The Joint Typhoon Warning Center (JTWC) has a rich history reaching back to the WWII era. While few people outside of JTWC’s forecasting AOR (Area of Responsibility) or members of the military are aware of JTWC, it has played a vital role to both civilian and military personnel safeguarding countless lives and billions of dollars of assets. This article will provide an overview of the history of JTWC, its function, and an explanation of the various jobs performed there which allow for typhoon forecasts to be accurately disseminated on time.
During WWII the U.S. Third Fleet under Admiral Halsey had more than the Japanese to worry about, nature itself was just as dangerous an adversary. Historical data shows that on December 17, 1944, alone three destroyers, 146 aircraft, and 778 men all were lost to the forces of nature in the North Pacific. It was such a problem that by the time the U.S. was making plans to conduct atomic bombing runs on Nagasaki and Hiroshima that USAAF Lt. Col. Nick Chavasse of the 655th B-24 Bombardment Squadron was dispatched to Guam to conduct weather reconnaissance. The previous weather center which was on Saipan was moved to Guam on New Years eve 1944.
Before JTWC existed officially as it is known today it was called FWC/TTC (Fleet Warning Center/Typhoon Tracking Center), and opened for business in May of 1945. The problem with this was that the unit had no aircraft to conduct reconnaissance and the technology available at that time was not good enough to stand alone as a means of accurately tracking typhoons with a high level of accuracy or timeliness. What prompted a swift change to this was Typhoon Viper which peaked around the 4-5 of June in 1945. Viper alone damaged 48 ships and 76 aircraft that the U.S. absolutely could not afford to lose. Warnings were issued but they lacked the timeliness needed to be of significant value through no fault of the forecasters tasked with a near impossible job.
That expensive loss prompted the reassignment of the 655th Bombardment Squadron to the 55th Reconnaissance Squadron on June 16, 1945. The first test run of FWC/TTC came in August when their product (Forecasts and advisories) allowed Admiral Halsey to weave between and around three typhoons en-route to Japan to accept their formal surrender. Having proved the value of such a unit to Halsey and the other brass involved the 54th Weather Reconnaissance Squadron (WRS) was officially formed on September 4, 1945, at Anderson AFB, Guam. Yokota, Japan, also had a warning center which at times rotated primary tracking responsibilities with WRS or acted as a backup.
For the most part it was business as usual until May of 1958 when JMC (Joint Meteorology Committee) to PACOM (Pacific Command) was formed in Hawaii. This was formed as the First Weather Wing under Col. Nick Chanasse and was made up of members of three branches of the military. Chavasse thought it would be prudent to form a unit of Air Force and Navy personnel at FWC Guam that would work out of Nimitz Hill. It took several months, but in January on 1959 CINCPAC formally okayed JTWC. At that time Lt. Col. Robert Hoffman was appointed as the Director of JTWC, but it was stipulated that he must be junior in rank to the Director FWC whom was CDR. Charles E. Tilden. Even as the years passed and agency names changed, that hierarchy remained consistent. In 1962 the original structure that housed JTWC was destroyed and operations were moved to COMNAVMAR where they remained until the 1990’s.
In general JTWC always had a fairly even distribution of manpower regarding the percentage of AF and Navy personnel. Shifts (Watches) ran 12 hours ending and beginning at 7am or pm local time. Each watch consists of a team made up of a TDO (Typhoon Duty Officer) and TDA (Typhoon Duty Assistant), and either can be AF or Navy, there is no rule mandating teams must be all one branch of the service or mixed. The TDO was always a commissioned officer, and the TDA an enlisted member, usually below E-5. The watch team also worked with AF satellite analysts whom used both computer assisted forecasting aids as well as good ‘ol manual eye fixes of photos to measure and try to pin down the best location for an eye fix. In addition to the Sat. Analysts, members of the Naval Oceanographic Command Center (NOCC) would contribute to the process providing NEDS charts (Naval Environmental Data System), and in turn use the JTWC product to help generate a variety of their own projects including OTSR’s (Optimum Track Ship Routes).
A typical watch would begin with the pass-down from the off-going team to the new. The TDA would prepare checkerboard reports which are site specific weather observations plotted on a sheet that show wind speed, direction, pressure, and total cloud cover so that there is a consistent handy hard copy of changes updated every three hours. The TDA would then begin plotting off-time ship reports which are weather observations in blue ink on an 850 millibar (Surface synoptic) chart, and then make preparations for either the ABPW or ABIO (Abbreviated Pacific West and Abbreviated Indian Ocean) reports which would include any points of meteorological interest. If warnings are due out, those too would be prepared with the TDA’s primary responsibility at that time being to make sure all PLA’s (Plain Language Addresses) are present and correct so that proper dissemination is attained.
Three hours into the watch the “Data Run” begins at which time the K4EB will begin spitting out data from every weather station reporting over a 53 million square mile area which was the JTWC AOR under normal operating circumstances. The data that was received consisted of land and sea synoptics, upper air reports, buoy reports via the LUT (Local Users Terminal), satellite winds and pilot reports for the 200mb upper air chart, and if necessary for a storm and available TTPA reports which provided an eye fix location and swath edge. Under normal circumstances a TDA would sift through all of this data and hand plot each piece available in the AOR in about 3 to 4 hours depending on the individual and any duties which divided their attention. All told, somewhere in the area of about 1,200 or more, depending on needs, pieces of data would be plotted with a goal of 97% or better accuracy.
In some cases a TDA would be qualified to perform a streamline analysis on each chart which provides a visual representation of the atmosphere at each level. If the TDA was not qualified this would be done by the TDO or in some cases the Sat. Analyst depending on need. While the TDA performed these tasks, the TDO would prepare a forecast for any weather system that had reached TD (Tropical Depression) or better. This would be done by reviewing the in progress work of the 850 and 200mb charts, checkerboards, NEDS charts, and satellite imagery along with computer generated forecast aids which ran different scenarios of what path a storm may take. For example RCVR (Recurve) ran a re-curve track scenario while others may run stair step tracks, straight runners, or a blend weighted track based on various input of a combination of tracks.
Should any warnings need to go out along with the advisories the TDA would print hard copies, stamp them the clearance necessary, have the TDO sign them, and then distribute them to each department which needed them. A copy would also accompany the disk (or in older day punch tape) version that would go to communications for broad external dissemination. Some watches may be rather slow, others unbelievably tedious and pressure packed.
All told some facts and figures of interest about JTWC are as follows:
The normal AOR was 53 million square miles although in support of Operation Desert Shield in 1990 this was expanded to include the Persian Gulf more fully. To get an idea of how big that is imagine a flat map laid in front of you. Start at the international dateline (180 degrees) and scan all the way to the left until you reach the east coast of Madagascar. Than visually widen that line into a box that expands to 40 degrees north (Approximately the southern end of Mother Russia) down to 40 degrees south which is approximately the bottom of Australia. Everything that falls in between those lines was the AOR.
Approximately 70% of the total worldwide tropical cyclones fell within the JTWC AOR.
The general standard for quality was the 100/200/300 – 24/48/72 goal. This means that the margin for error in a forecast was to be no more than 100nm at 24 hours, 200nm at 48 hours, and 300nm at 72 hours. Although not the norm, at times a forecast was extended to 96 hours.
For warnings in the Southern Pacific and Indian Ocean the release interval was every 12 hours. In the Northwest Pacific it was every 6 hours.
A TCFA (Tropical Cyclone Formation Alert) would be the first warning for a storm and the first mention of one aside from it being cited as a point of interest on an ABPW or ABIO.
The ABPW and ABIO were issued once per day meaning each watch would issue one or the other.
Prior to JTWC being moved from Nimitz Hill to Hawaii, Pearl Harbor (PWC) served as the primary AJTWC (Alternate JTWC).
JTWC issues the ATCR (Annual Tropical Cyclone Report) which provides an analysis of each system forecast and is considered the best recurring document of its nature in the world. It is fully written and edited in house by the very people that actually worked the storms.
In 1998 the Naval portion of JTWC was moved to Pearl Harbor while the Air Force portion was was made Det. 1, PACAF/AOS.
While JTWC does not exist as it once did, it enjoyed a proud history of inter-service cooperation which made it the premiere severe weather forecasting agency in the world. The work continues to be done, just under new names and configurations. While no hard estimate can be put on the number of lives saved by timely accurate forecasts produced by JTWC, or the literally billions of dollars of both military and civilian assets protected, it is known that without JTWC the impact of tropical cyclones in their AOR would have been felt in more severe terms.
