Bob blog 26 jan

WEATHERGRAM

YOTREPS

 

Compiled Sun 26 Jan 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 subsolar point (Overhead sun)

Recently I’ve been noticing the reflection of the sun in satellite imagery across the South Pacific as in images from meteo.nc

This is the subsolar point or the latitude of the overhead sun or the solar declination.

AT this time of the year the subsolar point is in the southern tropics and drifting north , it will reach the equator at the equinox in March.

 

Here is a table of its values for later part of January. Each date is at 00 UTC ( close to local noon in the South Pacific , and a negative latitude indicates southern hemisphere.

Jan 17date (2020) -20degrees 53minutes 11.3seconds

Jan 18 -20:41:27.6

Jan 19 -20:29:20.3

Jan 20 -20:16:49.6

Jan 21 -20:03:56.0

Jan 22 -19:50:39.9

Jan 23 -19:37:01.5

Jan 24 -19:23:01.2

Jan 25 -19:08:39.4

Jan 26 -18:53:56.6

Jan 27 -18:38:53.0

Jan 28 -18:23:29.0

Jan 29 -18:07:45.2

Jan 30 -17:51:41.7

Jan 31 -17:35:19.1

-=-=-=-=-=

The Tropics

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

Cyclones DIANE and ESAMI are in the Indian Ocean and a tropical depression is located near Niue in the South Pacific, with a moderate potential of developing briefly into a tropical cyclone in next 12 hours. This system is expected to weaken from tomorrow.

 

WATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is slowly rebuilding in the Coral sea and northern-Vanuatu area this week. There is also a persistent convergence zone over southern Cooks extending to the east/southeast.

There is a tropical depression near Niue tonight, it may briefly become a cyclone, but is expected to travel slowly off the south then southwest and weaken from tomorrow.

 

Subtropical ridge (STR)

HIGH is expected to stall around /east of northern NZ for the coming week.

Another High in the Tasman sea today is expected to travel slowly around northern NZ by Wednesday.

A third high is expected to enter the central Tasman Sea on Thursday and then onto northern NZ by the weekend.

 

Tasman Sea /NZ/Aus

For Northern NZ: Remaining high and dry with light winds and sea breezes. Maybe a SW wind and some showers on Wednesday.

Foe the South Island: trough on Monday/Tuesday followed by a few days of SW wind s then another trough by the weekend.

As for Noumea to Australia: Mainly SE/E winds, then NE near Aus coast so OK.

As for Sydney to NZ: trough net few days, then looking Ok from Thursday but will need to go SE to get around a High.

 

From Panama to Galapagos/Marquesas:

Northerly winds to around 4N. Then an active ITCZ and SW winds from 4N to 2N (will need some waypoints), then S /SE winds as far as Galapagos area, As for getting to Marquesas, not enough data for entire voyage but what data we have is looking OK .

 

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

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

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

Bob Blog 19 Jan

WEATHERGRAM

YOTREPS

Compiled Sun 19 Jan 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.

Sea Surface temp Anomalies shows a recent marine heat wave off to east of NZ.

Coastal upwelling and a persistent SW airflow over New Zealand have led to Sea Surface Temperatures (SST) approximately 2 degrees Celsius lower than usual for this time of year around New Zealand’s West Coast (based on long term averages).

A large SST anomaly (with SST of +5°C above the average) to the east of New Zealand has begun to weaken as it slowly moves eastwards.

The SST anomaly data were obtained from NOAA satellites, and represents the difference between the daily SST and the long-term average.

The resulting animation is at www.metocean.co.nz/news

-=-=-=-=-=

The Tropics

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

 

Cyclone TINO visited Fiji and Tonga this weekend and is now going southeast. It may do a loop near 35S and then continue as a mid-latitude cyclone southeast to 45S. .

The cyclone potential remains high north and northwest of Fiji, but the forecast is for no cyclones forming this week. TINO has taken a lot of the oomph out of the South Pacific Convergence zone.

 

SPCZ=South Pacific Convergence zone.

The SPCZ is quieter this week after TC TINO has taken most of its oomph. It is also north and east of its normal position, from east of PNG to Tuvalu to Samoa to Aitutaki area.

N to NW winds on its northern side and southeast wind s on its southern side.

Big swells and a storm surge which may lead to coastal flooding around the southern Cooks and some moderate easterly swell to eastern Northland.

 

Subtropical ridge (STR)

HIGH is expected to stall around /west of northern NZ for the coming week

Another High is expected to skirt around southern NZ and then, when it is east of the South Island, travel off to the northeast.

 

Tasman Sea /NZ/Aus

A trough is expected to stall in the western Tasman sea over the South Island slowly going south rather than east.

As for Noumea to Australia: Mainly SE winds so OK.

As for Sydney to NZ: should wait until the trough moves on, after 23 jan

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

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

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

Bob Blog 12 Jan

WEATHERGRAM

YOTREPS

 

Compiled Sun 12 Jan 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.

 

An active phase of the MJO (Madden Julian Oscillation)is visiting the western pacific

The Madden Julian Oscillation is an occasional visitor to the Pacific (a burst of extra convection that can trigger cyclones). It usually takes 10 to 20 days for the active part of an MJO event to travel across the Pacific

(as seen on the phase diagram at www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml

 

Another parameter that helps us watch convective patterns in the tropics is Outgoing longwave radiation or OLR. When the tropical convergence zones are active their cloud blocks radiation from escaping to outer space, and OLR is low, coloured blue (for bubbly). When skies are clear radiation can escape to outer space and OLR is high, coloured orange or (mellow) yellow.

A constructed analogue forecast of future values of the OLR 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.

Deeper blue indicates less OLR and that means MORE convective activity.

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

-=-=-=-=-=

The Tropics

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

Cyclone CLAUDIA is travelling westwards offshore of the NW Australian coast.

A tropical low just SE of Solomon Island s is likely to deepen into a Cyclone over northern Vanuatu on Monday and continue SE to Fiji by Thursday and maybe skirt south Tonga on Friday/Saturday and then go south to east of NZ next week.

 

SPCZ=South Pacific Convergence zone.

The SPCZ is active this week from Solomon Islands to Tonga, with a tropical cyclone travelling SE/ SSE along this path.

Not a good week for Island hopping.

 

Subtropical ridge (STR)

HIGH east of NZ over 1020hPa is expected to linger near 40S 160W until mid -week and then fade.

High in the Tasman sea today is expected to skirt around the South Island and then to travel east

to east of the South Island along 45S.

 

Tasman Sea /NZ/Aus

A trough over the South Island is expected to weaken over the North island on Monday.

This should be followed by a SE flow maintained by the High east of the South Island.

 

For Noumea to Aus: Mainly SE winds so OK.

 

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

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

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

Bob Blog 5 Jan 2020

WEATHERGRAM

YOTREPS

 

Compiled Sun 05 Jan 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 (December 2019)

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

The main changes are in the Indian Ocean and South Pacific Ocean.

The Indian Ocean has gone more into an Indian Ocean Dipole positive mode. With cool temps in the east Indian Ocean (upwelling), and warm temps in the west, this deprives Australia of rain, so the outlook is for more bushfires there next month or longer until the rain returns. Around NZ there are warm seas in the west Tasman Sea and also, (reason unknown), well to east of NZ in the central South Pacific. This is an unusual pattern and is likely to produce some unusual weather in the next few weeks.

During December there have also been some small change in the pattern around South America, but anomolies in the North Pacific remain much the same.

 

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 subtropical ridge in the southern hemisphere has shifted southwards. The area below 1010hPa in the equatorial area has expanded southwards, with a zone now over Northern Australia.

 

There remains Higher than normal air pressure over arctic and Antarctic and this is displacing cool air to mid- latitudes. Features have moved or rearranged in the Northern Hemisphere. Features in the Southern Hemisphere are in much the same position as last month, but are repositioning----That high pressure zone over eastern Australia encourages anticyclones. And lower pressures about and south of NZ are encouraging SW winds.

 

Zooming into the NZ area, and comparing monthly anomalies from last month with now, shows that the subtropical ridge STR has strengthened and shifted southwards, but the 1010 isobar is still over central NZ .

We now have a SW anomaly flow over NZ. Finally, we have an easing /lowering in the anomoly pressures over Antarctica.

 

-=-=-=-=-=

The Tropics

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

TC SARAI weakened over Tonga and Southern Cooks last week.

No named storms at present, but there is high potential for TC formation over N Australia this week, and some lower potential zones around PNG

 

WATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is snaking across the South pacific, from Coral Sea to north of Fiji to Southern Cooks, but is rather weak this week.

Ok to do some Island -hopping this week.

 

Subtropical ridge (STR)

HIGH in the north Tasman Sea is expected to fade across northern NZ quickly on Monday as a new high travels into the southern Tasman Sea. That new high is expected to stay put and get reinforced on Thursday , then travel east across central and northern NZ on Saturday.

 

Tasman Sea /NZ/Aus

Troughs travelling northeast across NZ on Monday, Wednesday night /Thursday and Sat/Sun maintain a mainly SW/S flow as far as 30S to north of NZ this week. Better wind and swell for getting from tropics to NZ from late this week

 

For Noumea to Aus: With a blocked High in the Tasman sea, should be OK with SE winds for this route until Friday, but may be showery for the weekend and strong SE winds early next week as a low possibly deepens over Coral Sea

 

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

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

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