NOAA Ocean Prediction Center

FIg. 1. Annual average frequency of the low-pressure centers with hurricane-force winds based on the NOAA OPC 6-hourly surface pressure analyses and QuikSCAT winds. Average was calculated based on data from Sep though May 2002-09. The track of Quirin at 6-hourly intervals from 0000 UTC on 13 Feb to 1800 UTC on 14 Feb is overplotted. The size of the circle symbol at each time step reflects the surface area of winds 24.5 m s -1 and the color represents the maximum wind speed (see

Abstract Extreme rainfall events contribute a large portion of wintertime precipitation to northern California. The motivations of this paper were to study the observed differences in the patterns between extreme and more commonly occurring lighter rainfall events, and to study whether anomaly fields might be used to discriminate between them. Daily (1200–1200 UTC) precipitation amounts were binned into three progressively heavier categories (12.5–50.0 mm, light; 50–100 mm, moderate; and >100 mm, heavy) in order to help identify the physical processes responsible for extreme precipitation in the Sierra Nevada range between 37.5° and 41.0°N. The composite fields revealed marked differences between the synoptic patterns associated with the three different groups. The heavy composites showed a much stronger, larger-scale, and slower-moving negative geopotential height anomaly off the Pacific coast of Oregon and Washington than was revealed in either of the other two composites. The heavy rainfall events were also typically associated with an atmospheric river with anomalously high precipitable water (PW) and 850-hPa moisture flux (MF) within it. The standardized PW and MF anomalies associated with the heavy grouping were higher and were slower moving than in either of the lighter bins. Three multiday heavy rainfall events were closely examined in order to ascertain whether anomaly patterns could provide forecast utility. Each of the multiday extreme rainfall events investigated was associated with atmospheric rivers that contained highly anomalous 850-hPa MF and PW within it. Each case was also associated with an unusually intense negative geopotential height anomaly that was similarly located off of the west coast of the United States. The similarities in the anomaly pattern among the three multiday extreme events suggest that standardized anomalies might be useful in predicting extreme multiday rainfall events in the northern Sierra range.

Abstract Hurricane Sandy (2012) was the second costliest tropical cyclone to impact the United States and resulted in numerous lives lost due to its high winds and catastrophic storm surges. Despite its impacts little research has been performed on the circulation on the continental shelf as Sandy made landfall. In this study, integrated ocean observing assets and regional ocean modeling were used to investigate the coastal ocean response to Sandy's large wind field. Sandy's unique cross‐shelf storm track, large size, and slow speed resulted in along‐shelf wind stress over the coastal ocean for nearly 48 h before the eye made landfall in southern New Jersey. Over the first inertial period (∼18 h), this along‐shelf wind stress drove onshore flow in the surface of the stratified continental shelf and initiated a two‐layer downwelling circulation. During the remaining storm forcing period a bottom Ekman layer developed and the bottom Cold Pool was rapidly advected offshore ∼70 km. This offshore advection removed the bottom Cold Pool from the majority of the shallow continental shelf and limited ahead‐of‐eye‐center sea surface temperature (SST) cooling, which has been observed in previous storms on the MAB such as Hurricane Irene (2011). This cross‐shelf advective process has not been observed previously on continental shelves during tropical cyclones and highlights the need for combined ocean observing systems and regional modeling in order to further understand the range of coastal ocean responses to tropical cyclones.

Large uncertainty in the predicted intensity of tropical cyclones (TCs) persists compared to the steadily improving skill in the predicted TC tracks. This intensity uncertainty has its most significant implications in the coastal zone, where TC impacts to populated shorelines are greatest. Recent studies have demonstrated that rapid ahead-of-eye-center cooling of a stratified coastal ocean can have a significant impact on hurricane intensity forecasts. Using observation-validated, high-resolution ocean modeling, the stratified coastal ocean cooling processes observed in two U.S. Mid-Atlantic hurricanes were investigated: Hurricane Irene (2011)-with an inshore Mid-Atlantic Bight (MAB) track during the late summer stratified coastal ocean season-and Tropical Storm Barry (2007)-with an offshore track during early summer. For both storms, the critical ahead-of-eye-center depth-averaged force balance across the entire MAB shelf included an onshore wind stress balanced by an offshore pressure gradient. This resulted in onshore surface currents opposing offshore bottom currents that enhanced surface to bottom current shear and turbulent mixing across the thermocline, resulting in the rapid cooling of the surface layer ahead-of-eye-center. Because the same baroclinic and mixing processes occurred for two storms on opposite ends of the track and seasonal stratification envelope, the response appears robust. It will be critical to forecast these processes and their implications for a wide range of future storms using realistic 3-D coupled atmosphere-ocean models to lower the uncertainty in predictions of TC intensities and impacts and enable coastal populations to better respond to increasing rapid intensification threats in an era of rising sea levels.

Abstract Sting jets, or surface wind maxima at the end of bent-back fronts in Shapiro–Keyser cyclones, are one cause of strong winds in extratropical cyclones. Although previous studies identified the release of conditional symmetric instability as a cause of sting jets, the mechanism to initiate its release remains unidentified. To identify this mechanism, a case study was selected of an intense cyclone over the North Atlantic Ocean during 7–8 December 2005 that possessed a sting jet detected from the NASA Quick Scatterometer (QuikSCAT). A couplet of Petterssen frontogenesis and frontolysis occurred along the bent-back front. The direct circulation associated with the frontogenesis led to ascent within the cyclonically turning portion of the warm conveyor belt, contributing to the comma-cloud head. When the bent-back front became frontolytic, an indirect circulation associated with the frontolysis, in conjunction with alongfront cold advection, led to descent within and on the warm side of the front, bringing higher-momentum air down toward the boundary layer. Sensible heat fluxes from the ocean surface and cold-air advection destabilized the boundary layer, resulting in near-neutral static stability facilitating downward mixing. Thus, descent associated with the frontolysis reaching a near-neutral boundary layer provides a physical mechanism for sting jets, is consistent with previous studies, and synthesizes existing knowledge. Specifically, this couplet of frontogenesis and frontolysis could explain why sting jets occur at the end of the bent-back front and emerge from the cloud head, why sting jets are mesoscale phenomena, and why they only occur within Shapiro–Keyser cyclones. A larger dataset of cases is necessary to test this hypothesis.

Abstract A new model is provided for estimating maritime near-surface wind speeds (U10) from satellite altimeter backscatter data during high wind conditions. The model is built using coincident satellite scatterometer and altimeter observations obtained from QuikSCAT and Jason satellite orbit crossovers in 2008 and 2009. The new wind measurements are linear with inverse radar backscatter levels, a result close to the earlier altimeter high wind speed model of Young (1993). By design, the model only applies for wind speeds above 18 m s−1. Above this level, standard altimeter wind speed algorithms are not reliable and typically underestimate the true value. Simple rules for applying the new model to the present-day suite of satellite altimeters (Jason-1, Jason-2, and Envisat RA-2) are provided, with a key objective being provision of enhanced data for near-real-time forecast and warning applications surrounding gale to hurricane force wind events. Model limitations and strengths are discussed and highlight the valuable 5-km spatial resolution sea state and wind speed altimeter information that can complement other data sources included in forecast guidance and air–sea interaction studies.

The SeaWinds scatterometer onboard the NASA QuikSCAT satellite has been providing forecasters in the Ocean Prediction Center (OPC) with near-real time (NRT) ocean vector winds over large ocean areas since 1999. The OPC forecasters routinely use QuikSCAT winds in their analysis and forecast process to position frontal features, centers of high and low pressure and to determine the category and location of short term wind warning areas. QuikSCAT has also given forecasters the ability to detect hurricane force conditions within extratropical cyclones. Since QuikSCAT has been fully integrated in to OPC operations, OPC forecasters' assessment of the surface wind field over the open oceans is more accurate than ever before. As part of the warning and forecast process, OPC forecasters prepare a manual sea level pressure (SLP) analysis four times daily for both the North Atlantic and North Pacific. These OPC SLP analyses are disseminated directly to ships at sea and are heavily relied upon by the marine community for safe and economic operations. These analyses are also a key element in the forecast process as accurate initial conditions are essential to the production of precise forecasts. Although QuikSCAT's impact on the analysis and forecast process has been significant to the short-term wind warning process, this positive impact has not carried over to the analysis of the sea level pressure field over the open oceans. In an effort to improve their SLP analyses, OPC began to run the University of Washington Planetary Boundary Layer (UWPBL) model to derive SLP, surface vorticity and surface wind speed fields using the NRT QuikSCAT winds from NOAA/NESDIS as input. The UWPBL model derived SLP, surface vorticity and surface wind speed fields were made available to OPC forecasters within their N-AWIPS workstations so that they could overlay these products with other observational fields and model guidance. The SLP fields from the UWPBL model were examined daily over a three-month period. The model was found to produce dynamically consistent SLP fields the majority of the time. A comparison of the SLP fields derived from the UWPBL model with the OPC manual surface analyses and the Global Forecast System Model (GFS) surface pressure fields revealed that in most cases the central pressure of the cyclones were not analyzed to be deep enough by either the OPC manual analyses or the GFS model output. There were occasional instances, however where the UPWBL model produced central pressures that were unrealistically low and/or high. This problem was determined to be related to stratification issues and to the method of assimilation of available ship and buoy observations into the model to seed the pressure gradient field. This paper will present several case studies illustrating the application of UWPBL derived sea level pressure and vorticity by OPC forecasters. Comparisons of OPC manual analyses, numerical model analyses and the UWPBL fields will be shown. The UWPBL model using QuikSCAT winds as input provides very high quality sea level pressure fields associated with intense ocean storms. In particular, the retrieved sea level pressures contain strong pressure gradients in areas of very high winds. This strength of the pressure retrieval system has made it very useful to OPC forecasters in daily operations and as a training tool

The National Oceanic and Atmospheric Administration (NOAA) Ocean Prediction Center (OPC) is responsible for issuing wind warnings for the High Seas waters of the Northern Hemisphere from 35 degrees W to 160 degrees E including the offshore waters of the continental United States. Wind warning categories are based on the Beaufort Scale and are: GALE (17.2 to 24.4 m s/sup -1/), STORM (24.5 to 32.6 m s/sup -1/) and HURRICANE FORCE (32.7 m s/sup -1/ or greater). Near real-time winds derived from the SeaWinds Scatterometer on board the NASA QuikSCAT satellite have proven to be extremely useful to OPC forecasters. A recent survey indicated that ten percent of all short-term wind warnings issued by the OPC were determined using QuikSCAT winds. QuikSCAT winds were also used to more accurately place one half to two thirds of all weather features on manual ocean surface analyses. QuikSCAT, with its wide swath width and large retrievable wind range is the first data set to consistently observe winds well into the Hurricane Force category in extratropical cyclones. Based on QuikSCAT winds OPC forecasters are now able to detect and warn for Hurricane Force extratropical cyclones. Large sea surface temperature (SST) gradients exist over the mid-Atlantic coastal and offshore waters of the U.S. Forecasting surface winds in these areas presents a challenge to OPC forecasters. QuikSCAT has revealed that large wind speed gradients often coincide with these SST gradients. With QuikSCAT, OPC forecasters can now factor in low-level stability when making wind forecasts. The overall impact of QuikSCAT on marine forecasting in NOAA has been very positive. In fact, QuikSCAT winds have revolutionized the ocean forecasters' ability to assess near surface winds over vast open ocean areas.

Fred Sanders’ career extended over 55 yr, touching upon many of the revolutionary transformations in the field of meteorology during that period. In this paper, his contributions to the transformation of synoptic meteorology, his research into the nature of explosive cyclogenesis, and related advances in the ability to predict these storms are reviewed. In addition to this review, the current status of forecasting oceanic cyclones 4.5 days in advance is presented, illustrating the progress that has been made and the challenges that persist, especially for forecasting those extreme extratropical cyclones that are marked by surface wind speeds exceeding hurricane force. Last, Fred Sanders’ participation in a forecast for the historic 1947 snowstorm (that produced snowfall amounts in the New York City area that set records at that time) is reviewed along with an attempt to use today’s operational global model to simulate this storm using data that were available at the time. The study reveals the predictive limitations involved with this case based on the scarcity of upper-air data in 1947, while confirming Fred Sanders’ forecasting skills when dealing with these types of major storm events, even as a young aviation forecaster at New York’s LaGuardia Airport.

Abstract Fred Sanders' career extended over 55 yr, touching upon many of the revolutionary transformations in the field of meteorology during that period. In this paper, his contributions to the transformation of synoptic meteorology, his research into the nature of explosive cyclogenesis, and related advances in the ability to predict these storms are reviewed. In addition to this review, the current status of forecasting oceanic cyclones 4.5 days in advance is presented, illustrating the progress that has been made and the challenges that persist, especially for forecasting those extreme extratropical cyclones that are marked by surface wind speeds exceeding hurricane force. Last, Fred Sanders' participation in a forecast for the historic 1947 snowstorm (that produced snowfall amounts in the New York City area that set records at that time) is reviewed along with an attempt to use today's operational global model to simulate this storm using data that were available at the time. The study reveals the predictive limitations involved with this case based on the scarcity of upper-air data in 1947, while confirming Fred Sanders' forecasting skills when dealing with these types of major storm events, even as a young aviation forecaster at New York's LaGuardia Airport.

Ocean surface winds play a significant role in the global ocean-atmosphere system. Surface winds drive the worlds ocean currents, transport atmospheric heat and moisture, force nutrient rich upwelling areas, create surface waves and swell, and can reach destructive force in both extratropical and tropical cyclones. Although the oceans cover 70% of the Earth's surface, the network of ocean wind observations obtained from conventional buoys and ships is very sparse. The measurement of ocean surface winds using remote sensing technologies is the only means of obtaining wind information over large portions of the global ocean in a timely manner. The Ocean Surface Vector Winds Team (OSVWT) of the Satellite Oceanography and Climatology Division (SOCD) within the NOAA/NESDIS/Center for Satellite Applications and Research (StAR) has been producing satellite-derived ocean surface wind data since the mid 1990s. Wind products from several remotely sensed sources such as QuikSCAT and WindSat are available in near real time (NRT) on the Internet and are also distributed within NOAA. These wind products are used by operational forecasters, scientific researchers and the marine community. The researchers and forecasters from NOAA Ocean Prediction Center (OPC), the NESDIS StAR Ocean Winds Team and the University Corporation for Atmospheric Research (UCAR) have partnered to increase awareness of the various ocean surface wind vector products available and to develop the educational materials needed to expose these products and to educate teachers at various levels about the latest technology for measuring and interpreting remotely sensed ocean vector winds. To accomplish this it has been proposed to host an educator workshop OPC. This workshop would target educators that train professional and future mariners in meteorology, oceanography and storm avoidance. Teachers from state maritime colleges, federal academies, and professional training institutions would be among those invited to participate. This workshop would be hosted by both researchers and forecasters and held within an operational forecast environment to promote hands-on experience. This paper will provide background information on current and new ocean surface wind remote sensing technologies, give examples of how products are used within the operational environment, and discuss the development of training material

Tropical cyclones can form over open ocean where in situ observations are limited, so forecasters rely on satellite observations to monitor their development and track. We explore the utility of an operational satellite sounding product for tropical forecasting by characterizing the products retrieval skill during research flights. Scientists from both the NOAA-Unique Combined Atmospheric Processing System (NUCAPS) research team and tropical cyclone communities collaborated to target relevant tropical cyclones during the campaign. This effort produced 130 dropsondes that are well-timed with satellite sounder overpasses over three different tropical cyclones and one Saharan Air Layer outbreak. For the combined infrared and microwave retrieval, the NUCAPS temperature has a root mean square error (RMSE) of 1.2 K near the surface (1000–600 mb) and 0.8 K in the mid-troposphere (600–300 mb), which is in line with global product requirements. The water vapor mixing ratio RMSE was 26% near the surface and 46% in the mid-troposphere. NUCAPS microwave-only retrievals can also be useful for cloudy scenes, with surface RMSE values of 4 K (temperature) and 23% (water vapor). Using information content analysis, we estimated that the vertical resolution near the surface was 1.7 km for the temperature retrievals and 2.2 km for the water vapor retrievals in this study. We discuss the feasibility of implementing NUCAPS in an operational forecasting setting, which requires rapid data delivery to forecaster software tools.