[NCEP Logo]

Preliminary Report
Hurricane Nora
16-26 September 1997

Edward N. Rappaport
National Hurricane Center
updated 30 October 1997

Tropical Storm Andres
Tropical Storm Blanca
Tropical Depression 3-E
Tropical Storm Carlos
Tropical Depression 5-E
Hurricane Dolores
Hurricane Enrique
Hurricane Felicia
Hurricane Guillermo
Tropical Storm Hilda
Tropical Storm Ignacio
Hurricane Jimena
Tropical Storm Kevin
Hurricane Linda
Tropical Storm Marty
Hurricane Nora
Tropical Storm Olaf
Hurricane Pauline
Hurricane Rick

[1997 EPAC Hurricane Season]

a. Synoptic History

Hurricane Nora formed early on the 16th of September about 250 nautical miles to the southwest of Acapulco (Table 1 and Fig. 1a [19K GIF]). It originated in a large area of disturbed weather that had slowly become better organized while drifting west-northwestward during the previous few days. Analysis of satellite pictures indicates that this activity was likely related to a westward-moving tropical wave that crossed from Africa into the Atlantic hurricane basin on the 30th and 31st of August. The northern part of the wave was associated with the formation of Hurricane Erika in the central tropical Atlantic, while the southern part continued westward through the Caribbean Sea and northern South America, and arrived in the eastern Pacific basin on 12 September.

Nora matured in an environment of relatively light wind shear, and much of its development appears to have been related to variations in sea-surface temperature (SST). Nora formed over very warm water (29-30C). Deep convection quickly increased and became organized in well-defined bands on the 16th, with Dvorak technique intensity estimates of T2.5 forming the basis for estimating that the system became a tropical storm at 1800 UTC on the 16th (Figs. 2 [17K GIF] and 3 [15K GIF]). Further strengthening occurred over the following two days. The first signs of what would become a rather large and ragged eye were detected in infrared satellite pictures early on the 18th. By late that day, Nora was a hurricane with 90-kt sustained winds.

During Nora's first few days, the winds around a mid-level high over northern Mexico helped direct the tropical cyclone slowly toward the west-northwest. From midday on the 18th to early on the 20th, however, Nora nearly stalled. The hurricane weakened during that period. The height, amount, and organization of convection decreased and the eye disappeared. The maximum wind speed is estimated to have decreased to 65 knots. This weakening is presumed to have occurred in response to the hurricane's prolonged stay over waters cooled by upwelling beneath its circulation. Analyses in this part of Nora's wake show SSTs cooled by about 2C, on average, to about 27C.

By late on the 20th, Nora was on the move again, at 5 to 10 knots toward the west-northwest or northwest, roughly parallel to the southwest coast of Mexico. Nora then rapidly restrengthened. The eye reappeared, initially with a diameter of 15 nautical miles, and cloud tops cooled. Nora reached its peak maximum wind speed of 115 kt near 1200 UTC on the 21st.

On the 21st through the 23rd, Nora's track converged with, and then followed, the track previously taken by Hurricane Linda (Fig. 1b [22K GIF]). In that area, Linda had been the strongest eastern Pacific hurricane on record just a few weeks earlier and its circulation had induced lower SSTs. Nora gradually weakened over Linda's wake, with the eye temporarily broadening to a diameter of about 50 nautical miles and the eyewall becoming broken. Estimated wind speeds decreased to about 70 knots at 1800 UTC on the 23rd.

An omega-like blocking pattern developed over the western United States during the last week of September. This left a weakness in the height pattern to the north of Nora and eventually a trough with a cut-off low to the northwest of the hurricane. The track of Nora became north-northwestward and then northward on the 24th. This carried Nora over yet another SST anomaly, a large patch of waters more than 2C above normal abutting the west coast of Baja California. Nora remained over waters of at least 26C all the way to its landfall on the morning of the 25th at Punta Euguenia and then about 50 nautical miles south-southeast of San Fernando, Baja California. Hence, Nora had restrengthened slightly, and then weakened less quickly than most tropical cyclones in that area. It was still at hurricane strength during its landfalls.

Nora was accelerating northward at landfall, steered by the flow associated with the trough to its northwest. The center of the cyclone crossed the Baja California peninsula at 20-25 knots and traveled up the western shoreline of the Gulf of California. It crossed into the United States, near the California/Arizona border, still as a tropical storm, near 2100 UTC on the 25th. Most of the heaviest precipitation was then located to the northeast of the center.

Rapid weakening ensued and winds dropped to tropical depression strength near 0000 UTC on the 26th, when the center was located about midway between Blythe and Needles, California. The low-level center was moving toward the north-northeast as it degenerated early on the 26th. A remnant circulation aloft apparently persisted, however, and is likely to have been responsible for a period of near hurricane-force winds observed at the NWS Cedar City Doppler radar, located in the mountains of southwestern Utah at an elevation of about 10,600 feet.

The residual area of cloudiness and showers gradually became more diffuse over the following two days while moving generally northeastward, through portions of Utah, Colorado, Idaho and Wyoming.

b. Meteorological Statistics

Table 1 provides the post-storm "best track" location and intensity estimates for Nora. Figures 2 and 3 show the hurricane's estimated central pressure and maximum one-minute wind speed, respectively, versus time and the associated satellite data. Position and intensity estimates from satellite pictures were provided by the Air Force Global Weather Center (AFGWC), NOAA Tropical Analysis and Forecast Branch (TAFB) and NOAA Synoptic Analysis Branch (SAB).

Table 2 lists the observations of tropical storm force winds. Most came from ships at sea. A 39-kt 2-minute sustained wind was observed at Yuma during Nora's passage. Such observations of tropical storm force winds are a rarity in the United States for eastern Pacific tropical cyclones. The peak gust observed at Yuma was 47 kt. A gust to 45 k t occurred at Ajo, AZ.

The NWS Doppler radar at Yuma showed a 40 nautical mile wide band of hurricane force winds aloft to the east of Nora's center near the Arizona/Sonora border near noon on the 25th. These winds were observed at about 4-5,000 ft, could have extended to higher altitudes, and likely were related to the patch of near-hurricane force winds observed over the high terrain of southwestern Utah 12-18 hours later.

The Yuma radar indicated a small area with near 10 inches of rain along the northern Gulf of California coast of Baja California. In the United States, the 11.97 inches recorded at the 5700 ft level in the Harquahala Mountains in Arizona was, by far, the largest total (Table 3). More than three inches occurred in some spots in Arizona, California, Nevada, and Utah. Some of the amounts were comparable to the local yearly average rainfall.

c. Casualty and Damage Statistics

Two deaths were reported from Mexico in association with Nora. One person was electrocuted by a downed power line in Mexicali. The other fatality occurred to a diver caught in strong underwater currents created by Nora off the coast of the San Quintin Valley. In the United States, there were no deaths directly related to Nora. The California Highway Patrol attributed three or four traffic fatalities in southern California to weather.

Although Nora remained well offshore from southwestern mainland Mexico, the Associated Press reported that waves to 16 feet hit that coastline, destroying dozens of homes. It also destroyed the Pie de la Cuesta beaches of Acapulco.

About 350 to 400 people were made homeless by floodwaters in the town of Arroyo de Santa Catarina in northern Baja California. Heavy damage and flooding was reported in San Felipe, on the northwestern shore of the Gulf of California. On the northeastern shore, at Puerto Peñasco, Nora's winds blew down trees, billboards, electric wires, taco stands, and ripped sheet-metal from homes. Waves of 10 feet were reported there.

Damage totals in the United States are incomplete at this time but media summaries of Nora included a loss to agriculture preliminarily estimated at several hundred million dollars. About a $30 to 40 million loss to lemon trees was estimated.

In Somerton, AZ, 10 miles south of Yuma, damage to mobile homes and flooding was reported. About 12,000 people lost power in Yuma.

In California, about 125,000 customers lost power in the Los Angeles area with scattered, much smaller outages elsewhere. In San Diego, El Centro, Palm Springs and Indio, street flooding was reported. Winds knocked down about 16 power poles in Seeley.

The remnant circulation aloft apparently downed and/or sheared off the tops of hundreds of large (1-2 ft diameter) trees in southwestern Utah, mainly at elevations above 10,000 feet in the area that includes the Dixie National Forest. Three residences in that region were damaged by falling trees and power was disrupted.

d. Forecast and Warning Critique

Table 4 shows the average track forecast errors of the numerical models and the NHC official forecast. On average, the best short-term track guidance was provided by the statistical track models run from the AVN and UKMET output (P91E and P9UK). The best 72-hour forecasts were made by the UKMET model. The average official forecasts were generally competitive with the best available guidance. The NHC errors were comparable to the long-term averages, except at 72 hours where they were about 20% larger than average.

The NHC intensity forecasts did not anticipate the variations in strength accompanying Nora's interaction with upwelled waters. A few forecast errors as large as 40 knots resulted. Otherwise, errors were comparable to long-term averages (which increase to about 20 kt at 72 hours).

Table 5 lists the tropical storm and hurricane watches and warnings issued by the government of Mexico. Warnings for high swells and waves were also posted for portions of the coast of Mexico.

The threat to the southwestern United States was unusual and required an unprecedented coordination between the NHC and offices in the NWS Western Region. In one instance, a conference call was held with about twelve offices (including the Salt Lake City RFC, Western Region MSD, HPC, and Navy METOC facility in San Diego). From the NHC perspective, the coordination was smooth and effective.


Operational assistance and data for this report were provided to the NHC by NWS offices in Phoenix, Tucson, Flagstaff, Las Vegas, Salt Lake City, San Diego and Oxnard.

Table 1. Preliminary best track, Hurricane Nora,16-26 September 1997.
Position Pressure
Wind Speed
Lat. (°N)Lon. (°W)
16/060012.7101.7100425 Tropical Depr.
120013.2101.9100330" "
180013.6102.1100135 Tropical Storm
17/000013.9102.3100040" "
060014.0102.499840" "
120014.1102.599650" "
180014.3102.799455" "
18/000014.3102.999055" "
060014.3103.299060" "
180014.1103.797090" "
19/000014.3103.997290" "
060014.4104.097385" "
120014.5104.197480" "
180014.6104.297680" "
20/000014.8104.597870" "
060015.1104.998270" "
120015.4105.598765" "
180015.6106.298570" "
21/000015.8106.797975" "
060016.1107.397095" "
120016.6108.0950115" "
180017.2108.9951110" "
22/000017.7109.7952110" "
060018.0110.5953110" "
120018.5111.2955110" "
180018.9111.8957105" "
23/000019.3112.396195" "
060019.8112.997390" "
120020.2113.398380" "
180020.7113.798070" "
24/000021.5114.197975" "
060022.3114.597975" "
120023.2114.897975" "
180024.2114.897975" "
25/000025.8114.897975" "
060027.5114.898175" "
120029.5114.898465" "
180031.7114.999055 Tropical Storm
26/000034.0114.799730 Tropical Depr.
060036.1114.1100425 Dissipating
25/063027.6114.898175 Landfall near Punta Eugenia, MX
25/110029.3114.898370 Landfall SSE of San Fernando, MX
21/120016.6108.0950115 Minimum Pressure

Table 2. Observations of 34 knots or higher sustained winds associated with Nora.
Lat. Lon.
(°N) (°W)
Wind Dir./Spd.
3FGI5-----18/180017.0 101.8110/44 ------
C6FA6Kenneth P. Hill18/210012.5 103.9250/40 994.0
PGROPauwgracht18/210016.1 99.8140/58 1009.0
C6FA6Kenneth P. Hill19/000012.3 103.3260/37 994.0
PGROPauwgracht19/0300---- -----130/35? 1009.0
PGROPauwgracht19/060017.0 101.5120/37 1008.8
3ERJ8Georgia Rainbow II21/000015.7 108.6320/48 999.0
3ERJ8Georgia Rainbow II21/120014.7 106.7180/39 1001.5
PFSJMagic21/180011.4 107.4220/47 1008.5
STORM-----22/1200---- -----110/35? 1006.0
STORM-----22/150021.3 106.6150/35 1007.5
ZCBD9-----23/000022.5 109.4110/40 1001.7
ZCBL6-----23/000020.3 106.8140/40 ------
ZCBD9-----23/060022.0 107.8140/40 1005.4
ZCBL6-----23/210022.1 110.9140/35 1002.8
YJZL7Wislanes24/120023.1 111.1140/35 1003.3
ZCBL6-----24/150025.0 113.5120/44 998.2
ZCBL6-----24/180025.2 113.8120/44 995.8
ZCBL6-----24/210025.3 113.8140/48 989.0
ZCBL6-----25/000025.2 113.7160/50 991.8
76723Socorro Island, MX22/000018.7 111.0340/45 992.8
76401El Medano(?), MX24/060024.4 111.3140/40? 998.5
76061Puerto Peñasco, MX25/150031.3 113.6 ---/35 
76061Puerto Peñasco, MX25/180031.3 113.6 100/351002.7
Yuma Arizona Marine Corps Naval Air Station ASOS25/2106 32.7 114.6150/39
Peak Gust 47 at 2107
994.6 at 25/2103

Table 3. Storm-total rainfall reports exceeding 3 inches (except for a few ALERT gauges in southern California), and selected additional sites with smaller totals, associated with Nora.
Reports of > 3 inches Selected Sites
Harquahala Mtns @5700', AZ11.97  Idyllwild, CA2.86
Yarnell Hill, AZ6.26  Prescott, AZ2.37
Harquahala Mountains, AZ5.97  Grand Canyon Nat. Pk., AZ2.05
Bagdad, AZ5.75  Blythe, CA2.03
Thumb Butte Tank, AZ5.75  Thermal, CA1.99
Mayer, AZ5.06  Escondido, CA1.84
Crown King, AZ4.79  Mt. Wilson, CA1.79
Mt. Laguna, CA4.70  Palm Springs, CA1.73
15 miles W Wickenberg, AZ4.53  Flagstaff, AZ1.70
Hualapai Mountain, AZ4.50  Daggett, CA1.55
Centennial Wash, AZ4.21  China Lake, CA1.49
Tiger Wash Fan, AZ4.17  Imperial Beach, CA1.35
Gladden, AZ4.02  Chula Vista, CA1.33
Upper Tiger Wash, AZ3.82  Henderson, NV1.27
Turtle People, AZ3.70  Kingman Airport, AZ1.13
Flores West, AZ3.66  Death Valley (Furnace Ck)1.11
Upper Morongo Creek, CA3.61  Organ Pipe Nat. Mon., AZ1.11
Yuma Marine Corps NAS3.59  Lake Havasu, AZ1.00
Upper Tahquitz Creek, CA3.58  Palmdale, CA0.97
Wilhoit, AZ3.54  Imperial, CA0.96
Horsethief Basin, AZ3.39  Twenty-Nine Palms, CA0.96
Lava Point, UT3.30  San Diego, CA0.80
Wickenberg, AZ3.25  San Gabriel, CA0.78
Mt. Charleston, NV3.25  Las Vegas (NWS office)0.77
Mt. Union, Az3.23  Pasadena, CA0.70
Hartman Wash, AZ3.19  Laughlin, NV0.60
Sols Tank, AZ3.15  Bullhead City, NV0.60
Mid-Martinez Creek, AZ3.11  LA Civic Center, CA0.45
Hassy @ Box Canyon, AZ3.07  Long Beach, CA0.44
Banning Bench, CA3.07  Tonopah, NV0.34
Raywood Flat, CA3.07  Los Angeles (LAX), CA0.26
     Bishop, CA0.13
    Phoenix, AZ0.03

Table 4
Preliminary forecast evaluation of Hurricane Nora: Heterogeneous sample.

(Errors in nautical miles for tropical storm and hurricane stages with number of forecasts in parenthesis)
Forecast TechniquePeriod (hours)
CLIP33 (35)65 (33)99 (31)141 (29)218 (25)
GFDI44 (29)82 (27)117 (25)157 (24)253 (20)
GFDL*52 (16)84 (15)119 (14)155 (13) 235 (11)
LBAR33 (35)68 (33)107 (31)155 (29)263 (25)
MRFO*42 (9)103 (8)167 (8)205 (7) 293 (6)
AVNO*40 (16)89 (15)147 (14)202 (13) 269 (11)
AVNI57 (28)118 (26)170 (24)210 (23)290 (19)
BAMD34 (34)72 (32)112 (30)157 (28)257 (24)
BAMM47 (34)93 (32)140 (30)192 (28)283 (24)
BAMS58 (34)114 (32)169 (30)221 (28)298 (24)
P91E28 (34)54 (32)83 (30)127 (28)231 (24)
NGPS*82 (20)129 (18)169 (18)198 (18) 273 (15)
NGPI57 (21)100 (20)140 (20)180 (20)297 (15)
UKM*38 (16)59 (16)90 (15)105 (14) 180 (12)
UKMI41 (34)75 (33)90 (31)118 (29)193 (25)
P9UK28 (15)55 (14)82 (13)113 (12)213 (10)
NHC OFFICIAL26 (35)57 (33)97 (31)144 (29) 233 (25)
(1988-1996 9-year average)
39 (2288)71 (2058) 105 (1822)138 (1607)194 (1228)

* Output not available until after the NHC forecast is issued.

Table 5. Tropical Cyclone watch and warning summary, Hurricane Nora.
16/2100Hurricane Watch issued Lazaro Cardenas to Cabo Corrientes, Mexico
17/0000Tropical Storm Warning issued Lazaro Cardenas to Punta Maldonado, Mexico
17/2100Tropical Storm Warning discontinued Lazaro Cardenas to Punta Maldonado, Mexico
18/2100Hurricane Watch discontinued Lazaro Cardenas to Cabo Corrientes, Mexico
21/0900Hurricane Watch issued Revillagigedo Islands, Mexico
21/1500Hurricane Warning issued-- replaced Hurricane WatchRevillagigedo Islands, Mexico
23/0300 Tropical Storm Warning issued Baja California south of 25N latitude
Hurricane Watch issued Baja California from north of 25N to Punta Eugenia
23/2100 Tropical Storm Warning extended Baja California from Punta Eugenia southward
Hurricane Warning discontinued Revillagigedo Islands, Mexico
24/0300Hurricane Watch extended Baja California from latitude 25N to Punta San Carlos
24/1200 Hurricane Warning revised Baja California Pacific coast from Bahia Ballenas to Punta Santo Tomas; Baja California Gulf of California Coast northward from Santa Rosalia
Tropical Storm Warning revised Baja California Pacific coast from Bahia Ballenas southward to latitude 24N
Hurricane Watch revised Mainland Mexico northward from Bahia Kino
Tropical Storm Watch issued Baja California from Punta Santo Tomas to Tijuana
25/0300Tropical Storm Warning issued Mainland Mexico northward from Bahia Kino
25/1200Tropical Storm Warning discontinued Baja California southward of line from Bahia Ballenas to Santa Rosalia
25/1500 Hurricane Watch, Hurricane Warning and Tropical Storm Watch discontinuedAll areas
Tropical Storm Warning revised Gulf of California coast north of 30N latitude
25/2100Tropical Storm Warning discontinued Gulf of California coast north of 30N latitude

Brian Maher
Jack Beven

Last updated December 26, 1998