Tropical Storm Bertha Model Runs

[PTrackerLA]

BAM's left shift is interesting but nothing to get worked up about unless some of the other major models start showing the same thing. Still feeling like this is a Bermuda storm as a possible major then out to sea.

Would be great if whoever was posting the model trend loops could update it to reflect shifts in the BAM.

[x-y-no]

How much creedence do you put towards the BAM model runs as of recent? Could it do a loop with a system this strong?

The BAMs aren't much use once one is out of the tropics. Not that this rules out looping if we get a stall down the line.

[LAwxrgal]

Hi everyone, been reduced to 'lurker' status over the last months... real life etc... anyway, don't rhink Bertha will come anywhere close to the US but do think she may be a threat to Bermuda...

My question is this, wouldn't a stronger storm tend to go poleward? AKA turn northward sooner?

[vacanechaser]

looks like the 12z gfs is slowing her down and maybe starting to stall bertha in the 138 hour time frame...



http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/carib/gfs/12/index_ten_m_loop.shtml



Jesse V. Bass III
http://www.vastormphoto.com
Hurricane Intercept Research Team

[Steve]

>>My question is this, wouldn't a stronger storm tend to go poleward? AKA turn northward sooner?

Often, sometimes not. It depends on more than just the strength of a storm (highs, lows, synoptics, steering and all that)...

Steve

[LAwxrgal]

12z still sees this as an open wave, but I'm not looking at the intensity but the possible synoptics, it looks like a bend to the north just at the end of that loop...

[vacanechaser]

yep, the ridge moves east and bertha turns with the ridge move... does slow her down a good bit however... could be interesting...

will have to see what happens



Jesse V. Bass III
http://www.vastormphoto.com
Hurricane Intercept Research Team

[Thunder44]

How much creedence do you put towards the BAM model runs as of recent? Could it do a loop with a system this strong?

The BAMs aren't much use once one is out of the tropics. Not that this rules out looping if we get a stall down the line.

I also believe the BAMS are for shallow tropical systems which this one is not either.

[deltadog03]

Ok, bams are not very good once we get out of the deep tropics. I will say this though, If Im not mistaken they are basically inputed from GFS data. Another met. confirm? Or anyone?

[x-y-no]

I also believe the BAMS are for shallow tropical systems which this one is not either.

Sorry, I wasn't clear - I was referring to "BAMs" as in the plural of "BAM". There are three BAM models, BAMS, BAMM and BAMD for shallow, medium and deep systems respectively.

[x-y-no]

Ok, bams are not very good once we get out of the deep tropics. I will say this though, If Im not mistaken they are basically inputed from GFS data. Another met. confirm? Or anyone?

Yes but as there's no dynamic feedback in the model, it can get lost pretty quickly once one is interacting with the circumpolar Rossby waves.

[deltadog03]

Ok, thats what I figured....thank!

[ronjon]

I'm wondering if we're starting to see an early trend with the BAM & 06Z GFS toward a westward track toward the end of the five day run. Perhaps high pressure may be stronger in western Atlantic than earlier thought. The problem this time of year is that we just don't get these strong troughs to sweep these storms out to sea. It looks like now that either Bertha will stall south of Bermuda or get pushed west.

https://my.sfwmd.gov/portal/page?_pageid=2854,19644915,2854_19644936:2854_19645022:2854_19645029&_dad=portal&_schema=PORTAL

Why is the NHC track keep shifting east after each advisory when like you said the Bam and 06zGFS are trending west.

Boca, that's why I mentioned an early trend. The dynamic models, GFDL and HWRF, have for sevral days been the most eastern tracks of the model suite. Most of the other globals, with the exception of the CMC, follow a track northward, albeit slightly west of the GFDL. I think the BAMs shift in itself is something to watch for in the other global models. If the other global models start trending this way then we might have something. I still say none of the models are kicking this storm out to sea - at least the next 5-7 days. The GFDL is down to a crawl at 3 kts the last day of its run. Wxman57 alluded to this scenario in his post this morning. A stalling scenario poses all kinds of problems for forecasters.

[NDG]

BAMs track shift to the west is a good example if the ridge over Bermuda was to hold longer or stay in place and the weakness exiting the US east coast does not pushes the ridge eastward as most models are indicating, but I would not bet anything on any BAM models, .

[dixiebreeze]

Maybe due to this in 72 hours?

http://www.nhc.noaa.gov/tafb_latest/atl ... testBW.gif

[Thunder44]

The 12z CMC initialized Bertha as open wave, but then it intensifies it as it crawls towards Bermuda by 144hrs.

http://moe.met.fsu.edu/cgi-bin/cmctc2.c ... =Animation

Meanwhile the 12z GFDL and 12z UKMET seemed to have initialized Bertha better, and they both recurve it well east of Bermuada:

http://moe.met.fsu.edu/cgi-bin/gfdltc2. ... =Animation

http://moe.met.fsu.edu/cgi-bin/ukmtc2.c ... =Animation

[cycloneye]

90kts,970 mbs,moving 290 degrees at 12kts.

440
WHXX01 KWBC 071832
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1832 UTC MON JUL 7 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) 20080707 1800 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
080707 1800 080708 0600 080708 1800 080709 0600

LAT LON LAT LON LAT LON LAT LON
BAMS 19.9N 51.6W 20.6N 54.3W 21.4N 56.5W 21.7N 58.3W
BAMD 19.9N 51.6W 20.8N 53.3W 21.6N 54.7W 22.3N 56.1W
BAMM 19.9N 51.6W 20.6N 53.6W 21.3N 55.3W 21.8N 56.8W
LBAR 19.9N 51.6W 20.7N 53.5W 21.8N 55.4W 22.6N 57.2W
SHIP 90KTS 94KTS 92KTS 88KTS
DSHP 90KTS 94KTS 92KTS 88KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
080709 1800 080710 1800 080711 1800 080712 1800

LAT LON LAT LON LAT LON LAT LON
BAMS 22.3N 60.2W 23.4N 63.1W 24.0N 65.0W 23.8N 66.9W
BAMD 23.1N 57.4W 25.1N 60.0W 26.6N 62.0W 27.3N 63.9W
BAMM 22.4N 58.3W 23.8N 61.2W 24.6N 63.4W 24.6N 65.4W
LBAR 23.6N 58.8W 25.9N 60.9W 27.2N 61.6W 28.0N 62.4W
SHIP 84KTS 71KTS 58KTS 56KTS
DSHP 84KTS 71KTS 58KTS 56KTS

...INITIAL CONDITIONS...
LATCUR = 19.9N LONCUR = 51.6W DIRCUR = 290DEG SPDCUR = 12KT
LATM12 = 19.1N LONM12 = 49.4W DIRM12 = 283DEG SPDM12 = 14KT
LATM24 = 18.4N LONM24 = 46.2W
WNDCUR = 90KT RMAXWD = 15NM WNDM12 = 65KT
CENPRS = 970MB OUTPRS = 1013MB OUTRAD = 200NM SDEPTH = D
RD34NE = 100NM RD34SE = 60NM RD34SW = 40NM RD34NW = 100NM

$$
NNNN



What does the BAMM seeing that the other globals dont?

[Extremeweatherguy]

The latest BAM models continue to want to bend Bertha back west and even south of west in a few days (which would be very concerning), but I would not worry too much about this actually happening unless the globals started to jump on board with this kind of scenario too (which, so far, they have not)...

[cycloneye]

The 18:00 UTC SHIP Forecast: Shear increases after 48 hours up to 27 kts.

Code: Select all

          *   ATLANTIC SHIPS INTENSITY FORECAST       *
                    *        GOES/OHC INPUT INCLUDED            *
                    *      BERTHA  AL022008  07/07/08  18 UTC   *

TIME (HR)          0     6    12    18    24    36    48    60    72    84    96   108   120
V (KT) NO LAND    90    94    94    93    92    88    84    78    71    65    58    56    56
V (KT) LAND       90    94    94    93    92    88    84    78    71    65    58    56    56
V (KT) LGE mod    90    96    97    95    92    87    82    78    73    69    64    61    58

SHEAR (KTS)       11    15    17    12    10    21    18    27    17    28    21    17    16
SHEAR DIR        227   231   256   273   242   244   224   230   239   230   252   315   321
SST (C)         26.9  27.0  27.1  27.3  27.4  27.5  27.6  27.8  28.0  28.0  27.6  27.1  26.7
POT. INT. (KT)   124   125   126   128   129   130   131   133   136   136   130   123   118
ADJ. POT. INT.   116   116   117   118   118   118   117   119   119   118   111   103    98
200 MB T (C)   -54.2 -54.3 -54.4 -54.7 -54.5 -54.8 -54.8 -55.1 -55.3 -55.4 -55.2 -54.8 -54.9
TH_E DEV (C)      10    10    10    10    10    10    10    10    10    10     9     9     8
700-500 MB RH     48    46    48    46    47    43    47    45    46    45    44    45    52
GFS VTEX (KT)     11    12    12    11    12    12    11    11    11    12    11    11    11
850 MB ENV VOR    24    13    -4    -9    -3   -22   -38   -56   -69   -83   -94   -80   -29
200 MB DIV        37     4    -6    11     0     0    18    18    10   -10    -5    17    41
LAND (KM)       1427  1376  1266  1170  1081   947   894   891   944  1062  1246  1311  1290
LAT (DEG N)     19.9  20.4  20.8  21.3  21.7  22.7  23.8  24.9  26.2  27.6  29.4  30.6  31.4
LONG(DEG W)     51.6  52.8  53.9  55.0  56.0  57.9  59.4  60.8  62.1  62.8  63.1  63.1  62.9
STM SPEED (KT)    12    12    11    11    10    10     8     9     8     8     8     5     4
HEAT CONTENT      17    19    21    24    27    23    22    26    29    18     9     7     4

  FORECAST TRACK FROM OFCI      INITIAL HEADING/SPEED (DEG/KT):290/ 12      CX,CY: -10/  4
  T-12 MAX WIND:  65            PRESSURE OF STEERING LEVEL (MB):  647  (MEAN=625)
  GOES IR BRIGHTNESS TEMP. STD DEV. 100-300 KM RAD:  14.6 (MEAN=20.0)
  % GOES IR PIXELS WITH T < -20 C    50-200 KM RAD:  97.0 (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         -1.  -1.  -1.  -2.  -5. -10. -16. -20. -25. -28. -31. -34.
  VERTICAL SHEAR        -1.  -3.  -5.  -5.  -7.  -7.  -7.  -6.  -6.  -6.  -4.  -2.
  PERSISTENCE            5.   6.   6.   6.   6.   6.   6.   5.   3.   1.   0.   0.
  200/250 MB TEMP.       0.   0.   0.   1.   1.   2.   3.   3.   4.   5.   6.   6.
  THETA_E EXCESS         0.   0.   0.   0.   0.   0.  -1.  -1.  -1.  -2.  -2.  -3.
  700-500 MB RH          0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.
  GFS VORTEX TENDENCY    0.   0.   0.   0.   0.   0.   0.  -1.   0.  -1.  -2.  -1.
  850 MB ENV VORTICITY   0.   0.   0.  -1.  -1.  -2.  -3.  -4.  -5.  -6.  -7.  -7.
  200 MB DIVERGENCE      0.   0.   0.  -1.  -1.  -1.  -2.  -2.  -3.  -3.  -3.  -2.
  ZONAL STORM MOTION     0.   0.   1.   1.   1.   2.   2.   2.   2.   3.   3.   3.
  STEERING LEVEL PRES    0.   0.   0.   0.   0.   0.  -1.  -1.  -1.  -1.  -1.  -1.
  DAYS FROM CLIM. PEAK   0.   0.   0.  -1.  -1.  -2.  -2.  -2.  -2.  -3.  -3.  -4.
                        ----------------------------------------------------------
  SUB-TOTAL CHANGE       4.   4.   3.   3.  -1.  -6. -11. -17. -23. -29. -31. -32.

  SATELLITE ADJUSTMENTS ----------------------------------------------------------
  MEAN ADJUSTMENT        0.   0.   0.   0.  -1.  -1.  -1.  -1.  -1.  -1.  -1.  -2.
  GOES IR STD DEV        0.   0.  -1.  -1.  -1.   0.   0.   0.   0.   0.   0.   0.
  GOES IR PIXEL COUNT    0.   1.   1.   1.   1.   1.   0.   0.  -1.  -1.  -1.   0.
  OCEAN HEAT CONTENT     0.   0.   0.   0.   0.   0.  -1.  -1.  -1.  -1.  -1.  -1.
                        ----------------------------------------------------------
  TOTAL ADJUSTMENT       0.   0.   0.   0.   0.  -1.  -1.  -2.  -3.  -3.  -3.  -2.
                        ----------------------------------------------------------
  TOTAL CHANGE (KT)      4.   4.   3.   2.  -2.  -6. -12. -19. -25. -32. -34. -34.

   ** 2008 ATLANTIC RI INDEX AL022008     BERTHA 07/07/08  18 UTC **
           ( 25 KT OR MORE MAX WIND INCREASE IN NEXT 24 HR)
 
 12 HR PERSISTENCE (KT):  25.0 Range:-45.0 to  30.0 Scaled/Wgted Val:  0.9/  1.7
 850-200 MB SHEAR (KT) :  12.9 Range: 35.1 to   3.2 Scaled/Wgted Val:  0.7/  1.1
 D200 (10**7s-1)       :   9.2 Range:-20.0 to 149.0 Scaled/Wgted Val:  0.2/  0.3
 POT = MPI-VMAX (KT)   :  27.0 Range: 25.1 to 130.7 Scaled/Wgted Val:  0.0/  0.0
 850-700 MB REL HUM (%):  64.8 Range: 56.0 to  88.0 Scaled/Wgted Val:  0.3/  0.1
 % area w/pixels <-30 C:  92.0 Range: 17.0 to 100.0 Scaled/Wgted Val:  0.9/  0.2
 STD DEV OF IR BR TEMP :   8.0 Range: 35.1 to   3.2 Scaled/Wgted Val:  0.8/  1.1
 Heat content (KJ/cm2) :  21.6 Range:  0.0 to 132.0 Scaled/Wgted Val:  0.2/  0.0
 
 Prob of RI for 25 kt RI threshold=    21% is   1.7 times the sample mean(12.3%)
 Prob of RI for 30 kt RI threshold=     3% is   0.3 times the sample mean( 7.8%)
 Prob of RI for 35 kt RI threshold=     1% is   0.3 times the sample mean( 4.5%)

   ##         ANNULAR HURRICANE INDEX (AHI) AL022008     BERTHA 07/07/08  18 UTC         ##
   ## STORM NOT ANNULAR, SCREENING STEP FAILED, NPASS=5 NFAIL=2                          ##
   ## AHI=  0   (AHI OF 100 IS BEST FIT TO ANN. STRUC., 1 IS MARGINAL, 0 IS NOT ANNULAR) ##
   ##     ANNULAR INDEX RAN NORMALLY

[NDG]

12z ECM still has Bertha passing barely east of Bermuda by Sunday