Tropical Storm Bertha Model Runs

[Aric Dunn]

will be great news if the trend of a right shift continues into tomorrow

I respect your opinion, and I agree with the idea of an eventual recurvature, but I'm not sure that you can definitely make this prognosis if the synoptics suggest a more westward track. I wouldn't eliminate the possibility of a NC brush/hit.

the likelihood that bertha would have have any major turn to the nw before 60w is becoming increasingly unlikely. a west motion for at least the next 36 hours in a good bet.

[Derek Ortt]

will be great news if the trend of a right shift continues into tomorrow

I respect your opinion, and I agree with the idea of an eventual recurvature, but I'm not sure that you can definitely make this prognosis if the synoptics suggest a more westward track. Some models have been struggling with the intensity forecasts for Bertha over the past few days, and they have continually depicted a more intense TC than reality. Additionally, they initially overestimated the strength of the upper level ridging. I wouldn't eliminate the possibility of a NC brush/hit.

I am not ruling out landfall just yet... but I will be watching the trends closely over the coming days. I am a bit more encouraged though than I was this time yesterday (GFDL solution seems suspect like today's HWRFs... I dont see recurvature at 60W)

[cycloneye]

will be great news if the trend of a right shift continues into tomorrow

i have to give you credit .. you are the king of one liners..

Ok Aric,lets take it easy,Anyone is entitled to its opinion and analisis in a big text way writing many paragraphs or in a single sentence.

[boca]

I think Bertha will start curving NW prior to the bahamas and scoot between the Carolina's and west of Bermuda due to the forecasted trough along the east coast.

[cheezyWXguy]

I dont know...it seems like the only reason we have a recurvature showing up in the models is because they forecast Bertha at a higher strength...what if that high is stronger than the models predict? it was stronger than the models predicted originally, which suddenly threw the early recurve scenario out the window. Im not ready to buy into this yet.

[cycloneye]

Moving 280 at 18kts.45kts

WHXX01 KWBC 060035
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0035 UTC SUN JUL 6 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) 20080706 0000 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
080706 0000 080706 1200 080707 0000 080707 1200

LAT LON LAT LON LAT LON LAT LON
BAMS 16.8N 40.3W 17.7N 43.5W 18.9N 46.6W 19.8N 49.4W
BAMD 16.8N 40.3W 17.9N 43.5W 19.1N 46.5W 20.3N 48.7W
BAMM 16.8N 40.3W 17.6N 43.8W 18.7N 47.1W 19.6N 49.5W
LBAR 16.8N 40.3W 17.7N 43.9W 18.9N 47.4W 19.9N 50.7W
SHIP 45KTS 49KTS 54KTS 61KTS
DSHP 45KTS 49KTS 54KTS 61KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
080708 0000 080709 0000 080710 0000 080711 0000

LAT LON LAT LON LAT LON LAT LON
BAMS 20.7N 51.9W 22.0N 56.0W 23.7N 59.4W 25.5N 61.7W
BAMD 21.5N 49.8W 23.4N 50.2W 25.2N 49.9W 25.5N 49.1W
BAMM 20.4N 51.1W 21.8N 53.2W 23.7N 54.8W 25.4N 56.2W
LBAR 20.9N 53.3W 23.2N 56.6W 25.7N 58.0W 26.4N 58.4W
SHIP 67KTS 71KTS 67KTS 70KTS
DSHP 67KTS 71KTS 67KTS 70KTS

...INITIAL CONDITIONS...
LATCUR = 16.8N LONCUR = 40.3W DIRCUR = 280DEG SPDCUR = 18KT
LATM12 = 16.4N LONM12 = 36.4W DIRM12 = 275DEG SPDM12 = 19KT
LATM24 = 15.8N LONM24 = 32.6W
WNDCUR = 45KT RMAXWD = 30NM WNDM12 = 45KT
CENPRS = 1000MB OUTPRS = 1012MB OUTRAD = 180NM SDEPTH = D
RD34NE = 75NM RD34SE = 30NM RD34SW = 0NM RD34NW = 75NM

[boca]

Also I don't think the GFDL 18z is correct on such a sharp WNW heading to NNW becaus ethe trough will not be strong enough to pull it that sharply but I think it will be more gradual turn once to 65w.

[Cyclone1]

SHIP keeps it at hurricane from 2- 5 days out.

[cycloneye]

00:00 UTC SHIP forecast=Shear is not a big issue in the 120 hour forecast.

Code: Select all

ATLANTIC SHIPS INTENSITY FORECAST       *
                    *        GOES/OHC INPUT INCLUDED            *
                    *      BERTHA  AL022008  07/06/08  00 UTC   *

TIME (HR)          0     6    12    18    24    36    48    60    72    84    96   108   120
V (KT) NO LAND    45    47    49    52    54    61    67    69    71    68    67    69    70
V (KT) LAND       45    47    49    52    54    61    67    69    71    68    67    69    70
V (KT) LGE mod    45    46    47    49    51    57    64    70    72    71    70    70    71

SHEAR (KTS)       12     7     5     7     9     6    13    20    18    20    21    17    10
SHEAR DIR        203   209   207   192   191   247   222   267   225   240   224   253   251
SST (C)         25.6  25.8  25.9  26.1  26.3  27.0  27.6  27.9  27.8  27.7  28.0  28.1  28.1
POT. INT. (KT)   113   115   116   118   119   126   133   136   135   134   138   138   138
ADJ. POT. INT.   111   113   114   115   116   123   127   128   125   124   127   124   122
200 MB T (C)   -54.1 -54.6 -54.8 -54.6 -54.4 -54.8 -54.6 -55.1 -55.0 -55.6 -55.5 -55.8 -55.5
TH_E DEV (C)       6     6     7     7     8     9     9     9    10    10    11    11    11
700-500 MB RH     55    53    50    49    46    43    45    48    46    45    43    40    42
GFS VTEX (KT)     13    13    13    12    11    12    14    14    14    12    10     9     9
850 MB ENV VOR   108    96    78    59    65    62    41    35    29     8    -3   -34   -48
200 MB DIV        19    28    31    37    52    29    -2     7    -2    12   -11    10    -1
LAND (KM)       1858  1757  1657  1586  1533  1377  1207   941   738   578   530   631   693
LAT (DEG N)     16.8  17.1  17.4  17.8  18.1  18.8  19.7  20.4  21.1  21.9  23.0  24.3  25.6
LONG(DEG W)     40.3  42.2  44.1  46.0  47.8  51.2  54.3  57.0  59.3  61.7  64.3  66.3  67.7
STM SPEED (KT)    18    18    18    18    17    16    14    12    11    13    12    10     9
HEAT CONTENT       0     0     0     2     7    22    33    45    37    30    32    34    34

  FORECAST TRACK FROM OFCI      INITIAL HEADING/SPEED (DEG/KT):280/ 18      CX,CY: -17/  3
  T-12 MAX WIND:  45            PRESSURE OF STEERING LEVEL (MB):  644  (MEAN=625)
  GOES IR BRIGHTNESS TEMP. STD DEV. 100-300 KM RAD:  16.7 (MEAN=20.0)
  % GOES IR PIXELS WITH T < -20 C    50-200 KM RAD:  66.0 (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.   1.   1.   2.   4.   7.   9.  10.  11.  12.  12.
  VERTICAL SHEAR         1.   2.   3.   4.   6.   7.   6.   5.   3.   1.   0.   1.
  PERSISTENCE            0.  -1.  -1.  -1.  -1.  -1.  -1.  -1.  -1.  -1.   0.   0.
  200/250 MB TEMP.       0.   0.   1.   1.   1.   2.   3.   3.   4.   5.   6.   8.
  THETA_E EXCESS         0.  -1.  -1.  -1.  -2.  -2.  -3.  -3.  -4.  -4.  -4.  -4.
  700-500 MB RH          0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.
  GFS VORTEX TENDENCY    0.   0.  -1.  -2.  -1.   0.   0.   0.  -3.  -4.  -5.  -5.
  850 MB ENV VORTICITY   1.   1.   1.   2.   2.   2.   3.   3.   2.   2.   1.   1.
  200 MB DIVERGENCE      0.   0.   0.   0.   1.   1.   1.   0.   0.  -1.  -1.  -1.
  ZONAL STORM MOTION     0.   0.   1.   1.   3.   3.   4.   5.   5.   6.   7.   8.
  STEERING LEVEL PRES    0.   0.   0.   0.   0.   0.   0.  -1.  -1.  -1.  -1.  -1.
  DAYS FROM CLIM. PEAK   0.   0.   0.  -1.  -1.  -2.  -2.  -2.  -2.  -3.  -3.  -4.
                        ----------------------------------------------------------
  SUB-TOTAL CHANGE       1.   4.   6.   8.  15.  22.  25.  27.  25.  24.  26.  27.

  SATELLITE ADJUSTMENTS ----------------------------------------------------------
  MEAN ADJUSTMENT        0.   0.   0.   0.  -1.  -1.  -1.  -1.  -1.  -1.  -1.  -2.
  GOES IR STD DEV        1.   1.   1.   1.   2.   1.   1.   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.  -1.  -1.  -1.  -1.  -1.  -1.
                        ----------------------------------------------------------
  TOTAL ADJUSTMENT       0.   1.   1.   1.   1.   0.   0.  -1.  -2.  -2.  -2.  -2.
                        ----------------------------------------------------------
  TOTAL CHANGE (KT)      2.   4.   7.   9.  16.  22.  24.  26.  23.  22.  24.  25.

   ** 2008 ATLANTIC RI INDEX AL022008     BERTHA 07/06/08  00 UTC **
           ( 25 KT OR MORE MAX WIND INCREASE IN NEXT 24 HR)
 
 12 HR PERSISTENCE (KT):   0.0 Range:-45.0 to  30.0 Scaled/Wgted Val:  0.6/  1.1
 850-200 MB SHEAR (KT) :   7.9 Range: 35.1 to   3.2 Scaled/Wgted Val:  0.9/  1.4
 D200 (10**7s-1)       :  33.4 Range:-20.0 to 149.0 Scaled/Wgted Val:  0.3/  0.5
 POT = MPI-VMAX (KT)   :  68.9 Range: 25.1 to 130.7 Scaled/Wgted Val:  0.4/  0.5
 850-700 MB REL HUM (%):  69.4 Range: 56.0 to  88.0 Scaled/Wgted Val:  0.4/  0.2
 % area w/pixels <-30 C:  55.0 Range: 17.0 to 100.0 Scaled/Wgted Val:  0.5/  0.1
 STD DEV OF IR BR TEMP :  11.8 Range: 35.1 to   3.2 Scaled/Wgted Val:  0.7/  1.0
 Heat content (KJ/cm2) :   1.8 Range:  0.0 to 132.0 Scaled/Wgted Val:  0.0/  0.0
 
 Prob of RI for 25 kt RI threshold=    22% is   1.8 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 07/06/08  00 UTC         ##
   ## STORM NOT ANNULAR, SCREENING STEP FAILED, NPASS=4 NFAIL=3                          ##
   ## AHI=  0   (AHI OF 100 IS BEST FIT TO ANN. STRUC., 1 IS MARGINAL, 0 IS NOT ANNULAR) ##
   ##     ANNULAR INDEX RAN NORMALLY       

[Derek Ortt]

something of note from the models

according to the shallow BAM (yes... it is from the NCEP global model), even a weak system will be turning more to the north

will check the rest of the guidance very soon

[RL3AO]

something of note from the models

according to the shallow BAM (yes... it is from the NCEP global model), even a weak system will be turning more to the north

will check the rest of the guidance very soon

That is very interesting. Good news.

[SouthFloridawx]

Looking at the 500mb vorticity forecast from the UKMET @ 12Z. It is forecasting for the ridge to hold on strong, until towards the end of the run. It's moving Bertha under the ridge very quickly.

http://moe.met.fsu.edu/cgi-bin/ukmtc2.cgi?time=2008070512&field=500mb+Vorticity&hour=Animation

[Aric Dunn]

something of note from the models

according to the shallow BAM (yes... it is from the NCEP global model), even a weak system will be turning more to the north

will check the rest of the guidance very soon

very true. but the ridge is not as strong as so there would be bend in the track.. vs. the ukmet which has a stronger ridge and also keeps bertha weaker.. but has a much more modest bend.

[cycloneye]

If the spagetti of models are right,then Bermuda will be in the crosshairs or go east of that island.

[RL3AO]

Does anyone think it could be another case of the models underestimating the ridge? Like it did with Dean and Felix last year?

[Matt-hurricanewatcher]

Does anyone think it could be another case of the models underestimating the ridge? Like it did with Dean and Felix last year?

I think it's possible, but we will have to watch the trend in see if it can hold. I would not be suprized to see this go all the way!

[cycloneye]

Does anyone think it could be another case of the models underestimating the ridge? Like it did with Dean and Felix last year?

Or those models that have Bertha strong go north.But lets see if one of our resident pro mets answer this important question.

[TreasureIslandFLGal]

Too much up in the air over the next 4 days. I'm sure the models will flip flop again. We'll know much more regarding any recurve possibilities in another 3 days.

[deltadog03]

I still think models are going to once again underestimate the strength of that ridge....Trofs that deep are not very common down here this time of the year. I think if Bertha is still moving due WEST tomorrow....then its really time to wonder about the mainland. I am not sure either way....

[Aric Dunn]

I still think models are going to once again underestimate the strength of that ridge....Trofs that deep are not very common down here this time of the year. I think if Bertha is still moving due WEST tomorrow....then its really time to wonder about the mainland. I am not sure either way....

Brilliant my dear Watson!!