Number range CHAPTERTropical Cyclone Report

Hurricane Ivo

(EP122007)

18-23 September 2007

James L. Franklin

National Hurricane Center

3 December 2007

Ivo was a category 1 hurricane (on the Saffir-Simpson Hurricane Scale)
that dissipated as it approached southern Baja California.

a.  Synoptic History

    Ivo developed from a tropical wave that moved across the west coast
    of Africa on 1 September. The wave was associated with little
    convection during its passage across the Atlantic basin until it
    reached the western Caribbean Sea. The wave crossed Central America
    and entered the eastern North Pacific basin on 15 September, when
    the wave began to show signs of increased organization. A broad area
    of low pressure formed within the wave the next day and Dvorak
    classifications were initiated. The organization of the system
    gradually increased as the low moved westward, and a tropical
    depression formed around 0600 UTC 18 September, about 400 n mi
    south-southwest of Manzanillo, 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. The depression initially moved west-northwestward to the
    south of a mid-level ridge that extended westward from northern
    Mexico. Under light northwesterly shear, the cyclone strengthened,
    becoming a tropical storm by 0000 UTC 19 September, about 525 n mi
    south of the southern tip of Baja California. Ivo continued to
    strengthen and became a hurricane at 0000 UTC 20 September, about
    450 n mi south-southwest of the southern tip of Baja California. As
    a large deep-layer low moved southward into California, the western
    periphery of the subtropical ridge eroded, and Ivo turned
    northwestward on 20 September. During the day microwave imagery
    showed a well-defined eye, although the eye was only intermittently
    visible in conventional satellite imagery; Ivo reached its estimated
    peak intensity of 70 kt around 1800 UTC that day.

    Early on 21 September, westerly flow associated with the large upper
    low began to undercut the outflow of Ivo, and the cyclone began to
    weaken. As Ivo turned northward around the periphery of the
    subtropical ridge, the cloud pattern began to deteriorate, and Ivo
    weakened to a tropical storm around 1800 UTC that day about 275 n mi
    southwest of the southern tip of Baja California. Ivo turned to the
    north-northeast on 22 September, and even though it remained over
    warm waters, continued to weaken in increasing westerly shear as it
    approached Baja California. The cyclone weakened to a depression
    near 0000 UTC 23 September about 130 n mi west-southwest of the
    southern tip of Baja California. Deep convection associated with the
    cyclone diminished, and Ivo degenerated into a remnant low later
    that day about 80 n mi southwest of the southern tip of Baja
    California. The remnant low moved slowly eastward and dissipated
    early on 25 September.

b.  Meteorological Statistics

    Observations in Ivo (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). 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 Ivo.

    There were no ship or land-based observations of tropical storm
    force winds reported in association with Ivo. The estimated maximum
    intensity of 70 kt was based on a blend of subjective Dvorak
    estimates of 77 kt and objective (ADT) estimates of around 65 kt
    from the University of Wisconsin/Cooperative Institute for
    Meteorological Satellite Studies.

c.  Casualty and Damage Statistics

    There were no reports of damage or casualties associated with Ivo.

d.  Forecast and Warning Critique

    The genesis of Ivo was well anticipated in Tropical Weather Outlook
    (TWO) products. The possibility of cyclogenesis was first mentioned
    in the TWO issued at 2300 UTC 16 September, about 31 hours prior to
    genesis.

    A verification of official and guidance model track forecasts is
    given in Table 2. Average official track errors for Ivo were 18, 26,
    38, 48, 52, 97, and 103 n mi for the 12, 24, 36, 48, 72, 96, and 120
    h forecasts, respectively. The number of forecasts ranged from 19 at
    12 h to 1 at 120 h. These errors are less than half as large as the
    average long-term official track errors (Table 2). The official
    forecasts beat nearly all of the available objective track guidance.

    A verification of official and guidance model intensity forecasts is
    given in Table 3. Average official intensity errors were 7, 13, 16,
    20, 22, 20, and 5 kt for the 12, 24, 36, 48, 72, 96, and 120 h
    forecasts, respectively. For comparison, the average long-term
    official intensity errors are 6, 11, 15, 17, 19, 19, and 19 kt,
    respectively. The official forecasts had a substantial positive
    bias, were a little worse than the long-term means, and in general
    were not quite as good as the guidance. The statistical SHIPS model
    outperformed the dynamical GFDL and HWRF models.

A tropical storm watch was briefly in effect as Ivo approached the Baja
California peninsula (Table 4).

Number range CHAPTERTable 1. Best track for Hurricane Ivo, 18-23
September 2007.

+---------+---------+---------+---------+---------+-----------------+
| Da      | L       | Lo      | P       | Wind    | Stage           |
| te/Time | atitude | ngitude | ressure | Speed   |                 |
|         |         |         |         |         |                 |
| (UTC)   | (°N)    | (°W)    | (mb)    | (kt)    |                 |
+---------+---------+---------+---------+---------+-----------------+
| 18 /    | 12.7    | 106.3   | 1007    | 25      | tropical        |
| 0600    |         |         |         |         | depression      |
+---------+---------+---------+---------+---------+-----------------+
| 18 /    | 13.2    | 107.1   | 1006    | 25      | \"              |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 18 /    | 13.7    | 107.9   | 1005    | 30      | \"              |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 19 /    | 14.2    | 108.8   | 1002    | 40      | tropical storm  |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 19 /    | 14.6    | 109.7   | 997     | 50      | \"              |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 19 /    | 15.0    | 110.7   | 994     | 55      | \"              |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 19 /    | 15.3    | 111.6   | 991     | 60      | \"              |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 20 /    | 15.7    | 112.1   | 987     | 65      | hurricane       |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 20 /    | 16.2    | 112.5   | 987     | 65      | \"              |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 20 /    | 16.8    | 112.8   | 986     | 65      | \"              |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 20 /    | 17.5    | 113.1   | 985     | 70      | \"              |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 21 /    | 18.2    | 113.4   | 984     | 70      | \"              |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 21 /    | 18.8    | 113.6   | 984     | 70      | \"              |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 21 /    | 19.3    | 113.6   | 987     | 65      | \"              |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 21 /    | 19.8    | 113.5   | 990     | 60      | tropical storm  |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 22 /    | 20.3    | 113.3   | 994     | 55      | \"              |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 22 /    | 20.7    | 113.1   | 997     | 50      | \"              |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 22 /    | 21.2    | 112.8   | 999     | 45      | \"              |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 22 /    | 21.6    | 112.5   | 1002    | 35      | \"              |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 23 /    | 21.9    | 112.1   | 1004    | 30      | tropical        |
| 0000    |         |         |         |         | depression      |
+---------+---------+---------+---------+---------+-----------------+
| 23 /    | 22.0    | 111.8   | 1006    | 25      | \"              |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 23 /    | 22.0    | 111.5   | 1007    | 25      | \"              |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 23 /    | 22.0    | 111.1   | 1007    | 25      | low             |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 24 /    | 22.0    | 110.7   | 1007    | 25      | \"              |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 24 /    | 22.0    | 110.4   | 1008    | 20      | \"              |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 24 /    | 22.0    | 110.1   | 1009    | 15      | \"              |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 24 /    | 21.9    | 109.9   | 1009    | 15      | \"              |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 25 /    | 21.8    | 109.6   | 1010    | 15      | \"              |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 25 /    |         |         |         |         | dissipated      |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 21 /    | 18.2    | 113.4   | 984     | 70      | minimum         |
| 0000    |         |         |         |         | pressure        |
+---------+---------+---------+---------+---------+-----------------+

Number range CHAPTERNumber range CHAPTERNumber range CHAPTERTable 2.
Preliminary track forecast evaluation (heterogeneous sample) for
Hurricane Ivo, 18-23 September 2007. 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.

+-----------+-------+-------+-------+-------+-------+-------+-------+
| Number    | For   |       |       |       |       |       |       |
| range     | ecast |       |       |       |       |       |       |
| CHAPTE    | P     |       |       |       |       |       |       |
| RForecast | eriod |       |       |       |       |       |       |
| Technique | (h)   |       |       |       |       |       |       |
+===========+=======+=======+=======+=======+=======+=======+=======+
|           | 12    | 24    | 36    | 48    | 72    | 96    | 120   |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| CLP5      | 28    | 59    | 105   | 165   | 309 ( | 430 ( | 457 ( |
|           | (19)  | (17)  | (15)  | (13)  | 9)    | 5)    | 1)    |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFNI      | 35    | 68    | 93    | 111   | 167 ( | 255 ( |       |
|           | (17)  | (15)  | (13)  | (11)  | 7)    | 3)    |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFDI      | 22    | 29    | 44    | 68    | 95 (  | 186 ( | 176 ( |
|           | (19)  | (17)  | (15)  | (13)  | 9)    | 5)    | 1)    |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| HWFI      | 24    | 38    | 52    | 69    | 91 (  | 102 ( | 122 ( |
|           | (19)  | (17)  | (15)  | (13)  | 9)    | 5)    | 1)    |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFSI      | 32    | 65    | 103   | 153   | 248 ( |       |       |
|           | (19)  | (17)  | (15)  | (13)  | 7)    |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| AEMI      | 31    | 59    | 90    | 136   | 175 ( |       |       |
|           | (19)  | (17)  | (15)  | (13)  | 3)    |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| NGPI      | 26    | 46    | 69    | 93    | 130 ( | 233 ( | 474 ( |
|           | (19)  | (17)  | (15)  | (13)  | 9)    | 5)    | 1)    |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| UKMI      | 29    | 49    | 75    | 118   | 144 ( | 130 ( |       |
|           | (16)  | (14)  | (12)  | (10)  | 6)    | 2)    |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| BAMD      | 34    | 62    | 90    | 118   | 120 ( | 113 ( | 104 ( |
|           | (19)  | (17)  | (15)  | (13)  | 9)    | 5)    | 1)    |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| BAMM      | 35    | 63    | 99    | 129   | 169 ( | 210 ( | 385 ( |
|           | (19)  | (17)  | (15)  | (13)  | 9)    | 5)    | 1)    |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| BAMS      | 39    | 80    | 125   | 173   | 234 ( | 289 ( | 388 ( |
|           | (19)  | (17)  | (15)  | (13)  | 9)    | 5)    | 1)    |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| CONU      | 18    | 26    | **34  | 49    | 75 (  | 205 ( | 324 ( |
|           | (19)  | (17)  | (     | (13)  | 9)    | 5)    | 1)    |
|           |       |       | 15)** |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GUNA      | 19    | 28    | **34  | **42  | **30  |       |       |
|           | (16)  | (14)  | (     | (     | (     |       |       |
|           |       |       | 12)** | 10)** | 5)**  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| FSSE      | 18    | 29    | 39    | **38  | 61 (  | 99 (  |       |
|           | (17)  | (15)  | (13)  | (     | 7)    | 3)    |       |
|           |       |       |       | 11)** |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| OFCL      | 18    | 26    | 38    | 48    | 52 (  | 97 (  | 103 ( |
|           | (19)  | (17)  | (15)  | (13)  | 9)    | 5)    | 1)    |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| NHC       | 33    | 57    | 79    | 99    | 140   | 188   | 233   |
| Official  | (     | (     | (     | (897) | (655) | (465) | (311) |
|           | 1349) | 1192) | 1039) |       |       |       |       |
| (         |       |       |       |       |       |       |       |
| 2002-2006 |       |       |       |       |       |       |       |
| mean)     |       |       |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+

Table 3. Preliminary intensity forecast evaluation (heterogeneous
sample) for Hurricane Ivo, 18-23 September 2007. Forecast errors (kt)
are followed by the number of forecasts in parentheses. Errors smaller
than the NHC official forecast are shown in bold-face type.

+-----------+-------+-------+-------+-------+-------+-------+-------+
| Number    | For   |       |       |       |       |       |       |
| range     | ecast |       |       |       |       |       |       |
| CHAPTE    | P     |       |       |       |       |       |       |
| RForecast | eriod |       |       |       |       |       |       |
| Technique | (h)   |       |       |       |       |       |       |
+===========+=======+=======+=======+=======+=======+=======+=======+
|           | 12    | 24    | 36    | 48    | 72    | 96    | 120   |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| SHF5      | **7.3 | *     | *     | *     | *     | 24.6  | 30.0  |
|           | (     | *10.2 | *12.7 | *16.2 | *21.9 | ( 5)  | ( 1)  |
|           | 19)** | (     | (     | (     | (     |       |       |
|           |       | 17)** | 15)** | 13)** | 9)**  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GHMI      | 9.5   | *     | *     | 20.8  | 25.1  | 24.8  | 11.0  |
|           | (19)  | *11.9 | *16.1 | (13)  | ( 9)  | ( 5)  | ( 1)  |
|           |       | (     | (     |       |       |       |       |
|           |       | 17)** | 15)** |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| HWFI      | 11.7  | 18.0  | 22.8  | 24.2  | *     | 20.8  | 9.0 ( |
|           | (19)  | (17)  | (15)  | (13)  | *14.7 | ( 5)  | 1)    |
|           |       |       |       |       | (     |       |       |
|           |       |       |       |       | 9)**  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| SHIP      | **6.9 | **9.7 | *     | *     | *     | 21.0  | 11.0  |
|           | (     | (     | *12.9 | *17.0 | *19.6 | ( 5)  | ( 1)  |
|           | 19)** | 17)** | (     | (     | (     |       |       |
|           |       |       | 15)** | 13)** | 9)**  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| DSHP      | **6.9 | **9.7 | *     | *     | *     | 21.0  | 5.0 ( |
|           | (     | (     | *12.9 | *17.0 | *19.6 | ( 5)  | 1)    |
|           | 19)** | 17)** | (     | (     | (     |       |       |
|           |       |       | 15)** | 13)** | 9)**  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| FSSE      | 7.6   | *     | *     | *     | *     | 27.7  |       |
|           | (17)  | *10.1 | *12.8 | *16.0 | *20.6 | ( 3)  |       |
|           |       | (     | (     | (     | (     |       |       |
|           |       | 15)** | 13)** | 11)** | 7)**  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| ICON      | 9.2   | 12.6  | *     | *     | *     | 21.2  | **3.0 |
|           | (19)  | (17)  | *15.7 | *19.2 | *19.9 | ( 5)  | (     |
|           |       |       | (     | (     | (     |       | 1)**  |
|           |       |       | 15)** | 13)** | 9)**  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| OFCL      | 7.4   | 12.6  | 16.3  | 20.0  | 22.2  | 20.0  | 5.0 ( |
|           | (19)  | (17)  | (15)  | (13)  | ( 9)  | ( 5)  | 1)    |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| NHC       | 6.3   | 11.0  | 14.6  | 16.9  | 18.9  | 18.5  | 19.3  |
| Official  | (     | (     | (     | (896) | (655) | (465) | (311) |
|           | 1349) | 1192) | 1039) |       |       |       |       |
| (         |       |       |       |       |       |       |       |
| 2002-2006 |       |       |       |       |       |       |       |
| mean)     |       |       |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+

Number range CHAPTERTable 4. Watch and warning summary for Hurricane
Ivo, 18-23 September 2007.

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

  22 / 2100               Tropical Storm Watch    Santa Fe to Cabo San
                          issued                  Lucas

  23 / 0900               Tropical Storm Watch    All
                          discontinued            
  ----------------------- ----------------------- -----------------------

![](media/image1.png){width="8.001388888888888in"
height="6.226388888888889in"}

Number range CHAPTERFigure 1. Best track positions for Hurricane Ivo,
18-23 September 2007.

![](media/image2.png){width="7.870833333333334in"
height="5.477777777777778in"}

Number range CHAPTERFigure 2. Selected wind observations and best track
maximum sustained surface wind speed curve for Hurricane Ivo, 18-23
September 2007. Objective Dvorak (ADT) estimate represents a linear
average over a three-hour period centered on the nominal observation
time.

![](media/image3.png){width="7.870833333333334in"
height="5.477777777777778in"}

Number range CHAPTERFigure 3. Selected pressure observations and best
track minimum central pressure curve for Hurricane Ivo, 18-23 September
2007. Objective Dvorak (ADT) estimate represents a linear average over a
three-hour period centered on the nominal observation time.