/metbobnz/

Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom).

Weathergram archive (with translator) is at weathergram.blogspot.co.nz.

Contact is bob@metbob.com or txt 6427 7762212

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14 November 2020

Bob Blog 15 Nov

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

Compiled Sun 15 Nov 2020

 

Why the Napier deluge?

On Monday 9 November, Napier City (east coast of North Island, NZ) got 242mm of rain ---463 per cent of its normal monthly rainfall -- in just a few hours. This was Napier’s second wettest day in 150 years. It caused floods and slips that left more than 100 homes uninhabitable.

This was due to a “collision” of warm moist air arriving from the north and cool air arriving from the south. These airflows combined and stayed in place like a hand-held-hose, bringing a stream of intense rain. Places north or south of this stream didn’t get the deluge.

The Low over northern NZ was “cut-off” - it had light variable winds above it and, lacking a steering field, was very slow-moving. This also allowed near vertical ascent in its clouds, accentuating the rain.

Moisture in the incoming northerly flow can be tracked back to Papua New Guinea, via Vanuatu. This is a weather pattern typical of our current LA NINA and should recur several times during next few months,

The intensity of this event also indicates how climate change is affecting us--- a warmer world allows these plumes of higher humidity and thus, when the moisture is cooled, zones of enhanced rainfall.

 

The Tropics

Cyclone ETA has moved offshore and weakened after leaving six dead in North Carolina and Florida, and is followed by IOTA now near central America.

Typhoon VAMCO brought extensive damage to Philippines, including Manila and is now making landfall over Vietnam.

Cyclone ALICIA in southern Indian Ocean is the first cyclone of the new Southern Hemisphere cyclone season.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

SPCZ is slowly shifting south to its normal position from Solomon Islands to Northern Vanuatu to between Fiji and Samoa, and is increasing in activity.

A trough is expected to linger about and south of the Tonga/Niue area early to mid-week.

 

Subtropical ridge (STR)

HIGH skirting around south of NZ today expected to travel NE to 40S 140W by mid-week and build to 1038hPa with enhanced trade winds on its northern side mainly around 20 to 30S.

Weak ridge of high pressure is expected to move into west Tasman Sea on local Tuesday and travel to NW of NZ by Friday/Saturday and then weaken away.

Another weak High should cross Tasmania on Friday and South Tasman Sea by 22 Nov.

 

NZ/Tasman troughs

Looks Ok to arrive in northern NZ any day this week/early next week, but avoid arriving around Fri 27/Sat 28 Nov.

Trough crossing South Island tonight and weakening over remainder of NZ on Monday.

LOW crossing South Tasman Sea on local Tuesday may deepen to 974 hPa then weaken and go southeast.

Associated trough expected to cross South Island on Tuesday night and North Island on Wednesday, and then deepen into a low 1004hpa east of North Island and move off to southeast from Thu to Sat.

Another trough expected to reach South Island by Saturday 21 Nov.

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If you would like more detail for your voyage, then check metbob.com to see what I offer.

Or Facebook at /www.facebook.com/metbobnz/

Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom).

Weathergram archive (with translator) is at weathergram.blogspot.co.nz.

Contact is bob@metbob.com or txt 6427 7762212

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

07 November 2020

Bob Blog 8 Nov

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

Compiled Sun 08 Nov 2020

 

The Tropics

Tropical Cyclone ETA  has been bringing damaging wind and rain to central America recently and is now heading to Cuba. In Guatemala a remote village has been buried by landslides and around 100 people are feared dead.  In Honduras, at least 23 deaths have been confirmed.

ATSANI is about to travelling southwestwards near Hong Kong.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

SPCZ is somewhat north of its normal position this week from Solomon islands to Samoa, with scattered activity around French Polynesia.

Another convergence zone or upper trough is expected to be over New Caledonia on Tuesday/Wednesday and Fiji on Wednesday/Thursday.

 

Subtropical ridge (STR)

HIGH 1028hpa easing to 1020 over Tasmania today should cross central Tasman Sea and then northern NZ Thursday/Friday

 

NZ/Tasman troughs

LOW 994 over central NZ tonight expected to move off to SE Monday.

However, trailing trough is expected to linger over northern NZ and deepen into low on Monday that travels slowly southeast over NE NZ on Tuesday and off to southeast on Wednesday and in Tasman sea moving slowly east along 30S should reach northern NZ by Friday.

NW flow over South Island on Friday 13th followed by a trough on Saturday.

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If you would like more detail for your voyage, then check metbob.com to see what I offer.

Or Facebook at /www.facebook.com/metbobnz/

Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom).

Weathergram archive (with translator) is at weathergram.blogspot.co.nz.

Contact is bob@metbob.com or txt 6427 7762212

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

 

 

01 November 2020

Bob Blog 1 Nov 2020

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

Compiled Sun 25 Oct 2020

REVIEW OF THE LAST MONTH (October 2020)

La NINA (the cool eastern equatorial Pacific) has intensified and widens during the past month. This means the coming cyclone season is likely to be less than normal for Cook Island s and French Polynesia, but it may be more active for New Caledonia. The South Pacific subtropical ridge line drifted south, bringing blockings Highs around northern NZ.

 

The monsoon is heading for Indonesia. The sub-tropical ridges in northern and southern hemisphere have shifted pole-wards and strengthened.

Zooming into the NZ area, and comparing monthly anomalies from last month with now, shows that

The 1015 isobar has drifted south over Queensland. The sub-tropical ridge is much the same intensity. The Antarctic high has weakened.

 

The Tropics

ZETA hit US Gulf Coast and inland hard last few days; nearly two million without power. That’s the Greek alphabet used up, but cyclones are still brewing and latest is called Twenty_Nine.

Super Typhoon GONI (local name ROLLY) is hitting Philippines tonight, one million people have been evacuated (so far) but maybe up to 31 million will be affected. ATSANI may hit the northern tip of the Philippines.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

SPCZ is expected to stretch from Solomon Islands to Vanuatu then Samoa with a tail southeast to south of French Polynesia

Trough over New Caledonia from Mon to Wednesday and then should go southeast to northern NZ by Friday. Also, a low may form south of French Polynesia late in the week and go south.

 

Subtropical ridge (STR)

HIGH 1030hpa is acting as a block east of north Island near 160W until Tuesday,

Another HIGH east of South Island on Monday should grow to 1032hPa as it travels east along 40 to 30S reaching 160W by end of the week. This is likely to enhance the trade winds on its northern side.

 

Tasman troughs

LOW 1010 in Tasman sea moving slowly east along 30S should reach northern NZ by Friday. Trough likely over NZ on Saturday, followed by a SW flow.

 

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If you would like more detail for your voyage, then check metbob.com to see what I offer.

Or Facebook at /www.facebook.com/metbobnz/

Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom).

Weathergram archive (with translator) is at weathergram.blogspot.co.nz.

Contact is bob@metbob.com or txt 6427 7762212

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