Number range CHAPTERTropical Cyclone Report

Tropical Storm Olivia

(EP162006)

09-12 October 2006

Stacy R. Stewart

National Hurricane Center

28 October 2006

Tropical Storm Olivia was a short-lived tropical cyclone that remained
over the open waters of the eastern North Pacific Ocean.

a.  Synoptic History

    Olivia originated from a tropical wave that moved off the west coast
    of Africa on 18 September 2006. Minor flareups of convection
    occurred on 19 and 20 September when the wave was located south and
    southwest, respectively, of the Cape Verde Islands. Otherwise, the
    wave marched uneventfully westward across the tropical Atlantic
    Ocean and northern South America remaining devoid of any significant
    convection. However, upon reaching the eastern North Pacific waters
    on 29 September, convection began to slowly increase. The wave
    continued westward at a slower forward speed around 10 kt, and by
    early on 5 October a broad surface low pressure system had developed
    along the wave axis. Convection gradually increased over the next
    few days and Dvorak satellite classifications were initiated on
    early on 7 October. The low pressure system continued to become
    better defined, while convection continued to increase both in
    vertical depth and horizontal coverage. However, moderate
    upper-level westerly wind shear did not allow the convection to
    persist near the low-level circulation center for more than a few
    hours at any given time, which prevented the system from obtaining
    the organization required of a tropical depression. As the low
    pressure system moved slowly westward, convection steadily increased
    and gradually organized into a long curved band in the northern
    semicircle, and it is estimated that a tropical depression formed by
    1800 UTC 9 October 2006 about 1180 n mi west-southwest of the
    southern tip of Baja California, 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.

    After forming, Tropical Depression Sixteen-E turned slowly northward
    and moved into a region of weaker vertical wind shear, and
    strengthened into a tropical storm at 0600 UTC 10 October. Shortly
    after obtaining tropical storm status, Olivia began to gradually
    accelerate toward the northeast at 8-12 kt and reached its estimated
    peak intensity of 40 kt just 6 h later. However, almost as quickly
    as Olivia strengthened, it weakened as it moved into a region of
    stronger upper-level southerly winds and drier air, which caused
    deep convection to decrease and become displaced away from the
    low-level circulation center (Fig. 4). The cyclone became a tropical
    depression by 1200 UTC 11 October about 900 n mi west-southwest of
    southern Baja California. The depression turned eastward and strong
    vertical shear caused the cyclone to degenerate into a
    non-convective remnant low pressure system early on 13 October. The
    remnant low moved east-southeastward and by 0000 UTC 15 October was
    absorbed into the southern portion of the larger remnant circulation
    of former Tropical Storm Norman (EP152006) when the latter system
    was centered about 130 n mi south-southwest of Manzanillo, Mexico.
    It is possible that the remnants of Olivia played a role in the
    redevelopment of Norman back into a tropical cyclone just 6 h later.

b.  Meteorological Statistics

    Observations in Olivia (Figs. 2 and 3) include satellite-based
    Dvorak technique intensity estimates from the Tropical Analysis and
    Forecast Branch (TAFB), the Satellite Analysis Branch (SAB) and
    the U. S. Air Force Weather Agency (AFWA). Microwave satellite
    imagery from NOAA polar-orbiting satellites, the NASA Tropical
    Rainfall Measuring Mission (TRMM), the NASA QuikSCAT, and Defense
    Meteorological Satellite Program (DMSP) satellites were also useful
    in tracking Olivia. The peak intensity of 40 kt is based on a blend
    of Dvorak satellite intensity estimates from TAFB, SAB, and AFWA and
    the ragged appearance in passive microwave satellite imagery.
    However, a minimum central pressure of 1000 mb, which typically
    corresponds to an intensity of 45 kt, was assigned due to the
    background environmental pressures being lower than average by at
    least 3 mb.

    No wind reports of tropical storm force were received in association
    with Olivia.

c.  Casualty and Damage Statistics

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

d.  Forecast and Warning Critique

    The genesis of Tropical Storm Olivia was well anticipated in the
    eastern North Pacific Tropical Weather Outlook product (TWO). The
    incipient disturbance was first mentioned in the 1700 UTC 5 October
    2006 TWO, and potential tropical cyclogenesis was explicitly
    mentioned in the 2300 UTC 6 October outlook. A tropical depression
    formed 67 h later.

    A verification of official and guidance model track forecasts is
    given in Table 2. Average official track errors for Olivia were 40,
    78, 105, 89, and 84 n mi for the 12, 24, 36, 48, and 72 h forecasts,
    respectively. The sample size was quite small with the number of
    forecasts ranging from 11 at 12 h to 1 at 72 h. These errors are
    greater than the average long-term official track errors (Table 4)
    through 36 h, and then considerably smaller than average at 48 and
    72 h. After turning northeastward, Olivia accelerated sooner than
    expected and this is the main reason for the larger track errors
    through 36 h.

    Average official intensity errors (Table 3) were 4, 4, 7, 9, and 10
    kt for the 12, 24, 36, 48, and 72 h forecasts, respectively. These
    errors are smaller than the average long-term official intensity
    errors of 6, 11, 14, 17, 19, and 18 kt, respectively. The negative
    effects of vertical wind shear were well anticipated, and the OFCL
    forecasts outperformed all of the statistical intensity forecast
    models.

Number range CHAPTERTable 1. Best track for Tropical Storm Olivia, 9-12
October 2006.

+----------+---+------+--------+----------+----------+-------------------+
| D        | L |      | Lon    | Pressure | Wind     | Stage             |
| ate/Time | a |      | gitude |          | Speed    |                   |
|          | t |      |        | (mb)     |          |                   |
| (UTC)    | i |      | (°W)   |          | (kt)     |                   |
|          | t |      |        |          |          |                   |
|          | u |      |        |          |          |                   |
|          | d |      |        |          |          |                   |
|          | e |      |        |          |          |                   |
|          |   |      |        |          |          |                   |
|          | ( |      |        |          |          |                   |
|          | ° |      |        |          |          |                   |
|          | N |      |        |          |          |                   |
|          | ) |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 09 /     |   | 12.8 | 127.7  | 1005     | 30       | tropical          |
| 1800     |   |      |        |          |          | depression        |
+----------+---+------+--------+----------+----------+-------------------+
| 10 /     |   | 13.3 | 127.7  | 1005     | 30       | \"                |
| 0000     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 10 /     |   | 13.9 | 127.7  | 1003     | 35       | tropical storm    |
| 0600     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 10 /     |   | 14.5 | 127.3  | 1001     | 40       | \"                |
| 1200     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 10 /     |   | 15.4 | 126.5  | 1000     | 40       | \"                |
| 1800     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 11 /     |   | 16.2 | 125.7  | 1001     | 40       | \"                |
| 0000     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 11 /     |   | 16.6 | 125.3  | 1003     | 35       | \"                |
| 0600     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 11 /     |   | 16.8 | 124.7  | 1004     | 30       | tropical          |
| 1200     |   |      |        |          |          | depression        |
+----------+---+------+--------+----------+----------+-------------------+
| 11 /     |   | 17.1 | 123.9  | 1005     | 30       | \"                |
| 1800     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 12 /     |   | 17.3 | 123.1  | 1006     | 30       | \"                |
| 0000     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 12 /     |   | 17.5 | 122.3  | 1007     | 25       | \"                |
| 0600     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 12 /     |   | 17.6 | 121.5  | 1007     | 25       | \"                |
| 1200     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 12 /     |   | 17.6 | 120.6  | 1008     | 25       | \"                |
| 1800     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 13 /     |   | 17.3 | 119.9  | 1008     | 25       | low               |
| 0000     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 13 /     |   | 17.1 | 119.3  | 1008     | 25       | \"                |
| 0600     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 13 /     |   | 16.8 | 118.6  | 1008     | 25       | \"                |
| 1200     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 13 /     |   | 16.5 | 117.8  | 1008     | 25       | \"                |
| 1800     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 14 /     |   | 16.2 | 116.8  | 1008     | 25       | \"                |
| 0000     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 14 /     |   | 15.8 | 115.6  | 1009     | 20       | \"                |
| 0600     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 14 /     |   | 15.3 | 114.4  | 1009     | 20       | \"                |
| 1200     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 14 /     |   | 14.8 | 113.0  | 1009     | 20       | \"                |
| 1800     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+
| 15 /     |   |      |        |          |          | Absorbed into     |
| 0000     |   |      |        |          |          | remnant           |
|          |   |      |        |          |          | circulation of TS |
|          |   |      |        |          |          | Norman            |
+----------+---+------+--------+----------+----------+-------------------+
| 10 /     |   | 15.4 | 126.5  | 1000     | 40       | minimum pressure  |
| 1800     |   |      |        |          |          |                   |
+----------+---+------+--------+----------+----------+-------------------+

Number range CHAPTERNumber range CHAPTERNumber range CHAPTERTable 2.
Preliminary track forecast evaluation (heterogeneous sample) for
Tropical Storm Olivia, 9-12 October 2006. Forecast errors (n mi) are
followed by the number of forecasts in parentheses. Errors smaller than
the NHC official forecast are shown in bold-face type. Verification
includes the depression stage.

+-----------+-------+-------+-------+-------+-------+-------+-------+
| Number    | For   |       |       |       |       |       |       |
| range     | ecast |       |       |       |       |       |       |
| CHAPTE    | P     |       |       |       |       |       |       |
| RForecast | eriod |       |       |       |       |       |       |
| Technique | (h)   |       |       |       |       |       |       |
+===========+=======+=======+=======+=======+=======+=======+=======+
|           | 12    | 24    | 36    | 48    | 72    | 96    | 120   |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| CLP5      | 58    | 143 ( | 240 ( | 370 ( | 669 ( |       |       |
|           | (11)  | 9)    | 7)    | 5)    | 1)    |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFNI      | *     | *     | 132 ( |       |       |       |       |
|           | *31** | *61** | 2)    |       |       |       |       |
|           | ( 4)  | ( 2)  |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFDI      | 47    | 85 (  | **    | 115 ( | 93 (  |       |       |
|           | (11)  | 9)    | 103** | 5)    | 1)    |       |       |
|           |       |       | ( 7)  |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFDL\*    | 51    | 86 (  | *     | 108 ( | *     |       |       |
|           | (11)  | 9)    | *98** | 5)    | *39** |       |       |
|           |       |       | ( 7)  |       | ( 1)  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFDN\*    | *     | *     | 109 ( |       |       |       |       |
|           | *39** | *50** | 2)    |       |       |       |       |
|           | ( 7)  | ( 2)  |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFSI      | 54    | 98 (  | 112 ( | 124 ( |       |       |       |
|           | (11)  | 9)    | 7)    | 4)    |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFSO\*    | 58    | 102 ( | 127 ( | 118 ( | 111 ( |       |       |
|           | (11)  | 9)    | 6)    | 4)    | 1)    |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| AEMI      | 43    | *     | *     | *     | *     |       |       |
|           | (11)  | *77** | *88** | *87** | *80** |       |       |
|           |       | ( 9)  | ( 7)  | ( 5)  | ( 1)  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| NGPI      | *     | 96 (  | 157 ( | 215 ( | 252 ( |       |       |
|           | *38** | 6)    | 4)    | 2)    | 1)    |       |       |
|           | ( 8)  |       |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| NGPS\*    | *     | *     | *     | 112 ( |       |       |       |
|           | *26** | *35** | *94** | 1)    |       |       |       |
|           | ( 7)  | ( 5)  | ( 3)  |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| UKMI      | 41 (  | *     | **    | 152 ( |       |       |       |
|           | 9)    | *68** | 101** | 3)    |       |       |       |
|           |       | ( 7)  | ( 5)  |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| UKM\*     | 64 (  | 88 (  | 120 ( | 174 ( |       |       |       |
|           | 5)    | 4)    | 3)    | 2)    |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| BAMD      | 92    | 199 ( | 351 ( | 480 ( | 774 ( |       |       |
|           | (11)  | 9)    | 7)    | 5)    | 1)    |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| BAMM      | 58    | 110 ( | 171 ( | 203 ( | 397 ( |       |       |
|           | (11)  | 9)    | 7)    | 5)    | 1)    |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| BAMS      | *     | *     | 108 ( | 138 ( | 239 ( |       |       |
|           | *35** | *72** | 7)    | 5)    | 1)    |       |       |
|           | (11)  | ( 9)  |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| CONU      | 43    | *     | *     | *     | *     |       |       |
|           | (11)  | *74** | *88** | *83** | *80** |       |       |
|           |       | ( 9)  | ( 7)  | ( 5)  | ( 1)  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GUNA      | *     | *     | *     |       |       |       |       |
|           | *15** | *29** | *56** |       |       |       |       |
|           | ( 6)  | ( 4)  | ( 2)  |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| FSSE      | *     | *     | *     | *     |       |       |       |
|           | *32** | *29** | *38** | *46** |       |       |       |
|           | ( 5)  | ( 5)  | ( 4)  | ( 2)  |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| OFCL      | 40    | 78 (  | 105 ( | 89 (  | 84 (  |       |       |
|           | (11)  | 9)    | 7)    | 5)    | 1)    |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| NHC       | 35    | 60    | 83    | 103   | 145   | 192   | 231   |
| Official  | (     | (     | (     | (877) | (652) | (465) | (313) |
|           | 1300) | 1152) | 1009) |       |       |       |       |
| (         |       |       |       |       |       |       |       |
| 2001-2005 |       |       |       |       |       |       |       |
| mean)     |       |       |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+

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

Table 3. Preliminary intensity forecast evaluation (heterogeneous
sample) for Tropical Storm Olivia, 9-12 October 2006. 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.
Verification includes the depression stage.

+-----------+-------+-------+-------+-------+-------+-------+-------+
| Number    | For   |       |       |       |       |       |       |
| range     | ecast |       |       |       |       |       |       |
| CHAPTE    | P     |       |       |       |       |       |       |
| RForecast | eriod |       |       |       |       |       |       |
| Technique | (h)   |       |       |       |       |       |       |
+===========+=======+=======+=======+=======+=======+=======+=======+
|           | 12    | 24    | 36    | 48    | 72    | 96    | 120   |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| SHF5      | 4.9   | 7.9 ( | 7.7 ( | 11.8  | 23.0  |       |       |
|           | (11)  | 9)    | 7)    | ( 5)  | ( 1)  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFDI      | 5.0   | 5.1 ( | **    | **    | **    |       |       |
|           | (11)  | 9)    | 5.3** | 4.8** | 2.0** |       |       |
|           |       |       | ( 7)  | ( 5)  | ( 1)  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFDL\*    | 3.9   | 5.9 ( | **    | **    | 11.0  |       |       |
|           | (11)  | 9)    | 5.7** | 7.8** | ( 1)  |       |       |
|           |       |       | ( 7)  | ( 5)  |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| SHIP      | 4.7   | 5.1 ( | 9.1 ( | 11.6  |       |       |       |
|           | (11)  | 9)    | 7)    | ( 5)  |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| DSHP      | 4.7   | 5.1 ( | 9.1 ( | 11.6  |       |       |       |
|           | (11)  | 9)    | 7)    | ( 5)  |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| FSSE      | 4.8 ( | 6.0 ( | 7.5 ( | **    |       |       |       |
|           | 5)    | 5)    | 4)    | 7.5** |       |       |       |
|           |       |       |       | ( 2)  |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| ICON      | 4.8   | **    | **    | 9.0 ( |       |       |       |
|           | (11)  | 4.3** | 6.1** | 5)    |       |       |       |
|           |       | ( 9)  | ( 7)  |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| OFCL      | 3.6   | 4.4 ( | 7.1 ( | 9.0 ( | 10.0  |       |       |
|           | (11)  | 9)    | 7)    | 5)    | ( 1)  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| NHC       | 6.2   | 10.8  | 14.3  | 16.5  | 18.7  | 18.3  | 19.3  |
| Official  |       |       |       |       |       |       |       |
|           | \(1   | \(1   | \(1   | \(    | \(    | \(    | \(    |
| (         | 300\) | 152\) | 009\) | 876\) | 652\) | 465\) | 313\) |
| 2001-2005 |       |       |       |       |       |       |       |
| mean)     |       |       |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+

\* Output from this model was unavailable at forecast time.

Number range CHAPTER

![](media/image1.wmf){width="7.798611111111111in"
height="5.975694444444445in"}

Number range CHAPTERFigure 1. Best track positions for Tropical Storm
Olivia, 9-12 October 2006.

![](media/image2.wmf){width="7.7965277777777775in"
height="5.436111111111111in"}

Number range CHAPTERFigure 2. Selected wind observations and best track
maximum sustained surface wind speed curve for Tropical Storm Olivia,
9-12 October 2006 Estimates during the remnant low stage are based on
analyses from the National Hurricane Center and the Tropical Analysis
and Forecast Branch.

![](media/image3.wmf){width="8.046527777777778in" height="5.43125in"}

Number range CHAPTERFigure 3. Selected pressure observations and best
track minimum central pressure curve for Tropical Storm Olivia, 9-12
October 2006. Estimates during the remnant low stage are based on
analyses from the National Hurricane Center and the Tropical Analysis
and Forecast Branch.

![](media/image4.jpeg){width="5.3in" height="5.3in"}

Figure 4. An SSMI 85GHz microwave overpass at 1634 UTC 10 October 2006,
which was near the time of Tropical Olivia's peak intensity. The center
of circulation was near 15.3^o^ N 126.6^o^ W at that time (image
courtesy of the U.S. Navy Fleet Numerical Meteorology and Oceanography
Command, Monterey, CA).