bob Blog 29 Jan 2023

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 Sunday 29 Jan 2023

The Auckland deluge, an eggbeater
On Friday 27 January , the day before a long holiday weekend, a deluge of
rain moved over Auckland delivering downpours of 100-200mm rain mainly in
around 5 hours.
These are tropical proportions, and Auckland's drains are engineered to cope
with up to around 30mm per hour, so many didn't cope.
In the past that 30mm/hr threshold has been briefly exceeded, and last
Friday it was well and truly exceeded for around 4 to 5 consecutive hours.
Even the airport was flooded, and Elton John's concert cancelled.

The weather pattern for this deluge is a typical example of what I call an
eggbeater with two main ingredients.
1: A large HIGH over 1030 east of NZ that is being held in place by light
winds aloft.
2: Low pressure areas are being formed in the Tasman sea, but can't move
east because of the blocking high.
These ingredients combine like an old-fashioned manual eggbeater.
One spinning one way, and the other spinning the other way..
To feed tropical air into the hose of northeast winds aimed at Aotearoa NZ.
Similar weather patterns in the past have produced similarly wet days.
This one was super charged, and the reason for that may be that the Oceans
are now the warmest ever measured ..
www.newsroom.co.nz/ideasroom/why-the-north-and-east-have-had-such-a-dreadful
-summer?utm_medium=Social&utm_source=Facebook&fbclid=IwAR0NHHISyC2D4dO7aYkAn
mbCtOi5183uwe8E-f3dH-YCvcTL5AzIaZlZKag#Echobox=1674961266


TROPICS
Cyclone CHENESO brought lots of damage to Madagascar and is now moving off
to the south.
There is potential this week for cyclone formation between Indonesia and
northern Australia.

WEATHER ZONES
South Pacific Convergence zone SPCZ
The SPCZ is expected to be very active from PNG all the way to French
Polynesia.
Low L1 near Norfolk Island is expected to intensify as it travels slowly
southwest to west of Northland by mid-week and then fade further south.
High H1 east of Chatham Islands is quasi -stationary and expected to crawl
east along 45S.
Low L2 is expected to form near 20S to south of Tahiti early in the week and
then travel southwestwards and deepen.
Low L3 in the monsoonal trough over inland Australia is expected to bud off
coastal Sydney on Tuesday and then go southeast and fade in the Tasman Sea.
A tropical Low may form near Fiji this weekend. Keep an eye out for this.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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 64277762212
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Bobgram 22 Jan

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 Sunday 22 Jan 2023

When at sea, Your barometer can be a navigator
Always watch your barometer when doing a long sail, as it forewarns you of
wind changes.
In the past week I have shifted from Auckland to Palmerston North.
On Monday night I was saying farewell to a few friends at the Royal New
Zealand Yacht Squadron, and then met a previous user of my services, Mark
Hipgrave freshly arrived in NZ to participate in the Round North island see
http://www.ssanz.co.nz/rni2023/ and then the 50th anniversary of the Solo
Trans-Tasman this year, see http://www.solo-tasman.co.nz/#
Mark reminded me of the advice I gave him when he was delivering his yacht
The Healer to New Plymouth for the 2014 Trans-Tasman and cyclone LISA
appeared.
He remembers me emailing "Go due north until the barometer starts rising
then resume."
He wrote up the story for the My Sailing magazine in Australia, see
http://www.mysailing.com.au/how-a-professional-weather-router-directed-a-yac
ht-around-a-tropical-cyclone/

Last week I mentioned some apps that can turn an iPhone to a sensitive
marine barometer and barograph.
I was reminded via feedback to also mention barometer and barograph n apps
for android phones to barometers and the one mentioned was
barograph-craftsoft.en.aptoide.com/app .I have not tried it myself.
Just make sure you take a barometer with you on your next sailing adventure
and know how to use it.

TROPICS
Cyclone CHENESO is a tropical depression over Madagascar, but it should fade
soon.
The potential map for cyclone development during the coming week has some
hotspots around northern Australia and Vanuatu, as well as the Philippines.

WEATHER ZONES
South Pacific Convergence Zone
The SPCZ is expected to be very active from PNG all the way to French
Polynesia.
Low L1 between New Caledonia and Norfolk Island is expected to weaken as it
travels slowly southwest and then southeast towards west of North Island.
High H1 in the Tasman Sea is travelling east along 45S around south of the
South Island and then along 40S east of NZ.
Low L2 over Gulf of Carpentaria is travelling south and may briefly trigger
another low off the ne South wales coast on Monday/Tuesday then weaken.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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 64277762212
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Bob Blog 15 Jan

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 Sunday 15 Jan 2023

A barograph on your mobile.

Barometric pressure. You want to know about wind and rain, but weather
forecasters talk about isobars and fronts. Isobars and fronts show a pattern
that is easy to draw and follow. Isobars are those lines on a weather map
joining together places with the same surface pressure. The shape of the
isobars describes the weather pattern, and the way this pattern changes can
be used to forecast wind and rain.

All this starts by measuring pressure change.
What causes pressure to fall?
. maybe there is an approaching low-pressure system (marked as an L on a
weather map).
. maybe the air is getting warmer (and less dense)
. maybe the air is becoming more cloudy/humid (YES- damp air weighs less
than dry air).
. maybe the air above is being removed faster than it can be replaced (this
happens when rising air is vented off by stronger winds).
. maybe it is just the time of the day. clip_image002This is due to a
solar-induced atmospheric tide and called the "diurnal pressure change".
Pressure rises between about 5 to 9 am or pm and falls between 11 and 3 am
or pm. Daylight saving alters these hours.

Any iPhone includes a pressure sensor which can turn even an old model 6 (or
later) into a sophisticated barograph (sim card not needed for this to
work). There are two apps from STARPATH for mariners to watch pressure
changes.

The basic free Marine Barometer app records time, date, Lat, Lon, and both
sea level and station pressures manually with the press of a button.

The Marine Barograph app, for a small charge, expands on this basic
functionality by storing pressure and navigation data automatically whenever
the app is showing. It creates versatile graphic plots of pressure versus
time, plus all data can be exported as CSV files. Your vessel track can also
be exported as a GPX file for navigation analysis. These tracks can load
into Google Earth. Great for recording your sailing adventures. For a full
youtube discussion on how to use this app see
//www.youtube.com/watch?v=ZdVHWTF-Gs4


TROPICS
The latest cyclone activity report is at zoom.earth and tropic.ssec.wisc.edu
and Tropical Cyclone Potential is from
www.ssd.noaa.gov/PS/TROP/TCFP/index.html
This is the last week of this MJO and there is good potential for cyclone
development in the South Pacific, especially around Vanuatu,

WEATHER ZONES
South Pacific Convergence Zone
The SPCZ is expected to be very active and somewhat erratic with tropical
lows L1 travelling from south of Fiji to east of North Island, and L2
deepening over Vanuatu /New Caledonia mid-week then going southeast Avoid.
HIGHS
HIGH H1 now east of the South Island is expected to travel east along 45S
and help steer L1 southwards .
HIGH H2 is expected to travel slowly north across Tasman Sa and fade by end
of the week. is travelling east along 45S to east of the South Island.
Trough crossing Tasmania/ New South wales mid-week is expected to cross NZ
at end of the week followed by a southerly change.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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 64277762212
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Bob Blog 8 Jan

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 Sunday 8 Jan 2023

A NEW YEAR and MJO ARRIVES

Proving once again to be a reliable indicator for tropical action, the MJO
(Madden Julian Oscillation) arrived this week into the South Pacific.
The MJO is a boost of extra energy that travels from the Indian ocean to the
Pacific as shown in blue in the OLR anomolies seen at

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/foregfs.shtml

It is expected to reach a peak in our region this and next week then weaken.
It has triggered Cyclone HALE and is also expected to trigger a few more
lows in the tropics this week.

Cyclone HALE was named by Fiji Met Service when south of New Caledonia
earlier today and is seen here on windy.com

It is travelling east southeast and expected to bump into a HIGH that is now
travelling east along 45S past the South Island. This HIGH is expected to
knock the remains of HALE southwards towards Aotearoa / Bay of plenty , as
shown in a MetService forecast loaded to Facebook at
https://www.facebook.com/MetService/videos/933975564433795

TROPICS
HALE is Cat 1 off New Caledonia

WEATHER ZONES
South Pacific Convergence Zone SPCZ

The SPCZ is expected to be very active and somewhat erratic with tropical
lows L2 forming over Austral Islands, L3 south of Tonga, and late in the
week L4 near Fiji.

Lots to avoid.

HIGHS and LOWS

HIGH H1 is travelling east along 45S to east of the South Island.

HALE is expected to weaken a bit when it leaves the tropics and bumps into
H1. It is then expected to be steered southwards and may re-intensify when
it ingests some colder air over Aotearoa NZ on Wednesday. Avoid.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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 64277762212
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Bob Blog 1 jan 2023

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 Sunday 1 Jan 2023

REVIEW OF THE LAST MONTH (December 2022)

Here is a link to a YouTube clip giving an animated loop of the isobars and
streamlines in the South pacific at youtu.be/aiRKyR3gUv0

Lots of lows formed in the Tasman Sea. And Highs lingers south of Tahiti.
The cool waters of La Nina are relaxing. Warm zones are in the far northern
Pacific and central southern Pacific remain much the same. Waters around New
Zealand have noticeably warmed.
Average isobars for past month: The Siberian High has intensified and so
has a High over the arctic
- the source of a recent polar outbreak over northern America. In the
southern hemisphere the subtropical ridge has drifted south and remains much
the same intensity.
Pressure anomolies for past month: In the northern hemisphere there are low
breeding areas in the Pacific and the Atlantic.
The Southern hemisphere is clearly in a 3-wave mode.
Zooming into the NZ area: Summer has come at last: On the tropical side the
1010 has drifted south to the centre of Australia. And on the southern side
the 1010 has shifted north from Taupo to Campbell Island.

TROPICS
DARIAN grew to be Cat 5 in the Indian ocean last week and is now fading as
it travels off to the southeast.

MJO
The active part of the MJO is now travelling across Indonesia and north
Australia.
Although nothing is expected in the coming week, the potential for
development around northern Australia and the Coral Sea is now rising
steadily.

WEATHER ZONES
South Pacific Convergence zone SPCZ:
The SPCZ is expected to have an active week across the Coral Sea to Fiji and
from Samoa to Southern Cooks.
A tropical low is expected to form over northern Australia late this week.
Be aware.

HIGHS and LOWS
HIGH H1 which gave Aoteroa wonderful Christmas weather is now south of
Chathams is expected to slowly travel slowly northeast this week.
Sadly this brings a change of pattern back to "troughy "weather.
Low L1 is now just south of New Caledonia and its frontal rain band us
expected to travel south across New Zealand from Wednesday to Friday as the
low centre becomes complex and lingers in the Tasman Sea.
There may be OK weather after L1 for sailing east across the Tasman but take
care and be watchful for changing patterns.
Low L2 now over Tong is travelling southeast to Southern Cooks and Austral
Islands.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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 64277762212
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>