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Tropical Cyclone Report

Tropical Storm Nicholas

13 - 23 October 2003

Jack Beven
National Hurricane Center
7 January 2004

Nicholas was a long-lived tropical storm that remained over the Atlantic far from land.

a. Synoptic History

Nicholas developed from a tropical wave that moved westward from the coast of Africa on 9 October. A broad low pressure area formed along the wave on 10 October, and convection slowly became better organized during the following two days. It is estimated that a tropical depression formed near 0000 UTC 13 October about 790 n mi west-southwest of the southern Cape Verde Islands. The "best track" chart of the tropical cyclone's path is given in Figure 1, with the wind and pressure histories shown in Figure 2 and Figure 3, respectively. The best track positions and intensities are listed in Table 1.

The cyclone formed in an area of southerly to southwesterly vertical wind shear, and it would remain in such an environment through its lifetime. The system moved slowly west-northwestward and gradually strengthened, becoming Tropical Storm Nicholas late on 14 October. It then moved northwestward for the next three days, reaching a peak intensity of 60 kt on 17 October. A slow and erratic northward motion occurred from 18-20 October while Nicholas gradually weakened due to the shear. The storm turned west-northwestward later on 20 October and westward on 21 October. This was accompanied by slight re-intensification. Nicholas again turned northwestward on 22 October and weakening resumed. The cyclone became a depression on 23 October as it turned northward, and it became a non-convective remnant low on 24 October. The low merged with a cold front later that day, becoming extratropical about 505 n mi east-southeast of Bermuda.

The post-tropical cyclone history of Nicholas is complex. After becoming extratropical, the remnant low made a large anticyclonic loop from 24-28 October. A subsequent west-northwestward to westward motion on 28-29 October occurred while Nicholas moved along the warm front associated with a non-tropical low to its southwest. A second anticyclonic loop took place on 29-31 October, which was followed by a small cyclonic loop early on 1 November while the Nicholas low separated from the frontal system. The Nicholas remnant was finally absorbed into a non-tropical low pressure area late that day about 300 n mi south-southwest of Bermuda. This low, which developed sporadic bursts of central convection, moved westward to the Florida Peninsula on 3 November and then northwestward to the northern coast of the Gulf of Mexico on 5 November.

b. Meteorological Statistics

Observations in Nicholas (Figure 2 and Figure 3) include satellite-based Dvorak technique intensity estimates from the Tropical Analysis and Forecast Branch (TAFB), the Satellite Analysis Branch (SAB) and the U. S. Air Force Weather Agency (AFWA). Microwave satellite imagery from the NOAA polar-orbiting satellites, the NASA Tropical Rainfall Measuring Mission (TRMM), the NASA QuikSCAT, and the Defense Meteorological Satellite Program (DMSP) satellites were also useful in tracking Nicholas.

Dvorak satellite intensity estimates from all agencies suggested that Nicholas could have been a hurricane near 1200 UTC 17 October. However, several microwave images made near that time showed that the cyclone was still partly sheared, with no evidence of an eye, an eyewall, or well-defined convective bands. Thus, it is estimated that Nicholas did not reach hurricane strength and that the maximum winds were 60 kt.

The remnants of Nicolas became involved in a complex weather pattern between 27 October and 1 November, and the exact time of dissipation occurred is uncertain. Operationally, the non-tropical low that crossed Florida was occasionally referred to as the remnants of Nicholas in tropical weather outlooks issued by the National Hurricane Center. Post-analysis suggests instead that this system absorbed the remnants of Nicholas.

There are no known surface observations of tropical-storm force or stronger winds associated with Nicholas.

c. Casualty and Damage Statistics

There were no reports of damages or casualties associated with Nicholas.

d. Forecast and Warning Critique

Average official track errors (with the number of cases in parentheses) for Nicholas were 39 (39), 64 (37), 95 (35), 127 (33), 171 (29), 185 (25), and 158 (21) n mi for the 12, 24, 36, 48, 72, 96, and 120 h forecasts, respectively1. These errors are lower than the average official track errors for the 10-yr period 1993-20022 (45, 81, 116, 150, 225, 282, and 374 n mi, respectively), (Table 2). The track forecast errors are also lower than the errors of the Climatology-Persistence model (44, 83, 125, 171, 305, 455, and 614 n mi for the 12, 24, 36, 48, 72, 96, and 120 h forecasts, respectively) including almost 75% lower at 120 h. By this measure, the track forecasts had significant skill.

Although the track forecast errors are quite small, the slow and erratic northward motion on 18-20 October was not well forecast. The track forecasts called for a continuing northwestward motion, which led to 24 hr track forecast errors of near 125 n mi and 48 h errors of near 200 n mi during that time.

The official track forecasts were for the most part better than the model guidance. The average errors of the GFDL model were generally the lowest of the dynamical models through 48 h and were less than those of the official forecast from 24-72 h. The GFS model (AVNO) and the medium BAM (BAMM) generally were the best of the models after 72 h and showed lower mean forecast errors than the official forecasts at 48-96 h. The consensus model GUNA had lower average errors than the official forecasts for the 36-72 hr period.

Average official intensity errors were 4, 5, 5, 7, 9, 11, and 15 kt for the 12, 24, 36, 48, 72, 96, and 120 h forecasts, respectively. For comparison, the average official intensity errors over the 10-yr period 1993-2002 are 6, 10, 13, 15, 19, 21, and 22 kt, respectively. The average intensity errors for Climatology-Persistence were 5, 7, 7, 9, 11, 15, and 20 kt, respectively. For the most part, the intensity forecasts correctly anticipated that vertical shear would restrict the development of Nicholas and eventually cause dissipation.

No watches or warnings were issued for Nicholas.

1All forecast verifications in this report include the depression stage of the cyclone. National Hurricane Center verifications presented in these reports prior to 2003 did not include the depression stage.

2Errors given for the 96 and 120 h periods are averages over the two-year period 2001-2002.



Table 1: Best track for Tropical Storm Nicholas, 13-23 October 2003.
Date/Time
(UTC)
PositionPressure
(mb)
Wind Speed
(kt)
Stage
Lat.
(°N)
Lon.
(°W)
 13 / 0000 9.5 37.0 1009 25 tropical depression
 13 / 0600 9.5 37.7 1008 25 "
 13 / 1200 9.6 38.4 1008 25 "
 13 / 1800 9.9 38.9 1007 30 "
 14 / 0000 10.2 39.5 1006 30 "
 14 / 0600 10.5 40.3 1006 30 "
 14 / 1200 10.7 41.1 1006 30 "
 14 / 1800 10.9 41.9 1005 35 tropical storm
 15 / 0000 11.2 42.5 1003 40 "
 15 / 0600 11.5 43.1 1000 45 "
 15 / 1200 11.8 43.7 1000 45 "
 15 / 1800 12.2 44.3 1000 45 "
 16 / 0000 12.6 45.0 1000 45 "
 16 / 0600 13.1 45.6 1000 45 "
 16 / 1200 13.5 46.0 997 50 "
 16 / 1800 14.0 46.6 994 55 "
 17 / 0000 14.4 47.2 995 55 "
 17 / 0600 15.0 47.6 994 55 "
 17 / 1200 15.5 48.0 990 60 "
 17 / 1800 16.1 48.1 994 55 "
 18 / 0000 16.3 48.1 994 55 "
 18 / 0600 16.3 47.9 994 55 "
 18 / 1200 16.5 47.8 994 55 "
 18 / 1800 16.7 47.7 997 50 "
 19 / 0000 17.0 47.6 997 50 "
 19 / 0600 17.3 47.4 997 50 "
 19 / 1200 17.6 47.3 997 50 "
 19 / 1800 17.6 47.5 1000 45 "
 20 / 0000 17.4 47.7 1000 45 "
 20 / 0600 17.6 47.9 1000 45 "
 20 / 1200 17.8 48.1 1002 40 "
 20 / 1800 18.1 48.9 1005 35 "
 21 / 0000 18.4 49.7 1005 35 "
 21 / 0600 18.6 50.3 1002 40 "
 21 / 1200 18.7 51.0 1000 45 "
 21 / 1800 18.6 52.0 1000 45 "
 22 / 0000 18.5 52.9 1002 40 "
 22 / 0600 18.5 53.6 1005 35 "
 22 / 1200 18.8 54.1 1005 35 "
 22 / 1800 19.5 54.6 1005 35 "
 23 / 0000 20.4 55.4 1005 35 "
 23 / 0600 21.5 56.0 1006 30 tropical depression
 23 / 1200 22.5 56.4 1007 30 "
 23 / 1800 23.6 56.9 1008 30 "
 24 / 0000 25.1 56.7 1009 25 low
 24 / 0600 27.1 56.4 1010 25 "
 24 / 1200 28.8 56.1 1011 25 "
 24 / 1800 30.2 55.7 1012 25 extratropical
 25 / 0000 31.4 54.8 1013 20 "
 25 / 0600 32.2 53.5 1014 20 "
 25 / 1200 32.4 52.0 1014 20 "
 25 / 1800 32.5 50.5 1013 20 "
 26 / 0000 31.9 49.5 1013 20 "
 26 / 0600 30.7 49.1 1012 25 "
 26 / 1200 29.3 49.0 1010 30 "
 26 / 1800 28.3 49.6 1008 30 "
 27 / 0000 27.4 50.5 1007 30 "
 27 / 0600 26.7 52.0 1007 35 "
 27 / 1200 26.4 53.7 1007 35 "
 27 / 1800 26.6 55.5 1007 35 "
 28 / 0000 27.1 57.3 1008 30 "
 28 / 0600 27.9 59.1 1009 30 "
 28 / 1200 28.9 60.8 1009 30 "
 28 / 1800 29.5 62.8 1009 30 "
 29 / 0000 29.4 65.1 1009 25 "
 29 / 0600 29.3 67.1 1009 25 "
 29 / 1200 29.5 68.0 1009 25 "
 29 / 1800 30.1 68.0 1009 25 "
 30 / 0000 30.4 67.2 1009 25 "
 30 / 0600 30.4 66.4 1009 25 "
 30 / 1200 30.0 65.8 1008 30 "
 30 / 1800 29.3 65.3 1008 30 "
 31 / 0000 28.7 65.5 1008 30 "
 31 / 0600 28.3 66.0 1008 30 low
 31 / 1200 27.7 66.3 1007 30 "
 31 / 1800 27.0 66.4 1006 30 "
 01 / 0000 26.4 66.3 1005 30 "
 01 / 0600 26.5 66.0 1005 30 "
 01 / 1200 27.0 66.3 1005 30 "
 01 / 1800 27.7 67.0 1005 30 "
 02 / 0000     absorbed by low pressure system
 17 / 1200 15.5 48.0 990 60 minimum pressure


Table 2: Preliminary forecast evaluation (heterogeneous sample) for Tropical Storm Nicholas, 13-23 October 2003. Forecast errors (n mi) are followed by the number of forecasts in parentheses. Errors smaller than the NHC official forecast are shown in bold-face type. Verification includes the depression stage, but does not include the extratropical stage.
Forecast TechniquePeriod (hours)
122436487296120
CLP544 (42) 83 (40) 125 (38) 171 (36) 305 (32) 455 (28) 614 (24) 
A90E44 (42) 82 (40) 122 (38) 167 (36) 270 (32) 394 (28) 496 (24) 
A98E44 (42) 83 (40) 120 (38) 163 (36) 265 (32) 387 (28) 487 (24) 
A9UK42 (20) 81 (19) 119 (18) 166 (17) 282 (15)   
LBAR43 (42) 75 (40) 99 (38) 124 (36)238 (32) 418 (28) 572 (24) 
BAMD55 (42) 89 (40) 112 (38) 129 (36) 178 (32) 239 (28) 333 (24) 
BAMM45 (42) 72 (40) 97 (38) 117 (36)167 (32)175 (28)187 (24) 
BAMS53 (42) 88 (40) 115 (38) 137 (36) 190 (32) 223 (28) 251 (24) 
AF1I72 (31) 149 (29) 236 (27) 309 (26) 425 (23)   
AFW1*92 (16) 152 (15) 239 (14) 333 (13) 435 (12)   
GFNI44 (30) 84 (28) 129 (28) 178 (26) 273 (26)   
GFDN*46 (15) 71 (15) 104 (14) 152 (14) 243 (13)   
GFDI36 (36)58 (35)77 (33)99 (29)162 (26)259 (23) 402 (19) 
GFDL*42 (38) 58 (37)74 (30)89 (28)145 (25)229 (23) 373 (19) 
UKMI44 (37) 78 (35) 106 (33) 136 (31) 194 (27) 231 (23) 234 (19) 
UKM*58 (19) 86 (18) 113 (17) 135 (16) 188 (14) 222 (12) 247 (10) 
NGPI48 (39) 96 (37) 146 (35) 207 (33) 315 (30) 415 (26) 479 (22) 
NGPS*49 (38) 92 (36) 141 (34) 194 (32) 304 (30) 398 (26) 465 (22) 
AVNI45 (37) 75 (35) 99 (33) 120 (31)133 (27)137 (23)173 (19) 
AVNO*53 (37) 82 (36) 105 (34) 122 (32)139 (28)148 (24)177 (19) 
AEMI52 (19) 95 (18) 136 (17) 164 (16) 226 (13) 351 ( 9) 458 ( 7) 
AEMN*59 (17) 87 (16) 116 (15) 143 (14) 188 (12) 235 (9) 426 (6) 
GUNS37 (34)68 (33) 97 (31) 128 (29) 181 (26) 247 (23) 307 (19) 
GUNA37 (34)65 (33) 91 (31)117 (29)155 (26)197 (23) 235 (19) 
FSSE40 (18) 72 (17) 97 (16) 127 (15) 170 (13)  
OFCI40 (38) 70 (36) 103 (34) 133 (32) 176 (28) 177 (24)157 (20)
OFCL39 (39) 64 (37) 95 (35) 127 (33) 171 (29) 185 (25) 158 (21) 
NHC Official (1993-2002 mean)45 (2985) 81 (2726) 116 (2481) 150 (2230) 225 (1819) 282 (265) 374 (216) 

*Output from these models was unavailable at time forecast issued.

Best track positions for Tropical Storm Nicholas

Figure 1: Best track positions for Tropical Storm Nicholas, 13-23 October 2003.

Selected wind estimates/observations and best track maximum sustained surface wind speed curve for Tropical Storm Nicholas

Figure 2: Selected wind estimates/observations and best track maximum sustained surface wind speed curve for Tropical Storm Nicholas, 13-23 October 2003.Solid black bars denote wind ranges for the Hebert-Poteat subtropical cyclone technique.

Selected pressure estimates and best track minimum central pressure curve for Tropical Storm Nicholas

Figure 3: Selected pressure estimates and best track minimum central pressure curve for Tropical Storm Nicholas, 13-23 October 2003.



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