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AfewUniversesBelowNormal

2018 Atlantic Hurricane Season

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Hurricane Leslie Discussion Number  61
NWS National Hurricane Center Miami FL       AL132018
1100 AM AST Thu Oct 11 2018

Leslie's structure has remained steady since last night. The
hurricane has a ragged banding eye surrounded by a somewhat patchy
central dense overcast. Recent Dvorak classifications from TAFB
and SAB are unchanged, and still support an initial intensity of
70 kt.

For days now, it has been clear that Leslie will accelerate
east-northeastward on the south side of a mid-latitude trough
moving across the North Atlantic. That acceleration is well underway
now, and the initial motion estimate is 060/14 kt. It has been
unclear, however, when (or if) Leslie could separate from this
trough and begin to drift southward over the eastern Atlantic. The
model spread has remarkably increased since yesterday, and nearly
1/3 of the members of the most recent GFS and ECMWF ensemble runs no
longer forecast Leslie to separate from the trough at all, instead
showing the cyclone approaching western Europe as an extratropical
low. Even the deterministic model spread has increased, and the
two NOAA regional hurricane models, the HWRF and HMON, are nearly
2300 miles apart at day 5. Through 48 h, the official track forecast
is very similar to the previous advisory, but it has been adjusted
eastward beyond that time, to bring it closer to the most recent
deterministic multi-model consensus. Confidence in the track
forecast is not high at 72 h and beyond, and it's possible that
large changes could still be required to future advisories.

Leslie should remain in a generally favorable environment for
strengthening during the next 24-36 h, and slight intensification
is still expected, though the official intensity forecast is now on
the high side of the guidance through this period. By 48 h and
onward, Leslie will be moving into a far more stable environment
and over cooler waters, so steady weakening is anticipated.  If
Leslie follows a track similar to the NHC forecast, it will likely
become a weak post-tropical low within 96 h. However, if Leslie
undergoes extratropical transition, its worth noting that the
maximum winds associated with the cyclone would likely be higher
than indicated here.

FORECAST POSITIONS AND MAX WINDS

INIT  11/1500Z 29.1N  38.3W   70 KT  80 MPH
 12H  12/0000Z 30.3N  35.5W   75 KT  85 MPH
 24H  12/1200Z 31.7N  30.3W   75 KT  85 MPH
 36H  13/0000Z 32.8N  24.6W   70 KT  80 MPH
 48H  13/1200Z 33.2N  20.0W   60 KT  70 MPH
 72H  14/1200Z 31.3N  17.3W   40 KT  45 MPH
 96H  15/1200Z 29.1N  19.0W   30 KT  35 MPH...POST-TROPICAL
120H  16/1200Z 27.5N  24.0W   30 KT  35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Zelinsky
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Leslie's track guidance has shifted north significantly due to deeper longwave trough interaction. Baroclinic influences by that interaction may also bring hurricane force gusts to Portugal coast as a post-tropical low. 10/12 12z GFS is now suggesting this as well. NHC 11 AM AST:
 

Quote
The intensity forecast shows Leslie only slowly weakening as a tropical cyclone during the next 24 hours due to a combination of cool SSTs and increasing shear from the trough. However, simulated satellite imagery and model fields suggest that Leslie will transition to a powerful post-tropical cyclone by 36 hours, likely still at hurricane intensity as shown by the global models.

e8731d229d0c266fc081002fd9719f8e.jpg

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Thanks to Leslie and Michael, Accumulate Cyclone Energy (ACE) is now 119 for the Atlantic Basin, pushing the 2018 season above climateological mean of 111 considered for an above-normal season. 153 ACE is the mark for a hyperactive season like the one we experienced in 2017.

 

So far 2018 has resulted in 14 storms, 7 hurricanes and 2 major hurricanes.

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This is the second year on a row we have had storms hold onto tropical characteristics extremely close to Europe. Ophelia last year and now Leslie.

 

Just an observation, but I wonder if we are getting to the point where a fully tropical land falling system in Western Europe is possible? 

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Leslie is coming in fast and aquiring extratropical characteristics now. Looks like it will complete transition to a post-tropical storm just before landfall. That low-level jet streak on the southern side and sting jet may still force surface winds that pack quite a wallop however.3902ad661a35a7026455f75f85d96c41.jpg

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000
WTNT43 KNHC 131433
TCDAT3

Hurricane Leslie Discussion Number  69
NWS National Hurricane Center Miami FL       AL132018
1100 AM AST Sat Oct 13 2018

Despite Leslie moving over 20C ocean and being embedded within
strong shear, satellite data indicate that Leslie has maintained
its deep warm core and is running ahead of a cold front. Although
convection has weakened considerably, Dvorak estimates indicate
that the winds are still 65 kt.  All indications are that Leslie
will acquire extratropical characteristics in the next several
hours, and by the time it reaches the Iberian peninsula later today,
the system will be a powerful post-tropical cyclone. After landfall,
rapid weakening is anticipated, and Leslie is forecast to degenerate
into a broad low pressure area over Spain in a day or so.

Leslie is racing toward the northeast or 055 degrees at about 29 kt
while embedded within the fast mid-latitude westerlies.  A continued
northeastward motion with gradual decrease in forward speed is
anticipated in the next 12 to 24 hours. This is consistent with
most of the track guidance, which unanimously brings the core of the
post-tropical cyclone over the Iberian peninsula tonight.

The meteorological services of Portugal and Spain are handling
hazards information for their respective countries via local weather
products.


Key Messages:

1. Leslie is expected to bring near hurricane-force winds to
portions of Portugal late today as a powerful post-tropical
cyclone.  Gale-force winds are also likely to affect portions of
western Spain tonight and Sunday.

2. Leslie is expected to produce rainfall amounts of 25 to 75 mm (1
to 3 inches) with isolated amounts as high as 125 mm (5 inches)
across portions of Portugal and Spain, which could cause flash
flooding.

3. For more information on Leslie, interests in Portugal should
refer to products from the Portuguese Institute for Sea and
Atmosphere at www.ipma.pt.  Interests in Spain should refer to
products from the State Meteorological Agency at www.aemet.es.


FORECAST POSITIONS AND MAX WINDS

INIT  13/1500Z 38.0N  12.6W   65 KT  75 MPH
 12H  14/0000Z 40.0N   8.0W   50 KT  60 MPH...POST-TROP/INLAND
 24H  14/1200Z 41.5N   4.0W   30 KT  35 MPH...POST-TROP/INLAND
 36H  15/0000Z...DISSIPATED

$$
Forecaster Avila

 

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000
WTNT43 KNHC 132036
TCDAT3

Post-Tropical Cyclone Leslie Discussion Number  70
NWS National Hurricane Center Miami FL       AL132018
500 PM AST Sat Oct 13 2018

After a total of 70 advisories, long-lived Leslie has become
post-tropical just west of the coast of Portugal, finally succumbing
to the combination of cool waters, strong vertical wind shear, and
interaction with an approaching cold front. The air mass ahead of
the cyclone has moistened up in the low levels with Faro, Portugal,
reporting a dewpoint of 70F/21C, but the dewpoints across central
and northern Portugal ahead of Leslie are only in the low-60F range,
which is not indicative of a tropical air mass. Thus, the cyclone is
now a powerful post-tropical low pressure system that even has a
partial eye noted in the most recent 2000Z Portuguese composite
radar imagery. After landfall, rapid weakening is anticipated, and
Leslie is forecast to degenerate into a broad low pressure area over
or just north of Spain by late Sunday.

Leslie is moving quickly toward the northeast or 050/30 kt.
Post-tropical Cyclone Leslie should continue in a fast northeastward
direction for the next 12-18 hours, making landfall near or just
south of Porto, Portugal by 14/0000Z. This forecast motion is
consistent with the previous advisory and the latest track model
guidance.

The meteorological services of Portugal and Spain are handling
hazards information for their respective countries via local weather
products. This is the last National Hurricane Center (NHC) advisory
on this system.


Key Messages:

1. Leslie is expected to bring near hurricane-force winds to
portions of Portugal later tonight as a powerful post-tropical
cyclone.  Gale-force winds are also likely to affect portions of
northwestern and northern Spain tonight and Sunday.

2. Leslie is expected to produce rainfall amounts of 25 to 75 mm (1
to 3 inches) with isolated amounts as high as 125 mm (5 inches)
across portions of Portugal and Spain, which could cause flash
flooding.

3. For more information on Leslie, interests in Portugal should
refer to products from the Portuguese Institute for Sea and
Atmosphere at www.ipma.pt.  Interests in Spain should refer to
products from the State Meteorological Agency at www.aemet.es.


FORECAST POSITIONS AND MAX WINDS

INIT  13/2100Z 40.5N   9.5W   60 KT  70 MPH...POST-TROPICAL
 12H  14/0600Z 43.0N   4.9W   35 KT  40 MPH...POST-TROPICAL INLAND
 24H  14/1800Z...DISSIPATED

$$
Forecaster Stewart

 

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On October 12, 2018 at 6:31 PM, Windspeed said:

ECMWF is now on board for a Portugal landfall as well. That stink jet though. Could be bad timing for landfall and PT transition.

Gust to 109 mph in Figueira da Foz  with the sting jet. Quite a bit of damage including blown out windows.

http://www.ipma.pt/pt/media/noticias/news.detail.jsp?f=/pt/media/noticias/textos/leslie-3.html

The IPMA station of Figueira da Foz / Vila Verde registered at 21:40 UTC (13:40 local time) on October 13, 2018, a gust of 49 m / s (about 176 km / h). This value is attributed to a phenomenon called sting jet . Sting jet is a strong downward current that sometimes develops on the western edge of extratropical depressions and can reach the surface. In these cases, the bursts may exceed 150 km / h in a reduced area, typically located southwest of the core of the depression. The formation of this meteorological phenomenon was first studied by the group of Professor Keith Browning of the University of Reading in the late 1980s.

The gusts observed near the surface result from evaporative processes occurring at medium levels of the storm's hazy mass. These processes result in cooling and consequent downward transport of air to lower levels with progressive acceleration. The designation of sting jet stems from the fact that the signature of this phenomenon in satellite and radar images (image below) resembles that of the tail of a sting .

In continental Portugal, a similar phenomenon was observed on December 23, 2009. However, at that time, the phenomenon was not associated to a depression resulting from the transition from tropical cyclone to extratropical depression, as presently it was verified. In fact, in 2009, the phenomenon resulted from a depression whose life cycle took place entirely in the middle latitudes. Then, the depression underwent a process of explosive cyclogenesis (rapid and intense decrease of atmospheric pressure in its center) to which a sting jet happened .

The value of the 176 km / h gust, now observed, is the highest recorded in stations of the national meteorological network (previous high of 169 km / h on October 17, 2015) and is compatible with the short-term forecasts issued by IPMA, based on the European Center model and the AROME mesoscale model, operated by IPMA.

 

 

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does anyone have any thoughts about this?

Quote
Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Tue Oct 23 2018

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

1. A broad area of low pressure is expected to form in a couple of
days several hundred miles east-northeast of the northern Leeward
Islands.  Some tropical or subtropical development of this system is
possible by the weekend while it meanders over the central Atlantic
Ocean.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...low...20 percent.

Forecaster Pasch

 

two_atl_5d0.png

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One more before the season ends looks like in the Atlantic

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Wed Oct 24 2018

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

1. A large area of disorganized showers and thunderstorms over the
central tropical Atlantic Ocean is associated with a broad area
of low pressure located a little over 900 miles east of the
northern Leeward Islands.  This system is expected to move slowly
northward over the next few days into an area where environmental
conditions are forecast to be more conducive for development.  A
tropical or subtropical depression could form over the weekend while
the system turns westward well to the northeast of the Lesser
Antilles.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 5 days...medium...60 percent.

Forecaster Roberts

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Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Thu Oct 25 2018

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

1. A low pressure system centered about 900 miles east-northeast of the
northern Leeward Islands is gradually becoming better defined and
the associated shower and thunderstorm activity is showing signs of
organization. This low is expected to move generally northward over
the next couple of days into an area where environmental conditions
are forecast to be conducive for further development, and a tropical
or subtropical storm is likely to form by early this weekend. After
that time, the system is forecast to turn westward well to the north
or northeast of the Lesser Antilles through early next week.
* Formation chance through 48 hours...high...70 percent.
* Formation chance through 5 days...high...80 percent.

Forecaster Zelinsky

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Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 AM EDT Fri Oct 26 2018

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

1. Showers and thunderstorms are gradually becoming better organized in
association with a low pressure system located about 1000
miles east-northeast of the northern Leeward Islands.  However,
recent satellite data indicate that the circulation is elongated and
the center is not yet well defined.  This system will likely become
a tropical or subtropical cyclone later today while it moves
generally northward over the central Atlantic.  After that
time, the low is forecast to turn westward well to the north or
northeast of the Lesser Antilles through early next week.
* Formation chance through 48 hours...high...90 percent.
* Formation chance through 5 days...high...90 percent.

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big difference between ECMWF and GFS for the track of Invest 95 - this is today's 6z GFS and 6z EC forecast for friday nov 2

GFS in blue, EC in black

fri nov 2.png

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Oscar has formed in the central Atlantic

FORECAST POSITIONS AND MAX WINDS

INIT  27/0300Z 26.7N  45.7W   40 KT  45 MPH
 12H  27/1200Z 27.2N  47.2W   45 KT  50 MPH
 24H  28/0000Z 26.6N  50.3W   50 KT  60 MPH
 36H  28/1200Z 25.6N  53.2W   50 KT  60 MPH
 48H  29/0000Z 25.3N  55.3W   55 KT  65 MPH...TROPICAL CYCLONE
 72H  30/0000Z 26.5N  57.5W   60 KT  70 MPH
 96H  31/0000Z 30.0N  55.5W   60 KT  70 MPH
120H  01/0000Z 34.0N  50.0W   55 KT  65 MPH

$$
Forecaster Beven
...SUBTROPICAL STORM OSCAR FORMS OVER THE CENTRAL ATLANTIC...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...26.7N 45.7W
ABOUT 1255 MI...2020 KM ENE OF THE NORTHERN LEEWARD ISLANDS
ABOUT 1210 MI...1945 KM ESE OF BERMUDA
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...NNW OR 330 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES

two_atl_0d0.png?270234

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Oscar's vortex is actually not too horrible at the moment despite its sheared and tilted appearance of a persistent MCS. It has been interesting watching its circulation rotate around the northern half of the mid-to-upper cutoff trough on visible and IR imagery today. You can actually see the transformation to a more tropical low. As such, the NHC forecasts Oscar to become a purely tropical storm over night. Oscar is also forecast to become a hurricane in a few days after turning poleward, if upper level winds cooperate.7e46d8049cb1a292b62620764dae1e85.gif

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Oscar's transformation to a deep tropical system has been gorgeous. A nice eye band is establishing and a core with CDO. May have a hurricane before too much longer.c236b9ffe42b0ea8b8fc9ee48a9da109.gif

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Adding more ACE to my already busted prediction for a low ACE season. Some models even get Oscar to CAT3 status.

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Adding more ACE to my already busted prediction for a low ACE season. Some models even get Oscar to CAT3 status.

HWRF has been intensifying Oscar down into the 950s with consistency. Based on SSTs and a cold upper troposphere analysis, convective instability should be great for a few days. A major seems most likely at this point.

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I saw this on twitter, as a reminder as just how powerful the storms have been that have affected the US and the US TerritoriesC9fg5iv.jpg&key=0869ab059189635c0867fc1add046129fe9109563d4c8ed27680513b5751d461

Michael's band of > -80°C cloudtops at landfall was the most impressive I can remember at landfall for an Atlantic hurricane.

 

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Oscar may be small, but not too shabby a hurricane. Wondering if the current westerly upper level flow is going to relax enough to allow Oscar to reach major status. I was confident of that last night. Now I am not so certain.804cc7dbf052ba2e113162f256d28ba3.gif

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