Non Tropical Low Pressure in NE Atlantic

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ChrisH-UK
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Non Tropical Low Pressure in NE Atlantic

#1 Postby ChrisH-UK » Mon Jun 05, 2023 7:27 am

Looks like NHC is taking intrest in the area near the Azores which the models for the last week or so have been showing a potential sub tropical storm.

 https://twitter.com/NHC_Atlantic/status/1665690896334192641


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Re: Non Tropical Low Pressure in NE Atlantic

#2 Postby cycloneye » Mon Jun 05, 2023 7:31 am

Split the post from the global models thread to make one for this area that NHC highlights.
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Re: Non Tropical Low Pressure in NE Atlantic

#3 Postby ChrisH-UK » Mon Jun 05, 2023 8:25 am

Here is a satellite loop of the area in question. The models have bene showing something in this area since last Wednesday, the latest runs seem to be less defined as they was and looking at the satellite loop I think the notice won't be around for long.

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Re: Non Tropical Low Pressure in NE Atlantic

#4 Postby TallyTracker » Mon Jun 05, 2023 10:06 am

Has there ever been a tropical storm develop that far to the northeast in June? I would think the waters are still too cool to support any development this time of year.
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Re: Non Tropical Low Pressure in NE Atlantic

#5 Postby USTropics » Mon Jun 05, 2023 10:58 am

TallyTracker wrote:Has there ever been a tropical storm develop that far to the northeast in June? I would think the waters are still too cool to support any development this time of year.


You are correct, the threshold for a purely tropical cyclone to form is around 80F. Looking at actual SST skins below, we can see the current location supports temperatures around 74-75F currently. While this makes the formation of a system less likely, it's not impossible for this region (and hence the reason the NHC is calling this a 'complex non-tropical low pressure area').
Image

So how would this be possible then? We have to look beyond the SST profile and look at the surrounding factors, such as atmospheric conditions and the presence of baroclinic processes (i.e., the interaction between temperature gradients and atmospheric dynamics). In this instance, if the atmospheric conditions are favorable, the presence of warm waters below the threshold (74-75F) and the cooler surrounding atmosphere can provide the necessary baroclinic forcing for the system to develop characteristics of a subtropical system. Below is a more explicit breakdown of the interaction between atmospheric conditions and baroclinic processes.

  • Temperature Gradient: If there is a sharp contrast between the relatively warm water and the cooler surrounding atmosphere, it can create an unstable environment that supports storm development. The greater the temperature difference and its vertical gradient, the more favorable it is for the development of a subtropical system.
  • Upper-Level Divergence: Upper-level divergence refers to the horizontal outflow of air at higher atmospheric levels. If there is an area of enhanced divergence above the region with the 75°F water temperatures, it can help to remove air and maintain a low-pressure system near the surface. This divergence encourages the ascent of air, aiding in the formation and organization of a subtropical system.
  • Jet Stream Location: The presence of a strong and well-positioned jet stream can provide favorable conditions for the development of a subtropical system. Jet streams are fast-flowing currents of air in the upper atmosphere, and they help to enhance atmospheric dynamics. If the jet stream is oriented in a way that allows it to interact with the temperature gradient and the low-level circulation, it can provide additional energy and vorticity to the system, contributing to its development.
  • Upper-Level Shear: Shear refers to the change in wind speed and direction with height. In the case of baroclinic forcings, a moderate amount of vertical wind shear can be beneficial for subtropical system development. Shear helps to separate the upper-level and lower-level circulations, allowing the storm to maintain its identity and organization. It also aids in the ventilation of the system, preventing the development of a fully tropical structure.
  • Moisture Flux: Moisture flux, or the transport of moisture within the atmosphere, is another important factor. If there is sufficient moisture available in the lower levels of the atmosphere, it can contribute to the development of deep convection and cloud formation. Moisture convergence, where air masses converge and uplift, can further enhance the potential for storm development by providing a source of instability and latent heat release.

As for your other question (the formation of systems this far north in June), Chris from 2012 (which obtained hurricane strength at 41.1N in June) and Hurricane One from 1893 are examples of formation at more northerly latitudes, albeit not nearly as far NE as this system is currently positioned. A system forming in this location in June would be unprecedented.
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Re: Non Tropical Low Pressure in NE Atlantic

#6 Postby ChrisH-UK » Mon Jun 05, 2023 1:01 pm

Just had a look at the ASCAT winds and look like they was a pass over the system today with 30 knot winds but the circulation is stretched out.

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Re: Non Tropical Low Pressure in NE Atlantic

#7 Postby Sciencerocks » Mon Jun 05, 2023 9:09 pm

I'd be kind of floored if a tropical cyclone formed northeast of the azores this time of the year but it does appear to be developing some convection. So who knows.
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Re: Non Tropical Low Pressure in NE Atlantic

#8 Postby Hurricanehink » Mon Jun 05, 2023 10:03 pm

TallyTracker wrote:Has there ever been a tropical storm develop that far to the northeast in June? I would think the waters are still too cool to support any development this time of year.


I seem to recall an invest in that part of the world in June a decade or so back.
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Re: Non Tropical Low Pressure in NE Atlantic

#9 Postby Category5Kaiju » Mon Jun 05, 2023 10:38 pm

On one hand it wouldn't be surprising to see this get overwhelmed by climatology/shear and simply not develop. On the other hand you have a scalding Canary Current. :lol:
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Re: Non Tropical Low Pressure in NE Atlantic

#10 Postby ChrisH-UK » Tue Jun 06, 2023 4:48 am

Ascat pass from this morning now have 40 knot winds but still the circulation is stretch out.

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Re: Non Tropical Low Pressure in NE Atlantic

#11 Postby cycloneye » Tue Jun 06, 2023 7:21 am

Tropical Weather Outlook...Amended
NWS National Hurricane Center Miami FL
800 AM EDT Tue Jun 6 2023

Amended to add Portugal meteorological service information

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

1. Northeastern Atlantic Ocean:
A complex, non-tropical area of low pressure located between the
Azores and Canary Islands is producing disorganized showers and
thunderstorms with winds to gale force over the northeastern
Atlantic Ocean. This system could acquire some subtropical
characteristics during the next day or so while it meanders to the
east and southeast of the Azores. By late Wednesday, the system is
forecast to move northeastward over cooler waters, and further
development is not expected. Regardless of development, heavy
rains and gusty winds will continue across portions of the Canary
Islands, Madeira Island, and the Azores over the next day or so.
For additional information on this system, see products issued by
the State Meteorological Agency of Spain, the Portuguese Institute
of the Sea and Atmosphere, and High Seas Forecasts issued by Meteo
France.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 7 days...low...10 percent.

High Seas Forecasts issued by Meteo France under WMO header FQNT50
LFPW and available on the web at
www.meteofrance.com/previsions-meteo-ma ... randlarge/
metarea2. Products issued by State Meteorological Agency of Spain
are available on the web at
https://www.aemet.es/en/eltiempo/prediccion/avisos, and products
issued by the Portuguese Institute of the Sea and Atmosphere are
available at https://ipma.pt/en.

Forecaster Berg/Kelly
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Re: Non Tropical Low Pressure in NE Atlantic

#12 Postby Sciencerocks » Tue Jun 06, 2023 2:03 pm

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