Tropical Storm Bertha Model Runs

[gatorcane]

To me that is an awfully small weakness the GFS thinks this system will squeeze through (Notice how close the H symbols are to each other north of the "Bertha"). If we are talking a deep hurricane Bertha then I buy it...but if Bertha is tropical storm or less I think she is staying on a W to WNW course past 55W and then she looks like she can hitch a ride on the Bermuda High.

[gatorcane]

CMC at 126 hours from above comment

[Blown Away]

That is a tight space for TD2 to squeeze through. I still think the recurve will happen closer to 55-60W.

[ronjon]

Gatorcane, this is what the storm is reacting to in the GFS. The 200 mb upper level low which will turn soon to be Bertha NW and N. Now, this weakness is not so dominant at 500 mb so like others have said, the stronger it gets the more steering by upper levels rather than lower or mid-levels.

[cycloneye]

As I mentioned earlier,the text that came out was the 6:00 UTC one,not the 12:00 UTC.But the graphics are updated with the 12:00 tracks from the BAM Models.

[cycloneye]

BERTHA!

288
WHXX01 KWBC 031354
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1354 UTC THU JUL 3 2008

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

TROPICAL CYCLONE BERTHA (AL022008) 20080703 1200 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
080703 1200 080704 0000 080704 1200 080705 0000

LAT LON LAT LON LAT LON LAT LON
BAMS 13.1N 24.2W 13.6N 27.1W 14.3N 30.0W 15.2N 32.6W
BAMD 13.1N 24.2W 13.9N 26.7W 15.0N 29.4W 16.5N 32.1W
BAMM 13.1N 24.2W 13.8N 26.8W 14.8N 29.5W 16.2N 32.1W
LBAR 13.1N 24.2W 13.8N 26.7W 14.8N 29.7W 15.9N 33.0W
SHIP 35KTS 42KTS 51KTS 57KTS
DSHP 35KTS 42KTS 51KTS 57KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
080705 1200 080706 1200 080707 1200 080708 1200

LAT LON LAT LON LAT LON LAT LON
BAMS 16.3N 35.1W 19.7N 41.1W 23.0N 46.1W 24.9N 49.0W
BAMD 18.2N 35.3W 21.5N 41.8W 25.5N 44.2W 28.2N 41.7W
BAMM 17.8N 35.1W 21.0N 41.3W 24.1N 45.5W 26.4N 46.6W
LBAR 17.2N 36.4W 20.3N 42.9W 22.9N 46.8W 25.3N 46.9W
SHIP 64KTS 71KTS 73KTS 65KTS
DSHP 64KTS 71KTS 73KTS 65KTS

...INITIAL CONDITIONS...
LATCUR = 13.1N LONCUR = 24.2W DIRCUR = 285DEG SPDCUR = 12KT
LATM12 = 12.3N LONM12 = 21.8W DIRM12 = 289DEG SPDM12 = 11KT
LATM24 = 11.9N LONM24 = 20.2W
WNDCUR = 35KT RMAXWD = 30NM WNDM12 = 30KT
CENPRS = 1006MB OUTPRS = 1013MB OUTRAD = 210NM SDEPTH = M
RD34NE = 30NM RD34SE = 30NM RD34SW = 0NM RD34NW = 30NM

[Dean4Storms]

This storm has Fish written all over it, in front of it and even behind it with it forming this time of year as far east and north that it formed. That said, only a weaker system maybe borderline TD/TS system would stand a chance at making it further west as the latest CMC run suggests in my opinion. I think the NHC has a good handle on this one early on, gradual slow strengthening and a WNW movement and then a turn into the weakness beyond 4 days or so.

If only they would all do this the rest of the year!!!!!

[KWT]

I think some of the models like the GFS are a little agressive with that NW turn and I think it will take a touch longer, in the long run its not going to matter, maybe it will bne the difference between recurving at 45W and recurving at 55W, tohugh it may make a difference in terms of strength.

Also 35kts Bertha....just like 1996 a very early Cape Verde storm, but unlike that one this should stick well away from land...hopefully!

[cycloneye]

The 12:00 SHIP Shear Forecast.Light shear until 120 hours when it goes up to 37kts.

Code: Select all

               *   ATLANTIC SHIPS INTENSITY FORECAST       *
                    *     GOES AND/OR OHC INPUT MISSING         *
                    *      BERTHA  AL022008  07/03/08  12 UTC   *

TIME (HR)          0     6    12    18    24    36    48    60    72    84    96   108   120
V (KT) NO LAND    35    38    42    46    51    57    64    66    71    72    73    68    65
V (KT) LAND       35    38    42    46    51    57    64    66    71    72    73    68    65
V (KT) LGE mod    35    38    40    43    46    52    57    62    66    68    71    72    68

SHEAR (KTS)        3     7     0     4     6     8     3    10    12    10    10    33    37
SHEAR DIR        179   125   311   248   232   205   163   176   248   249   228   229   243
SST (C)         25.6  25.5  25.5  25.5  25.3  24.7  25.0  25.4  25.7  26.1  26.8  27.1  27.1
POT. INT. (KT)   111   110   111   111   109   105   108   110   113   117   124   126   125
ADJ. POT. INT.   108   107   108   108   106   103   105   107   109   113   117   114   112
200 MB T (C)   -53.8 -53.0 -53.6 -53.9 -53.7 -53.5 -53.6 -53.2 -53.7 -53.4 -53.6 -53.4 -53.4
TH_E DEV (C)       4     4     4     4     4     4     5     5     6     7     8     9     8
700-500 MB RH     77    73    73    72    68    63    56    52    51    43    42    41    45
GFS VTEX (KT)     18    18    18    20    22    21    22    19    20    20    20    17    20
850 MB ENV VOR    55    73    90    97    98   116   125   112    99    76    64    42    52
200 MB DIV        69    67    64    60    40    63    33    12     4    39    73    15    18
LAND (KM)        746   875  1007  1147  1289  1610  1989  1995  1839  1771  1733  1589  1498
LAT (DEG N)     13.1  13.5  13.8  14.2  14.6  15.6  16.7  17.6  18.3  19.5  21.3  22.8  24.0
LONG(DEG W)     24.2  25.5  26.8  28.2  29.5  32.5  36.0  39.3  42.5  45.7  49.0  51.2  52.6
STM SPEED (KT)    13    13    14    14    14    17    17    16    16    17    15    11     9
HEAT CONTENT       0     0     0     0     0     0     0     0     0     2    13    14    14

  FORECAST TRACK FROM OFCI      INITIAL HEADING/SPEED (DEG/KT):285/ 12      CX,CY: -11/  3
  T-12 MAX WIND:  30            PRESSURE OF STEERING LEVEL (MB):  529  (MEAN=625)
  GOES IR BRIGHTNESS TEMP. STD DEV. 100-300 KM RAD: -99.0 (MEAN=20.0)
  % GOES IR PIXELS WITH T < -20 C    50-200 KM RAD: -99.0 (MEAN=68.6)

                        INDIVIDUAL CONTRIBUTIONS TO INTENSITY CHANGE
                         6   12   18   24   36   48   60   72   84   96  108  120
                        ----------------------------------------------------------
  SAMPLE MEAN CHANGE     1.   2.   3.   4.   6.   8.   9.  10.  11.  12.  12.  13.
  SST POTENTIAL          0.   0.   0.   0.   0.   2.   5.   8.  10.  12.  13.  14.
  VERTICAL SHEAR         1.   3.   4.   6.   8.  11.  12.  11.  11.  11.   8.   4.
  PERSISTENCE            1.   1.   2.   2.   3.   2.   2.   2.   2.   1.   1.   0.
  200/250 MB TEMP.       0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.
  THETA_E EXCESS         0.  -1.  -2.  -2.  -3.  -5.  -6.  -8. -10. -11. -11. -12.
  700-500 MB RH          0.   0.   0.   0.   0.   0.   0.   0.   0.   0.  -1.  -1.
  GFS VORTEX TENDENCY    0.   0.   1.   2.   1.   2.  -1.   1.   0.   0.  -2.   0.
  850 MB ENV VORTICITY   0.   1.   1.   2.   3.   4.   5.   6.   6.   7.   7.   6.
  200 MB DIVERGENCE      0.   1.   1.   2.   3.   3.   3.   3.   3.   4.   4.   4.
  ZONAL STORM MOTION     0.   0.   1.   1.   1.   2.   2.   2.   3.   3.   4.   4.
  STEERING LEVEL PRES    0.   0.   1.   1.   1.   2.   1.   2.   2.   2.   2.   1.
  DAYS FROM CLIM. PEAK   0.   0.   0.  -1.  -1.  -2.  -2.  -2.  -3.  -3.  -3.  -4.
                        ----------------------------------------------------------
  SUB-TOTAL CHANGE       3.   7.  11.  16.  22.  29.  31.  36.  37.  38.  33.  31.

  SATELLITE ADJUSTMENTS ----------------------------------------------------------
  MEAN ADJUSTMENT        0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.
  GOES IR STD DEV        0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.
  GOES IR PIXEL COUNT    0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.
  OCEAN HEAT CONTENT     0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.
                        ----------------------------------------------------------
  TOTAL ADJUSTMENT       0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.
                        ----------------------------------------------------------
  TOTAL CHANGE (KT)      3.   7.  11.  16.  22.  29.  31.  36.  37.  38.  33.  31.

   ** 2008 ATLANTIC RI INDEX AL022008     BERTHA 07/03/08  12 UTC **
           ( 25 KT OR MORE MAX WIND INCREASE IN NEXT 24 HR)
 
 12 HR PERSISTENCE (KT):   5.0 Range:-45.0 to  30.0 Scaled/Wgted Val:  0.7/  1.2
 850-200 MB SHEAR (KT) :   4.0 Range: 35.1 to   3.2 Scaled/Wgted Val:  1.0/  1.6
 D200 (10**7s-1)       :  60.0 Range:-20.0 to 149.0 Scaled/Wgted Val:  0.5/  0.7
 POT = MPI-VMAX (KT)   :  72.5 Range: 25.1 to 130.7 Scaled/Wgted Val:  0.4/  0.5
 850-700 MB REL HUM (%):  73.4 Range: 56.0 to  88.0 Scaled/Wgted Val:  0.5/  0.2
 % area w/pixels <-30 C:9999.0 Range: 17.0 to 100.0 Scaled/Wgted Val:999.0/999.0
 STD DEV OF IR BR TEMP : 999.9 Range: 35.1 to   3.2 Scaled/Wgted Val:999.0/999.0
 Heat content (KJ/cm2) :   0.0 Range:  0.0 to 132.0 Scaled/Wgted Val:  0.0/  0.0
 
 Prob of RI for 25 kt RI threshold=   999% is 999.0 times the sample mean(12.3%)
 Prob of RI for 30 kt RI threshold=   999% is 999.0 times the sample mean( 7.8%)
 Prob of RI for 35 kt RI threshold=   999

[Extremeweatherguy]

I think this will probably make the north turn closer to 55-60W too, but who knows. We will just have to watch and wait. The GFS and a few other models do seem a bit aggressive with their early turn (near 45W) though, IMO.

[deltadog03]

Canes will be steered by the H5 flow not 200mb winds.

[KWT]

Well current track is 285 so its close to WNW already. I think the NHC forecast is probably the best guide right now right in the middle of the guidence.

SHIPS has low shear low sea temps for its forecast then just as temps rise the forecasted shear rises through the roof as it heads towards the upper low. We shall have to wait and see.

[Aric Dunn]

The 12Z gfs is much farther west on the recurve ... hmmm..
and actually keeps it on more west track in the short term,...

will see if the other models follow suit

http://www.nco.ncep.noaa.gov/pmb/nwprod ... loop.shtml

[KWT]

Well its a little slower in the recurve but the ultimate point where it turns more to the north is about the same amount west as it has been on the last few runs.

[brunota2003]

The thing that concerns me is that, even if it crosses 20N before 50W, it could still impact the East Coast easily with the right set-up. Anyone remember Isabel in 2003? Granted this time it is not even close to my b-day (Isabel made landfall on my head, literally, on my 13th b-day), but she was at 20.0N while still at 47.3W. The longer the recurve is delayed, the more nail biting we get.

Isabel was "supposed" to follow Fabian North through the weakness that he had left behind as he impacted Bermuda and points northward. She did not. And guess what? She was even a Category 5 for a good span of her life! Granted she formed further west than Bertha did, but I would not be surprised to see Bertha's track similar to hers, in that the models prog it to turn north into a weakness around or a little before Bermuda and it actually ends up traveling further west than most anticipate.

Granted, I wouldn't be surprised to see this storm go Fishing, either. Time will tell.

http://www.wunderground.com/hurricane/at20039.asp

[gatorcane]

Brun

The thing that concerns me is that, even if it crosses 20N before 50W, it could still impact the East Coast easily with the right set-up. Anyone remember Isabel in 2003? Granted this time it is not even close to my b-day (Isabel made landfall on my head, literally, on my 13th b-day), but she was at 20.0N while still at 47.3W. The longer the recurve is delayed, the more nail biting we get.

Isabel was "supposed" to follow Fabian North through the weakness that he had left behind as he impacted Bermuda and points northward. She did not. And guess what? She was even a Category 5 for a good span of her life! Granted she formed further west than Bertha did, but I would not be surprised to see Bertha's track similar to hers, in that the models prog it to turn north into a weakness around or a little before Bermuda and it actually ends up traveling further west than most anticipate.

Granted, I wouldn't be surprised to see this storm go Fishing, either. Time will tell.

http://www.wunderground.com/hurricane/at20039.asp

The models are expecting her to turn north 5+ days from now and it looks like they are trending to start the recurve further out. We know how inaccurate forecasts get after 5+ days. As an aside the models were wrong on several other invests that actually never recurved including the invest that created Katrina and Andrew. The Azores High ridge is progged to strengthen over the next 2-3 days which could easily shove Bertha nearly due west, especially if she stays relatively weak. Then models may not latch on to a recurve so fast. Right now Bertha is heading 285 which makes a downstream recurve probability more plausible.

[ronjon]

12Z CMC - around 55W when it makes the turn north.

http://moe.met.fsu.edu/cgi-bin/cmctc2.cgi?time=2008070312&field=Sea+Level+Pressure&hour=Animation

[LaBreeze]

Bertha is going fishing.

[GeneratorPower]

The 12Z gfs is much farther west on the recurve ... hmmm..
and actually keeps it on more west track in the short term,...

will see if the other models follow suit

http://www.nco.ncep.noaa.gov/pmb/nwprod ... loop.shtml

The big news here is that it's forecasting a huge trough off the US east coast, and Bertha going around the edge of the Bermuda high. To find out whether that sucker is going to recurve, we need to watch the behavior of the Bermuda high and whether or not the models are forecasting that trough to be there.

Point being, I don't think small left/right changes in the GFS track are important. Look at the overall pattern (i.e., major high/low pressure areas) especially after day 3.

[cycloneye]

12z GFDL:Recurve

978
WHXX04 KWBC 031728
CHGQLM
ATTENTION...NATIONAL HURRICANE CENTER

NCEP COUPLED GFDL HURRICANE MODEL FORECAST MADE FOR

TROPICAL DEPRESSION TWO 02L

INITIAL TIME 12Z JUL 3

DISCLAIMER ... THIS INFORMATION IS PROVIDED AS GUIDANCE. IT
REQUIRES INTERPRETATION BY HURRICANE SPECIALISTS AND SHOULD
NOT BE CONSIDERED AS A FINAL PRODUCT. PLEASE SEE THE TPC/NHC
OFFICIAL FORECAST.


FORECAST STORM POSITION

HOUR LATITUDE LONGITUDE HEADING/SPEED(KT)

0 12.9 24.4 285./12.0
6 12.9 25.3 265./ 8.8
12 13.1 26.4 282./11.1
18 13.7 27.6 298./13.3
24 14.4 29.1 296./15.9
30 15.2 30.8 293./17.6
36 15.9 32.5 294./18.4
42 16.7 34.4 293./19.8
48 16.9 36.3 275./18.9
54 17.3 38.2 282./18.6
60 17.7 40.2 282./19.4
66 18.5 42.3 290./21.4
72 18.9 44.5 281./21.1
78 19.4 46.2 286./16.7
84 20.7 47.4 316./16.8
90 21.6 48.8 304./15.2
96 22.2 49.7 302./10.9
102 23.0 50.4 320./10.7
108 23.8 51.1 319./10.0
114 24.7 51.7 329./10.6
120 25.8 52.4 326./12.0
126 26.6 53.2 316./11.0