Tropical Cyclone Report

Tropical Storm Barbara

(EP022007)

29 May -- 2 June 2007

Richard D. Knabb

National Hurricane Center

21 August 2007

Barbara was a short-lived tropical storm that made landfall near the
Mexico-Guatemala border.

a.  Synoptic History

    The genesis of Barbara appears to have been associated with a
    tropical wave that left the west coast of Africa on 14 May. The wave
    crossed Central America on 25 May and emerged over the eastern North
    Pacific the next day. The wave interacted with the Intertropical
    Convergence Zone, and on 27 May a broad area of surface low pressure
    formed a couple hundred miles south of Puerto Escondido, Mexico.
    Limited and disorganized shower activity accompanied the low as it
    edged northward during the next couple of days. On 29 May, however,
    convection increased and became more concentrated near the center of
    the low, and a tropical depression formed by 1800 UTC that day about
    100 n mi south-southeast of Puerto Escondido. 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.

    Initially stationary, the depression did not gain any strength
    during the first 12 hours or so following genesis. The cyclone then
    strengthened gradually on 30 May while inching toward the
    south-southeast within an environment of very weak steering
    currents. It became a tropical storm by 1200 UTC that day and
    reached an intensity of 40 kt six hours later. Northerly wind shear
    contributed to Barbara's weakening early on 31 May, and the storm
    moved very slowly eastward that day under the influence of a mid- to
    upper-level trough over the western Gulf of Mexico. By 0000 UTC 1
    June, the cyclone had weakened to a tropical depression while
    centered about 200 n mi west-southwest of the Mexico-Guatemala
    border. Later that day, however, as wind shear decreased, Barbara
    strengthened over warm waters and reached an intensity of 45 kt by
    1200 UTC 1 June. By that time the storm had also begun a general
    northeastward motion at about 6 kt that would continue during the
    next 24 hours. The intensity also remained steady during that
    period, and Barbara made landfall at about 1300 UTC 2 June, roughly
    20 n mi northwest of the Mexico-Guatemala border, with maximum
    sustained winds of 45 kt. The cyclone quickly deteriorated inland
    over the rugged terrain of extreme southeastern Mexico while passing
    near the town of Tapachula. Barbara became a depression by 1800 UTC
    2 June and completely dissipated by the end of that day.

b.  Meteorological Statistics

    Observations in Barbara (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).
    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 Barbara.

    No ship reports of sustained winds of tropical storm force were
    reported in association with Barbara. Sustained winds of 40 kt were
    reported, however, at Tecun Uman, Guatemala (located near the border
    with Mexico about 15 miles from the Pacific coast) near the time of
    Barbara's landfall on the morning of 2 June. An automated surface
    station at Puerto Madero, Mexico (along the coast about 20 miles
    southwest of Tapachula), operated by the Mexican Navy, reported
    sustained winds of 31 kt with gusts to 46 kt near the time of
    landfall. Nearly 5 inches of rain was reported on 2 June at Huixtla,
    Mexico. A few other reports of 2-4 inches of rain in extreme
    southeastern Mexico were also received.

    The maximum best track intensity for Barbara of 45 kt on 1-2 June is
    based on subjective Dvorak intensity estimates and data from two
    QuikSCAT overpasses. The temporary weakening to 30 kt at 0000 UTC 1
    June is based on Dvorak data-T numbers of 2.0 from TAFB and SAB at
    that time.

c.  Casualty and Damage Statistics

    Structural damages in Mexico and Guatemala caused by Barbara were
    confined mostly to some damaged roofs and downed trees in coastal
    areas near the border between the two countries. Rain-induced river
    floods led to a bridge being washed out in coastal Guatemala.
    Significant damages to agricultural crops, with an estimated cost of
    more than \$50 million (U.S. dollars), were reported in southeastern
    Mexico.

d.  Forecast and Warning Critique

    Tropical Weather Outlooks issued by the National Hurricane Center
    first mentioned the incipient area of disturbed weather southwest of
    the Gulf of Tehuantepec about 48 hours prior to formation of the
    tropical depression that later became Barbara. Beginning about 13
    hours prior to genesis, the Outlooks explicitly mentioned that a
    tropical depression could form.

    A verification of official and guidance model track forecasts is
    given in Table 2. Average official track errors (with number of
    cases in parentheses) for Barbara were 32 (15), 62 (13), 98 (11),
    141 (9), 226 (5), and 333 (1) n mi for the 12, 24, 36, 48, 72, and
    96 h forecasts, respectively; due to Barbara's short life span, only
    one 96-h forecast and no 120-h forecasts could be verified. Despite
    the small number of cases, especially at longer lead times, it is
    clear that most of the official track forecasts were biased well to
    the west, leading to errors that were noticeably larger than the
    corresponding 5-year (2002-06) averages. The first two days of
    forecasts called for a slow northward motion toward Mexico followed
    by a northwestward turn near the coast. Forecasts were shifted
    eastward thereafter but retained a west bias. Model guidance from
    the U.S. Navy, including both the GFDN (GFNI) and NOGAPS (NGPI), had
    smaller average errors than the official forecasts, since those
    models more frequently forecast an eastward component of motion.
    Overall, however, all of the available models were quite erratic, as
    is often the case in a weak steering environment, and none of them
    consistently forecast the eastward motion of Barbara that was
    ultimately observed.

    Average official and guidance model intensity forecast errors
    (Table 3) were 7, 10, 12, 19, 29, and 60 kt for the 12, 24, 36, 48,
    72, and 96 h forecasts; again note that only one forecast could be
    verified at 96 h. Most of the official intensity forecasts were
    biased high, and errors beyond 36 h were larger than the
    corresponding 5-year averages. The first several official forecasts
    for Barbara called for intensification to a hurricane, based largely
    on the SHIPS model guidance that generally had an even higher bias
    than the official forecasts (although SHIPS depends on the official
    forecast track that had large errors in this case). GFDL intensity
    forecasts were also biased a little high but were far more
    conservative, and they exhibited smaller errors than the official
    forecasts.

Coastal watches and warnings issued by Mexico and Guatemala in
association with Barbara are summarized in Table 4.

Table 1. Best track for Tropical Storm Barbara, 29 May -- 2 June 2007.

+---------+--------+--------+---------+------------+-----------------+
| Da      | La     | Lon    | P       | Wind Speed | Stage           |
| te/Time | titude | gitude | ressure |            |                 |
|         |        |        |         | (kt)       |                 |
| (UTC)   | \(N\)  | \(W\)  | (mb)    |            |                 |
+---------+--------+--------+---------+------------+-----------------+
| 29 /    | 14.2   | 97.5   | 1007    | 30         | tropical        |
| 1800    |        |        |         |            | depression      |
+---------+--------+--------+---------+------------+-----------------+
| 30 /    | 14.2   | 97.5   | 1007    | 30         | \"              |
| 0000    |        |        |         |            |                 |
+---------+--------+--------+---------+------------+-----------------+
| 30 /    | 14.2   | 97.4   | 1006    | 30         | \"              |
| 0600    |        |        |         |            |                 |
+---------+--------+--------+---------+------------+-----------------+
| 30 /    | 14.0   | 97.3   | 1005    | 35         | tropical storm  |
| 1200    |        |        |         |            |                 |
+---------+--------+--------+---------+------------+-----------------+
| 30 /    | 13.6   | 97.2   | 1003    | 40         | \"              |
| 1800    |        |        |         |            |                 |
+---------+--------+--------+---------+------------+-----------------+
| 31 /    | 13.2   | 96.9   | 1002    | 40         | \"              |
| 0000    |        |        |         |            |                 |
+---------+--------+--------+---------+------------+-----------------+
| 31 /    | 13.1   | 96.5   | 1002    | 40         | \"              |
| 0600    |        |        |         |            |                 |
+---------+--------+--------+---------+------------+-----------------+
| 31 /    | 13.0   | 96.1   | 1004    | 35         | \"              |
| 1200    |        |        |         |            |                 |
+---------+--------+--------+---------+------------+-----------------+
| 31 /    | 12.9   | 95.7   | 1004    | 35         | \"              |
| 1800    |        |        |         |            |                 |
+---------+--------+--------+---------+------------+-----------------+
| 01 /    | 12.9   | 95.3   | 1005    | 30         | tropical        |
| 0000    |        |        |         |            | depression      |
+---------+--------+--------+---------+------------+-----------------+
| 01 /    | 13.0   | 94.9   | 1004    | 35         | tropical storm  |
| 0600    |        |        |         |            |                 |
+---------+--------+--------+---------+------------+-----------------+
| 01 /    | 13.2   | 94.4   | 1001    | 45         | \"              |
| 1200    |        |        |         |            |                 |
+---------+--------+--------+---------+------------+-----------------+
| 01 /    | 13.4   | 93.8   | 1000    | 45         | \"              |
| 1800    |        |        |         |            |                 |
+---------+--------+--------+---------+------------+-----------------+
| 02 /    | 13.7   | 93.3   | 1000    | 45         | \"              |
| 0000    |        |        |         |            |                 |
+---------+--------+--------+---------+------------+-----------------+
| 02 /    | 14.1   | 92.8   | 1000    | 45         | \"              |
| 0600    |        |        |         |            |                 |
+---------+--------+--------+---------+------------+-----------------+
| 02 /    | 14.6   | 92.5   | 1000    | 45         | \"              |
| 1200    |        |        |         |            |                 |
+---------+--------+--------+---------+------------+-----------------+
| 02 /    | 15.2   | 92.3   | 1006    | 25         | tropical        |
| 1800    |        |        |         |            | depression      |
+---------+--------+--------+---------+------------+-----------------+
| 03 /    |        |        |         |            | dissipated      |
| 0000    |        |        |         |            |                 |
+---------+--------+--------+---------+------------+-----------------+
| 01 /    | 13.4   | 93.8   | 1000    | 45         | minimum         |
| 1800    |        |        |         |            | pressure        |
+---------+--------+--------+---------+------------+-----------------+
| 02 /    | 14.7   | 92.5   | 1000    | 45         | landfall just   |
| 1300    |        |        |         |            | northwest of    |
|         |        |        |         |            | the             |
|         |        |        |         |            | M               |
|         |        |        |         |            | exico-Guatemala |
|         |        |        |         |            | border          |
+---------+--------+--------+---------+------------+-----------------+

Table 2. Preliminary track forecast evaluation (heterogeneous sample)
for Tropical Storm Barbara, 29 May -- 2 June 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.
Verification includes the depression stage.

+-----------+-------+-------+-------+-------+-------+-------+-------+
| Forecast  | For   |       |       |       |       |       |       |
| Technique | ecast |       |       |       |       |       |       |
|           | P     |       |       |       |       |       |       |
|           | eriod |       |       |       |       |       |       |
|           | (h)   |       |       |       |       |       |       |
+===========+=======+=======+=======+=======+=======+=======+=======+
|           | 12    | 24    | 36    | 48    | 72    | 96    | 120   |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| CLP5      | 44    | 106   | 176   | 252 ( | 454 ( | 599 ( |       |
|           | (15)  | (13)  | (11)  | 9)    | 5)    | 1)    |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFNI      | 40    | **61  | **77  | **132 | **163 |       |       |
|           | (13)  | (     | (     | (     | (     |       |       |
|           |       | 11)** | 9)**  | 7)**  | 2)**  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFDI      | 43    | 72    | 100   | **123 | **181 | 410 ( |       |
|           | (15)  | (13)  | (11)  | (     | (     | 1)    |       |
|           |       |       |       | 9)**  | 5)**  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFSI      | 53    | 99    | 155   | 208 ( | **174 |       |       |
|           | (15)  | (13)  | (11)  | 8)    | (     |       |       |
|           |       |       |       |       | 4)**  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| AEMI      | 55    | 102   | 158   | 295 ( |       |       |       |
|           | (15)  | (13)  | (11)  | 6)    |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| NGPI      | **31  | **50  | **79  | **122 | **160 | **158 |       |
|           | (     | (     | (     | (     | (     | (     |       |
|           | 15)** | 13)** | 11)** | 9)**  | 5)**  | 1)**  |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| UKMI      | 56 (  | 100 ( |       |       |       |       |       |
|           | 2)    | 1)    |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| BAMD      | 69    | 144   | 223   | 318 ( | 529 ( | 767 ( |       |
|           | (15)  | (13)  | (11)  | 9)    | 5)    | 1)    |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| BAMM      | 55    | 117   | 187   | 277 ( | 446 ( | 672 ( |       |
|           | (15)  | (13)  | (11)  | 9)    | 5)    | 1)    |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| BAMS      | 52    | 110   | 168   | 233 ( | 358 ( | 466 ( |       |
|           | (15)  | (13)  | (11)  | 9)    | 5)    | 1)    |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| CONU      | 35    | **58  | **92  | **128 | **170 | **279 |       |
|           | (15)  | (     | (     | (     | (     | (     |       |
|           |       | 13)** | 11)** | 9)**  | 5)**  | 1)**  |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GUNA      | 41    | 77    | 120 ( | 168 ( | 229 ( |       |       |
|           | (13)  | (11)  | 9)    | 7)    | 3)    |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| FSSE      | 40    | 81 (  | 122 ( | 157 ( | 232 ( |       |       |
|           | (11)  | 9)    | 7)    | 7)    | 3)    |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| OFCL      | 32    | 62    | 98    | 141 ( | 226 ( | 333 ( |       |
|           | (15)  | (13)  | (11)  | 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 Tropical Storm Barbara, 29 May -- 2 June 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. Verification includes the depression stage.

+-----------+-------+-------+-------+-------+-------+-------+-------+
| Forecast  | For   |       |       |       |       |       |       |
| Technique | ecast |       |       |       |       |       |       |
|           | P     |       |       |       |       |       |       |
|           | eriod |       |       |       |       |       |       |
|           | (h)   |       |       |       |       |       |       |
+===========+=======+=======+=======+=======+=======+=======+=======+
|           | 12    | 24    | 36    | 48    | 72    | 96    | 120   |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| SHF5      | 7.5   | 11.0  | *     | *     | **8.2 | *     |       |
|           | (15)  | (13)  | *11.8 | *16.4 | (     | *19.0 |       |
|           |       |       | (     | (     | 5)**  | (     |       |
|           |       |       | 11)** | 9)**  |       | 1)**  |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFDI      | 7.0   | **9.6 | *     | *     | *     | *     |       |
|           | (15)  | (     | *11.3 | *13.3 | *10.0 | *12.0 |       |
|           |       | 13)** | (     | (     | (     | (     |       |
|           |       |       | 11)** | 9)**  | 5)**  | 1)**  |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| SHIP      | 8.2   | 11.2  | 16.1  | 26.2  | 38.8  | *     |       |
|           | (15)  | (13)  | (11)  | ( 9)  | ( 5)  | *53.0 |       |
|           |       |       |       |       |       | (     |       |
|           |       |       |       |       |       | 1)**  |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| DSHP      | 7.5   | 11.2  | 16.1  | 26.2  | 38.8  | *     |       |
|           | (15)  | (13)  | (11)  | ( 9)  | ( 5)  | *35.0 |       |
|           |       |       |       |       |       | (     |       |
|           |       |       |       |       |       | 1)**  |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| FSSE      | **6.4 | 12.3  | 16.9  | 22.0  | 34.0  |       |       |
|           | (     | ( 9)  | ( 7)  | ( 7)  | ( 3)  |       |       |
|           | 11)** |       |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| ICON      | 6.8   | 10.2  | 15.5  | 21.9  | *     | *     |       |
|           | (15)  | (13)  | (11)  | ( 9)  | *28.0 | *17.0 |       |
|           |       |       |       |       | (     | (     |       |
|           |       |       |       |       | 5)**  | 1)**  |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| OFCL      | 6.7   | 10.0  | 12.3  | 19.4  | 29.0  | 60.0  |       |
|           | (15)  | (13)  | (11)  | ( 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)     |       |       |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+

Table 4. Watch and warning summary for Tropical Storm Barbara, 29 May --
2 June 2007.

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

  1 / 1500                Tropical Storm Watch    Sipacate, Guatemala to
                          issued                  Barra De Tonala, Mexico

  1 / 2100                Tropical Storm Watch    Sipacate to Barra De
                          changed to Tropical     Tonala
                          Storm Warning           

  1 / 2100                Tropical Storm Watch    Barra De Tonala to
                          issued                  Salina Cruz, Mexico

  2 / 1800                Tropical Storm Watch    All
                          discontinued            

  2 / 1800                Tropical Storm Warning  All
                          discontinued            
  ----------------------- ----------------------- -----------------------

![](media/image1.wmf){width="7.374305555555556in"
height="5.851388888888889in"}

Figure 1. Best track positions for Tropical Storm Barbara, 29 May -- 2
June 2007.

![](media/image2.wmf){width="7.746527777777778in"
height="5.2868055555555555in"}

Figure 2. Selected wind observations and best track maximum sustained
surface wind speed curve for Tropical Storm Barbara,

> 29 May -- 2 June 2007.

![](media/image3.wmf){width="8.000694444444445in"
height="5.455555555555556in"}

Figure 3. Selected pressure observations and best track minimum central
pressure curve for Tropical Storm Barbara, 29 May -- 2 June 2007.