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The 1971 Central Pacific Tropical Cyclone Season
Perhaps Tropical Storm Sarah should not be included in this chronology since it was never classified as a tropical cyclone while in the Central North Pacific. However, the extra- tropical LOW which was once a tropical storm in the Western North Pacific created more havoc, with stronger winds and higher seas, in the Central North Pacific than at any time while a tropical cyclone farther west.
Additionally, strong winds and locally heavy rains over the entire State of Hawaii were observed on the 15th as the LOW moved north of the Islands.
Surface weather map analyses on the 6th indicated a suspicious area of low pressure development near 2N 155E. That area moved northwestward and was spotted as a tropical disturbance by satellite interpretation on the 8th. The following day, a Navy reconnaissance plane found an organized depression near 10N-138E.
By 1700 GMT on the 9th the depression had gained tropical storm strength. Within 24 hours the still northwestward moving SARAH attained maximum strength as a purely tropical system with winds of 50 knots near the center. SARAH weakened early on the 11th and became extratropical near 17N 142E later that day.
Extratropical SARAH followed an east-northeasterly track until the middle of the 15th when, 250 miles northwest of Honolulu, the storm turned to the northeast and accelerated to a forward speed of nearly 60 knots.
As the LOW moved north of the State of Hawaii on the 15th, strong southwest winds preceding its associated cold front did over $100,000 in damage on Oahu alone. Peak gusts of 62, 63, and 69 m.p.h. were recorded on Oahu at Wheeler AFB (Wahiawa), Kaneohe, and Kaena Poi,nt, respectively. Powerlines and trees were downed in many areas. In Windward Oahu winds, made more blustery in passing over the mountains, damaged 28 homes, a classroom, an armory and a warehouse, and in Waimanalo toppled a 40-foot ironwood tree onto a car, injuring the two occupants.
Lanai Airport was closed down and five homes were damaged in Molokai's Hoolehua district.
On Kauai peak gusts of 61 to 66 m.p.h. were observed at Kokee.
Rainfall was general over the State on both the 15th and 16th with many storm totals of 3 to 6 inches on most of the islands.
After passing to the north of the islands, SARAH, as an extratropical cyclone, continued to be a menace to Central North Pacific shipping. The SUSQUEHANNA encountered unwelcome 30-foot swells and 55-knot south-southwesterlies at 160600 GMT near 36N 142W, ahead of the storm's cold front. Six hours later a minimum central pressure of 987 mb (29.15") was analyzed at 40N 139W.
Before breaking up over the mountains of southern British Columbia during the early morning of the 18th, the storm brought gusts of over 60 m.p.h. to the state of Oregon as well as locally heavy precipitation to the Pacific Northwest, occurring as rain in the lowlands and snow at higher elevations.
DENISE, one of the stronger Eastern North Pacific hurricanes observed up to that time, began to develop on the 2nd in an area of showers observed by satellite near 11.0N 99.5W. A low pressure circulation, with winds to 25 knots and a minimum pressure of about 1009 mb (29.80") was analyzed near 12N 103 the next day.
Tropical storm intensity, with winds to 45 knots around a center at 14N 108W, was estimated from an ESSA-8 satellite picture made at 1737 GMT on the 4th. The storm then intensified steadily for the next 4 days while moving towards the westsouthwest. Its forward speed was initially 10 knots but increased to 16 knots on the 7th.
Hurricane intensity was achieved on the 6th, apparently a few hours after the ROBIN HOOD passed near the center, reporting a northwesterly wind of 35 knots and a 999.5 mb (29.52") pressure at 0600 GMT. Winds were estimated as strong as 125 knots around the eye of DENISE, upon penetration by USAF weather reconnaissance on the 8th. The aircraft reported the eye wall to be 5 nautical miles thick and extending to 38,000 feet.
The hurricane then turned gradually toward the west-northwest at 15 knots with little change in intensity for the next 2 days.
The continued movement of DENISE at low latitudes and the presence of Tropical Storm (ex-hurricane) CARLOTTA to the west=northwest through July 8 minimized inflow of air from cool waters north of 20N.
At 15.7N 137.6W at 1815 GMT on the 10th, just before DENISE entered the Central North Pacific, AF reconnaissance reported 700 mb winds of 100 knots 30 miles north-northeast of the center and estimated 100-knot maximum surface winds within 25 nautical miles of the center. The eye wall had begun to dissipate and was poorly defined on radar. The 700 mb temperature in the eye was 12C, or 1 cooler than 2 days earlier. The temperature at 700 mb in the rain area had cooled 3C during the same period increasing the contrast to 2C. Also, the weakening of the wall cloud indicated that the means for concentrating energy in the core of the hurricane was decreasing.
The following "Postflight Report" from the July 11 reconnaissance flight (Air Force Lark 07 Denise) told of continued weakening:
A July 12 reconnaissance flight found only 40-knot maximum surface winds when fixing the center of DENISE at 17l9'N 14946'W at 1800 GMT. Another flight was made into the dissipating storm center at 0340 GMT on the 13th because of its proximity to the Hawaiian Islands. Winds were no more than 35 knots with the strongest in the northwest quadrant and light .wind in the others. A final flight into remains of the storm at 16.5N 155.5W at 1800 GMT on the 13th reported no surface winds in excess of 20 knots.
Although the center of the remnants of DENISE was last located some 150 miles south of South Point, Hawaii, moisture laden clouds extended northward over Hawaii Island. Beneficial rains of more than an inch relieved the Hamakua district's parched pastures and sugar plantation, while in the Kailua-Kona area, flooding streams blocked Kuakini Highway, Alii Drive, and Middle Road and stranded motorist.
Beneficiaries of DENISE, other than the farmers and ranchers of Hawaii Island were Sheila Scott, a British Aviatrix flying solo around the world, and WINDWARD PASSAGE, winner of the Transpacific Yacht Race--both of whom, bound from San Francisco to Honolulu, were helped on their way by the strong easterly winds along DENISE's northern fringe.
The forecast staff at the WSFO Honolulu must, during the summer and fall months, be constantly on the alert for tropical systems developing just east of the International Date Line. Aviation forecast responsibility extends westward to 153E while marine forecast responsibility extends to 160E.
Since such developments usually occur over data sparse areas of the Central North Pacific, the forecasters are obliged to make maximum use of satellite data, their expertise in surface analysis, and their knowledge of tropical cyclone development in recognizing whether or not a particular disturbance has the potential for further development.
Even though a disturbance may not reach tropical storm or hurricane strength in the CPHC area of responsibility, the aviation and marine forecast sections should always be alert to the fact that it could reach tropical storm or typhoon intensity shortly after crossing the Date Line. Although the tropical cyclone advisory responsibility then passes to JTWC, aviation SIGMET (information issued by a meteorological watch office concerning the occurrence or expected occurrence of specified en route weather phenomena which, may affect the safety of aircraft operations) and specialized marine forecast responsibilities remain at WSFO, Honolulu as long as the system is east of 153E or 160E, respectively.
For that reason, short synopses of typhoon MARY and a few similar tropical cyclones are included in this chronology since there is documented evidence of their birth in the Central North Pacific.
MARY developed from a circulation induced from an upper tropospheric low in the TUTT (Tropical Upper Atmospheric Trough). Traced back to 24N 175W, south-southwest of Midway Island on July 11, the system drifted westward to a location halfway between Wake Island and Ocean Station VICTOR before aircraft reconnaissance identified it as a tropical storm on the 17th.
MARY began to take a northward course later on the 17th as it rounded the southeastern periphery of a high cell north of the western Hawaiian Islands. The small size of MARY, the uncertainty of forward acceleration, the storm's position outside the FWC APT coverage area on the 18th made its location uncertain. However, a valuable and timely positioning of MARY based on a geostationary ATS-1 satellite picture was relayed to JTWC by NESS at Suitland, Md. A reconnaissance aircraft was then vectored toward MARY and found that it had achieved typhoon strength.
Remaining at minimal typhoon strength for 24 hours, MARY passed 150 nautical miles west of Ocean Station VICTOR on the 20th but then diminished to a tropical storm as it headed northward. By the morning of the 21st MARY was beyond the range of reconnaissance aircraft as it accelerated eastward at 16 knots. By that afternoon satellite pictures showed cooler air entering the storm as it headed northeastward and became extratropical.
MARY stayed within the WSFO Honolulu aviation and marine forecast areas of responsibility throughout its life. Reports from the AMERICAN RANGER near 27N 165E (80 nautical miles south-southwest of MARY on the 17th), the OSIJMI MARU near 30N 167
E at 18/0000Z, and from the PICA near 29N 163E on the 19th helped in surface map analysis and marine forecasting during MARY's progress.
HILARY was the last tropical cyclone of the 1971 season in the Eastern North Pacific to attain tropical storm intensity west of 105W. The slow westward progress of this cyclone between 110W and 125W suggested the weakening of the subtropical high pressure belt to the north and an impending change in the pattern of storm activity.
Cyclonic curvature of cumulonimbus bands in the Intertropical Convergence Zone (ITCZ) was seen near Clipperton Island in a July 25 ESSA-9 photo. A circulation organized rapidly and a young tropical storm was seen at 10.8N 111.6W in the July 26 ESSA-8 pictures.
A reconnaissance flight at 700 mb about 1730 GMT on July 28 found a well-organized, symmetrical hurricane at 12.3N 115.5W. Its eye diameter was 13 nautical miles with an excellent stadium effect in the 35,000-foot wall cloud and a small hole in the cirrostratus above.
Twenty-four hours later the tall, unbroken wall cloud could not be penetrated safely by a WC-135 aircraft. Well-formed feeder bands encircled the storm and converged into the north and southwest parts of the wall cloud, which was strongest on the south side. The concurrent ESSA-8 picture showed that these bands had lost connection with the ITCZ.
A reconnaissance flight found a break on the east side of the eyewall and entered at 700 mb at 1800 GMT on the 30th, fixing the center at 14.5N 119.6W. The eye had become elliptical with 15 and 25 nautical mile axes. Moderate turbulence and moderate icing were reported in the feeder bands at 27,000 feet. Satellite pictures showed the feeder bands still separated from the ITCZ--sometimes an indication of weakening. A stratocumulus sheet revealed the presence of stable air about 300 nautical miles northwest of the center.
HILARY was still a vigorous hurricane on the 31st, though the height of its clouds had decreased. There had been no ship reports telling of HILARY's winds even though it was a full hurricane for nearly a week. However, the British ore carrier CHIYODA reported swells higher than 20 feet for more than 36 hours while overtaking and passing HILARY about 200 nautical miles north of the center between July 29 and 30.
The direction of HILARY's motion became erratic early on the 31st with a turn to the west-southwest followed by a turn to the northwest the following day. The latter turn brought the system closer to colder water and stable air.
HILARY was barely a tropical storm with 35-knot maximum surface winds when fixed by satellite imagery at 19.6N 130.5w at 1705 GMT on August 5. Dissipation occurred west of 14OW during the next two days.
Tropical Depression #24 was first detected by satellite near 14.5N 147W on the 23rd d all advisories were based on information provided by ESSA-8. A reconnaissance flight was scheduled but dissipation occurred near 14.5N 149.8W on the 24th and the mission was canceled.
The system that developed into FAYE was first sighted in satellite photos near 10N 175W as a weak tropical disturbance south of Johnston Island on September 27. Ill defined, it drifted west-northwestward for a week, passing near Eniwetok on October 3. The U.S. Coast Guard station on the atoll reported a sharp wind shift. By the 4th, satellite pictures showed signs of greater organization in the cloudiness. An aircraft investigation early the following morning located a tropical storm with 50-knot peak winds about 70 nautical miles east of the Marianas. From that point FAYE gradually weakened and continued nearly due westward, regained tropical storm strength and crossed Luzon on a track north of Manila into the South China Sea where it became a typhoon and commenced a highly unusual looping track which caused it to cut across Luzon for the second time--this time to the south of Manila.
FAYE briefly reached typhoon strength late on October 5 but dropped to tropical storm intensity as it passed north of Saipan on the 6th.