ATL: DORIAN - Post-Tropical - Discussion

[Hurricaneman]

The GFS doesnt seem to develop this despite having an anticyclone over it, could it have something to do with the SAL

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products

[meriland23]

The GFS doesnt seem to develop this despite having an anticyclone over it, could it have something to do with the SAL

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products

SAL?

[RL3AO]

The GFS doesnt seem to develop this despite having an anticyclone over it, could it have something to do with the SAL

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products

SAL?

Saharan Air Layer. Basically a cloud of dust from the Saharan Desert that blows off of Africa over the ocean.

[Hurricaneman]

The GFS doesnt seem to develop this despite having an anticyclone over it, could it have something to do with the SAL

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products

SAL?

Saharan Air Layer which makes the air dry and dusty so I'm assuming that the models are hinting at this

[meriland23]

ah yes, we had that prob last time with Chantal, though she never ingested it ..

[beoumont]

That we are! The GFS painted a bullseye on me on Saturday. That got my attention

I have a friend in Ft. Lauderdale that is always hoping a hurricane will hit his area. Whenever the official forecast (not the GFS, but probably still relevant) has a 5 day position of a current storm over S. Florida I send that prog to him with this message: "Save this forecast map, because things will not get any more promising with this storm for you again."

I guess there are exceptions to this rule; but very very rarely. IE: if the 5 day progs have a hurricane hitting you, you are likely quite safe from this threat.

[meriland23]

That we are! The GFS painted a bullseye on me on Saturday. That got my attention

I have a friend in Ft. Lauderdale that is always hoping a hurricane will hit his area. Whenever the official forecast (not the GFS, but probably still relevant) has a 5 day position of a current storm over S. Florida I send that prog to him with this message: "Save this forecast map, because things will not get any more promising with this storm for you again."

I guess there are exceptions to this rule; but very very rarely. IE: if the 5 day progs have a hurricane hitting you, you are likely quite safe from this threat.

LOL! I think quite the opposite, model runs tend to be quite accurate in terms of path 5-7 days in advance, then the path starts to skew 1-4 days .. and once it hits, you realize it was right a way long time ago.. at least that is what I have noticed more recently.

[beoumont]

LOL! I think quite the opposite, model runs tend to be quite accurate in terms of path 5-7 days in advance, then the path starts to skew 1-4 days .. and once it hits, you realize it was right a way long time ago.. at least that is what I have noticed more recently.

The forecasting error from the NHC has certainly improved over the years; but still the average 120 hr. forecast error is about 220 nautical miles (253 miles). Hence, to debate, the error for five days will just as often be greater than 253 (regular) miles than it is less than 253 miles.

Now looking at the progs. run to run, it is most common to see the trajectory of the current storm swing back and forth; so in hindsight, like a broken clock, it was "right on" at a few points in time.

I have noticed repeatedly, that once they fly the high level jets out in front of each soon to be making landfall storm, the short term forecasts are almost always dead on (24-36 hrs.). This is a testament to the ability to forecast hurricane motion IF the multi-level data is available to plug into the methodology.

Below are error trends for NHC official forecasts:

[Fego]

Up to 40 % but moving wnw.

ABNT20 KNHC 230503
TWOAT

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT TUE JUL 23 2013

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SHOWERS AND THUNDERSTORMS HAVE BECOME A LITTLE MORE CONCENTRATED
NEAR THE CENTER OF A SURFACE LOW PRESSURE SYSTEM LOCATED A COUPLE
HUNDRED MILES SOUTH-SOUTHEAST OF THE CAPE VERDE ISLANDS.
ADDITIONAL DEVELOPMENT OF THIS SYSTEM IS POSSIBLE LATER TODAY
BEFORE ENVIRONMENTAL CONDITIONS BECOME LESS CONDUCIVE FOR
DEVELOPMENT ON WEDNESDAY. THIS SYSTEM HAS A MEDIUM CHANCE...40
PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS
AS IT MOVES WEST-NORTHWESTWARD AT 15 TO 20 MPH. INTERESTS IN THE
CAPE VERDE ISLANDS SHOULD MONITOR THE PROGRESS OF THIS DISTURBANCE.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BERG

[TropicalAnalystwx13]

West-northwest?

HIGHLY disagree.

http://tropicaltidbits.com/satellite/images/eatl_ir.gif

[meriland23]

West-northwest?

HIGHLY disagree.

http://tropicaltidbits.com/satellite/images/eatl_ir.gif

That looks almost WSW :\

[Aric Dunn]

West-northwest?

HIGHLY disagree.

[img]http://tropicaltidbits.com/satellite/images/eatl_ir.gif[/ig]

That looks almost WSW :\

Like I said a little bit ago.. due to rotational effects ( fluid dynamics) some wsw motion is quite likely during the development stages.

[meriland23]

West-northwest?

HIGHLY disagree.

[img]http://tropicaltidbits.com/satellite/images/eatl_ir.gif[/ig]

That looks almost WSW :\

Like I said a little bit ago.. due to rotational effects ( fluid dynamics) some wsw motion is quite likely during the development stages.

Oh no I knew that, this was just in regards to NHC's new update saying it was now moving WNW

[fci]

Interesting to me that SST's are marginal at this time of the year.
Isn't that a bit unusual?

[GCANE]

Nice looking 850mb vorticity.

http://tropic.ssec.wisc.edu/real-time/e ... wm7vor.GIF

It appears anti-cyclone is just to the NW of the LLC.

It will be tracking into a large slot of low-shear.

http://tropic.ssec.wisc.edu/real-time/e ... wm7shr.GIF

This may keep the vorticity column intact even though convection may diminish.

IMHO, SAL doesn't look all that bad immediately around it.

http://tropic.ssec.wisc.edu/real-time/sal/splitE.jpg

Looks like sporadic convection firing pretty close to the LLC

http://rammb.cira.colostate.edu/product ... 230330.jpg

Latest AMSU Sat Wind Analysis has a classic TD look.

http://rammb.cira.colostate.edu/product ... 0_SWHR.GIF

Latest pass from TRMM at 02:53Z had it's precip radar showing a small hot tower at 11N 24W

http://www.nrlmry.navy.mil/tcdat/tc13/A ... W.58pc.jpg

[NDG]

Interesting to me that SST's are marginal at this time of the year.
Isn't that a bit unusual?

This time of the year that far east is not unusual for SSTs to only marginal for development, they don't really start warming up in that part of the Atlantic until the trade winds start dying down later in the summer.

[NDG]

It seems to me that 98L has been moving almost due west during the night hugging the 12th latitude.
Not sure if that would last much longer with a weakness in the Atlantic ridge NW of 98L over the next couple of days.
However, the GFS builds one heck of a Central Atlantic ridge of 600 dm at h50 by Thursday that it shows to retrograde westward towards Bermuda by early next week. So if there is anything left of the system by then it should be on more westerly track through early next week.

[NDG]

Nice almost naked LLC on vis sat this morning due to the easterly shear but once the apparent LLC starts picking up speed it should keep up with the easterly shear.

[cycloneye]

Here is the TWD Special Feature from 8 AM but came out early.

...SPECIAL FEATURES...
A TROPICAL WAVE ASSOCIATED WITH A 1010 MB SURFACE LOW HAS ITS
AXIS JUST E OF THE CAPE VERDE ISLANDS EXTENDING FROM 15N22W TO
07N23W AND MOVING W NEAR 5 KT. THIS SYSTEM IS EMBEDDED IN A HIGH
MOIST ENVIRONMENT AT THE LOWER AND MIDDLE LEVELS WHICH COMBINED
WITH UPPER LEVEL DIFFLUENCE IS SUPPORTING SCATTERED MODERATE
CONVECTION FROM 09N-13N BETWEEN 21W-27W. ENVIRONMENTAL
CONDITIONS ARE EXPECTED TO BECOME MORE FAVORABLE FOR TROPICAL
CYCLONE DEVELOPMENT. CURRENTLY...THERE IS A MEDIUM CHANCE FOR
THIS SYSTEM TO BECOME A TROPICAL CYCLONE DURING THE NEXT 48
HOURS.

[abajan]

West-northwest?

HIGHLY disagree.

Well, even though it may not be currently moving WNW, the TWO is referring to the average direction over the next 48 hours. At least, that's the way I understand it.