ATL: MARIA - Post-Tropical - Discussion

[USTropics]

From SSD

06/0600 UTC 10.2N 32.5W T1.5/1.5 95L
05/2345 UTC 10.3N 31.2W T1.5/1.5 95L

IF 95L is truly only close to 32.5W as of 6Z, then I could say with certainty that the 0Z and 6Z GFS runs are initializing 95L quite a bit too far west...about 4 degrees. That 4 deg. may be quite crucial as both the GFS and Euro runs of the last few cycles are insisting on a pretty strong and persistent ridging pattern setting up along the U.S. east coast around 9/15, which, if accurate, would be a major pattern change. This means that a slower, more easterly position of 95L vs. the last two gfs runs may mean it would actually miss that trough that takes it well east of the US and get trapped underneath the building ridge around midmonth. IF that were to occur, 95L would likely make a move toward FL or some other portion of the SE US soon afterward. So, this is why what appear to be too far west gfs initializations may mean that the latest 95L recurves on the gfs may verify to be incorrect.

Excellent post. I mentioned this earlier in the models thread as well (comparing the GFS/Euro 00z runs).

I've been comparing the GFS/Euro 00z model runs and through 96 hours the overall upper air pattern is quite similar. It appears the major difference is the initialization point. The GFS initializes the LLC on the northwestern side of the convection, whereas the Euro initializes the LLC on the southeastern side of the convection. Given the current satellite presentation, NHC/NRL coordinates, and the 850mb vorticity chart, the Euro initialization point appears more accurate.

[meriland23]

Wouldn't it just curve even sooner and further east if it were 4 deg ahead of actual positioning? Don't mind me, I am just really REALLY unexperienced here lol.

[Gustywind]

000
AXNT20 KNHC 060539
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT TUE SEP 05 2011

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST
FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED
ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...SPECIAL FEATURES...

A BROAD AREA OF LOW PRESSURE ASSOCIATED WITH 1009 MB LOW IS
CENTERED SW OF THE CAPE VERDE ISLANDS NEAR 10N31W MOVING W 10-15
KT. THIS FEATURE IS EMBEDDED WITHIN AN BROAD AREA OF DEEP LAYER
MOISTURE AS DEPICTED ON THE TOTAL PRECIPITABLE WATER IMAGERY.
SCATTERED MODERATE/ STRONG CONVECTION IS NW OF THE CENTER FROM
10N-14N BETWEEN 32W-38W. ORGANIZATION OF THIS SYSTEM HAS CHANGED
LITTLE DURING THE PAST SEVERAL HOURS. ENVIRONMENTAL CONDITIONS
APPEAR FAVORABLE FOR A TROPICAL DEPRESSION TO FORM DURING THE
NEXT DAY OR TWO. THIS SYSTEM HAS A HIGH CHANCE OF BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

[USTropics]

Wouldn't it just curve even sooner and further east if it were 4 deg ahead of actual positioning? Don't mind me, I am just really REALLY unexperienced here lol.

The reasoning for 95L turning towards the north and eventually recurving has to do with the persistent trough over the northeastern U.S. seen in model runs. In both the GFS and Euro model runs the pattern begins to change around day 8, and the trough begins to lift out. If 95L were to initialize further east/move slower then the GFS is currently forecasting, the trough could potentially lift out before pulling 95L to the north, allowing ridging to build back in and steering 95L more westward.

[meriland23]

000
AXNT20 KNHC 060539
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT TUE SEP 05 2011

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST
FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED
ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...SPECIAL FEATURES...

A BROAD AREA OF LOW PRESSURE ASSOCIATED WITH 1009 MB LOW IS
CENTERED SW OF THE CAPE VERDE ISLANDS NEAR 10N31W MOVING W 10-15
KT. THIS FEATURE IS EMBEDDED WITHIN AN BROAD AREA OF DEEP LAYER
MOISTURE AS DEPICTED ON THE TOTAL PRECIPITABLE WATER IMAGERY.
SCATTERED MODERATE/ STRONG CONVECTION IS NW OF THE CENTER FROM
10N-14N BETWEEN 32W-38W. ORGANIZATION OF THIS SYSTEM HAS CHANGED
LITTLE DURING THE PAST SEVERAL HOURS. ENVIRONMENTAL CONDITIONS
APPEAR FAVORABLE FOR A TROPICAL DEPRESSION TO FORM DURING THE
NEXT DAY OR TWO. THIS SYSTEM HAS A HIGH CHANCE OF BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

Tuesday the 5th eh?

[cycloneye]

70%

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT TUE SEP 6 2011

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

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON HURRICANE
KATIA...LOCATED ABOUT 400 MILES SOUTH OF BERMUDA.

EARLY VISIBLE SATELLITE IMAGES INDICATE THAT THE SHOWER ACTIVITY
ASSOCIATED WITH A LOW PRESSURE AREA CENTERED ABOUT 680 MILES WEST-
SOUTHWEST OF THE SOUTHERNMOST CAPE VERDE ISLANDS IS GRADUALLY
BECOMING BETTER ORGANIZED...AND A TROPICAL DEPRESSION COULD FORM
LATER TODAY OR WEDNESDAY. THIS SYSTEM IS EXPECTED TO MOVE TOWARD
THE WEST OR WEST-NORTHWEST AT ABOUT 15 MPH AND HAS A HIGH
CHANCE...70 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.

CLOUDINESS AND SHOWERS ASSOCIATED WITH A NEARLY STATIONARY AREA OF
LOW PRESSURE HAVE INCREASED IN THE SOUTHERN GULF OF MEXICO. THIS
SYSTEM HAS A LOW CHANCE...20 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.


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

$$
FORECASTER AVILA

[Gustywind]

Discussion from Rob Lightbown on September 6, 2011, 7:10 am

Invest 95L In The Eastern Atlantic:
We are also keeping an eye on a tropical disturbance, designated Invest 95L, in the eastern Atlantic about 600 miles to the southwest of the Cape Verde Islands. Environmental conditions are favorable enough for slow development during the rest of this week and this may become a tropical depression or a tropical storm in the next couple of days or so.

As for a track, a general west to west-northwest track is likely over the next 2 to 3 days. After that, the potential track of this system may bring it near the northern Leeward Islands this weekend and everyone in the Leeward Islands and Virgin Islands should closely monitor this system as indications are that it may affect you as a strong tropical storm or a Category 1 hurricane.

After potentially affecting the Leeward Islands and the Virgin Islands this weekend, this potential tropical cyclone could be pulled north and then northeastward away from the US East Coast next week due to a deep trough of low pressure over the eastern United States.

Another potential track idea that will need to be watched is that this disturbance stays south and tracks into the Caribbean this weekend. This is a scenario that is being presented by the European model.

I will be monitoring Invest 95L closely over the next several days and will keep you all updated.

[cycloneye]

This mornings discussion of 95L by Rob of Crown Weather:

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.

Invest 95L In The Eastern Atlantic:
We are also keeping an eye on a tropical disturbance, designated Invest 95L, in the eastern Atlantic about 600 miles to the southwest of the Cape Verde Islands. Environmental conditions are favorable enough for slow development during the rest of this week and this may become a tropical depression or a tropical storm in the next couple of days or so.

As for a track, a general west to west-northwest track is likely over the next 2 to 3 days. After that, the potential track of this system may bring it near the northern Leeward Islands this weekend and everyone in the Leeward Islands and Virgin Islands should closely monitor this system as indications are that it may affect you as a strong tropical storm or a Category 1 hurricane.

After potentially affecting the Leeward Islands and the Virgin Islands this weekend, this potential tropical cyclone could be pulled north and then northeastward away from the US East Coast next week due to a deep trough of low pressure over the eastern United States.

Another potential track idea that will need to be watched is that this disturbance stays south and tracks into the Caribbean this weekend. This is a scenario that is being presented by the European model.

I will be monitoring Invest 95L closely over the next several days and will keep you all updated.

[rainstorm]

as far as the ridge building on the models it may happen but it seems the models in the long range have been building ridges only for them not to actually show up. we will see if this time the ridge appears and actually locks in.

[Gustywind]

000
AXNT20 KNHC 061148
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT TUE SEP 05 2011

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST
FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED
ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1045 UTC.

...SPECIAL FEATURES...

A BROAD AREA OF LOW PRESSURE ASSOCIATED WITH 1009 MB LOW IS
CENTERED SW OF THE CAPE VERDE ISLANDS NEAR 10N32W MOVING W 10-15
KT. THIS FEATURE IS EMBEDDED WITHIN AN BROAD AREA OF DEEP LAYER
MOISTURE AS DEPICTED ON THE TOTAL PRECIPITABLE WATER IMAGERY.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS MOSTLY NW OF
THE CENTER FROM 10N-15N BETWEEN 31W-41W. SHOWER ACTIVITY
ASSOCIATED WITH THIS FEATURE GRADUALLY IS BECOMING BETTER
ORGANIZED. ENVIRONMENTAL CONDITIONS APPEAR FAVORABLE FOR A
TROPICAL DEPRESSION TO FORM DURING THE NEXT DAY OR TWO. THIS
SYSTEM HAS A HIGH CHANCE OF BECOMING A TROPICAL CYCLONE DURING
THE NEXT 48 HOURS.

[weatherwindow]

From SSD

06/0600 UTC 10.2N 32.5W T1.5/1.5 95L
05/2345 UTC 10.3N 31.2W T1.5/1.5 95L

IF 95L is truly only close to 32.5W as of 6Z, then I could say with certainty that the 0Z and 6Z GFS runs are initializing 95L quite a bit too far west...about 4 degrees. That 4 deg. may be quite crucial as both the GFS and Euro runs of the last few cycles are insisting on a pretty strong and persistent ridging pattern setting up along the U.S. east coast around 9/15, which, if accurate, would be a major pattern change. This means that a slower, more easterly position of 95L vs. the last two gfs runs may mean it would actually miss that trough that takes it well east of the US and get trapped underneath the building ridge around midmonth. IF that were to occur, 95L would likely make a move toward FL or some other portion of the SE US soon afterward. So, this is why what appear to be too far west gfs initializations may mean that the latest 95L recurves on the gfs may verify to be incorrect.

Excellent post. I mentioned this earlier in the models thread as well (comparing the GFS/Euro 00z runs).
____good catch on both your parts....IMHO, the actual timing of this system approaching 50-55deg W will be the crux of the eventual tracking solution...however, their may be yet another player in the mix(besides katia) that being the developing low in the BOC and its track and timing. it may have a major influence on how rapidly the ridge builds behind a departing katia...rich___

I've been comparing the GFS/Euro 00z model runs and through 96 hours the overall upper air pattern is quite similar. It appears the major difference is the initialization point. The GFS initializes the LLC on the northwestern side of the convection, whereas the Euro initializes the LLC on the southeastern side of the convection. Given the current satellite presentation, NHC/NRL coordinates, and the 850mb vorticity chart, the Euro initialization point appears more accurate.

[caribepr]

This mornings discussion of 95L by Rob of Crown Weather:

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.

Invest 95L In The Eastern Atlantic:
We are also keeping an eye on a tropical disturbance, designated Invest 95L, in the eastern Atlantic about 600 miles to the southwest of the Cape Verde Islands. Environmental conditions are favorable enough for slow development during the rest of this week and this may become a tropical depression or a tropical storm in the next couple of days or so.

As for a track, a general west to west-northwest track is likely over the next 2 to 3 days. After that, the potential track of this system may bring it near the northern Leeward Islands this weekend and everyone in the Leeward Islands and Virgin Islands should closely monitor this system as indications are that it may affect you as a strong tropical storm or a Category 1 hurricane.

After potentially affecting the Leeward Islands and the Virgin Islands this weekend, this potential tropical cyclone could be pulled north and then northeastward away from the US East Coast next week due to a deep trough of low pressure over the eastern United States.

Another potential track idea that will need to be watched is that this disturbance stays south and tracks into the Caribbean this weekend. This is a scenario that is being presented by the European model.

I will be monitoring Invest 95L closely over the next several days and will keep you all updated.

I'll be home on Friday, prepped for the worst, hoping for the best and especially that I can fly to Culebra from SJU!

[Blown Away]

Saved Image. 06Z BAMS & TVCN.

Follow the NHC hugging TVCN.

[cycloneye]

I'll be home on Friday, prepped for the worst, hoping for the best and especially that I can fly to Culebra from SJU!

Mj, I dont see any problems for your friday flight. Yes,let's be prepared for the worse but hoping for the best.

[Aric Dunn]

As I said yesterday. It should be a depression later today. if not then tomorrow morning for unless some unexpected weakening occurs.

[Aric Dunn]

I should also be a Caribbean runner till about Jamaica when it should begin to turn into a weakness left by the low in the BOC after it moves NE.

[rainstorm]

http://www.atmos.washington.edu/cgi-bin/latest.cgi?ir-e

just looking at that and with katia getting ready to take a hard right, that trough just east of katia is going to dig way south. 95L is going to have a tough road ahead.

[Adoquín]

whether it passes south, through or north of Puerto Rico depends on the strength of the ridge post Katia and the timing of that happening, forward speed and center location. Of course jokers such as center reformations as was the case of H. Irene. Since we are not sure where the center is you reslly have to draw a big cone of uncertainty at this point.

Also you don't need a major to wreck Puerto Rico or the Leewards. 100 mph with lots of water will suffice. Sooooooo, bears watching.

[CourierPR]

I should also be a Caribbean runner till about Jamaica when it should begin to turn into a weakness left by the low in the BOC after it moves NE.

Aric, where do you think it will go from there?

[Aric Dunn]

I should also be a Caribbean runner till about Jamaica when it should begin to turn into a weakness left by the low in the BOC after it moves NE.

Aric, where do you think it will go from there?

well a recurve would be likely since that trough is rather persistent just farther to the west now instead of just off the east coast its sitting over the ohio valley. so somewhere along the central to to eastern gulf. I dont see this going north of the islands. the ridging should build in quite strong behind katia. it could come quite close to PR and Hispaniola however. Thats my present thinking.