The Synoptic Flow era
With Hurricane Debby in 1982 the Lab began a
series of experiments using Omega dropwindsondes to fill in the
vast oceanic data voids in the forecast models. One or both P3s
would fly synoptic scale patterns around the hurricane, and every
20 minutes or so drop a sonde out of the plane. The dropwindsonde
would drift down on a parachute and radio back to the plane the
temperature, humidity, and pressure, and using the Omega navigational
signals, triangulate its position. This information was used by
the plane's computer to estimate the winds the sonde was falling
through. Put together with other drops a three dimensional profile
of the synoptic-scale atmosphere surrounding the storm was synthesized.
Including this vital information in the hurricane track forecast
models was shown to improve the accuracy by 20-30%.
Computer modeling during the early 1980's involved work on a 12 level nested grid model as well as quasi-spectral and non-hydrostatic models. On going studies at this time included hurricane forecast track errors, rainfall estimates from land based radars near land-falling storms, and air-sea interactions under hurricanes.
HRD and AOC used films taken during hurricane flights to update the long out-of-date sea surface catalog used to estimate surface wind speeds by flight directors. Thousands of frames of 35mm and 16mm film were searched for examples, and then correlated to the aircraft wind speed. Sophisticated planetary boundary layer models were used to estimate the surface wind speed that went with those flight level pictures.
A new remote sensing instrument, the Step Frequency Microwave Radiometer (SFMR), was installed in 1983 on one of the P3s. Using the returned microwaves from a downward pointing antenna, and comparing them with an ideal return, the device could estimate the wind speed on the ocean's surface. HRD scientists have been involved in several modifications to the SFMR in efforts to make it an operational part of the aircraft's instrument suite.
The dramatic El Niño of 1982/83 spurred research into the relationship of ENSO and Atlantic hurricane frequency, and also renewed interest in hurricane climatology. The historical record was searched for possible precursor signals that might hint at future tropical activity. AOML researchers began looking at decadal and longer patterns in hurricane occurrence that might be linked to long term oceanic cycles.
The mid-1980's was a period when research concentrated on the new Doppler radar and cloud physics data. Papers were published on heat budgets, storm structure, wind fields, and drop spectra.
HRD's microphysicists and radar specialist participated in the preliminary STORM (pre_STORM) experiment in the spring of 1985. Pre_STORM studied mesoscale convective complexes in the vicinity of Oklahoma to better understand their structure, dynamics, and predictability. Although the STORM experiment itself never achieved funding, the data from pre-STORM were processed by the Division scientists and gave them experience in collaborating in a large, multi-agency operation that would become invaluable over the next few years.
Theoretical studies were undertaken to define how asymmetries in the hurricane wind field would affect the track. Model symmetrical storms had asymmetries introduced into their wind fields and the tracks compared. The evolution of the wind field was also studied.
The skills of several Division scientist in dropsonde processing, airborne weather research, and land based radar recording led to them be involved in the Genesis of Atlantic Lows Experiment (GALE) in 1986. The experiment was designed to examine winter storms off the east coast of the United States, with an emphasis on explosively developing storms. Of value in itself, it was also hoped the knowledge gained from GALE would give new insights into rapidly intensifying hurricanes.
The following year, HRD scientists traveled with the NOAA P3s to Darwin, Australia to participate in the Equatorial Mesoscale Experiment (EMEX). EMEX was to profile oceanic cloud clusters in the monsoonal flow near the equator. This data would be important in topical meteorology, climate studies, and in global climate models.
In 1991 the USAF tried to end its hurricane reconnaissance duties, but under public pressure opted instead to transfer Hurricane Hunter responsibilities to a Reserve squadron.
In 1993 they were again designated the 53rd WRS.
During the Summer of 1991 HRD personnel travelled to Acapulco, Mexico with the NOAA P3s to participate in the Tropical EXperiment in MEXico (TEXMEX). Headed by Dr. Kerry Emmanuel (MIT), the experiment was designed to investigate incipient tropical cyclones as they moved into the Eastern North Pacific, off the Mexican coast, and look at the role of moisture, as measured by equivalent potential temperature, in the formation of hurricanes.
Troubles forecasting the intensity changes of Hurricane Joan in 1988 inspired HRD scientists to try and improve on SHIFOR, the climate and persistence intensity forecast model used as a benchmark. By 1989 work had begun on the Statistical Hurricane Intensity Prediction Scheme (SHIPS). The scheme became operational at NHC in 1995, and by 1997 was showing skill over SHIFOR. The field of intensity forecasting still presents an area where considerable improvment may be made, and HRD continues to collaborate with Co-operative Institute for Research in the Atmosphere (CIRA) scientists on research to improve the SHIPS.
Hurricane Andrew had a major impact on south Florida and on HRD in August of 1992. The AOML facility had only minor damage, as the eyewall struck further south, on the tip of Key Biscayne. But many Division personnel's homes were damaged or destroyed, with the lives of some scientists in jeopardy. Andrew also precipitated a move by AOC to the Tampa area, ending thirty-two years of Miami based operation. It also sparked NHC to move from their Gables One Tower facility to a hurricane-proof center built specifically for them at Florida International University in west Dade county. Andrew also generated a number of scientific papers by HRD, examining its wind field, damage patterns, and its explosive intensification during landfall. Indeed, rapid intensification (RI) is a problem which HRD continues to explore, with experiments designed to measure the role of warm sea eddies, and parameters added to the SHIPS to attempt to predict RI. By 2000 SHIPS was also forecasting intensity change for storms after landfall. The decay rate of tropical cyclones over land was the basis of several studies by HRD and CIRA scientists.
Late in 1992 and early in 1993 HRD scientists once again traveled with the NOAA P3s to participate in yet another international weather science project, the Tropical Ocean-Global Atmosphere Coupled Ocean Atmosphere Response Experiment (TOGA COARE). Based at Guadalcanal, the experiment was designed to measure the heat, moisture, and momentum fluxes as well as the rainfall over the warm pool in the western Pacific. This is a critical area in driving the heat engine of the atmosphere.
Over the past decade, a series of experiments were conducted on the daily formation and growth of the south Florida sea breeze, that included P3 flights into evolving sea breeze fronts. These studies were supervised by Dr. Robert Burpee, who in 1993 succeeded Dr. Rosenthal as HRD Director. Dr. Rosenthal continued to work for a couple more years as a co-operative researcher. Dr. Burpee had headed the Division's Hurricane Field Program for a number of years, and had spearheaded the Synoptic Flow experiments, which had long needed an aircraft that would fly much higher than the P3s, and sample more of the atmosphere.
Links of Interest
AOML Tools & Resources