August 15th, 2021

PITD 2021 Webinar #4 – Aviation weather: A pilot’s perspective

Please join us Wednesday, August 18th, at 3pm Hawaii Standard Time (8/19/21 0100 UTC) when the Pacific International Training Desk will be holding its fourth webinar of the 2021 season. This webinar will be on the subject of aviation forecasts and how they are understood and applied by commercial pilots. The discussion will cover the key weather components going into the making of the flight plan and during takeoff and landing. Our speaker, John Zahneis is a pilot with United Airlines who frequently flies the island hopper route. Please see the attached flyer and remember to register for the webinar in advance here.

June 9th, 2021

PITD 2021 Webinar #3: Communicating the Weather: Weather Ready Nation, Social Media, and Disaster Preparedness

Please join us Monday, June 14th, at 3pm Hawaii Standard Time (6/15/21 0100 UTC) when the Pacific International Training Desk will be holding its third webinar of the spring 2021 season. This webinar will be on the subject of effective communication in the field of meteorology. The discussion will cover Weather Ready Nation (WRN), social media for professional use, and disaster preparedness. Our speaker, Landon Aydlett, is the Warning Coordination Meteorologist for the National Weather Service at WFO Guam. Please see the attached flyer and remember to register for the webinar in advance here.

April 26th, 2021

Marine Forecasting: Wave Modeling Webinar Recap

A crucial component of wave modeling is establishing the structure of the wave spectrum, the namesake of spectral models. The spectrum is a plot of the wave energy over various frequencies and directions. This is most often seen in the representation of buoy data.  A spectrum is particularly useful because it provides most of the information about a given sea state.  It also represents the wave data in the form of energy, which the model can propagate through space and time to make predictions of the future sea state. While tracking individual waves would be much too complicated, a wave spectrum evolves rather slowly and is therefore the chosen medium for forecasting waves. 

Dr. Justin Stopa began Tuesday’s webinar with a presentation on deep water wave evolution in spectral models.  He first summarized the model structure by saying that it is comprised of 3 source/sink terms: the input term, the wave-wave interaction term and the dissipation term.  The governing equation of the spectral model keeps track of the energy moving in, out and within the spectra. The terms marked by a capital E are various elements of energy, the delta terms indicate changes within the field of space, the C terms indicate wave speed, and the S terms indicate the aforementioned source and sink terms.  Sin(k) represents wind, Snl(k) represents the way wave energy changes within the spectrum and Sdis(k) represents energy loss due to turbulence and breaking. The first term on the left side of the governing equation is particularly important because it allows us to integrate over time, i.e. make predictions.

Dr. Stopa’s discussion about the guts of the spectral model illustrates an important point about all earth systems modeling, including meteorology.  Each numerical computer model first requires a conceptual model. The conceptual model is then translated into a mathematical model, usually beginning with a rather simple set of equations but becoming ever more complex as the model goes through revision after revision. At some stage, the numerical model mimics the real phenomena to close enough a degree that it is deemed successful and capable of being used operationally.  The conceptual model that Dr. Stopa begins with, i.e. the Miles theory, deals with how energy from the wind is transferred to the ocean to create waves.  This conceptual model considers a pressure difference perpendicular to the crest of the wave, which helps the wave propagate forward and develop further.  To this conceptual model, a fairly simple mathematical model relating wind speed to wave speed is applied. However, this model does not account for the waves’ slowing of the wind and further complication is added by the fact that some elements of the mathematical model, e.g. wind stress and surface roughness, must be parameterized and are approximated by empirical measurements.  Janssen (1991) ultimately added several terms to the Miles’ mathematical model in order to take into account the effect of the waves on the atmosphere.  Ardhuin (2010) also factored in the effect of wind sheltering on the leeward side of the wave, effectively putting an upper limit on wave growth.

In speaking about wave-wave interaction, Dr. Stopa indicated that the mathematics are so complex that global wave models can not be run operationally using the full mathematical solution.  Therefore, the simulated spectra lack accuracy particularly in the higher frequencies.  Moreover, dissipation is the most difficult term to formulate in a conceptual model because there is a good degree of randomness in this process. Like other problems in earth science, where there is no firm theory to rest upon probabilistic methods are substituted instead. A “breaking spectrum” has been offered as a solution, however, testing the validity of this probabilistic model is difficult due to a limit on the resolution of observations.  In general, constraining the model, getting it truly on track with real, observed ocean conditions, depends on high-resolution observations, some of which are beyond the limit of the current instrumentation. Hence, the current conceptual and mathematical models may both be correct, but we lack the capacity to constrain the empirical parameterizations upon which the model depends, and this leads to model errors. 

Dr. Ning Li began her portion of the talk by stressing the unique complexity of predicting ocean conditions for the Pacific Islands, which often experience wind seas and swells from various directions simultaneously.  Hawaii, and the U.S. territories, are fortunate to have an array of buoys maintained by PacIOOS, which help to monitor the wave climate of these regions. Still, forecasters rely heavily on spectral wave models due to the expensive nature of buoy observations and their limited spatial coverage. 

Dr. Li explained the reasons for using a near shore model and how these differ from running the global wave model in a regional, high-resolution domain.  Moreover, by downscaling the local wind field one can address the complex airflow near the Hawaiian Islands as it effects wave model output.

Lastly, Dr. Li showed that the performance of the wave models near shore is nearly perfect for wave heights up to 4 meters.  However, correctly modeling the upper end of wave heights is better achieved through hindcasting, whereby the model is run using the historical analysis of weather model winds.  This undertaking is very important to ocean engineering for it allows one to estimate the necessary strength of shoreline structures in anticipation of future large wave events.  Using even a limited time series, such as 30-years, one can extrapolate outward to estimate what a 100-year, or even a 500-year, wave event might look like. 

Since very large waves are often associated with tropical cyclones, special attention has been taken in recent years to modeling of these events.  This includes taking into account the projected occurrence and strength of tropical cyclones based on current global climate projections. Once identified, these events are downscaled to examine the relative impacts to a particular island or archipelago.  For further information on this and more please find the webinar in its entirety here.

April 14th, 2021

PITD 2021 Webinar #2: Marine Forecasting: Wave Modeling

Please join us Tuesday, April 20th, at 3pm Hawaii Standard Time (4/21/21 0100 UTC) when the Pacific International Training Desk will be holding its second webinar of the spring 2021 season. This webinar will be on the subject of marine wave prediction using the WaveWatch III (WWiii) and SWAN nearshore models. The discussion will cover model biases and limitations and the necessity for using a high-resolution wave model in the near shore environment. Our first speaker, Justin Stopa, is an Assistant Professor in the Dept. of Ocean and Resources Engineering (ORE) at the University of Hawai’i, while our second speaker, Ning Li, is the Ocean Wave Model Systems Specialist for PacIOOS and the US Navy’s Wave Energy Test Site. Please see the attached flyer and remember to register for the webinar in advance here.

March 11th, 2021

Inundation Forecasts for Low-Lying Pacific Islands Webinar Recap

In the first webinar of the PITD 2021 webinar series, Dr. Moritz Wandres spoke about inundation forecasts designed specifically for regional Met offices in the Pacific.  Dr. Wandres is a member of the Pacific Community (SPC), a regional, inter-governmental organization made up of 26 countries, specializing in Geo, Energy and maritime related sciences.  He works specifically in the areas of coastal monitoring, numerical model development, coastal hazard early warning systems and risk assessment.

Factors influencing inundation are not limited to waves.  A combination of wave height, period and direction can influence what are called wave setup and infragravity waves, the latter of which are longer period surges from the ocean associated with large swells.  Storms arriving on shore may also raise the local sea level, compounding the effect of the waves.  How much protection a given reef provides often depends on factors like how far out the reef extends and whether there is a lagoon between the reef and shore.  Lastly, run up, the water from the breaking waves that rushes beyond the tide level, is dependent upon the steepness of the beach.  Coastal vulnerability depends not only on meteorological and oceanographic factors, such as wind, waves, tides and sea level, but also on geographic variables, such as bathymetry, local morphology and topography. 

The approach to creating an inundation model involves taking the simplest and most consistent factors into account first.  These are the mean sea level and tide predictions, which together equate to the water level forecast.  Such data is most frequently acquired from satellite (altimetry).  Secondly, the global wind and wave conditions are obtained from the global forecast models (NOAA/BOM/ECMWF).  Downscaling may be required to create accurate local wave forecasts.  Once this is done, by combining the local wave forecast with the water lever forecast one arrives at a run up forecast.

One of the difficulties with preparing a run up forecast for remote areas is that these locations often lack a historical record of mean sea level.  To surmount this problem, special tide gauges are installed (geodetic) which provide a reference to how sea level is changing with respect to the rest of the globe. 

In order to downscale the global wave models, UnSWAN is used to take into account the shadowing effect of small, near shore islands.  The smaller the islands, the higher the resolution the model grid must be.  For instance, for an island such as Tarawa (Kiribati), the model resolution may be as high as 15m. 

For the run up portion of the model, the XBeach non-hydrostatic model is used, which even takes in to account the waves breaking along the shore!  This model also resolves near shore currents and the amount of overtopping along the coast.  This model is very computationally expensive, so using it operationally is typically unfeasible.  Because of this, a statistical/historical approach is used in the forecasting of real time inundation events.  For further information on this and more please find the webinar in its entirety here.

February 24th, 2021

PITD 2021 Webinar #1: Inundation Forecasts for Low-Lying Pacific Islands

Please join us Tuesday, March 2nd, at 3pm Hawaii Standard Time (3/3/21 0100 UTC) when the Pacific International Training Desk will be holding its first webinar of the spring 2021 season. This webinar will be on the subject of forecasting inundation events for low-lying Pacific Islands. Our speaker, a Physical Oceanographer at the Geoscience, Energy and Maritime Division of the Pacific Community (SPC), is currently developing an inundation forecast system in conjunction with several South Pacific Met Service members.  His talk will cover applications of these models to several Pacific Island countries, including the Marshall Islands, illustrating the possibilities for improvements in coastal hazard vulnerability assessments and operational impact-based multi-hazard forecast systems for coastlines. Please remember to register for the webinar in advance here.

January 13th, 2021 Update

PITD Webinar #6: Virtual Office Tours

Please join us Wednesday, December 16th, at 3:30pm Hawaii Standard Time (12/17/20 0130 UTC) (RESCHEDULED for Tuesday January 19th at 3pm Hawaii Standard Time (1/20/21 0100 UTC). Registration page remains the same) when the Pacific International Training Desk will be holding its sixth webinar. This webinar will feature an opportunity for two staff members from Weather Service Offices in the tropical Pacific to show off their office, fill us in on their daily operations, and introduce us to their staff! Our presenters include two past Pacific Desk participants and fellow National Oceanic and Atmospheric Administration (NOAA) affiliates, currently working for the National Weather Service (NWS) in American Samoa and Chuuk State, Micronesia. Please remember to register for the webinar in advance here.

November 30th, 2020

Emerging Satellite Techniques Webinar Recap

Last week’s webinar explored the topic of satellite products and techniques which have been introduced or become more widely used in the Pacific Region over the past five years. Due to the remote location of most of the Pacific Islands, in what is referred to in meteorology as a ‘data void’, our weather service offices are particularly reliant on existing and emerging satellite technologies.  Our first speaker, Roger Edson, is the Science and Operations Officer at Weather Forecast Office (WFO) Guam where he is responsible for overseeing the training program of the National Weather Service (NWS) staff and incorporating new technologies into the WFO programs. Our second speaker, Moeka Yamaji, is a researcher at the Earth Observation Research Center in the Japan Aerospace Exploration Agency (JAXA, equivalent to our NASA here in the U.S.). She has been in charge of the Global Satellite Mapping of Precipitation (GSMaP) applications, especially for the Pacific region, for the past 5 years and has visited many of the Pacific Islands.  Both speakers are experts in the field of weather satellite technology.

Roger began his talk with a refresher on microwave satellite data as used in the analyses of tropical cyclones.  Microwave sensors are used specifically to see rain bands and the wind speed distribution within TCs.  In this context, he also introduced the SAR technology, or Synthetic Aperture Radar, which allows one to see the surface wind speeds over the ocean at the highest possible resolution so far.  The SAR data currently available to the public comes primarily from the Sentinel satellites, which allow one to see winds well over 100 kts.  SAR is particularly valuable for verifying decisions made when using the Dvorak technique and establishing a valid “fix” early in a TC’s development.  Knowing the exact intensity of the storm, and where the TC is in its life cycle, is very important for forecasting the strengthening of the cyclone, and its weakening as well.

Roger also gave a survey of the types of microwave satellite data available and where to find them on the web.  As well as some new sites, which may be unfamiliar to our students, Roger pointed out some special features, like the Storm folder, on the NOAA/NESDIS site.  He also introduced another very useful tool, the KNMI multi-platform product, which allows one to see all available scatterometry data in one location on the web.  Here, you can also overlay and compare the ECMWF model winds with those from the scatterometers. 

Returning to SAR, Roger explained that the more you increase your satellite image resolution the more you must either increase the length of your antenna or decrease the size of the wavelength of energy you are looking at. In the latter case, rain interference becomes an issue. SAR solves the antenna length dilemma by ‘synthetically’ increasing it through combining images from several bursts along the antenna. The separate images are then joined and, voila, you have a very high resolution picture over one small area of the earth.

Moeka spoke on the satellite based rainfall product out of Japan, “GSMaP”, which is particularly useful for weather monitoring in the Pacific Islands as well as tracking of features related to tropical rainfall climatology. The GSMaP tool is critical to measuring rainfall over large areas of the Pacific Ocean, where land based observations are not feasible. The GSMaP rainfall products are built upon observations from the Global Precipitation Measurement (GPM) Mission (NASA), which is a microwave passive sensor imager, and the the Dual-frequency Precipitation Radar (DPR) (JAXA), an active sensor radar.  The GPM gives you a high resolution picture over large swaths of the globe, while the DPR provides visualization of the 3-D structure of clouds along those swaths.  The GSMaP product is created by merging all available information from both data sets around the globe.  Information from an infrared imager, such as Himawari or GOES, is then used to fill in the gaps and to further estimate rainfall intensity based upon cloud top height.  The Japanese DPR sensor is currently the only one in existence. 

If you were unable to attend, the webinar it can be watched on our facebook page or on youtube in its entirety.

If you are interested in giving a webinar talk with the Pacific Desk please contact us at

November 17th, 2020

Webinar #5: Emerging Satellite Technologies

Please join us Monday, November 23rd, at 3pm Hawaii Standard Time (11/24/20 0100 UTC) when the Pacific International Training Desk will be holding its fifth fall webinar. This webinar will be on the subject of emerging satellite techniques in the tropical Pacific. Our panelists include two experts in the subject of satellite meteorology, Roger Edson of WFO Guam and Moeka Yamaji of the Japan Aerospace Exploration Agency (JAXA).  The discussion will cover meteorological applications of Synthetic Aperture Radar (SAR) and Dual-frequency Precipitation Radar (DPR) for high-resolution, near real-time assessments of winds and rainfall over remote sections of the Pacific. Please remember to register for the webinar in advance here.

October 28th, 2020

Surf Forecasting and Reporting Webinar Recap

Yesterday’s webinar explored the topic of surf forecasting and surf reporting as it pertains to the Pacific Islands. Our first speaker, Gary Kewley, is the owner of Surf News Network (SNN), a very popular surf forecasting and reporting outlet in Hawaii.  SNN has been in operation since 1976 and facilitates the transmission of local surf information to a wide audience by means of TV, radio, phone messaging and the internet. Our second speaker, Patrick Caldwell, has been the NOAA/NESDIS National Centers for Environmental Information Liaison for Hawaii and the US-Flag Islands in the Pacific since 1987. He is also the National Weather Service Surf Forecaster for Hawaii.  Both speakers came as experts in the field to talk on the subjects of wave science, forecasting methods, surf reporting and communicating with the public.

Gary began his portion of the presentation by discussing the complexities of reporting for surf spots island-wide on a daily basis to an audience of over 100,000 people.   He explains that some difficulty arises from the broad spectrum of public perception concerning wave heights, with some groups of surfers systematically underestimating wave heights at particular breaks.  He goes on to say that there is a balancing act between keeping this portion of his audience happy while still offering accurate estimates, in the name of safety, to less experienced ocean users.   This topic lead to further discussion between Gary and Pat on the difference between local, or Hawaii, scale and face scale surf heights. Face scale is the literal measurement in feet of the wave face and is used by the National Weather Service and some news outlets.  The Hawaii scale is a more traditional measuring system used by local surfers as equates to approximately 3/5 the face scale. Pat added the further nuance that wave measurements are by nature coarse in resolution and, therefore, always to some extent rough estimates. 

After discussing some of the unique opportunities that our students have in terms of creating their own surf forecasting websites in locations where there are currently no media outlets like Surf News Network, Pat began his discussion with a tour of some of the material he produces for the National Weather Service in Hawaii ( including the Oahu Surf Climatology. Pat explains that not only is there a peak in north shore surf heights some time around the middle of the winter season, but there is also variability in the direction of swells throughout the winter, with more northerly swells early on and more westerly swells during the middle of the season. Next, Pat brought up the difficulty in doing accurate surf reporting due to the spatial and temporal variability inherent in ocean waves.  Spatial variability is a common factor in Hawaii and other Pacific islands due to the irregular shape of the seafloor, creating refraction in one area and diffraction in another. Temporal variability, on the other hand, is responsible for the so-called ‘envelopes’ in swell energy during which intermittent periods of larger waves arrive (Gary referred to this also, more figuratively, as the ‘swell breathing’).

Pat also gives a refresher in basic wave theory, refraction and how to determine swell arrival time based on fetch length, duration, wind speed and the corresponding swell period.  And, by way of recounting a memorable south swell from earlier this year, he illustrates many of the concepts and techniques he brings up earlier in his talk.

If you were unable to attend, the webinar can be watched on our facebook page or on youtube in its entirety.

If you are interested in giving a webinar talk with the Pacific Desk please contact us at

October 15th, 2020

Webinar #4: Surf Forecasting and Reporting

Please join us Wednesday, October 21st, at 3pm Hawaii Standard Time (10/22/20 0100 UTC) (POSTPONED until Tuesday October 27th at 3pm Hawaii Standard Time (10/28/20 0100 UTC). Registration page remains the same.) when the Pacific International Training Desk will be holding its fourth fall webinar. This webinar will be on the subject of surf forecasting and reporting for the Pacific Islands. Our panelists include two well-known voices in Hawaiian surf forecasting over the past decades, Patrick Caldwell and Gary Kewley.  The topic of discussion will range from general wave science and modeling techniques to surf reporting conventions and availability of wave observations.  The discussion will also touch on methods of communicating surf forecasts to a large and varied audience. Please remember to register for the webinar in advance here.

October 10th, 2020

Tropical Climatology in the Pacific Webinar Recap

Wednesday’s webinar focused on climatological features in the tropical Pacific, particularly ENSO and climate change. Our first speaker, Malte Stuecker, who is an assistant professor in the Oceanography Department at the University of Hawaii, spoke on El Niño and sea level variability while Brandon Bukunt, the climate focal point at WFO Guam, spoke on the current ENSO situation and the 2020 north western Pacific typhoon season.  Our past PITD Level 2 students are well familiar with the ENSO cycle and the various atmospheric teleconnections affecting their respective islands. 

Malte began his talk by discussing the history of El Niño, its name’s origin, and its relation to SSTs and rainfall over South America.  Then he gave an explanation of how El Niño changes sea level heights throughout the Pacific.  Under ‘normal’ conditions, the trade winds blow the ocean water along the equator from east to west, effectively bunching up the ocean on the western side of the basin (i.e. normally, sea level is higher in the west Pacific and lower in the east Pacific).  When an El Niño occurs, the equatorial winds switch direction and blow west to east, dragging the ocean waters eastward which are then confined near the equator by Ekman transport (think Coriolis: turns to the right in the N.H. and to the left in the S.H.).  This convergence of sea water leads to rising sea level heights in the east Pacific and decreasing heights in the west Pacific. Variations in trade wind strength lead to a ‘zonal seesaw’ effect in sea level heights across the equatorial Pacific with far-reaching consequences in the tropical Pacific, such as prolonged sea level drops in the southwest Pacific which can be damaging to corals. 

Malte also addressed the topic of sea level rise due to global warming, explaining that there are varying projections of the rate of increase based on how much CO2 continues to be emitted by human industry.  Satellite and buoy data of sea level trends throughout the world’s oceans are already showing that sea level rise is on track with many climate model projections.  The natural variations in sea level change, e.g. ENSO, add complication to these general trends, however, Malte states that the “changes due to global warming are already outpacing these natural variations”.

Brandon Bukunt’s presentation, entitled “It’s All Connected”, focused on the present La Niña conditions, how they came about, and how they may have influenced the, so far, very uneventful 2020 western Pacific typhoon season.  Brandon took us back to March of 2020 when conditions in the equatorial Pacific were suggestive of a future El Niño.  How did things swing toward La Niña?  Brandon suggests that a record breaking positive Indian Ocean Dipole, in response to strong trades off of Indonesia, favored the development of La Niña in the Pacific, as occurred in 1994 and 1997.  Typhoon development is generally favored toward Asia during a La Niña year, but Brandon blames the extremely quiet typhoon season over Micronesia on a  number of factors including a standing Indian Ocean wave, strong upper-level wind shear, large-scale subsidence over much of the Pacific basin, and a busy Atlantic tropical cyclone season.  Possible concerns for Micronesia during the current La Niña are higher than normal sea levels, extreme drought for more southerly islands (e.g. Kapingamarangi), coral bleaching, and heavy rain events, particularly for the more westerly islands.  Brandon also demonstrated how Typhoon Mayasak, which became ingested in the mid-latitude jet stream during September 2020, influenced the record heat in California leading to the historic fires there.

If you were unable to attend, the webinar can be watched here and here (starts ~8:20) in its entirety.

If you are interested in giving a webinar talk with the Pacific Desk please contact us at

September 30th, 2020

Please join us next Wednesday, October 7th, at 3pm Hawaii Standard Time when the Pacific International Training Desk will be holding its third in a series of fall webinars. The webinar will be on the subject of climatology particular to the tropical Pacific Ocean. Our panelists include an assistant professor from the Oceanography Department at the University of Hawaii and a meteorologist from the National Weather Service Forecast Office on Guam. Topics of discussion will include seasonal changes in sea level height due to the the ENSO cycle and climatological features in the western Pacific unique to the current 2020 wet season. Please remember to register for the webinar in advance here to receive a link to attend.

September 21st, 2020

Island Mesoscale Meteorology Webinar Recap

Last weeks webinar topic, Island Mesoscale Meteorology, emphasized several unique mesoscale weather features prevalent in the Hawaiian Islands.  Our three panelists included a professor and a researcher from the University of Hawaii and a research scientist from the Chinese Meteorological Academy of Sciences.  They spoke on the simultaneous occurrence of heavy rainfall and fire weather during Hurricane Lane (2018), rainfall and flooding over semi-arid central Oahu during seasonal transition periods, and mountain lee waves downstream of Oahu under prefrontal southwesterly flow.  Our past Pacific Desk students are familiar with mesoscale phenomena in the form of orographic lift over mountainous islands and diurnal sea breeze/land breeze flow.  The mesocale features discussed each pose a possible hazard to the residents and visitors of Hawaii in terms of flooding, fire and turbulence for aircraft.  Forecasting these features is difficult due to the short time and small spatial scales associated with them, often requiring the application of a mesoscale numerical model.

Our first speaker, Alison Nugent, is an assistant professor in the Atmospheric Sciences Department at the University of Hawaii at Manoa. Alison’s work combines the knowledge of scientists from various disciplines including meteorology, hydrology, ecology and geography.  She began by explaining her background in the field of mountain meteorology, which is the ‘study of how mountains modify weather and climate’. The crux of Alison’s talk was the unique ability of Hurricane Lane to drop abundant amounts of rainfall on the windward side of the island of Hawaii while simultaneously igniting fires on the leeward sides of both Oahu and Maui. These sets of events were the result of orographic lifting of the hurricane rainbands on the windward slopes of the Big Island and descending and warming of the airflow in the lee of Oahu and Maui, where very dry vegetation was already present. 

Our next speaker, Feng Hsiao, is a postdoctoral researcher at the University of Hawaii with expertise in numerical mesoscale modeling.  Feng’s talk focused on heavy rainfall events over central Oahu, a region of the island which is typically quite dry.  These types of events occur during the transition from the cool season to warm season and vice versa.  Feng also found that they are associated with an upper level trough, a conditionally unstable atmosphere, a moist tongue extending from the deep tropics, and weak local surface winds.  He showed how using local observations, radar, and the WRF mesoscale model, nowcasting of these events can be accomplished with a lead time of 2-3 hours.

Finally, our last speaker, Liye Li, a research scientist at the Chinese Meteorological Academy of Sciences, addressed the topic of trapped mountain lee waves near Oahu. She explained that these waves can be seen with the GOES 1-km resolution visible channel when there is enough moisture to create clouds.  When there is no moisture, the waves are difficult to detect and pose a threat to aviation in the form of clear air turbulence and strong downslope winds.  Mountain waves are a form of internal gravity wave and are dependent upon a stably stratified atmosphere.  It is also required that the prevailing winds be perpendicular to the mountain slopes and fast enough to ascend and surmount the ridge tops.  Typically, a critical level is absent.  This set of criteria may be met during the approach of a cold front.  Liye’s WRF simulations of trapped lee waves are valuable for nowcasting such events, particularly when there is not enough moisture for the waves to form clouds and be seen. 

If you were unable to attend, the webinar can be watched here and here (starts ~6 min. in) in its entirety.

If you are interested in giving a webinar talk with the Pacific Desk please contact us at

September 10th, 2020

Webinar #2: Island Mesoscale Meteorology

Please join us next Thursday, September 17th, at 3pm Hawaii Standard Time when the Pacific International Training Desk will be holding its second in a series of webinars. This webinar will be on the subject of mesoscale meteorology, particularly in regards to tropical and subtropical islands. Our panelists come from an academic background this time, including a professor from the University of Hawaii, a postdoctoral researcher, also from UH, and a research scientist from the Chinese Meteorological Academy of Sciences. The topics of discussion will include localized heavy rainfall, mountain waves and the interaction of topical cyclones with complex topography. Please remember to register for the webinar here in advance to receive a link to attend.

Note, for those who may have issues connecting through Zoom please contact us directly at for a temporary alternative. We are looking into a more permanent solution for future webinars.

August 27th, 2020

Hurricane Douglas Webinar Recap

On August 25th, the Pacific International Training Desk held its first webinar of 2020.  We were very pleased with the turnout (more than 60 people!), who came from a wide range of backgrounds in meteorology as well as various locations throughout the Pacific.  The topic of discussion was recent Hurricane Douglas, which impacted the Hawaiian Islands in late July.  Our panelists were comprised of various members of the NOAA/NWS team in Hawaii.  The forecast of Douglas was particularly challenging, and harrowing, because of the absence of environmental wind shear, which typically weakens tropical cyclones as they approach Hawaii.

Bob Ballard, the Science and Operations Officer (SOO) at the Central Pacific Hurricane Center (CPHC), took us on a ‘whirlwind, lightning fast tour’ of Hurricane Douglas’ approach toward Hawaii, one of the closest calls the islands have ever had with a tropical cyclone.   Bob showed us just how lucky Oahu actually was, with scatterometry showing  hurricane force winds only 30 miles (50 km) away from the NE end of the island on the afternoon of 26 July.   Bob also stressed the benefit of having mesoscale guidance added to the global model ensembles, as these models revealed the storm making a leftward turn toward the island of Oahu, prompting a continuance of the hurricane warning for that island.   

John Bravender, Warning Coordination Meteorologist (WCM) at CPHC, discussed communication challenges, particularly in regard to Douglas’ rapid approach and in briefing emergency management partners in a Covid-19 environment.  John stressed the importance of having a unified message, knowing your audience and making sure you are in contact with emergency managers on a consistent basis.  He also emphasized refraining from underestimating or overestimating potential storm impacts, but rather having your audience understand the uncertainties involved in a TC forecast as well as the importance of preparing in a timely manner. The message should be simple, unified and hit key points several times.

Finally, Leigh Anne Eaton, Emergency Response Specialist at the Pacific Region Regional Operations Center (PR-ROC), spoke on the functions of PR-ROC, which provides support to the Marianas, Micronesia, American Samoa as well as Hawaii.  Leigh Anne explained that PR-ROC acts as technical expert to FEMA, providing weather input so that they can make informed decisions for their readiness and recovery missions.  PR-ROC also transfers messages from John and Bob’s offices to FEMA and senior leadership in the National Weather Service.  In keeping with John’s goals, the main task of PR-ROC is to keep the message consistent between forecasters and emergency managers.  Much of PR-ROC’s current support is conducted virtually in adaption to the Covid-19 environment. 

If you missed it, the webinar can be watched here in its entirety.

If you are interested in giving a webinar talk with the Pacific Desk please contact us at


August 15th, 2020

Introduction to the Pacific Desk Webinar Series

In order to adapt to the Covid-19 pandemic, the Pacific International Training Desk will be temporarily providing instruction by means of online webinars.

The goal of the webinar series is to keep us all in touch, whether it be with the Pacific Desk instructors or the the staff at WFO Guam and WFO Honolulu. It is also a good way for our students from the South Pacific to make or reestablish contact with the students coming from the United States based WSOs in American Samoa and Micronesia.

The first of the webinars will take place on August 25th (Hawaii Standard Time, see flyer below) and will be provided by staff at WFO Honolulu. Please note that you will need to register here in order to receive the link to attend.

Jennifer and I look forward to seeing everyone again. Please contact us at if you have any questions.