Bob Blog 29 March 2020

WEATHERGRAM

YOTREPS

 

Compiled Sun 29 March 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.

 

There is a brief MJO active period expected in South Pacific during next two weeks and this increase the chances of a tropical cyclone.

 

At this stage the extended GFS model is starting to show a tropical low may form over Vanuatu around Thu 2 April and this MAY develop into a tropical cyclone for New Caledonia from 5 to 10 April and then move off Southeast to east of North Island during Easter.

 

Since most of the South Pacific has closed borders or increased restrictions on people from countries with Covid19 outbreaks there are NO vessels that I know of planning to sail around at present, so no need for my weekly blog.

I’ll resume my blog when we can start sailing again

Meanwhile, work on staying safe.

bob@metbob.com

Bob Blog 22 March

WEATHERGRAM

YOTREPS

Compiled Sun 22 March 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.

Voyaging in a COVIDI9 world:

Most countries have now implemented strict controls at ports of entry for visiting yachts in reaction to COVID-19 Coronavirus with many closing their borders and some enforcing a 14-day quarantine on arrival. The only places that are “open for yachts” in the South Pacific at present are American Samoa, Fiji, and Solomon Islands. Follow the links in this report to stay updated. www.noonsite.com and https://travel.state.gov/content/travel/en/traveladvisories/COVID-19-Country-Specific-Information.html

 

World Met Day 2020.

This year’s World Water Day and World Meteorological Day, on 22 and 23 March respectively, share the theme “Water and Climate Change”. They are being celebrated under extraordinary circumstances as The UN family comes together to tackle the coronavirus pandemic, with each institution playing its part.

One of the most effective ways to slow down transmission is to wash or sanitize our hands. However, globally three billion people do not have access to even basic hand washing facilities at home. Lack of access to clean water affects vulnerability to disease and ill health. It is especially acute among those living in extreme poverty in rural areas, as well as in informal urban settlements. Access to safe water is an essential component of the 2030 Agenda for Sustainable Development..

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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

 

No cycones around at present.

The MJO is now weakening in the South Pacific, but keeps a potential area north of PNG. However this may be too close to the equator to form a cyclone.

 

WATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stay much the same from Solomon Islands to north Vanuatu to Fiji.

Trough travelling across Fiji and Tonga between now and Tuesday.

 

Subtropical ridge (STR)

HIGH over Tasmania Tuesday night is expected to travel NE across the Tasman Sea this week and fade over northern NZ wed/Thu.

Another High is expected to cross Tasmania on Thursday night and reach southern NZ for the weekendby Friday local.

 

Tasman Sea /NZ/Aus

Trough crossing North Island on Monday followed by cool SW flow on Tuesday. Weak high for northern NZ on Wednesday then another trough o Thursday and cold southerly flow on Friday.

As for sailing east across the Tasman: it may be possible with a departure between tuday and Thursday, and again on Saturday.

As for New Caledonia to Australia: looks Ok this week, but for the border closures.

From Panama to Galapagos/Marquesas:

Borders are closed. If you are already out there then go to Marquesas via north of the Galapagos then to avoid the squalls of the “mirror” convergence zone, aim for 4;50 S 110W then go west to 125W then go direct.

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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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Bob Blog 15 March 2020

WEATHERGRAM

YOTREPS

Compiled Sun 15 March 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.

 

EQUINOX

The sun is directly over the equator on Friday 20 March at 03:49UTC (in NZ that’s Friday afternoon at 4:49 NZDT) and that’s the equinox. Australia, New Zealand and Samoa switch from Daylight or Summer-time to standard time on 5 April, the first Sunday in April.

The equinox is when the latitude of the overhead sun (or declination) becomes zero.

You can find your solar altitude (local sun angle at solar noon) by computing (for the southern hemisphere) 90-L-D, where L is our latitude in degrees South, and D is the declination

SO at the equinox, latitude L of Auckland is 37 degrees so solar angle/altitude is 90-L-D = 90-37-0 = 53 degrees.

There is a period in early March when the overhead sun is just south of the equator, and on 8 March is was directly above 5S.

It so happens that this direct sunlight helps to form a “mirror ITCZ convergence zone” with extra convection mainly along around 5S from around 100W to 85W. This often happens in March, and once formed the zone lasts a few weeks even though the overhead sun continues northward. This has happened this March as seen on today’s windy rain accumulation map for the next 5 days. This affects the yachts sailing between Galapagos and Marquesas and probably the best strategy to avoid these squalls is to stay north of 5S as far as is desirable.

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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

The MJO is spreading into the western South Pacific helping TC GRETEL which is expected to brush past northern NZ on local Tuesday/Saint Pats day. There is also TC HEROLD just east of Madagascar and travelling off to the Southeast.

 

WATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to become less active in the Coral Sea as GRETEL travels off to the southeast, and it should stay much the same from Solomon Islands to Vanuatu to Fiji to Tonga to southern Cooks.

Tropical Cyclone GRETEL down to 976hPa just south of New Caledonia tonight is expected to travel Southeast and brush past north and far east of North Island on Monday night /Tuesday local.

 

Subtropical ridge (STR)

HIGH over Tasmania tonight is expected to travel NE across the Tasman Sea this week and reach northern NZ by Friday local.

 

Tasman Sea /NZ/Aus

The cyclone is expected to give 3 to 5m swells in East Tasman Sea on Monday night/Tuesday with swells to 8-9m near the cyclone.

After the SE winds that follow that cyclone move off on Wednesday, a High is expected with a zone of light winds. This should be followed by an increasing westerly floe south of 35S.

As for sailing east across the Tasman: it may be possible south of 35S after swells ease with Tuesday or Wednesday departure.

As for New Caledonia to Australia: swells are over 3metres until Friday

 

From Panama to Galapagos/Marquesas:

North to northeast winds to 5N this week, but easing to light and variable next week, then a good current and Easterly winds to Galapagos.

To get to Marquesas this week there is a change: NORTH of Galapagos is now the way to go with stronger current and better wind. That mirror ITCZ along 5S 10 is also worth avoiding. When west of 95W aim for 5S 105W.

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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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Bob Blog 2020

Bob Blog 8 March 2020

WEATHERGRAM

YOTREPS

Compiled Sun 08 March 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.

 

THE MJO IS BACK AGAIN

The Madden Julian Oscillation is a burst of extra convection that can trigger cyclones. It visits the South Pacific for around 10 to 20 days once every 4 to 6 weeks.

One way of showing a passing MJO is to look at the forecast for OLR or outgoing longwave radiation. When the tropical convergence zones are active the sky is full of cloud and this blocks the outgoing radiation from getting away to outer space, so OLR is low and coloured blue (for bubbly). When skies are clear radiation can escape to outer space and OLR is high, and coloured orange or (mellow) yellow.

A constructed analogue forecast of future values of the OLR, using the MJO, show that we are expected to have a phase of low OLR (blue values) over the next few weeks, and that means an active South Pacific convergence zone and increased cyclone risk gradually spreading east.

As seen at www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/forca.shtml

 

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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

There is an increasing risk of Cyclone formation in the northern Australia to Coral Sea region this week.

 

WATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to become more active in the Coral Sea and stay much the same from Tuvalu to Tokelau to Fiji to Southern Cooks.

A tropical low is expected to form over Gulf of Carpentaria by Wed and move into the north Coral Sea by Saturday. Another Tropical Low may form in the Coral Sea by Friday and move onto New Caledonia this weekend. These lows may become tropical cyclones and should move ESE.

There is an increasing risk for more tropical cyclones in the coming fortnight.

 

Subtropical ridge (STR)

HIGH east of NZ is expected to fade on Monday.

High moving across Tasmania on Tuesday is expected to travel along 40S across the Tasman Sea and then stall near NZ on sat.

 

Tasman Sea /NZ/Aus

Trough crossing NZ on Monday followed by a southerly flow on Tuesday.

Another trough/Low may form NE of NZ by Thursday and travel SW onto northern NZ on Friday 13th and then move off to the SE.

Another trough is expected to cross Tasmania on Friday and then move into the Tasman Sea this weekend.

 

As for Noumea to Australia. This may well be affected by a tropical cyclone in Coral sea.

As for sailing east across the Tasman: it may be possible south of 35S after trough with a Wednesday or Thursday departure, so long as possible cyclone in Coral Sea follows its forecast.

 

From Panama to Galapagos/Marquesas:

North to northeast winds to 5N this week, then a good current and light winds to Galapagos.

To get to Marquesas this week shows that SOUTH of Galapagos is now the way to go (the winds north of Galapagos are expected to become light an d occasional westerly this week)

The ITCZ has a gap in it between 89W and 79W but does bloom at times just north of Galapagos.

 

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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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Bob Blog 1 March

Bob Blog 1 March 2020

WEATHERGRAM

YOTREPS

 

Compiled Sun 01 March 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.

 

REVIEW OF THE LAST MONTH (January 2020)

Sea Surface temperature anomalies as at start of January compared with the start of Feb may be seen at www.weatherzone.com.au/climate/indicator_sst.jsp?lt=global&lc=global&c=ssta

 

The main changes are in the South Pacific Ocean, with the hot pool in the Tasman Sea relaxing.

 

According to BoM (Australia) the Indian Ocean Dipole IDO and ENSO and SAM are all neutral – so there are no major climate drivers active at present. That means that it is the short-term drivers (such as MJO) that we need to watch to work out weather changes in advance.

 

During February anomolies in the North Pacific have relaxed and there have also been some small changes in the pattern around South America.

 

To see how the annual weather cycle and the seasons are working out, we can check the average isobar maps for past 30 days and their anomaly from www.esrl.noaa.gov/psd/map/images/fnl/slp_30b.fnl.html

 

The weather pattern hasn’t changed much, but for an intensification in the low in the north Pacific. One interesting feature is the rise to 1020+ for the Antarctic High. This may increase the SW winds in the mid-latitudes, perhaps.

 

There has been fair amount of change in the pressure anomolies since January, but higher than normal pressures remain over NZ area.

 

Zooming into the NZ area, and comparing monthly anomalies from last month with now, shows that the subtropical ridge STR has strengthened a little (as far as the 1015 isobar is concerned) but hasn’t shifted much. The 1010hpa isobar remains in much the same place.

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The Tropics

Latest cyclone activity report is from tropic.ssec.wisc.edu .

We seem to be having a lull in activity at present.

 

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stay much the same this week, from Tuvalu to Tokelau to Southern Cooks.

A sub-tropical low is expected to form south of Niue on Tuesday local then travel south along around 160W.

 

Subtropical ridge (STR)

HIGH near 45S 150W is expected to fade by Thursday local.

High just east of the North island tonight is expected to go SE and fade away by Tuesday.

New HIGH is expected to move into south Tasman Sea on local Tuesday, over southern NZ on Thursday and then east of the SI along 45S.

 

Tasman Sea /NZ/Aus

Trough over southern NZ on Mon fading over the North Island on Tues and Wed. local.

Low expected to move for interior of Aus to Tasmania on local Thurs an d then off to SE.

Associated trough is expected to stall over the South Island from Sat 7 March.

OK for Noumea to Australia.

As for sailing east across the Tasman: it may be possible south of 35S but avoid the troughs and their swells, and the passing High late in the week.

 

From Panama to Galapagos/Marquesas:

Northerly winds to around 4N this week, then light winds to 2N, then SE winds to Galapagos.

The ITCZ has a gap in it between 90W and 79W but does have outliers that reach as far south as Galapagos at times.

Winds are occasionally expected to be SE/S to north of Galapagos, so that’s an OK short cut to Marquesas this week, albeit showery and light winds at times.

 

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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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