Number range CHAPTERTropical Cyclone Report

Hurricane Norbert

(EP152008)

4-12 October 2008

James L. Franklin

National Hurricane Center

7 January 2009

Norbert, the strongest October eastern North Pacific hurricane since
Kenna in 2002, attained category four strength on the Saffir-Simpson
Hurricane Scale before weakening and striking the west coast of the Baja
California peninsula as a category two hurricane. It later struck
mainland Mexico as a category one hurricane.

a.  Synoptic History

    Norbert originated out of a large and slow-moving area of low
    pressure that developed south of the Gulf of Tehuantepec on 28
    September. The initial surface low appears to have been associated
    with a tropical wave that crossed Central America on 26-27
    September, with a second tropical wave reaching the area on 2
    October. The following day convection associated with the low became
    more concentrated and persistent, and it is estimated that a
    tropical depression formed around 0000 UTC 4 October, centered about
    210 n mi south-southeast of Acapulco, Mexico.

    The "best track" chart of the tropical cyclone's path is given in
    Fig. 1, with the wind and pressure histories shown in Figs. 2 and 3,
    respectively. The best track positions and intensities are listed in
    Table 1[^1]. Initially nearly stationary, the depression soon began
    to move slowly westward to the south of a building mid-level high
    pressure ridge. Easterly vertical wind shear limited development,
    and the depression took 24 h to reach tropical storm strength,
    around 0000 UTC 5 October, when the system was centered about 170 n
    mi south-southwest of Acapulco. The easterly shear abated somewhat
    over the next couple of days, but Norbert continued to intensify
    only slowly, becoming a hurricane around 0600 UTC 7 October while
    centered about 270 n mi south-southwest of Manzanillo, Mexico.

    Now moving west-northwestward around the periphery of the
    subtropical ridge, the hurricane began a period of rapid
    strengthening on 7 October. By midday, microwave imagery revealed a
    partially closed banding eyewall, and the cirrus outflow became
    better defined. Norbert intensified by 40 kt over the ensuing 24 h
    and reached its peak intensity of 115 kt (category four strength)
    near 1800 UTC 8 October. At this time the center was about 390 n mi
    south of Cabo San Lucas, Mexico.

    Norbert was still over warm waters and embedded within light
    vertical shear, however structural changes within the hurricane
    appear to have prevented additional strengthening. Microwave imagery
    around the time of peak intensity showed the eyewall of Norbert was
    surrounded by several well-defined spiral bands. By 0900 9 October,
    additional microwave passes indicated that the eyewall had eroded
    significantly, with more-circular (albeit not quite concentric)
    outer banding, while infrared imagery indicated that the core deep
    convection had weakened, suggesting the onset of an eyewall
    replacement cycle. By the time a reconnaissance aircraft arrived at
    the center of Norbert near 1800 UTC, the hurricane had weakened to
    category one strength, with maximum winds of near 70 kt.

    On 10 October Norbert turned northward and its forward motion slowed
    when it reached the westward extent of the subtropical ridge. Wind
    shear was still light, and Norbert began to re-strengthen as it
    completed its eyewall replacement cycle. Norbert turned to the
    north-northeast ahead of a mid- to upper-level trough dropping
    southward over the southwestern United States, the hurricane's
    maximum winds reaching 100 kt near 0600 UTC 11 October. At this
    point the center of Norbert was about 160 n mi west of Cabo San
    Lucas. Turning northeastward and accelerating, Norbert weakened
    slightly as it approached Baja California, making landfall on the
    peninsula near Puerto Chale in the state of Baja California Sur,
    just southeast of Bahia Magdalena, around 1630 UTC 11 October. At
    the time of landfall, Norbert's maximum winds are estimated to have
    been near 90 kt (category two strength), making Norbert the
    strongest hurricane on record to strike the western Baja California
    coast.

    Norbert crossed the peninsula and its center emerged into the Gulf
    of California around 2100 UTC. Strong vertical wind shear and
    Norbert's passage over land caused the hurricane to continue to
    weaken. Norbert reached the coast of mainland Mexico about 20 n mi
    east-southeast of Huatabampo in the state of Sonora near 0400 UTC 12
    October, as a category one hurricane with estimated peak winds of 75
    kt. The landfall location is also about 50 n mi north-northeast of
    Los Mochis. Norbert then continued moving northeastward and rapidly
    weakened, becoming a tropical storm within a few hours of making
    landfall and becoming a tropical depression by 1200 UTC that day. By
    1800 UTC, the circulation had dissipated over the mountains of
    northeastern Mexico.

b.  Meteorological Statistics

    Observations in Norbert (Figs. 2 and 3) 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 two 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 Norbert.

    The estimated peak intensity of Norbert at 1800 UTC 8 October was
    based on subjective Dvorak classifications from TAFB and SAB. When
    the first reconnaissance aircraft reached Norbert 24 h later, they
    found a much weaker system than that suggested by the concurrent
    satellite classifications (see Figure 2). This raises the
    possibility that the satellite-based intensity estimates may have
    been high at other times during Norbert's life cycle, in particular
    when Norbert is assessed to have reached category four strength, and
    when it reacquired category three status. Given the structural
    changes that were occurring during the period of the aircraft
    observations, however, it is assumed that the satellite/aircraft
    disconnect was mostly confined to the period when Norbert's inner
    eyewall was eroding.

    There were no believable ship reports of winds of tropical storm
    force associated with Norbert, and land-based observations from the
    affected areas are extremely limited. Sustained winds of 50 kt, with
    gusts to 60 kt, were reported at the airport at Los Mochis (MMLM)
    around 0200 UTC 12 October. The maximum 24 h reported rainfall was
    4.78 in (121.3 mm) at Ciudad Constitucion on the Baja California
    peninsula.

c.  Casualty and Damage Statistics

    Information from meteorological and civil defense officials in
    Mexico indicates there were five deaths directly associated with
    Norbert in Alamos, Sonora. These deaths, two women and three men,
    were associated with river floodwaters.

    Media reports indicate that nearly half of the homes were totally or
    partially damaged, mostly from roof damage, on the islands of
    Margarita and Magdalena, near the first landfall site, with
    electricity reportedly cut off to roughly 20,000 homes in Baja
    California. Rushing, knee-deep water was reported in the town of
    Ciudad Constitucion. Unspecified surge flooding was reported in the
    fishing town of Puerto San Carlos.

d.  Forecast and Warning Critique

    The genesis of Norbert was reasonably well anticipated. The
    disturbance from which Norbert developed was introduced in the
    Tropical Weather Outlook (TWO) five days prior to genesis.
    Experimental 48-h genesis probabilities first reached the "high"
    category (greater than 50% chance of genesis within 48 h) a little
    early - about 60 h prior to genesis.

    Official track forecasts for Norbert were outstanding. A
    verification of official and guidance model track forecasts is given
    in Table 2. Average official track errors for Norbert (with the
    number of cases in parentheses) were 24 (33), 33 (31), 40 (29), 50
    (27), 80 (23), 94 (19), and 130 (15) n mi for the 12, 24, 36, 48,
    72, 96, and 120 h forecasts, respectively. These errors are
    substantially lower than the average 5-yr official track errors
    (Table 2). Although no individual dynamical model performed
    particularly well with Norbert, the consensus models (e.g., TVCN)
    performed exceptionally. The GFS performed unusually poorly; early
    on it over-developed a disturbance to the east of Norbert and
    consequently forecast an interaction between the two systems that
    did not occur. The GFS was also one of the last models to forecast
    Norbert's capture by the upper-level trough over the southeastern
    United States.

    A verification of official and guidance model intensity forecasts is
    given in Table 3. Average official intensity errors were 10, 16, 17,
    17, 16, 21, and 22 kt for the 12, 24, 36, 48, 72, 96, and 120 h
    forecasts, respectively. For comparison, the average 5-yr official
    intensity errors are 6, 10, 14, 16, 19, 19, and 19 kt, respectively.
    That the official errors were somewhat above the 5-yr means can be
    attributed to the large swings in intensity that occurred during the
    last half of Norbert's life cycle -- changes that are generally not
    captured by official forecasts (e.g., Fig. 4). The objective
    intensity guidance for Norbert had similar difficulties. The
    significant strengthening of Norbert on 7-8 October was indicated at
    times by the SHIPS rapid intensification (RI) index, although the
    index was inconsistent.

Watches and warnings issued by the government of Mexico in association
with Norbert are given in Table 4.

Number range CHAPTERTable 1. Best track for Hurricane Norbert, 4-12
October 2008.

+--------+---------+---------+---------+---------+--------------------+
| Dat    | L       | Lo      | P       | Wind    | Stage              |
| e/Time | atitude | ngitude | ressure | Speed   |                    |
|        |         |         |         |         |                    |
| (UTC)  | (°N)    | (°W)    | (mb)    | (kt)    |                    |
+--------+---------+---------+---------+---------+--------------------+
| 04 /   | 13.5    | 99.1    | 1006    | 30      | tropical           |
| 0000   |         |         |         |         | depression         |
+--------+---------+---------+---------+---------+--------------------+
| 04 /   | 13.8    | 99.0    | 1006    | 30      | \"                 |
| 0600   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 04 /   | 14.0    | 99.5    | 1006    | 30      | \"                 |
| 1200   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 04 /   | 14.1    | 100.1   | 1006    | 30      | \"                 |
| 1800   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 05 /   | 14.1    | 100.6   | 1005    | 35      | tropical storm     |
| 0000   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 05 /   | 14.0    | 101.1   | 1003    | 40      | \"                 |
| 0600   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 05 /   | 13.9    | 101.7   | 1000    | 50      | \"                 |
| 1200   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 05 /   | 13.9    | 102.4   | 1000    | 50      | \"                 |
| 1800   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 06 /   | 13.9    | 103.0   | 1000    | 50      | \"                 |
| 0000   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 06 /   | 14.0    | 103.6   | 996     | 55      | \"                 |
| 0600   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 06 /   | 14.2    | 104.3   | 993     | 55      | \"                 |
| 1200   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 06 /   | 14.4    | 104.9   | 990     | 60      | \"                 |
| 1800   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 07 /   | 14.6    | 105.4   | 988     | 60      | \"                 |
| 0000   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 07 /   | 14.9    | 106.0   | 987     | 65      | hurricane          |
| 0600   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 07 /   | 15.0    | 106.8   | 985     | 70      | \"                 |
| 1200   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 07 /   | 15.2    | 107.7   | 980     | 75      | \"                 |
| 1800   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 08 /   | 15.5    | 108.6   | 970     | 90      | \"                 |
| 0000   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 08 /   | 15.8    | 109.5   | 960     | 100     | \"                 |
| 0600   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 08 /   | 16.1    | 110.2   | 952     | 110     | \"                 |
| 1200   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 08 /   | 16.4    | 110.9   | 945     | 115     | \"                 |
| 1800   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 09 /   | 16.8    | 111.6   | 948     | 110     | \"                 |
| 0000   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 09 /   | 17.2    | 112.1   | 954     | 100     | \"                 |
| 0600   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 09 /   | 17.6    | 112.5   | 960     | 85      | \"                 |
| 1200   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 09 /   | 18.0    | 112.8   | 973     | 70      | \"                 |
| 1800   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 10 /   | 18.6    | 113.1   | 973     | 70      | \"                 |
| 0000   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 10 /   | 19.3    | 113.3   | 973     | 70      | \"                 |
| 0600   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 10 /   | 20.0    | 113.5   | 970     | 75      | \"                 |
| 1200   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 10 /   | 20.9    | 113.5   | 968     | 80      | \"                 |
| 1800   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 11 /   | 21.8    | 113.2   | 960     | 90      | \"                 |
| 0000   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 11 /   | 22.8    | 112.8   | 953     | 100     | \"                 |
| 0600   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 11 /   | 23.7    | 112.3   | 954     | 95      | \"                 |
| 1200   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 11 /   | 24.6    | 111.4   | 957     | 90      | \"                 |
| 1800   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 12 /   | 25.8    | 110.2   | 961     | 80      | \"                 |
| 0000   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 12 /   | 27.0    | 108.7   | 975     | 65      | \"                 |
| 0600   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 12 /   | 27.2    | 108.4   | 978     | 60      | tropical storm     |
| 0700   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 12 /   | 28.3    | 107.0   | 995     | 30      | tropical           |
| 1200   |         |         |         |         | depression         |
+--------+---------+---------+---------+---------+--------------------+
| 12 /   |         |         |         |         | dissipated         |
| 1800   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+
| 11 /   | 24.4    | 111.6   | 956     | 90      | Landfall near      |
| 1630   |         |         |         |         | Puerto Chale,      |
|        |         |         |         |         | Mexico             |
+--------+---------+---------+---------+---------+--------------------+
| 12 /   | 26.6    | 109.3   | 964     | 75      | Landfall 20 n mi   |
| 0400   |         |         |         |         | ESE of Huatabampo, |
|        |         |         |         |         | Mexico             |
+--------+---------+---------+---------+---------+--------------------+
| 08 /   | 16.4    | 110.9   | 945     | 115     | minimum pressure   |
| 1800   |         |         |         |         |                    |
+--------+---------+---------+---------+---------+--------------------+

Number range CHAPTER

Number range CHAPTERTable 2. Track forecast evaluation (heterogeneous
sample) of selected models for Hurricane Norbert, 4-12 October 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      | 39    | 75    | 122   | 165   | 239   | 306   | 350   |
|           | (33)  | (31)  | (29)  | (27)  | (23)  | (19)  | (15)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFNI      | 34    | 57    | 75    | 90    | 124   | 157   | 212   |
|           | (30)  | (28)  | (26)  | (24)  | (19)  | (14)  | (10)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFDI      | 28    | 46    | 53    | 65    | 127   | 206   | 212   |
|           | (33)  | (31)  | (29)  | (27)  | (23)  | (19)  | (15)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| HWFI      | 39    | 62    | 82    | 104   | 168   | 288   | 439   |
|           | (33)  | (31)  | (29)  | (27)  | (22)  | (17)  | (13)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFSI      | 35    | 48    | 65    | 92    | 165   | 297   | 458   |
|           | (33)  | (31)  | (29)  | (27)  | (23)  | (19)  | (13)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| AEMI      | 35    | 59    | 86    | 118   | 180   | 254   | 317   |
|           | (33)  | (31)  | (29)  | (27)  | (23)  | (19)  | (15)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| NGPI      | 27    | 46    | 52    | 57    | 116   | 227   | 244   |
|           | (30)  | (29)  | (27)  | (25)  | (21)  | (17)  | (13)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| UKMI      | 34    | 49    | 66    | 78    | 126   | 185   | 217   |
|           | (32)  | (30)  | (28)  | (26)  | (22)  | (18)  | (14)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| EGRI      | 30    | 43    | 57    | 68    | 110   | 158   | 201   |
|           | (30)  | (28)  | (26)  | (24)  | (20)  | (16)  | (12)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| EMXI      | 26    | 43    | 60    | 73    | 112   | 172   | 224   |
|           | (23)  | (21)  | (21)  | (20)  | (17)  | (15)  | (13)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| BAMD      | 45    | 81    | 110   | 116   | 130   | 168   | 305   |
|           | (33)  | (31)  | (29)  | (27)  | (23)  | (19)  | (15)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| BAMM      | 33    | 50    | 74    | 101   | 164   | 255   | 408   |
|           | (33)  | (31)  | (29)  | (27)  | (23)  | (19)  | (15)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| BAMS      | 40    | 67    | 98    | 122   | 193   | 312   | 462   |
|           | (31)  | (29)  | (27)  | (25)  | (21)  | (18)  | (14)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| LBAR      | 37    | 87    | 137   | 181   | 342   | 634   | 987   |
|           | (32)  | (30)  | (28)  | (26)  | (22)  | (19)  | (14)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| TVCN      | 24    | **32  | **34  | **41  | **59  | 100   | **128 |
|           | (33)  | (     | (     | (     | (     | (19)  | (     |
|           |       | 31)** | 29)** | 27)** | 23)** |       | 15)** |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GUNA      | **21  | **27  | **33  | **43  | **66  | **87  | **99  |
|           | (     | (     | (     | (     | (     | (     | (     |
|           | 29)** | 28)** | 26)** | 24)** | 20)** | 16)** | 10)** |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| FSSE      | **21  | **30  | **33  | **42  | **63  | **73  | **114 |
|           | (     | (     | (     | (     | (     | (     | (     |
|           | 29)** | 27)** | 25)** | 23)** | 19)** | 15)** | 11)** |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| OFCL      | 24    | 33    | 40    | 50    | 80    | 94    | 130   |
|           | (33)  | (31)  | (29)  | (27)  | (23)  | (19)  | (15)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| NHC       | 31.9  | 55.1  | 77.4  | 97.9  | 136.2 | 180.1 | 226.1 |
| Official  | (     | (     | (979) | (849) | (620) | (439) | (293) |
|           | 1282) | 1129) |       |       |       |       |       |
| (         |       |       |       |       |       |       |       |
| 2003-2007 |       |       |       |       |       |       |       |
| mean)     |       |       |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+

Table 3. Intensity forecast evaluation (heterogeneous sample) of
selected models for Hurricane Norbert, 4-12 October 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   |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| OCD5      | 10.1  | *     | 19.0  | 19.4  | 20.4  | 31.2  | 33.9  |
|           | (33)  | *15.4 | (29)  | (27)  | (23)  | (19)  | (15)  |
|           |       | (     |       |       |       |       |       |
|           |       | 31)** |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GHMI      | 9.6   | *     | *     | *     | 20.5  | 31.8  | 32.5  |
|           | (33)  | *13.7 | *15.1 | *16.0 | (23)  | (19)  | (15)  |
|           |       | (     | (     | (     |       |       |       |
|           |       | 31)** | 29)** | 27)** |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| HWFI      | 11.9  | 17.2  | 21.0  | 21.1  | 19.3  | *     | 27.5  |
|           | (33)  | (31)  | (29)  | (27)  | (22)  | *16.4 | (13)  |
|           |       |       |       |       |       | (     |       |
|           |       |       |       |       |       | 17)** |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| LGEM      | **8.8 | *     | 20.4  | 20.7  | 22.7  | 30.1  | 33.1  |
|           | (     | *15.5 | (29)  | (27)  | (23)  | (19)  | (15)  |
|           | 33)** | (     |       |       |       |       |       |
|           |       | 31)** |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| DSHP      | **9.1 | 16.3  | 19.6  | 19.7  | 18.8  | 26.5  | 26.9  |
|           | (     | (31)  | (29)  | (27)  | (23)  | (19)  | (15)  |
|           | 33)** |       |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| FSSE      | 10.3  | 16.4  | 19.2  | 18.2  | 19.3  | *     | 25.5  |
|           | (29)  | (27)  | (25)  | (23)  | (19)  | *19.9 | (11)  |
|           |       |       |       |       |       | (     |       |
|           |       |       |       |       |       | 15)** |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| ICON      | **8.2 | *     | 17.5  | 17.6  | 16.5  | *     | 25.7  |
|           | (     | *14.2 | (29)  | (27)  | (22)  | *20.3 | (13)  |
|           | 33)** | (     |       |       |       | (     |       |
|           |       | 31)** |       |       |       | 17)** |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| OFCL      | 9.5   | 16.0  | 17.2  | 16.5  | 16.3  | 20.5  | 22.3  |
|           | (33)  | (31)  | (29)  | (27)  | (23)  | (19)  | (15)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| NHC       | 6.2   | 10.4  | 13.9  | 16.3  | 18.7  | 19.2  | 19.1  |
| Official  | (     | (     | (979) | (848) | (620) | (439) | (293) |
|           | 1282) | 1129) |       |       |       |       |       |
| (         |       |       |       |       |       |       |       |
| 2003-2007 |       |       |       |       |       |       |       |
| mean)     |       |       |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+

Number range CHAPTERTable 4. Watch and warning summary for Hurricane
Norbert, 4-12 October 2008.

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

  10 / 0300    Hurricane Watch issued         Puerto San Andresito to
                                              Loreto

  10 / 0600    Hurricane Watch modified to    Loreto to Agua Blanca

  10 / 0600    Hurricane Warning issued       Puerto San Andresito to Agua
                                              Blanca

  10 / 1500    Tropical Storm Watch issued    Topolobampo to Guaymas

  10 / 1500    Tropical Storm Warning issued  Agua Blanca to Mulege

  10 / 2100    Tropical Storm Watch changed   Topolobampo to Guaymas
               to Tropical Storm Warning      

  10 / 2100    Tropical Storm Watch changed   Topolobampo to Guaymas
               to Hurricane Watch             

  11 / 0300    Tropical Storm Warning changed Topolobampo to Guaymas
               to Hurricane Warning           

  11 / 0300    Tropical Storm Warning         La Paz to Agua Blanca
               modified to                    

  11 / 0300    Hurricane Watch discontinued   Topolobampo to Guaymas

  11 / 0300    Hurricane Watch modified to    La Paz to Agua Blanca

  11 / 0300    Hurricane Warning issued       La Paz to Loreto

  11 / 2100    Tropical Storm Warning issued  Topolobampo to Altata

  12 / 0300    Tropical Storm Warning         La Paz to Agua Blanca
               discontinued                   

  12 / 0300    Tropical Storm Warning         Loreto to Mulege
               discontinued                   

  12 / 0300    Hurricane Watch discontinued   All

  12 / 0300    Hurricane Warning discontinued Puerto San Andresito to Agua
                                              Blanca

  12 / 0300    Hurricane Warning discontinued La Paz to Loreto

  12 / 0900    Tropical Storm Warning         All
               discontinued                   

  12 / 0900    Hurricane Warning discontinued All
  ------------ ------------------------------ ----------------------------

![](media/image1.jpeg){width="7.74375in" height="5.983333333333333in"}

Number range CHAPTERFigure 1. Best track positions for Hurricane
Norbert, 4-12 October 2008.

![](media/image2.png){width="7.495833333333334in"
height="5.098611111111111in"}

Number range CHAPTERFigure 2. Selected wind observations and best track
maximum sustained surface wind speed curve for Hurricane Norbert, 4-12
October 2008. Aircraft observations have been adjusted for elevation
using 90%, 80%, and 80% adjustment factors for observations from 700 mb,
850 mb, and 1500 ft, respectively. Dropwindsonde observations include
actual 10 m winds (sfc), as well as surface estimates derived from the
mean wind over the lowest 150 m of the wind sounding (LLM), and from the
sounding boundary layer mean (MBL). Objective (ADT) Dvorak estimates
represent linear averages over a three-hour period centered on the
nominal observation time. Dashed vertical lines correspond to 0000 UTC,
and solid vertical lines indicate landfalls.

![](media/image3.png){width="7.495833333333334in"
height="5.122916666666667in"}

Number range CHAPTERFigure 3. Selected pressure observations and best
track minimum central pressure curve for Hurricane Norbert, 4-12 October
2008. Objective (ADT) Dvorak estimates represent linear averages over a
three-hour period centered on the nominal observation time. Dashed
vertical lines correspond to 0000 UTC, and solid vertical lines indicate
landfalls.

![](media/image4.png){width="7.75in" height="5.409027777777778in"}Number
range CHAPTER

Number range CHAPTERFigure 4. Selected official intensity forecasts for
Hurricane Norbert, 4-12 October 2008. The best track intensity is given
by the thick solid line.

[^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 years' data are located in the *archive* directory.