ATL: TROPICAL DEPRESSION DANNY (05L)

[KWT]

Probably strengthening by the upper trough I suppose, enhancement, you do see that happen at times with northerly latitude systems.

[srainhoutx]

HPC thoughts this afternoon...

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
234 PM EDT MON AUG 24 2009

VALID 12Z THU AUG 27 2009 - 12Z MON AUG 31 2009

MODELS AND THEIR ENSEMBLES HAVE MAINTAINED GOOD CONTINUITY WITH
PRIOR RUNS IN ALLOWING A SERIES OF POWERFUL UPPER LOWS TO TRAVERSE
THE NORTHEAST PACIFIC AND GULF OF ALASKA DURING THE MEDIUM RANGE
PERIOD...WHICH HELPS TO SUSTAIN A NEGATIVE ANOMALY IN THE
NORTHEAST PACIFIC. THIS ANOMALY FAVORS RIDGING ACROSS THE WEST
AND LEADS TO AMPLIFICATION OF A DOWNSTREAM UPPER TROUGH OVER
SOUTHEAST CANADA/NORTHEAST/GREAT LAKES. OVERALL...THE GUIDANCE IS
RELATIVELY CLOSE THROUGH THE PERIOD...THOUGH LATER ON THE 00Z
CANADIAN SOLUTION IS CLOSEST TO THE ENSEMBLE MEAN PROGRESSION OF
THE TROUGH IN THE NORTHEAST THIRD OF THE COUNTRY. USED A 00Z
CANADIAN/00Z ECMWF COMPROMISE IN MOST SPOTS...EXCEPT WHERE 00Z
MULTI-MODEL ENSEMBLE LOW CLUSTERING INDICATED OTHERWISE. THIS
SOLUTION FAVORS A WET PATTERN FROM THE CENTRAL AND SOUTHERN
PLAINS/NORTHEAST GULF COAST NORTH AND EASTWARD IN ADVANCE OF THE
MAIN UPPER TROUGH AND POSSIBLE TROPICAL CYCLONE EXPECTED TO MOVE
CLOSE TO THE EASTERN SEABOARD.

POSSIBLE TROPICAL SYSTEM MOVING UP THE EAST COAST...
THE PROGRESS OF AN AREA OF DISTURBED WEATHER NEAR 18N/57W
CONTINUES TO BE MONITORED AND THE BIGGEST FORECAST PROBLEM OF THE
DAY...WHICH IS FORECAST BY ALL OF THE GUIDANCE TO STRENGTHEN AS IT
MOVES EAST OF THE BAHAMAS BEFORE LIFTING NORTHWARD AND JUST
OFFSHORE THE EAST COAST/ATLANTIC CANADA FROM THIS WEEKEND ONWARD
AHEAD OF THE NORTHEAST TROUGHING. THE 00Z CANADIAN...AS
USUAL...WAS THE MOST BULLISH WITH ITS STRENGTH. THE GFS WAS THE
WEAKEST. THE ECMWF/CANADIAN MODELS HAVE GENERALLY TRENDED TOWARDS
A STRONGER/QUICKER SOLUTION OVER THEIR PAST COUPLE DAYS OF
RUNS...WITH THEIR SOLUTIONS CONVERGING WITH THE SYSTEMS POSSIBLE
TRACK OVER THAT TIME FRAME. THIS COMBINED WITH THE 00Z
MULTI-MODEL ENSEMBLE CLUSTERING DECREASES THE UNCERTAINTY
ASSOCIATED WITH THIS EVENT.

ALONG THE EAST COAST...THE FORECAST TRACK OF THE LOW IS CLOSE TO
THE SLOW 24/12Z ECMWF THROUGH FRIDAY NIGHT AFTER COORDINATION WITH
TPC AT 16Z...WHEN HPC SPLIT THE DIFFERENCE BETWEEN HPC CONTINUITY
AND NHCS SIGNIFICANTLY SLOWER PROPOSED TRACK TO COME UP WITH THE
CURRENT SOLUTION. THEREAFTER...THERE IS NOT A SHRED OF MODEL
GUIDANCE AS SLOW AS THE MEDIUM RANGE PROGS...WHICH NOW LIE ALONG
THE SLOW/EXTREME SOUTHWEST FRINGE OF THE 90 MEMBER 00Z MULTI-MODEL
ENSEMBLE SPREAD.

ROTH/JAMES

[KWT]

SHIPS still making it a hurricane and so this one certainly needs watching, there do seem to be some comprasions to Bob in 1991.

[GeneratorPower]

12z ECMWF is more agressive on this system,Tracks towards Carolinas and then rides up the coast.

http://www.ecmwf.int/products/forecasts ... 12!!!step/

That loop seems to indicate a direct hit on the Outer Banks of NC. This is the EURO, too.

[Hurricaneman]

SHIPS still making it a hurricane and so this one certainly needs watching, there do seem to be some comprasions to Bob in 1991.

If you are somehow right, I feel like I need to watch this like a hawk

[cycloneye]

This is the EURO, too

The best model of 2009 by far.

[KWT]

Yeah but of course its very early days and any outcome like that is going to require the 'top end' of what is possible however if you have a developing system going over the Gulf stream at the peak of the season you always need to watch it.

[Nederlander]

This is the EURO, too

The best model of 2009 by far.

Or the best model of all time... at least thats what wx_warrior would tell you lol..

[KWT]

Yeah the fact is the duo that did best with Bill, the ECM and the CMC are both progging something that could hit the Carolinas and track up the east coast.

[otowntiger]

18 UTC BAM Models

SHIP is very bullish as it makes it a hurricane in 96 hours.

169
WHXX01 KWBC 241907
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1907 UTC MON AUG 24 2009

DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.

ATLANTIC OBJECTIVE AIDS FOR

DISTURBANCE INVEST (AL922009) 20090824 1800 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
090824 1800 090825 0600 090825 1800 090826 0600

LAT LON LAT LON LAT LON LAT LON
BAMS 17.0N 58.0W 18.9N 61.7W 21.2N 64.9W 23.1N 67.2W
BAMD 17.0N 58.0W 19.0N 60.4W 21.0N 62.6W 22.9N 64.4W
BAMM 17.0N 58.0W 18.8N 61.1W 20.8N 63.7W 22.4N 65.6W
LBAR 17.0N 58.0W 18.6N 61.0W 20.4N 63.8W 22.0N 66.4W
SHIP 20KTS 23KTS 30KTS 36KTS
DSHP 20KTS 23KTS 30KTS 36KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
090826 1800 090827 1800 090828 1800 090829 1800

LAT LON LAT LON LAT LON LAT LON
BAMS 25.0N 69.4W 28.5N 72.6W 31.5N 73.9W 35.4N 71.8W
BAMD 24.4N 65.9W 26.5N 68.5W 28.1N 70.2W 30.9N 71.0W
BAMM 23.9N 67.4W 26.3N 70.4W 28.6N 72.1W 32.1N 71.6W
LBAR 23.4N 68.5W 25.7N 71.5W 27.7N 72.9W 30.2N 72.6W
SHIP 44KTS 56KTS 67KTS 75KTS
DSHP 44KTS 56KTS 67KTS 75KTS

...INITIAL CONDITIONS...
LATCUR = 17.0N LONCUR = 58.0W DIRCUR = 290DEG SPDCUR = 20KT
LATM12 = 15.9N LONM12 = 54.0W DIRM12 = 289DEG SPDM12 = 20KT
LATM24 = 14.6N LONM24 = 50.0W
WNDCUR = 20KT RMAXWD = 0NM WNDM12 = 20KT
CENPRS = 1010MB OUTPRS = 1012MB OUTRAD = 200NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM

Yep, this looks like the season of the re-curve. Yawn. Next.

[BigA]

Consensus seems pretty solid at this point; the CMC, Euro, NOGAPS, NAM, and GFS all develop a closed low of varying intensity in the western Atlantic in the next four days.

[cycloneye]

HWRF always is right of the rest of the models as it has that bias.

[gatorcane]

Keep in mind if it takes long for this to develop that consensus will just keep shifting left.

I expect things will change with that track guidance as its going to be a few days before anything gets going, so they should shift left.

[SEASON_CANCELED]

18 UTC BAM Models

SHIP is very bullish as it makes it a hurricane in 96 hours.

169
WHXX01 KWBC 241907
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1907 UTC MON AUG 24 2009

DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.

ATLANTIC OBJECTIVE AIDS FOR

DISTURBANCE INVEST (AL922009) 20090824 1800 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
090824 1800 090825 0600 090825 1800 090826 0600

LAT LON LAT LON LAT LON LAT LON
BAMS 17.0N 58.0W 18.9N 61.7W 21.2N 64.9W 23.1N 67.2W
BAMD 17.0N 58.0W 19.0N 60.4W 21.0N 62.6W 22.9N 64.4W
BAMM 17.0N 58.0W 18.8N 61.1W 20.8N 63.7W 22.4N 65.6W
LBAR 17.0N 58.0W 18.6N 61.0W 20.4N 63.8W 22.0N 66.4W
SHIP 20KTS 23KTS 30KTS 36KTS
DSHP 20KTS 23KTS 30KTS 36KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
090826 1800 090827 1800 090828 1800 090829 1800

LAT LON LAT LON LAT LON LAT LON
BAMS 25.0N 69.4W 28.5N 72.6W 31.5N 73.9W 35.4N 71.8W
BAMD 24.4N 65.9W 26.5N 68.5W 28.1N 70.2W 30.9N 71.0W
BAMM 23.9N 67.4W 26.3N 70.4W 28.6N 72.1W 32.1N 71.6W
LBAR 23.4N 68.5W 25.7N 71.5W 27.7N 72.9W 30.2N 72.6W
SHIP 44KTS 56KTS 67KTS 75KTS
DSHP 44KTS 56KTS 67KTS 75KTS

...INITIAL CONDITIONS...
LATCUR = 17.0N LONCUR = 58.0W DIRCUR = 290DEG SPDCUR = 20KT
LATM12 = 15.9N LONM12 = 54.0W DIRM12 = 289DEG SPDM12 = 20KT
LATM24 = 14.6N LONM24 = 50.0W
WNDCUR = 20KT RMAXWD = 0NM WNDM12 = 20KT
CENPRS = 1010MB OUTPRS = 1012MB OUTRAD = 200NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM

Yep, this looks like the season of the re-curve. Yawn. Next.

Looks like it stays off the coast

[Sanibel]

Obviously NHC saw something more than the weak open wave being agreed upon here.

[gatorcane]

Again see my post above....

[SEASON_CANCELED]

:uarrow:

Again see my post above....

Agree but its too early. Wednesday we will have a firm grasp on where this is headed.

[SEASON_CANCELED]

Yeah but of course its very early days and any outcome like that is going to require the 'top end' of what is possible however if you have a developing system going over the Gulf stream at the peak of the season you always need to watch it.

Gulf Stream can and does support Cat-3 storms. Just because a recurve scenario has started doesnt mean a weakening storm has to occur.

[KWT]

Yeah but most of those models firstly assume we have a system to track. Then notice that this is still heading WNW and as dErek said thats not really changing at all at the moment.

Watch those models shift westwards over the next day or so into better agreement with the other models. The HWRF is only following the GFS.

Put it this way, how likely is it to be at 30N and 68W like the HWRF has in about 48hrs?
That would require a motion similar to what Bill did when it was heading for the upper weakness!

[Derek Ortt]

Keep in mind if it takes long for this to develop that consensus will just keep shifting left.

I expect things will change with that track guidance as its going to be a few days before anything gets going, so they should shift left.

why do people keep making this mistake? Why? Weak does not mean west! Did we not learn anything from Ike where it went west because it was STRONGER than expected?

Weak means low level flow. Strong means deep flow

GFS seems to be an outlier with regards to all flow at this time