Number range CHAPTERTropical Cyclone Report

Hurricane Bertha

(AL022008)

3-20 July 2008

Jamie R. Rhome

National Hurricane Center

15 October 2008

Bertha was an early season category 3 hurricane (on the Saffir-Simpson
Hurricane Scale) that brought tropical storm conditions to Bermuda and
became the longest-lived Atlantic July tropical cyclone on record.

a.  Synoptic History

    Bertha developed from a well-defined tropical wave that crossed the
    west coast of Africa on 1 July. The wave was accompanied by a closed
    surface low and a large area of convection even before it emerged
    into the Atlantic. Within an environment of light vertical shear but
    marginally warm sea surface temperatures, the wave slowly developed
    and by 0600 UTC 3 July had acquired enough organized convection to
    be designated a tropical depression about 220 n mi south-southeast
    of the Cape Verde Islands. The organization of the depression
    continued to increase, and the cyclone strengthened to a tropical
    storm six hours later while passing south of the Cape Verde Islands.
    Bertha's strength changed little during the next couple of days as
    the storm moved west-northwestward. Bertha reached warmer waters by
    6 July and became the first hurricane of the 2008 season early on 7
    July while centered about 750 n mi east of the northern Leeward
    Islands.

    During the next several days, Bertha's intensity fluctuated due to
    varying atmospheric conditions. On 7 July, as the cyclone turned
    northwest into a weakness in the subtropical ridge, Bertha underwent
    a period of rapid intensification, with the maximum sustained winds
    increasing 45 kt during the 15-h period beginning at 0600 UTC.
    Bertha became a major hurricane with a peak intensity of 110 kt at
    2100 UTC that day. Bertha then encountered an environment of strong
    vertical shear on 8 July, resulting in a period of rapid weakening
    with maximum sustained winds decreasing 40 kt during the 24-h period
    ending at 0600 UTC 9 July. The shear weakened on 9 July, however,
    and Bertha once again quickly intensified with maximum sustained
    winds increasing from 65 kt to 90 kt during the 18-h period
    beginning at 0600 UTC 9 July. By 10 July, an outer convective band
    began to wrap around the center forming a second outer eyewall
    (Fig. 1) and associated wind maximum. As the cyclone continued
    moving northward, the inner eyewall weakened and dissipated by 12
    July. The completion of the eyewall replacement cycle coupled with
    slightly cooler waters resulted in gradual weakening, and the
    cyclone became a tropical storm early on the 13^th^.

    Bertha moved into an area with light steering currents, resulting in
    a slowing of the cyclone's forward speed on the 12^th^, and became
    nearly stationary on the 13^th^ near Bermuda. On 14 July, Bertha
    resumed its northward motion and brought tropical storm conditions
    to the island while its center passed about 40 n mi to the island's
    east. The cyclone then turned eastward and southeastward on the
    16^th^ and 17^th^ while it moved cyclonically around a large
    deep-layer low over the central Atlantic. Bertha accelerated
    northeastward on the 18^th^ in strong southwesterly flow ahead of a
    trough moving off the east coast of the United States. The cyclone
    became a hurricane once again during that period. Bertha passed
    about 400 n mi southeast of Cape Race, Newfoundland, on the 19^th^
    and became an extratropical cyclone over the north Atlantic on 20
    July. The extratropical low continued northeastward toward Iceland,
    where it merged with a larger mid-latitude low pressure area on 21
    July.

    The "best track" chart of the tropical cyclone's path is given in
    Fig. 2, with the wind and pressure histories shown in Figs. 3 and 4,
    respectively. The best track positions and intensities are listed in
    Table 1[^1].

b.  Meteorological Statistics

    Observations in Bertha (Figs. 3 and 4) include satellite-based
    Dvorak technique intensity estimates from the Tropical Analysis and
    Forecast Branch (TAFB) and the Satellite Analysis Branch (SAB), as
    well as flight-level, stepped frequency microwave radiometer (SFMR),
    and dropwindsonde observations from four flights of the 53^rd^
    Weather Reconnaissance Squadron of the U. S. Air Force Reserve
    Command. Data and imagery from NOAA polar-orbiting satellites, the
    NASA Tropical Rainfall Measuring Mission (TRMM), the NASA QuikSCAT,
    and Defense Meteorological Satellite Program (DMSP) satellites,
    among others, were also useful in tracking Bertha. The maximum
    intensity and minimum pressure at 2100 UTC 7 July are based on 3-h
    objective Dvorak intensity estimates, which peaked between 1800 UTC
    7 July and 0000 UTC 8 July.

    Ship reports of tropical storm force winds associated with Bertha
    are given in Table 2, and selected surface observations from land
    stations and data buoys are given in Table 3. The highest
    ship-reported wind was 44 kt from the ship ***WDC692*** at 0600 UTC
    20 July.

    Bertha brought tropical storm conditions to Bermuda on 14 July
    (Table 3). An elevated instrument at the Bermuda Maritime Operations
    Centre reported a peak 1-minute sustained wind of 59 kt at 2035 UTC
    and a wind gust of 79 kt.

c.  Casualty and Damage Statistics

    Bertha produced tropical storm conditions over Bermuda as it passed
    east of the island, resulting in broken tree branches, downed power
    lines, and scattered power outages. A total of 4.76 inches of rain
    fell at the Bermuda International Airport, resulting in the flooding
    of a few roads. Many commercial flights into and out of Bermuda were
    disrupted on 14 July.

    Long-period swells generated by Bertha caused dangerous surf
    conditions and rip currents along much of the east coast of the
    United States. Over 1500 ocean rescues were reported in Ocean City,
    New Jersey, during a seven-day period beginning on 9 July, and 3
    persons drowned along the New Jersey coast during the height of the
    event.

d.  Forecast and Warning Critique

    The genesis of Bertha was well anticipated, as the tropical wave
    that ultimately spawned Bertha was first mentioned in the Atlantic
    Tropical Weather Outlook (TWO) at 0600 UTC 1 July, approximately 48
    h prior to genesis. At that time, the TWO noted that environmental
    conditions could allow for some slow development. The first mention
    of the potential formation of a tropical depression occurred 24 h in
    advance of genesis. At this time, the pre-Bertha disturbance was
    given a "medium" probability of tropical cyclone formation,
    corresponding to a 20-50% probability of genesis in the experimental
    graphical TWO. Subsequent TWOs continued to show a "medium"
    probability of genesis.

    A verification of official and guidance model track forecasts is
    given in Table 4. Average official track errors for Bertha were 24,
    43, 61, 82, 118, 164, and 200 n mi for the 12, 24, 36, 48, 72, 96,
    and 120 h forecasts, respectively. The number of forecasts ranged
    from 67 at 12 h to 49 at 120 h. These errors are considerably lower
    than the average long-term official track errors (Table 4) and
    represent a 21-29% improvement over the average track error.
    However, the official forecast was bested by the dynamical model
    consensus, TVCN, at nearly all forecast times. Of the dynamical
    models, the GFDL had the lowest track errors and beat the official
    forecast for the 12-h through 72-h time periods.

    Average official intensity errors were 6, 11, 12, 11, 11, 11 and 10
    kt for the 12, 24, 36, 48, 72, 96, and 120 h forecasts,
    respectively. For comparison, the average long-term official
    intensity errors are 7, 10, 12, 14, 18, 20, and 22 kt, respectively.
    With the exception of the 12-h forecast error, the official forecast
    errors were much smaller than the long-term average intensity errors
    despite the challenges associated with Bertha's rapid intensity
    fluctuations during the 3-day period of 7-10 July. The average
    intensity errors at 96 and 120 h were 49% and 53% better than the
    long-term average error for those forecast times.

Watches and warnings associated with Bertha are given in Table 5. A
tropical storm warning was issued for Bermuda at 1500 UTC July 12,
approximately 36 h prior to the arrival of tropical storm force winds.
As Bertha began pulling away from Bermuda late on the 14^th^, it
strengthened to just below hurricane strength prompting the issuance of
a hurricane watch at 1900 UTC that day.

*Acknowledgements*

Mark Guishard of the Bermuda Weather Service provided the data on
Bertha's impact on Bermuda.

Number range CHAPTERTable 1. Best track for Hurricane Bertha, 3-20 July
2008.

+-----------+-----------+-----------+-----------+-----------+-----------+
| Date/Time | Latitude  | Longitude | Pressure  | Wind      | Stage     |
|           |           |           |           | Speed     |           |
| (UTC)     | (°N)      | (°W)      | (mb)      |           |           |
|           |           |           |           | (kt)      |           |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 03 / 0600 | 12.7      | 22.9      | 1008      | 30        | tropical  |
|           |           |           |           |           | d         |
|           |           |           |           |           | epression |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 03 / 1200 | 13.1      | 24.0      | 1006      | 35        | tropical  |
|           |           |           |           |           | storm     |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 03 / 1800 | 13.2      | 25.2      | 1006      | 35        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 04 / 0000 | 13.4      | 26.5      | 1006      | 40        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 04 / 0600 | 14.0      | 27.8      | 1003      | 40        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 04 / 1200 | 14.8      | 29.2      | 1000      | 45        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 04 / 1800 | 15.4      | 30.8      | 1000      | 45        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 05 / 0000 | 15.8      | 32.6      | 1000      | 45        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 05 / 0600 | 16.3      | 34.4      | 1000      | 45        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 05 / 1200 | 16.4      | 36.4      | 1000      | 45        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 05 / 1800 | 16.6      | 38.4      | 1000      | 45        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 06 / 0000 | 16.8      | 40.3      | 1000      | 45        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 06 / 0600 | 17.0      | 42.3      | 1000      | 45        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 06 / 1200 | 17.6      | 44.3      | 1000      | 45        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 06 / 1800 | 18.4      | 46.2      | 1000      | 45        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 07 / 0000 | 18.8      | 47.9      | 994       | 55        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 07 / 0600 | 19.1      | 49.4      | 987       | 65        | hurricane |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 07 / 1200 | 19.4      | 50.7      | 975       | 80        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 07 / 1800 | 19.9      | 51.6      | 960       | 100       | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 07 / 2100 | 20.3      | 51.9      | 952       | 110       | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 08 / 0000 | 20.6      | 52.2      | 955       | 105       | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 08 / 0600 | 21.1      | 52.9      | 955       | 105       | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 08 / 1200 | 21.8      | 53.5      | 970       | 90        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 08 / 1800 | 22.4      | 54.4      | 980       | 75        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 09 / 0000 | 22.7      | 55.2      | 985       | 70        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 09 / 0600 | 23.2      | 56.1      | 987       | 65        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 09 / 1200 | 23.8      | 57.0      | 987       | 65        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 09 / 1800 | 24.5      | 57.8      | 974       | 85        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 10 / 0000 | 25.2      | 58.6      | 970       | 90        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 10 / 0600 | 25.7      | 59.1      | 970       | 90        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 10 / 1200 | 26.3      | 59.8      | 977       | 80        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 10 / 1800 | 26.9      | 60.5      | 980       | 75        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 11 / 0000 | 27.4      | 61.0      | 980       | 75        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 11 / 0600 | 27.8      | 61.5      | 980       | 75        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 11 / 1200 | 28.3      | 61.8      | 980       | 75        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 11 / 1800 | 28.8      | 62.1      | 976       | 80        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 12 / 0000 | 29.3      | 62.3      | 976       | 80        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 12 / 0600 | 29.5      | 62.5      | 976       | 80        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 12 / 1200 | 29.7      | 62.5      | 976       | 75        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 12 / 1800 | 29.9      | 62.5      | 983       | 65        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 13 / 0000 | 29.9      | 62.4      | 984       | 65        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 13 / 0600 | 29.8      | 62.5      | 985       | 65        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 13 / 1200 | 29.9      | 62.7      | 988       | 60        | tropical  |
|           |           |           |           |           | storm     |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 13 / 1800 | 30.1      | 62.9      | 991       | 55        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 14 / 0000 | 30.5      | 63.1      | 990       | 55        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 14 / 0600 | 31.0      | 63.5      | 990       | 55        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 14 / 1200 | 31.6      | 63.8      | 994       | 55        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 14 / 1800 | 32.5      | 64.1      | 995       | 60        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 15 / 0000 | 33.5      | 63.8      | 995       | 60        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 15 / 0600 | 34.3      | 63.5      | 995       | 60        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 15 / 1200 | 35.3      | 63.0      | 995       | 60        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 15 / 1800 | 36.2      | 62.5      | 995       | 60        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 16 / 0000 | 36.7      | 61.8      | 995       | 60        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 16 / 0600 | 36.8      | 61.3      | 995       | 60        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 16 / 1200 | 36.8      | 60.9      | 995       | 60        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 16 / 1800 | 36.3      | 60.7      | 995       | 60        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 17 / 0000 | 35.7      | 60.3      | 996       | 55        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 17 / 0600 | 34.9      | 59.7      | 997       | 50        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 17 / 1200 | 34.3      | 58.9      | 997       | 50        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 17 / 1800 | 33.9      | 57.8      | 997       | 50        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 18 / 0000 | 33.7      | 56.0      | 997       | 50        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 18 / 0600 | 34.4      | 54.4      | 995       | 55        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 18 / 1200 | 35.5      | 53.0      | 995       | 55        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 18 / 1800 | 36.9      | 51.5      | 989       | 65        | hurricane |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 19 / 0000 | 38.6      | 49.7      | 989       | 65        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 19 / 0600 | 40.4      | 48.0      | 989       | 65        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 19 / 1200 | 42.1      | 46.3      | 989       | 65        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 19 / 1800 | 43.7      | 44.3      | 989       | 65        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 20 / 0000 | 45.3      | 42.4      | 990       | 60        | tropical  |
|           |           |           |           |           | storm     |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 20 / 0600 | 47.6      | 40.0      | 985       | 60        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 20 / 1200 | 50.0      | 37.0      | 985       | 60        | extr      |
|           |           |           |           |           | atropical |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 20 / 1800 | 53.0      | 34.0      | 990       | 55        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 21 / 0000 | 55.1      | 31.0      | 990       | 50        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 21 / 0600 | 58.5      | 27.0      | 990       | 45        | \"        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 21 / 1200 |           |           |           |           | merged    |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 07 / 2100 | 20.3      | 51.9      | 952       | 110       | minimum   |
|           |           |           |           |           | pressure  |
+-----------+-----------+-----------+-----------+-----------+-----------+

Number range CHAPTERTable 2. Selected ship reports with winds of at
least 34 kt for Hurricane Bertha, 3-20 July 2008.

+-----------+-----------+-----------+-----------+-----------+-----------+
| Date/Time | Ship call | Latitude  | Longitude | Wind      | Pressure  |
| (UTC)     | sign      |           |           |           |           |
|           |           | (°N)      | (°W)      | dir/speed | (mb)      |
|           |           |           |           | (kt)      |           |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 18 / 0600 | DHZR      | 30.3      | 52.1      | 200 / 35  | 1015.1    |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 18 / 1200 | DHZR      | 29.9      | 54.2      | 210 / 36  | 1015.5    |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 19 / 1200 | SBLW      | 48.2      | 40.3      | 180 / 35  | 1014.4    |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 20 / 0600 | WDC692    | 47.8      | 40.5      | 080 / 44  | 989.5     |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 20 / 0900 | PHPO      | 47.1      | 34.8      | 180 / 37  | 1014.3    |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 20 / 1100 | WDC692    | 48.1      | 39.2      | 280 / 41  | 1000.0    |
+-----------+-----------+-----------+-----------+-----------+-----------+

Number range CHAPTERTable 3. Selected surface observations for Hurricane
Bertha, 3-20 July 2008.

+-----------------+-----+-----+-----+-------+-----+-----+-----+-----+
| Location        | M   |     | M   |       |     | St  | St  | To  |
|                 | ini |     | axi |       |     | orm | orm | tal |
|                 | mum |     | mum |       |     | su  |     |     |
|                 | Sea |     | S   |       |     | rge | t   | r   |
|                 | Le  |     | urf |       |     |     | ide | ain |
|                 | vel |     | ace |       |     | (   |     |     |
|                 | Pr  |     |     |       |     | ft) | (   | (   |
|                 | ess |     | W   |       |     | ^c^ | ft) | in) |
|                 | ure |     | ind |       |     |     | ^d^ |     |
|                 |     |     | Sp  |       |     |     |     |     |
|                 |     |     | eed |       |     |     |     |     |
+=================+=====+=====+=====+=======+=====+=====+=====+=====+
|                 | Da  | Pre | Da  | Sust  | G   |     |     |     |
|                 | te/ | ss. | te/ | ained | ust |     |     |     |
|                 |     |     |     |       |     |     |     |     |
|                 | t   | (   | t   | (k    | (   |     |     |     |
|                 | ime | mb) | ime | t)^b^ | kt) |     |     |     |
|                 |     |     |     |       |     |     |     |     |
|                 | (U  |     | (U  |       |     |     |     |     |
|                 | TC) |     | TC) |       |     |     |     |     |
|                 |     |     | ^a^ |       |     |     |     |     |
+-----------------+-----+-----+-----+-------+-----+-----+-----+-----+
| **Bermuda**     |     |     |     |       |     |     |     |     |
+-----------------+-----+-----+-----+-------+-----+-----+-----+-----+
| Bermuda Airport |     | 988 | 1   | 43    | 59  |     |     | 4   |
| (TXKF) ^e^      |     |     | 4/2 |       |     |     |     | .76 |
|                 |     |     | 011 |       |     |     |     |     |
+-----------------+-----+-----+-----+-------+-----+-----+-----+-----+
| Bermuda         |     |     | 1   | 59    | 72  |     |     |     |
| Maritime ^fg^   |     |     | 4/2 |       |     |     |     |     |
| Operations      |     |     | 035 |       |     |     |     |     |
| Centre          |     |     |     |       |     |     |     |     |
+-----------------+-----+-----+-----+-------+-----+-----+-----+-----+
| Fort Prospect   |     |     | 1   | 43    | 63  |     |     |     |
| ^eh^            |     |     | 4/2 |       |     |     |     |     |
|                 |     |     | 010 |       |     |     |     |     |
+-----------------+-----+-----+-----+-------+-----+-----+-----+-----+
| St. David's     |     |     | 1   | 42    | 67  |     |     |     |
| ^ei^            |     |     | 4/1 |       |     |     |     |     |
|                 |     |     | 910 |       |     |     |     |     |
+-----------------+-----+-----+-----+-------+-----+-----+-----+-----+
| Commisioner's   |     |     | 1   | 54    | 79  |     |     |     |
| Point ^ej^      |     |     | 4/1 |       |     |     |     |     |
|                 |     |     | 610 |       |     |     |     |     |
+-----------------+-----+-----+-----+-------+-----+-----+-----+-----+

^a^ Date/time is for sustained wind when both sustained and gust are
listed.

^b^ Except as noted, sustained wind averaging periods for C-MAN and
land-based ASOS reports are 2 min; buoy averaging periods are 8 min.

^c^ Storm surge is water height above normal astronomical tide level.

^d^ Storm tide is water height above National Geodetic Vertical Datum
(1929 mean sea level).

^e^ 10-minute average wind

^f^ 1-minute average wind speed.

^g^ Instrument height 255 ft above mean seal level.

^h^ Instrument height 230 ft above mean seal level.

^i^ Instrument height 159 ft above mean seal level.

^j^ Instrument height 262 ft above mean seal level.

Number range CHAPTERTable 4. Track forecast evaluation (heterogeneous
sample) for Hurricane Bertha, 3-20 July 2008. Forecast errors (n mi) are
followed by the number of forecasts in parentheses. Errors smaller than
the NHC official forecast are shown in boldface type.

+-----------+-------+-------+-------+-------+-------+-------+-------+
| Number    | For   |       |       |       |       |       |       |
| range     | ecast |       |       |       |       |       |       |
| CHAPTE    | P     |       |       |       |       |       |       |
| RForecast | eriod |       |       |       |       |       |       |
| Technique | (h)   |       |       |       |       |       |       |
+===========+=======+=======+=======+=======+=======+=======+=======+
|           | 12    | 24    | 36    | 48    | 72    | 96    | 120   |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| CLP5      | 42    | 99    | 168   | 229   | 280   | 286   | 341   |
|           | (67)  | (65)  | (63)  | (61)  | (57)  | (53)  | (49)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFNI      | 33    | 60    | 88    | 113   | 162   | 225   | 249   |
|           | (53)  | (51)  | (49)  | (47)  | (43)  | (34)  | (29)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFDI      | *     | *     | *     | *     | **    | 175   | 230   |
|           | *23** | *36** | *52** | *72** | 110** | (53)  | (49)  |
|           | (66)  | (65)  | (63)  | (61)  | (57)  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| HWFI      | 30    | 56    | 81    | 107   | 132   | 191   | 235   |
|           | (67)  | (65)  | (63)  | (61)  | (57)  | (53)  | (49)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFSI      | 25    | 43    | 65    | 95    | 153   | 219   | 262   |
|           | (67)  | (65)  | (63)  | (61)  | (57)  | (53)  | (49)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| AEMI      | 32    | 59    | 87    | 117   | 154   | 180   | **    |
|           | (67)  | (65)  | (63)  | (61)  | (49)  | (37)  | 180** |
|           |       |       |       |       |       |       | (30)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| NGPI      | 32    | 54    | 77    | 106   | 176   | 249   | 246   |
|           | (56)  | (54)  | (52)  | (50)  | (46)  | (42)  | (36)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| UKMI      | 29    | 55    | 87    | 127   | 208   | 289   | 366   |
|           | (58)  | (57)  | (55)  | (53)  | (49)  | (43)  | (39)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| BAMD      | 33    | 61    | 94    | 132   | 198   | 304   | 414   |
|           | (67)  | (65)  | (63)  | (61)  | (57)  | (53)  | (49)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| BAMM      | 38    | 74    | 113   | 153   | 224   | 309   | 375   |
|           | (66)  | (64)  | (62)  | (60)  | (56)  | (52)  | (48)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| BAMS      | 45    | 90    | 136   | 181   | 284   | 390   | 457   |
|           | (66)  | (64)  | (62)  | (60)  | (56)  | (52)  | (48)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| TVCN      | 24    | *     | *     | *     | **    | **    | **    |
|           | (67)  | *39** | *56** | *77** | 111** | 161** | 188** |
|           |       | (65)  | (63)  | (61)  | (57)  | (53)  | (49)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GUNA      | 24    | *     | *     | 86    | 145   | 199   | 202   |
|           | (53)  | *39** | *59** | (48)  | (43)  | (37)  | (31)  |
|           |       | (51)  | (50)  |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| FSSE      | *     | *     | *     | 87    | 133   | 179   | 222   |
|           | *23** | *39** | *60** | (60)  | (56)  | (52)  | (48)  |
|           | (66)  | (64)  | (62)  |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| OFCL      | 24    | 43    | 61    | 82    | 118   | 164   | 200   |
|           | (67)  | (65)  | (63)  | (61)  | (57)  | (53)  | (49)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| NHC       | 34.0  | 58.2  | 82.2  | 106.2 | 154.2 | 207.5 | 272.5 |
| Official  | (     | (     | (     | (     | (996) | (787) | (627) |
|           | 1742) | 1574) | 1407) | 1254) |       |       |       |
| (         |       |       |       |       |       |       |       |
| 2003-2007 |       |       |       |       |       |       |       |
| mean)     |       |       |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+

Table 5. Intensity forecast evaluation (heterogeneous sample) for
Hurricane Bertha, 3-20 July 2008. Forecast errors (kt) are followed by
the number of forecasts in parentheses. Errors smaller than the NHC
official forecast are shown in boldface type.

+-----------+-------+-------+-------+-------+-------+-------+-------+
| Number    | For   |       |       |       |       |       |       |
| range     | ecast |       |       |       |       |       |       |
| CHAPTE    | P     |       |       |       |       |       |       |
| RForecast | eriod |       |       |       |       |       |       |
| Technique | (h)   |       |       |       |       |       |       |
+===========+=======+=======+=======+=======+=======+=======+=======+
|           | 12    | 24    | 36    | 48    | 72    | 96    | 120   |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| SHF5      | 6.7   | 11.3  | 12.5  | 12.0  | 11.4  | 9.9   | 10.7  |
|           | (67)  | (65)  | (63)  | (61)  | (57)  | (53)  | (49)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GHMI      | 7.0   | **    | **    | **1   | 14.5  | 13.1  | 10.7  |
|           | (66)  | 9.5** | 9.6** | 0.5** | (57)  | (53)  | (49)  |
|           |       | (65)  | (63)  | (61)  |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| HWFI      | 7.4   | 11.3  | 12.4  | 12.9  | 17.0  | 17.2  | 18.6  |
|           | (67)  | (65)  | (63)  | (61)  | (57)  | (53)  | (49)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| SHIP      | **    | **1   | 11.9  | 12.1  | 13.4  | 12.4  | 11.9  |
|           | 6.0** | 0.1** | (62)  | (60)  | (56)  | (52)  | (48)  |
|           | (66)  | (64)  |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| DSHP      | **    | **1   | 11.9  | 12.1  | 13.4  | 12.4  | 11.9  |
|           | 6.0** | 0.1** | (62)  | (60)  | (56)  | (52)  | (48)  |
|           | (66)  | (64)  |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| FSSE      | **    | **    | **1   | 10.8  | 12.9  | **1   | **    |
|           | 6.0** | 9.9** | 1.1** | (60)  | (56)  | 0.2** | 9.4** |
|           | (66)  | (64)  | (62)  |       |       | (52)  | (48)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| ICON      | **    | **    | **1   | **    | 12.0  | **    | **    |
|           | 6.2** | 9.3** | 0.2** | 9.4** | (56)  | 9.4** | 7.7** |
|           | (65)  | (64)  | (62)  | (60)  |       | (52)  | (48)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| OFCL      | 6.4   | 10.7  | 11.5  | 10.7  | 11.2  | 10.9  | 10.3  |
|           | (67)  | (65)  | (63)  | (61)  | (57)  | (53)  | (49)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| NHC       | 6.7   | 10.0  | 12.3  | 14.3  | 18.2  | 19.7  | 21.8  |
| Official  | (     | (     | (     | (     | (996) | (787) | (627) |
|           | 1742) | 1574) | 1407) | 1254) |       |       |       |
| (         |       |       |       |       |       |       |       |
| 2003-2007 |       |       |       |       |       |       |       |
| mean)     |       |       |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+

Number range CHAPTERTable 6. Watch and warning summary for Hurricane
Bertha, 3-20 July 2008.

  ----------- -------- ----------------------------- ---------- ------------------------------
  Date/Time   Action                                 Location   
  (UTC)                                                         

  12/1500              Tropical Storm Warning issued            Bermuda

  14/1900              Hurricane Watch issued                   Bermuda

  15/0300              Hurricane Watch Discontinued             Bermuda

  15/0600              Tropical Storm Warning                   Bermuda
                       Discontinued                             
  ----------- -------- ----------------------------- ---------- ------------------------------

![](media/image1.png){width="7.122916666666667in"
height="5.310416666666667in"}

Number range CHAPTERFigure 1. Series of 85 GHz color composite images
from the NASA Tropical Rainfall Measuring Mission satellite showing the
evolution of Bertha's eyewall replacement between 9-12 July. From bottom
to top, microwave passes correspond to the following times: 1646 UTC 9
July, 1728 UTC 10 July, and 2031 UTC 12 July. The solid green line
represents the advisory positions that do not precisely correspond to
the final NHC best track.

![](media/image2.jpeg){width="7.831944444444445in"
height="6.043055555555555in"}

Number range CHAPTERFigure 2. Best track positions for Hurricane Bertha,
3-20 July 2008. Track during the extratropical stage is based on
analyses from the NOAA Ocean Prediction Center.

Number range CHAPTER![](media/image3.png){width="7.625in"
height="5.298611111111111in"}

Figure 3. Selected wind observations and best track maximum sustained
surface wind speed curve for Hurricane Bertha, 3-20 July 2008. Aircraft
observations have been adjusted for elevation using 90%, 80%, and 80%
reduction factors for observations from 700 mb, 850 mb, and 1500 ft,
respectively. Objective Dvorak estimates represent linear averages over
a three-hour period centered on the nominal observation time. Estimates
during the extratropical stage are based on analyses from the NOAA Ocean
Prediction Center.

![](media/image4.png){width="7.879861111111111in"
height="5.479166666666667in"}

Number range CHAPTERFigure 4. Selected pressure observations and best
track minimum central pressure curve for Hurricane Bertha, 3-20 July
2008. Objective Dvorak estimates represent linear averages over a
three-hour period centered on the nominal observation time. Estimates
during the extratropical stage are based on analyses from the NOAA Ocean
Prediction Center. Dashed vertical lines correspond to 0000 UTC.

Number range CHAPTER

[^1]: A digital record of the complete best track, including wind radii,
    can be found on line at <ftp://ftp.nhc.noaa.gov/atcf>. Data for the
    current year's storms are located in the *btk* directory, while
    previous year's data are located in the *archive* directory.