Jump to content
  • Member Statistics

    17,606
    Total Members
    7,904
    Most Online
    ArlyDude
    Newest Member
    ArlyDude
    Joined

September 2014


Rtd208

Recommended Posts

  • Replies 992
  • Created
  • Last Reply
Guest Imperator

Looks like it rounds the southern periphery of the subtropical high and moves back west next week. Bizarre. Has not worked out yet, but this one looks less frontal and has more potential to acquire TC characteristics.

 

Update: Euro is quite amped up and wet with this.

 

 

LOL what else is new with you, you think every off shore low has the potential to develop tropical characteristics.

Link to comment
Share on other sites

NYCVP gets an alert every time someone posts anything about the GGEM or Tropical in the NYC subforum, if all else fails he creates a straw man or just attacks JB as if we all swear by him. Why be a part of a weather forum only to attack other posters and never add anything of substance?

Link to comment
Share on other sites

Looks like it rounds the southern periphery of the subtropical high and moves back west next week. Bizarre. Has not worked out yet, but this one looks less frontal and has more potential to acquire TC characteristics.

 

Update: Euro is quite amped up and wet with this.

I'm not sure about subtropical, but there is a pretty significant disagreement between the 12z ECMWF and 12z GFS in terms of qpf for the Thursday-Friday period (9/25-26). Select examples:

 

Atlantic City: ECMWF: 1.61"; GFS: 0.04"

Dover: ECMWF: 2.38"; GFS: 0.01"

Islip: ECMWF: 0.01"; GFS: 0.39"

Philadelphia: ECMWF: 0.67"; GFS: None

Link to comment
Share on other sites

Guest Imperator

NYCVP gets an alert every time someone posts anything about the GGEM or Tropical in the NYC subforum, if all else fails he creates a straw man or just attacks JB as if we all swear by him. Why be a part of a weather forum only to attack other posters and never add anything of substance?

 

 

I don't spend every waking moment of the day caring about the weather like some of you, but I do have an interest in it. But on the occasion I do react to a post, it is because of a constant lack of substance or stupidity by some people on here.

Link to comment
Share on other sites

If you look at 500mb, you will see there is no other high/ridge between the equator and 40N, at least not anywhere close in upper heights. This would be the boundary between the Horse Latitudes and Ferrel/Polar Cell.

 

I'm not necessarily fully disagreeing w/you as I value your opinion and expertise strongly DonS. Lower 70's with easterly wind is fairly sub-tropical for this time of year.

 

 

The subtropical ridge starts migrating poleward in late spring reaching its zenith in early autumn before retreating equatorward during the late fall, winter, and early spring. The equatorward migration of the subtropical ridge during the cold season is due to increasing north-south temperature differences between the poles and tropics.[3] The latitudinal movement of the subtropical ridge is strongly correlated with the progression of the monsoon trough or Intertropical Convergence Zone.

Most tropical cyclones form on the side of the subtropical ridge closer to the equator, then move poleward past the ridge axis before recurving into the main belt of the Westerlies.[4] When the subtropical ridge shifts due to ENSO, so will the preferred tropical cyclone tracks. Areas west of Japan and Korea tend to experience much fewer September–November tropical cyclone impacts during El Niño and neutral years, while mainland Chinaexperiences much greater landfall frequency during La Niña years. During El Niño years, the break in the subtropical ridge tends to lie near 130°E, which would favor the Japanese archipelago, while in La Niña years the formation of tropical cyclones, along with the subtropical ridge position, shift west, which increases the threat to China.[5] In the Atlantic basin, the subtropical ridge position tends to lie about 5 degrees farther south during El Niño years, which leads to a more southerly recurvature for tropical cyclones during those years.

When the Atlantic Multidecadal Oscillation's mode is favorable to tropical cyclone development (1995–present), it amplifies the subtropical ridge across the central and eastern Atlantic.[6]

Link to comment
Share on other sites

If you look at 500mb, you will see there is no other high/ridge between the equator and 40N, at least not anywhere close in upper heights. This would be the boundary between the Horse Latitudes and Ferrel/Polar Cell.

 

I'm not necessarily fully disagreeing w/you as I value your opinion and expertise strongly DonS. Lower 70's with easterly wind is fairly sub-tropical for this time of year.

I'd be more comfortable if the cyclone phase evolution charts were indicating that the system could become warm core. So far, that hasn't been the case, but the charts associated with the 12z ECMWF are not yet available. I don't think there's a zero probability, but right now think the probability isn't very high. Of course, there's still time to see how things develop and I don't think one can completely rule out the prospects right now. I could be wrong, as well.

Link to comment
Share on other sites

I'd be more comfortable if the cyclone phase evolution charts were indicating that the system could become warm core. So far, that hasn't been the case, but the charts associated with the 12z ECMWF are not yet available. I don't think there's a zero probability, but right now think the probability isn't very high. Of course, there's still time to see how things develop and I don't think one can completely rule out the prospects right now. I could be wrong, as well.

I can see this system as a non-traditional noreaster with thermal enhancement and a pseudo warm front on the periphery. We have had a few of these systems since Late August and I cannot recall so many in rapid succession. I guess this is what happens with a +AMO/+NAO.

 

Even so, TC genesis seems like a low probability and I agree. SSTs are somewhat supportive SE of the region.

 

color_newdisp_sst_100W_35W_15N_65N_ophi0

Link to comment
Share on other sites

If you look at 500mb, you will see there is no other high/ridge between the equator and 40N, at least not anywhere close in upper heights. This would be the boundary between the Horse Latitudes and Ferrel/Polar Cell.

I'm not necessarily fully disagreeing w/you as I value your opinion and expertise strongly DonS. Lower 70's with easterly wind is fairly sub-tropical for this time of year.

Trade winds at our latitude?
Link to comment
Share on other sites

Trade winds at our latitude?

Not necessarily, the default wind direction south of 30-40N is southeasterly or northerly this time of the year with slight occasional cold front intrusions leading to westerly winds. It is displaced northward with this upcoming pattern. In some regards, this pattern relates nicely with KLGA seeing their most easterly flow summer on record. What this implies remains to be seen.

 

In tropics below 20-25N, they are always easterly. Trade winds are generated by convergence at the ITCZ whereas this is driven by the sub-tropical high.

 

Map_prevailing_winds_on_earth.png

 

 

 

The trade winds (sometimes called trades) are the prevailing pattern of easterly surface winds found in the tropics, within the lower portion of the Earth's atmosphere, in the lower section of the troposphere near the Earth's equator.[1] The trade winds blow predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere, strengthening during the winter and when the Arctic oscillation is in its warm phase. Historically, the trade winds have been used by captains of sailing ships to cross the world's oceans for centuries, and enabled European empire expansion into the Americas and trade routes to become established across the Atlantic and Pacific oceans.  
Link to comment
Share on other sites

Hadley cell expansion[edit]

There is some evidence that the expansion of the Hadley cells is related to climate change.[2] The majority of earth's driest and arid regions are located in the areas underneath the descending branches of the Hadley circulation around 30 degrees latitude.[3] Both idealised and more realistic climate model experiments show that the Hadley cell expands with increased global mean temperature (perhaps by 2 degrees latitude over the 21st century [4]); this can lead to large changes in precipitation in the latitudes at the edge of the cells.[3] Scientists fear that the ongoing presence of global warming might bring changes to the ecosystems in the deep tropics and that the deserts will become drier and expand.[4] As the areas around 30 degrees latitude become drier, those inhabiting that region will see less rainfall than traditionally expected, which could cause major problems with food supplies and livability.[5]

 

2 degrees seems conservative, move to CC if necessary. Impossible to discuss wind dynamics without mentioning hadley cells.

;) 

 

The major driving force of atmospheric circulation is solar heating, which on average is largest near the equator and smallest at the poles. The atmospheric circulation transports energy polewards, thus reducing the resulting equator-to-pole temperature gradient. The mechanisms by which this is accomplished differ in tropical and extratropical latitudes.

Between 30°N and 30°S latitude, this energy transport is accomplished by a relatively simple overturning circulation, with rising motion near the equator, poleward motion near the tropopause, sinking motion in the subtropics, and an equatorward return flow near the surface. In higher latitudes, the energy transport is instead accomplished by cyclones and anticyclones that cause relatively warm air to move polewards and cold air to move equator wards in the same horizontal plane. The tropical overturning cell is referred to as the Hadley cell. Why it extends only to 30 degrees latitude and what determines its strength are questions addressed by modern dynamical meteorology.

300px-HadleyCross-sec.jpg
 
The Hadley cell carries heat and moisture from the tropics to the northern and southern mid-latitudes.

Near the tropopause, as the air moves polewards in the Hadley cell it is turned eastward by the Coriolis effect, which turns winds to the right in the Northern hemisphere and to the left in the Southern Hemisphere, creating the subtropical jet streams that flow from west to east. Analogously, near the surface, the equatorward return flow is turned to the west by the Coriolis effect. These resulting surface winds, with both an equatorward and a westward component, are referred to as the trade winds.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

  • Recently Browsing   0 members

    • No registered users viewing this page.

×
×
  • Create New...