ABHW40 PHNL 020210 PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE HONOLULU HI 415 PM HST WED APR 1 1998 ...DROUGHT CONDITIONS CONTINUE IN HAWAII... BELOW AVERAGE PRECIPITATION OCCURRED ACROSS THE STATE OF HAWAII. ALL FIRST ORDER AND ALL AUTOMATED RAIN GAGES RECEIVED LESS THAN AVERAGE RAINFALL IN MARCH. HAWAII HAS FOUR FIRST ORDER NATIONAL WEATHER SERVICE OFFICES AND 69 AUTOMATED (TIPPING BUCKET ) RAIN GAGES. 67 OF THESE 73 REPORTED LESS THAN 50 PERCENT OF AVERAGE RAINFALL FOR THE MONTH OF MARCH WITH 35 OF THE 73 RECEIVING LESS THAN 25 PERCENT OF AVERAGE FOR THE MONTH. THIS CONTINUED THE SIX MONTH TREND STATEWIDE OF DRIER THAN USUAL CONDITIONS. THE FIRST HALF OF MARCH 1998 WEATHER PATTERN WAS DOMINATED BY A STRONG JET STREAM ACROSS THE PACIFIC OCEAN AND MULTIPLE UPPER LEVEL HIGH PRESSURE RIDGES OVER AND TO THE WEST OF THE ISLANDS. DURING THE LAST PART OF THE MONTH... THE JET STREAM REMAINED STRONG TO THE NORTH OF THE ISLANDS... BUT THE HIGH PRESSURE RIDGE SHIFTED NORTH OF THE ISLAND CHAIN. THE STRONG HIGH PRESSURE TO THE NORTH AND NORTHEAST OF THE ISLAND CHAIN AND THE RESULTING INCREASED PRESSURE GRADIENT OVER HAWAII BROUGHT A MORE SEASONABLE SHIFT TO A TRADE WIND PATTERN. THE DEPTH OF THE MOIST LAYER OF MARINE AIR APPEARS AT THIS TIME TO STILL BE SUPPRESSED... BUT DEEP ENOUGH TO ALLOW TRADE SHOWERS TO DEVELOP IN WINDWARD SECTIONS OF THE ISLANDS. THIS HAS HELPED BRING MUCH NEEDED MOISTURE IN THE LAST FEW DAYS TO WINDWARD SECTIONS OF THE ISLANDS. THE RECENT RAINFALL HAS PROVIDED SOME RELIEF TO WINDWARD LOCATIONS... HOWEVER MORE RAINFALL IS NEEDED. SOME LEEWARD AREAS HAVE RECEIVED VERY SMALL AMOUNTS OF RAINFALL. RESEARCH AND CURRENT FORECASTS INDICATE THE WINDWARD TRADE SHOWERS WILL LIKELY CONTINUE INTO MAY. RAINFALL AMOUNTS STILL MAY NOT MAKE SEASONAL AVERAGES... BUT SHOULD BE MORE THAN THE VERY SMALL AMOUNTS THAT WERE RECEIVED IN THE FIRST PART OF THE YEAR. THE FOLLOWING ARE RAINFALL STATISTICS FOR SELECTED LOCATIONS AROUND THE STATE AND COMPARATIVE DATA FROM RECENT YEARS AND SIGNIFICANT EL NINO EVENTS. THE ISLAND AND STATION NAME ARE LISTED WITH THE MARCH 1998 RAINFALL TOTAL. FOR COMPARISON... THE AVERAGE FOR THE MONTH AND PERCENT OF AVERAGE ARE LISTED FOR THE STATION IN THE FOLLOWING TWO COLUMNS. LONGER TERM STATISTICS FOR HYDROLOGIC PURPOSES ARE LISTED WITH JANUARY... FEBRUARY AND MARCH THREE MONTH RAINFALL ACCUMULATIONS AND AVERAGE FOR THOSE THREE MONTHS IN COLUMNS FIVE AND SIX. THE FINAL THREE COLUMNS ARE COMPARATIVE DATA TO PAST EL NINO YEARS RAINFALL FROM THESE SITES OR NEARBY NWS RECORDING STATIONS. (Second message, from later on 980403) MONTHLY PRECIPITATION SUMMARY State of Hawaii portion of Honolulu HSA MONTH: March 1998 PREPARED April 2, 1998 State: No significant Flash flooding was reported. Significant drought conditions are occurring across the state. This was the third driest March of record in Honolulu since record keeping began in 1874. This was the third driest January, February and March combined in Honolulu since record keeping began. Below average precipitation occurred state wide with all first order and all automated rain gages receiving less than average rainfall in March. Hawaii has four first order National Weather Service Offices and 69 automated rain gage stations. 67 of these 73 reported less than 50 percent of average rainfall for the month of March with 35 of the 73 receiving less than 25 percent of average for the month. This continued the six month trend state wide of drier than usual conditions. The first half of March1998 weather patterns were dominated by a strong upper level jet stream across the Pacific Ocean north of the islands and multiple periods with upper level high pressure ridges over and to the west of the islands. This strong upper level ridge pattern and its effects to limited precipitation amounts is clearly indicating the effects of the El Nino phenomena on the islands. In the second half of the month the ridge of high pressure shifted north of the islands at all levels of the atmosphere. This allowed the surface high northeast of the islands to strengthen to nearer to average position and strength. This shift in weather patterns came with the shift to the spring season and has brought stronger trade winds and thus trade wind showers to the windward sides of the islands. This added rainfall in windward areas has helped relieve some of the very dry conditions there. However much more rainfall is needed to get beyond the longer term drought situation. Kauai: All reporting stations had below average precipitation for the month. The most negative anomalous precipitation pattern in the month of March occurred on the south and southwest sides of the island with only 22 to 38 percent of average rainfall in those areas. The east side of the island from Kapahi to Lihue received the greatest amount of precipitation month, but was still only 73 to 45 percent of average. Oahu: Below average precipitation again occurred this month as frontal systems that usually pass through or near the islands in March did not materialize. The greatest negative anomaly in March, was the leeward areas of the island, especially the central and southwest sections. The greatest negative precipitation anomaly along the southwest side of the island, in the area known as the Waianae area (leeward of the Waianae Mountain range) where only 2 to 20 percent of average (.04 to .61 inches) precipitation occurred. The entire island experienced a strong negative precipitation anomaly with the wettest sections of the island, northeast facing windward areas and higher elevations of the Koolau Mountains receiving 25 to 45 percent of average rainfall. Maui County: Molokai and Lanai were below average at reporting stations with Lanai City receiving 44 percent of average rainfall (1.64 inches). The Island of Maui reporting stations indicated below average precipitation at all locations. Negative anomalies were particularly noted in the areas with dependence on synoptic scale precipitation in March, such as Lahainaluna, Kihei and Ulupalakua. This continues the several months' period of very dry conditions in those areas. 0 to 18 percent of average rainfall occurred in those areas this month with rainfall amounts of 0.00 at Kihei to 0.42 at Lahaninaluna. The running eight months rainfall total for Kihei has only been 1.83 inches, which is 11.67 inches below average. Hawaii County: A generally dry precipitation pattern was noted on the Big Island with all areas having well below average precipitation. However this is one of the areas where the return of trade winds and showers were significant in helping relieve some of the drier conditions in the state. The island wide negative precipitation anomaly is likely due to the decreased frequency of synoptic scale weather pattern days and possibly due to weaker or drier than average trade winds in the first half of this month. The Kona side of the island, dependent on convective precipitation and this time of year synoptic scale precipitation patterns, was well below average at all reporting locations. Honaunau (south of Captain Cook, Hawaii) and Kealakekua were stations with the greatest negative precipitation anomaly with only 8 and 18 percent of average rainfall, 0.42 and 0.99 respectively. Again, this is due to weak or drier than average synoptic scale weather systems. The following are rainfall statistics for selected locations around the state and comparative data from recent years and significant El Nino events. The island and station name are listed with the March 1998 rainfall total. For comparison, the average for the month and percent of average is listed for the station in the following two columns. Longer term statistics for hydrologic purposes are listed with January, February and March, three month rainfall accumulations and the average for those three months in columns five and six. The final three columns are comparative data to past El Nino years rainfall from these sites or nearby National Weather Service recording stations. MAR98 AVG % AVG 3 MONTH AVG MAR94 MAR87 MAR83 Kauai Lihue 1.87 4.20 45 8.08 13.40 3.33 2.13 TRACE Hanalei 3.83 14.00 27 12.31 35.40 3.91 2.92 M Hanapepe 0.71 3.20 22 2.49 11.20 1.87 M 1.19 Oahu Honolulu 0.03 2.20 1 1.01 8.00 3.77 0.31 0.53 Waianae 0.04 2.50 2 0.87 8.60 4.23 0.15 1.66 Hawaii Kai 0.87 3.90 22 2.48 11.70 4.80 0.40 M Manoa Lyon A. 5.92 14.40 41 14.69 37.80 27.43 4.17 2.12 Waialua 0.24 3.80 6 2.90 13.30 4.14 1.62 2.03 Ahuimanu (windward) 2.30 10.60 22 10.43 31.90 M 4.80 M Molokai Kaunakakai 0.38 1.80 21 2.51 7.70 0.00 0.00 0.40 Lanai Lanai City 1.64 3.70 44 4.69 13.90 3.25 1.26 0.42 Maui Kahului 0.18 2.70 7 1.03 9.70 4.23 0.57 1.12 Hana 1.16 9.50 12 2.36 25.80 27.54 3.50 2.32 Kihei 0.00 2.10 0 0.73 8.40 2.07 0.03 0.18 Lahainaluna 0.42 2.40 18 0.64 9.50 1.28 0.00 0.00 Wailuku 0.71 3.60 20 2.27 12.60 9.99 2.27 1.40 Hawaii Hilo 3.67 13.90 26 6.21 34.10 18.48 4.79 0.05 Pahala 0.32 6.30 5 0.54 20.10 8.20 0.96 0.52 Honaunau (Captain Cook) 0.42 5.10 8 1.46 12.00 2.66 2.00 0.01 Kamuela 2.57 7.90 33 7.58 20.50 3.31 1.35 0.09 Kamuela (Higher Elev.) 3.08 6.70 46 10.16 18.10 m m m Laupahoehoe 6.02 19.50 31 9.46 46.20 m 4.77 0.01 Data Sources: First order climate network weather observations stations of the National Weather Service at Lihue, HI, Honolulu, HI, Kahalui, HI, Hilo, HI. Additional data were taken from the HYDRONET state network of automated rain gages. Data collected in the automated gages are not certified and information used above should be used for information purposes only. Roger V. Pierce, Senior Service Hydrologist National Weather Service Forecast Office Honolulu, Hawaii