Number range CHAPTERTropical Cyclone Report

Hurricane Maria

1-10 September 2005

Richard J. Pasch and Eric S. Blake

National Hurricane Center

8 February 2006

Maria was briefly a major hurricane, but it remained well out at sea.

a.  Synoptic History

    On 27 August, the axis of a large and strong tropical wave crossed
    the coast of Africa and moved into the far eastern tropical
    Atlantic. Cloudiness and showers associated with the wave soon
    became organized and by 28 August two areas of concentrated deep
    convection, each showing signs of circulation, were evident within
    the wave. One of the areas moved northwestward to a location just
    west of the Cape Verde Islands, and subsequently became
    disorganized. The other area, which was broader, moved westward for
    a day or so and then turned northwestward. This system developed a
    well-defined low-level circulation on 31 August. However, an
    adjacent upper-tropospheric cyclone produced strong
    south-southwesterly shear that prevented the formation of persistent
    deep convection near or over the center. By 1200 UTC 1 September,
    convection became persistent enough near the center to designate
    that a tropical depression had formed about 910 n mi east of the
    northernmost Leeward Islands. 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.

    A cell of the subtropical ridge was situated to the northeast of the
    tropical cyclone. This was the primary steering feature, and it
    drove the system on a west-northwestward to northwestward track for
    several days. The nearby upper-level low continued to exert a
    shearing influence, and this hindered significant intensification
    for about a day. As the effects of the upper-level low lessened, the
    depression was able to strengthen into a tropical storm by around
    1200 UTC 2 September. However, the environment was still not very
    conducive for strengthening, and the storm intensified at a rather
    slow pace for a couple of days. While continuing to move well out at
    sea around the western periphery of the subtropical high, Maria
    eventually became a hurricane at about 0600 UTC 4 September.
    Upper-level winds became more favorable for strengthening on 4-5
    September. Maria developed a well-defined eye on 5 September and
    reached its peak intensity, estimated to be near 100 kt, around 0000
    UTC 6 September. The hurricane was centered about 415 n mi east of
    Bermuda at this time and had begun its recurvature around the
    subtropical anticyclone. It has often been observed that Atlantic
    tropical cyclones reach their peak intensity around the time of
    recurvature.

    Maria was a major hurricane very briefly; in fact, a weakening trend
    was already underway at 0600 UTC 6 September. The hurricane turned
    toward the northeast that day and there was a gradual increase in
    forward speed over the next couple of days, due to deep-layer
    southwesterly flow on the northwest side of the subtropical high.
    The slow weakening trend was halted on UTC 7 September, when Maria
    appeared to combine with an upper-level trough and re-intensified
    slightly to about 75 kt. By 8 September, slow weakening was again
    underway, and the cyclone diminished to tropical storm strength by
    about 0000 UTC 9 September. Although Maria stubbornly hung on to
    tropical characteristics as it moved into the mid-latitudes, it was
    eventually transformed into an extratropical storm around 1200 UTC
    10 September while accelerating north-northeastward. In response to
    strong baroclinic forcing, the storm intensified and acquired
    hurricane-force winds over the north Atlantic on 11 September. It
    began weakening again on 12 September and passed near Iceland on 13
    September. Finally, as the system approached Norway, it merged with
    another strong extratropical cyclone.

b.  Meteorological Statistics

    Observations in Maria (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 Maria. QuikSCAT wind speed data were particularly useful
    on 7 September and provided the main basis for designating Maria as
    a hurricane even though most Dvorak intensity estimates indicated
    that it had weakened to a tropical storm.

    Only three ship reports of winds of tropical storm force associated
    with Maria were received. These are listed in Table 2.

c.  Casualty and Damage Statistics

    There were no reports of damages or casualties during the tropical
    cyclone stages of Maria. However, the post-Maria merger with another
    extratropical low was a powerful cyclone, and it triggered a
    landslide in Norway that killed one person.

d.  Forecast and Warning Critique

    Average official track errors (with the number of cases in
    parentheses) for Maria were 33 (34), 56 (32), 74 (30), 85 (28), 120
    (24), 156 (20), and 218 (16) n mi for the 12, 24, 36, 48, 72, 96,
    and 120 h forecasts, respectively. These errors are lower than the
    average official track errors for the 10-yr period 1995-2004[^1] of
    42, 75, 107, 138, 202, 236, and 310 n mi, respectively. Table 3
    shows a comparison of the mean track errors for selected numerical
    guidance with those of the official forecasts. The GUNA consensus
    and Florida State University Superensemble (FSSE) had lower errors
    than the official forecast (OFCL) at most forecast times. At 72 h
    and beyond, however, those two numerical techniques had
    significantly fewer cases than the official (i.e., were frequently
    unavailable). It should also be noted that the mean official error
    was slightly higher than CLP5 (Five-day Climatology and Persistence)
    at 120 h \-- indicating no skill, on average, for the official
    forecasts at five days.

    Average official intensity errors were 6, 6, 8, 8, 12, 13, and 9 kt
    for the 12, 24, 36, 48, 72, 96, and 120 h forecasts, respectively.
    For comparison, the average official intensity errors over the 10-yr
    period 1995-2004 are 6, 10, 12, 15, 18, 20, and 22 kt, respectively.
    The official intensity forecasts were substantially better than
    average at two through five days. A number of official forecasts
    were premature (as much as 48-54 h too early) in predicting Maria's
    extratropical transition.

    For as long as four days in advance of its formation, the National
    Hurricane Center's Tropical Weather Outlooks anticipated the
    formation of a tropical depression from the wave that eventually
    spawned Maria. However, these outlooks first focused on the
    disturbed weather area that moved northwestward toward the Cape
    Verde Islands and failed to develop. By 29 August, the Outlooks
    correctly began to identify a second, larger area of weather within
    the wave as a candidate for tropical cyclone formation.

    Watches and/or warnings were not required for any land areas.

Number range CHAPTERTable 1. Best track for Hurricane Maria, 1-10
September 2005.

+---------+---------+---------+---------+---------+-----------------+
| Da      | L       | Lo      | P       | Wind    | Stage           |
| te/Time | atitude | ngitude | ressure | Speed   |                 |
|         |         |         |         |         |                 |
| (UTC)   | (°N)    | (°W)    | (mb)    | (kt)    |                 |
+---------+---------+---------+---------+---------+-----------------+
| 01 /    | 18.8    | 45.5    | 1008    | 30      | tropical        |
| 1200    |         |         |         |         | depression      |
+---------+---------+---------+---------+---------+-----------------+
| 01 /    | 19.3    | 46.2    | 1008    | 30      | \"              |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 02 /    | 19.9    | 47.2    | 1008    | 30      | \"              |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 02 /    | 20.5    | 48.3    | 1008    | 30      | \"              |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 02 /    | 21.1    | 49.4    | 1006    | 35      | tropical storm  |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 02 /    | 21.5    | 50.2    | 1003    | 40      | \"              |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 03 /    | 22.0    | 51.0    | 1001    | 45      | \"              |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 03 /    | 23.0    | 52.0    | 1000    | 45      | \"              |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 03 /    | 24.4    | 53.1    | 997     | 50      | \"              |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 03 /    | 25.5    | 54.0    | 994     | 55      | \"              |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 04 /    | 26.5    | 54.6    | 990     | 60      | \"              |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 04 /    | 27.5    | 55.1    | 987     | 65      | hurricane       |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 04 /    | 28.6    | 55.5    | 987     | 65      | \"              |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 04 /    | 29.6    | 56.0    | 980     | 75      | \"              |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 05 /    | 30.2    | 56.5    | 980     | 75      | \"              |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 05 /    | 30.9    | 56.8    | 977     | 80      | \"              |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 05 /    | 31.5    | 56.8    | 975     | 85      | \"              |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 05 /    | 32.1    | 56.7    | 970     | 90      | \"              |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 06 /    | 32.6    | 56.6    | 962     | 100     | \"              |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 06 /    | 33.0    | 56.5    | 970     | 90      | \"              |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 06 /    | 33.5    | 56.0    | 975     | 80      | \"              |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 06 /    | 33.9    | 55.4    | 980     | 75      | \"              |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 07 /    | 34.4    | 54.6    | 987     | 65      | \"              |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 07 /    | 34.8    | 53.3    | 983     | 70      | \"              |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 07 /    | 35.6    | 51.8    | 980     | 75      | \"              |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 07 /    | 36.5    | 50.8    | 980     | 75      | \"              |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 08 /    | 37.2    | 49.9    | 982     | 70      | \"              |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 08 /    | 37.9    | 49.0    | 985     | 65      | \"              |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 08 /    | 38.7    | 48.0    | 985     | 65      | \"              |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 08 /    | 39.1    | 47.2    | 985     | 65      | \"              |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 09 /    | 39.4    | 46.4    | 987     | 60      | tropical storm  |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 09 /    | 39.8    | 44.9    | 987     | 55      | \"              |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 09 /    | 40.4    | 43.4    | 988     | 55      | \"              |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 09 /    | 41.1    | 42.1    | 988     | 50      | \"              |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 10 /    | 41.9    | 40.6    | 988     | 50      | \"              |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 10 /    | 42.9    | 39.2    | 988     | 50      | \"              |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 10 /    | 44.5    | 37.7    | 980     | 50      | extratropical   |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 10 /    | 46.0    | 36.3    | 975     | 55      | \"              |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 11 /    | 48.0    | 35.0    | 975     | 60      | \"              |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 11 /    | 50.0    | 34.0    | 974     | 60      | \"              |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 11 /    | 52.0    | 32.9    | 971     | 65      | \"              |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 11 /    | 54.0    | 32.0    | 968     | 65      | \"              |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 12 /    | 55.5    | 31.0    | 962     | 65      | \"              |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 12 /    | 57.0    | 29.0    | 967     | 65      | \"              |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 12 /    | 58.5    | 26.0    | 970     | 65      | \"              |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 12 /    | 61.0    | 23.0    | 972     | 60      | \"              |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 13 /    | 62.0    | 21.0    | 974     | 55      | \"              |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 13 /    | 62.9    | 19.0    | 976     | 50      | \"              |
| 0600    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 13 /    | 63.5    | 16.0    | 980     | 45      | \"              |
| 1200    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 13 /    | 63.0    | 10.0    | 983     | 45      | \"              |
| 1800    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 14 /    | 63.0    | 0.0     | 984     | 45      | \"              |
| 0000    |         |         |         |         |                 |
+---------+---------+---------+---------+---------+-----------------+
| 14 /    |         |         |         |         | Merged with     |
| 0600    |         |         |         |         | extratropical   |
|         |         |         |         |         | cyclone         |
+---------+---------+---------+---------+---------+-----------------+
| 06 /    | 32.6    | 56.6    | 962     | 100     | minimum         |
| 0000    |         |         |         |         | pressure        |
+---------+---------+---------+---------+---------+-----------------+

Number range CHAPTERTable 2. Selected ship reports with winds of at
least 34 kt for Hurricane Maria, 1-10 September 2005.

+-----------+-----------+-----------+-----------+-----------+-----------+
| Date/Time | Ship call | Latitude  | Longitude | Wind      | Pressure  |
| (UTC)     | sign      |           |           |           |           |
|           |           | (°N)      | (°W)      | dir/speed | (mb)      |
|           |           |           |           | (kt)      |           |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 07 / 1200 | PECS      | 33.8      | 49.5      | 200 / 37  | 1008.3    |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 09 / 0000 | HPII      | 37.5      | 38.3      | 180 / 36  | 1015.0    |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 10 / 0500 | WRYX      | 48.1      | 36.9      | 090 / 37  | 1010.0    |
+-----------+-----------+-----------+-----------+-----------+-----------+

Number range CHAPTER

Number range CHAPTERTable 3. Preliminary forecast evaluation
(heterogeneous sample) for Hurricane Maria, 1-10 September 2005.
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, but does not
include the extratropical stage, if any.

+-----------+-------+-------+-------+-------+-------+-------+-------+
| Number    | For   |       |       |       |       |       |       |
| range     | ecast |       |       |       |       |       |       |
| CHAPTE    | P     |       |       |       |       |       |       |
| RForecast | eriod |       |       |       |       |       |       |
| Technique | (h)   |       |       |       |       |       |       |
+===========+=======+=======+=======+=======+=======+=======+=======+
|           | 12    | 24    | 36    | 48    | 72    | 96    | 120   |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| CLP5      | 46    | 86    | 119   | 146   | 181   | 201   | **    |
|           | (34)  | (32)  | (30)  | (28)  | (24)  | (20)  | 217** |
|           |       |       |       |       |       |       | (16)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFNI      | 37    | 70    | 103   | 137   | 191   | 266   | 354 ( |
|           | (31)  | (29)  | (27)  | (24)  | (20)  | (13)  | 9)    |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFDI      | 35    | *     | 76    | 101   | 162   | 223   | 219   |
|           | (34)  | *54** | (30)  | (27)  | (22)  | (14)  | (10)  |
|           |       | (32)  |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GFSI      | 42    | 68    | 91    | 124   | 210   | 353   | 375 ( |
|           | (34)  | (31)  | (29)  | (25)  | (18)  | (11)  | 5)    |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| AEMI      | 40    | 67    | 92    | 131   | 199   | 314   | 365 ( |
|           | (34)  | (32)  | (30)  | (28)  | (18)  | (14)  | 9)    |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| NGPI      | 35    | 60    | 85    | 113   | 178   | 226   | 339   |
|           | (33)  | (31)  | (29)  | (27)  | (23)  | (18)  | (14)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| UKMI      | 43    | 70    | 88    | 87    | **    | 170   | 332   |
|           | (33)  | (31)  | (29)  | (27)  | 100** | (19)  | (15)  |
|           |       |       |       |       | (23)  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| A98E      | 42    | 62    | 101   | 166   | 264   | 402   | 538   |
|           | (34)  | (32)  | (30)  | (28)  | (24)  | (20)  | (16)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| A9UK      | 49    | 68    | 92    | 132   | 220   |       |       |
|           | (16)  | (16)  | (15)  | (14)  | (12)  |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| BAMD      | 38    | 72    | 104   | 128   | 212   | 354   | 579   |
|           | (33)  | (31)  | (29)  | (27)  | (23)  | (19)  | (15)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| BAMM      | 35    | *     | *     | 107   | 182   | 286   | 392   |
|           | (33)  | *54** | *73** | (27)  | (23)  | (19)  | (15)  |
|           |       | (31)  | (29)  |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| BAMS      | 50    | 84    | 117   | 161   | 260   | 380   | 473   |
|           | (33)  | (31)  | (29)  | (27)  | (23)  | (19)  | (15)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| CONU      | *     | *     | 74    | 91    | 122   | **    | 263   |
|           | *32** | *54** | (30)  | (28)  | (24)  | 153** | (14)  |
|           | (34)  | (32)  |       |       |       | (18)  |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| GUNA      | *     | *     | *     | *     | **    | 162   | **    |
|           | *32** | *53** | *71** | *73** | 116** | (10)  | 208** |
|           | (32)  | (29)  | (27)  | (22)  | (16)  |       | ( 4)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| FSSE      | *     | *     | *     | *     | **    | **    | **    |
|           | *31** | *50** | *67** | *81** | 105** | 155** | 160** |
|           | (29)  | (27)  | (22)  | (21)  | (17)  | (11)  | ( 7)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| OFCL      | 33    | 56    | 74    | 85    | 120   | 156   | 218   |
|           | (34)  | (32)  | (30)  | (28)  | (24)  | (20)  | (16)  |
+-----------+-------+-------+-------+-------+-------+-------+-------+
| NHC       | 42    | 75    | 107   | 138   | 202   | 236   | 310   |
| Official  | (     | (     | (     | (     | (     | (649) | (535) |
|           | 3400) | 3116) | 2848) | 2575) | 2117) |       |       |
| (         |       |       |       |       |       |       |       |
| 1995-2004 |       |       |       |       |       |       |       |
| mean)     |       |       |       |       |       |       |       |
+-----------+-------+-------+-------+-------+-------+-------+-------+

Number range CHAPTER

![](media/image1.wmf){width="7.740277777777778in"
height="6.000694444444444in"}

Number range CHAPTERFigure 1. Best track positions for Hurricane Maria,
1-10 September 2005. Track during the extratropical stage is based
partially on analyses from the NOAA Ocean Prediction Center.

![](media/image2.wmf){width="6.930555555555555in"
height="4.819444444444445in"}

Number range CHAPTERFigure 2. Selected wind observations and best track
maximum sustained surface wind speed curve for Hurricane Maria, 1-10
September 2005. Objective Dvorak estimates represent linear averages
over a three-hour period centered on the nominal observation time.
Estimates during the extratropical stage are based partially on analyses
from the NOAA Ocean Prediction Center.

![](media/image3.wmf){width="6.930555555555555in"
height="4.819444444444445in"}

Number range CHAPTERFigure 3. Selected pressure observations and best
track minimum central pressure curve for Hurricane Maria, 1-10 September
2005. Objective Dvorak estimates represent linear averages over a
three-hour period centered on the nominal observation time. Estimates
during the extratropical stage are based partially on analyses from the
NOAA Ocean Prediction Center.Number range CHAPTER

[^1]: Errors given for the 96 and 120 h periods are averages over the
    four-year period 2001-4.